MeteorologyandoceanographyoftheNorthernGulf ofAlaskadepts.washington.edu/fish437/resources/Week 2/stab goa.pdf · rent. The Alaska Current is a typical eastern boundarycurrent,richwitheddiesandmeanders

ARTICLE IN PRESS

Continental Shelf Research 24 (2004) 859ndash897

Correspondin

E-mail addre

0278-4343$ - see

doi101016jcsr

Meteorology and oceanography of the Northern Gulfof Alaska

PJ Stabenoa NA Bondb AJ Hermannb NB KachelbCW Mordyb JE Overlanda

aPacific Marine Environmental LaboratoryNOAA 7600 Sand Point Way NE Seattle WA 98115 USAbJISAOUniversity of Washington and PMEL 7600 Sand Point Way NE Seattle WA 98115 USA

Abstract

The Gulf of Alaska shelf is dominated by the Alaska Coastal current (ACC) which is forced by along-shore winds

and large freshwater runoff Strong cyclonic winds dominate from fall through spring and substantial runoff occurs

from late spring through fall with annual distributed freshwater discharge greater than that of the Mississippi River We

examine the ACC from Icy Bay to Unimak Pass a distance of over 1500 km Over this distance the ACC is a nearly

continuous feature with a marked freshwater core The annual mean transport as measured from current meters is

approximately 10 106m3 s1 along the Kenai Peninsula with transport decreasing as the ACC travels westwardEven though the coastal GOA is a predominately downwelling system it supports a productive ecosystem Macro

nutrients from the basin are provided to the coastal system through a number of processes including topographic

steering eddies upwelling in response to horizontal shear in the barrier jets and during winter the on-shelf flux in the

surface Ekman layer Micronutrients (eg iron) are supplied from mechanisms such as resuspension of shelf sediments

and river discharge While strong seasonal cycles and interannual variability are dominant scales in atmospheric forcing

and the oceanic response there is also forcing on ENSO and decadal time scales

Keywords Gulf of Alaska Alaska Coastal Current Alaskan Stream Cross-shelf mechanisms Coastal winds

1 Introduction

The Gulf of Alaska (GOA) is a semi-enclosedbasin in the North Pacific Ocean bounded by themountainous coast of Alaska to the west northand east and open to the south The bottomtopography is complex the depth of basin shoalstoward the north with many deep canyonsintruding onto the continental shelf and numer-

g author Tel +1-206-526-6453

ss stabenopmelnoaagov (PJ Stabeno)

front matter r 2004 Elsevier Ltd All rights reserve

200402007

ous bays and inlets intersecting the coast Theregion is dominated by strong storms whosefrequency vary on monthly to decadal scalesThe regional meteorology in turn impacts theocean circulation and nutrient supply whichultimately support the rich ecosystem that char-acterizes the GOATwo current systems dominate the circulation of

the GOA the subarctic gyre in the ocean basin andthe Alaska Coastal Current (ACC) on the con-tinental shelf (Fig 1) The southern boundary ofthe subarctic gyre is the West Wind Drift which

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W e s t W i n d D r i f t

Alaska Current

Alaska

Peninsu

Kodiak I

Bering Sea

Peninsula

Current

Pr inceWi l l iamSound

YakutatBay

Kayak I

Coastal

Akaska

UnimakPass

A l a s k a n S t r e a mShumagin

SamalgaPass

60degN

QueenCharlotte Is

170degW

140degW150deg160deg 130degW170deg

Fig 1 Map of the Gulf of Alaska The flow of the Alaska Coastal Current and subarctic gyre are indicated as are several geographic

place names (After Reed and Schumacher 1986)

PJ Stabeno et al Continental Shelf Research 24 (2004) 859ndash897860

divides as it approaches the west coast of NorthAmerica into the southward flowing CaliforniaCurrent and the northward flowing Alaska Cur-rent The Alaska Current is a typical easternboundary current rich with eddies and meandersAt the head of the GOA it turns southwestwardfollowing the isobaths This is the beginning of theAlaskan Stream the western boundary current ofthe eastern subarctic gyre Near the southwesternedge of Kodiak Island (B155W) the AlaskanStream is a narrow (B50 km) high speed(gt50 cm s1) current that flows southwestwardalong the slope of the Alaska Peninsula andAleutian Islands to 180W where the AleutianArc turns northwestward (Reed and Stabeno1989 Reed 1984)The ACC driven by winds and freshwater

runoff dominates circulation of the shelf andcontrols the transport of dissolved substances andplanktonic material (Stabeno et al 1995a bRoyer 1981) While much is known throughdrifter trajectories and current meter mooringsabout the continuity seasonal variability andmean flow of the ACC from the Seward Line(B149W) westward less is known in the regionsouth and east of PrinceWilliam Sound Observations

from Icy Point (B137W Fig 2) to Kayak Islandreveal a baroclinic current with a strong seasonalsignal in the freshwater core typical of the ACCfarther west (Hayes and Schumacher 1976) TheACC flows westward along the Kenai Peninsula andbifurcates at Kennedy-Stevenson Entrance with themajority of annual transport continuing downShelikof Strait (Stabeno et al 1995ab Schumacheret al 1989) Approximately 70 of the transportcontinues down the Shelikof Sea Valley with less thanhalf joining the Alaskan Stream the remainder flowsalong Alaska Peninsula to Unimak Pass andSamalga Pass the western terminus of the ACC(Schumacher et al 1989)The continental shelf of the GOA supports a

productive ecosystem which includes numerousspecies of fishes marine mammals and sea birdsThe larvae of many species of vertebrates andinvertebrates occur in surface waters For manylarvae the ACC is their main path of dispersalCoastal waters also provide a conduit for youngsalmon upon entering the oceanic environment Atfirst impression such high productivity is surpris-ing because GOA coastal winds are downwellingfavorable However other mechanisms such aseddies and advection in canyons may replenish

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Icy Bay

Kayak I

Chirikof I

Shelik

of Str

GorePt

CKekurnoi

a l le

Kennedy EStevenson E

SewardLine

G u l f o f A l a s k a

SemidiiIs

Prince WilliamSound

HinchinbrookCanyon

AmatouliTrough

Fig 2 Geographic place names and the locations of hydrographic sections (solid black lines) discussed in the paper The Seward line is

shown as a dashed line

PJ Stabeno et al Continental Shelf Research 24 (2004) 859ndash897 861

nutrients to the shelf and support this richecosystem Global warming decadal variabilitypatterns (Pacific Decadal Oscillation PDO PacificNorth American PNA) El Nino-Southern Oscil-lation (ENSO) and large interannual variability allimpact the ecosystem through changes in fresh-water flux water temperatures and regional winds(Hare and Mantua 2000 Whitney et al 1999)Changes in the physical system influence not onlythe supply of nutrients to the shelf but also larvaldispersal and the timing and extent of phyto-plankton blooms (Hermann et al 1996 Stabenoet al 1996 Napp et al 1996)In this paper we integrate the knowledge about

the ACC from Icy Bay along the shelf to its end inthe eastern Aleutian Passes While many papershave been published that focus on parts (ie alongthe Kenai Peninsula Shelikof Strait etc) of theACC few exist that treat the system as a whole(Reed and Schumacher 1986 Royer 1998) Ourpurpose is to bring together historical and new

information on the ACC that permits us to explorepossible mechanisms generating cross- and along-shelf flow and to provide a basis for future researchThe length of the coast and the varying

mountainous terrain around the coastal GOAresult in large spatial variability in the atmosphericforcing (wind and precipitation) This forcingtogether with the complex bathymetry results inchanging oceanographic conditions around theperimeter of the GOA To investigate theseconditions we first examine atmospheric forcingincluding variability on seasonal to interannualtime scales in three regions (near Yakutat theKenai Peninsula and the Shumagin Islands) Thisis followed by a review and update of thefreshwater input along the Alaska Coast inparticular its spatial and temporal variability andchemical constituency Next we examine theoceanography (physics through primary produc-tion) of the ACC at three locations (near KayakIsland Kenai Peninsula and Shelikof Strait)

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Finally we integrate the results with a focus on themechanisms that result in the cross-shelf flux ofnutrients and salts

J F M A M J J A S O N D

Yakutat

Ketchikan

Seward

Fig 3 The seasonal signal of (a) precipitation and (b) runoff

along the Gulf of Alaska coastline The lower panel is after

Royer (1982) and dashed lines are7one standard deviation

2 The atmosphere

The atmospheric forcing of the GOA is domi-nated by the effects of cyclonic storm systemsTheir cumulative precipitation is the principalcause of the upper oceanrsquos baroclinicity in thecoastal zone and their winds are a primarycontributor to the local ocean circulation Previoussummaries of the meteorology of the GOA areprovided by Wilson and Overland (1986) andRoyer (1998) We include a brief review of theweather of the GOA as background for theprimary objective of this section the presentationof time series of coastal wind forcingThe GOA is the terminus of the Pacific storm

track Even though these storm systems aregenerally in the latter stages of their lifecyclesthey are so prevalent that the Gulf experiencesmean wind speeds and frequency of gale-forcewinds similar to that of the western and centralNorth Pacific (US Navy Marine Climatic Atlas1969) Storms tend to linger while slowly spinningdown largely due to the coastal mountainsbordering the Gulf (eg Wilson and Overland1986) This terrain inhibits the eastward progres-sion of the storms can intensify the winds andcauses large amounts of precipitation in coastalwatersheds The individual storms that constitutethe atmospheric forcing have characteristic timescales of a few days while their frequency andintensity vary on time scales of weeks to decadesThe weather of the GOA includes a pro-

nounced if not sharply defined seasonal cycleThere is a strong tendency for the winds in theGulf to be cyclonic during fall through springwith a broad peak in storminess from Octoberthrough March These winds result in systematicupward Ekman pumping in the central GOA(Reed 1984) and downwelling along the coastThe stronger of these storms which result in mostof the deepening of the ocean mixed layer occurduring the cool season During May throughSeptember the winds are variable with cyclonic

systems of weak to moderate intensity interspersedwith periods of high sea level barometric pressureThe latter periods are accompanied by anticyclonicwinds and cause intermittent upwelling alongthe coast These upwelling events in particularthe interannual fluctuations in their character areelaborated upon belowThe seasonal variability in precipitation in the

coastal GOA (as observed at three coastal weatherstations Fig 3a) features a prominent wet periodfrom September through November and a minorrelatively dry period in June and July Examina-tion of the limited number of direct observationstogether with those from satellites of precipitationin the central GOA suggest that the annual meanprecipitation in the central Gulf is about half ofthe 240 cm of water estimated to fall in coastalwatersheds (Royer 1979 Spencer 1993) Becauseprecipitation falls in the form of snow duringwinter and rain in the summer which melts thesnow and ice in coastal watersheds the coastal

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GOA experiences a stronger seasonal signal inrunoff than in precipitation (Fig 3b) As estimatedby Royer (1982) this runoff features an annualcycle with a peak in October of approximately4 104m3 s1 and a minimum in February ofapproximately 1 104m3 s1 The freshwater orbaroclinic contribution to the transport of the ACCleads the maximum local wind forcing by about 3months (Royer 1998) The annual freshwaterdischarge into the GOA of B24 104m3 s1 iscomparable to that of the Mississippi RiverB2 104m3 s1 (Dinnel and Wiseman 1986)

21 Interannual to decadal scales

There is a growing appreciation that interdeca-dal variability in the atmosphere strongly influ-ences the physical and biological systems of theNorth Pacific (Ingraham et al 1998 Mantua et al1997 Francis and Hare 1994 Hare and Mantua2000) Much of this variability can be attributed toa few fundamental patterns or modes In generalmuch more attention has been paid to describingthe decadal variability for winter than for summerThe leading contribution to the regional atmo-spheric variability in winter is the Pacific NorthAmerican or PNA (Wallace and Gutzler 1981Barnston and Livezey 1986) This mode relates tothe strength and position of the Aleutian low(and hence wind temperature and precipitationanomalies) over the GOA Variations in the PNAthrough its influence on surface fluxes of heat andmomentum are coupled to the PNArsquos counterpartin the ocean the Pacific Decadal Oscillation(PDO Wallace et al 1992 Wallace 2000)On 3- to 7-year time scales El Nino-Southern

Oscillation (ENSO) can be an important influenceon the GOA El Nino events are typicallyaccompanied by positive anomalies in wintertimeair temperature precipitation along-shore wind(ie downwelling favorable) and sea level La Ninaperiods tend to include anomalies in the oppositesense When the ENSO cycle is relatively weakother sources of variability intrinsic to the extra-tropical circulation dominate on interannual scalesOn decadal time scales the PDO (Mantua et al

1997) is the leading mode of North Pacificvariability The PDO features strong coupling

between anomalies in sea surface temperature(SST) and sea level pressure (SLP) in the west-central North Pacific with a secondary expressionin the GOA The atmospheric circulation anoma-lies associated with the PDO in the GOA resemblethose for ENSO and it is unclear how much thesetwo sources of variability are separable (Zhanget al 1997) In discussing decadal variabilityhowever it is important to note that less than 38of the wintertime interannual variance of theAleutian low is on time scales greater than 5 years(Overland et al 1999a) The primary east-westpattern of spatial variability of the PNA in wintergives way to the more northndashsouth dipole inspring referred to as the North Pacific Pattern(Barnston and Livezey 1986 Overland et al2002) Less is known about the causes of coastalGOA summertime variability but it is expectedthat the key variables are the amount of cloudcoverage hence solar heating of the surface mixedlayer (Norris et al 1998) the frequency andmagnitude of coastal upwelling events and theoccurrence of storms which impact both mixedlayer depth and the strength of the ACCWhile these large-scale linkages between the

ocean and atmosphere are reasonably well estab-lished for the North Pacific as a whole it is stillunclear how the large-scale atmosphere-oceanclimate system relates to the coastal zone alongthe GOA Essentially a different set of lsquolsquorulesrsquorsquoapplies to airndashsea interactions in this regionbecause of the presence of the mountainouscoastal terrain This terrain is particularly impor-tant through its impact on the along-shore windswhich forces cross-shelf Ekman transports andprecipitation which impacts the upper oceanrsquosbaroclinicity Relatively subtle differences in thelarge-scale atmospheric flow (eg low-level staticstability and wind direction) can result in sub-stantial differences in the atmospheric response tothe coastal terrain Without further study wecannot relate important mechanisms involving theACC such as the timing of seasonal reversals inthe normally downwelling-favorable winds to thelarge-scale variations in the climate forcing Yet itis these downscale effects of climate variations thatare liable to be crucial to the ACC and to themarine ecosystem in the coastal GOA

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22 Winds

Airndashsea interaction mechanisms important tothe coastal GOA are presented below The focus ison time series of seasonal mean along-shore windsand wind mixing in the cool season and upwellingin the summer The analysis consists of time seriesat selected points along the coast These results arenot so much definitive as illustrative of theinteractions between wind and buoyancy on upperocean in the coastal GOA and are related to theforcing of physical oceanographic observationsnoted in later sectionsThe coastal winds are estimated using daily data

from the NCEPNCAR Reanalysis (Kalnay et al1996) with a simple correction for the effects ofcoastal terrain on nearshore winds This correctionwas arrived at through comparisons betweensynthetic aperture radar (SAR) estimates of thewinds (as provided by Johns Hopkins UniversityApplied Physics Laboratory see manatiwwbnoaagovsar pub 5s APL windswind imagesindexhtml) with those from the Reanalysis forthe cool season of 1999ndash2000 and the warm seasonof 2000 at selected locations along the coastalGOA The wind speeds from SAR averaged about50 higher than those estimated from theReanalysis during periods of positive (southerlyor easterly) along-shore winds (ie with theterrain on the right) but were similar in magnitudeduring conditions of negative (westerly or north-erly) along-shore winds Similar enhancementswere found at the different locations surveyedBased on these results we assumed that the along-shore component of the winds were 50 greater inmagnitude than in the Reanalysis when positiveand equal in magnitude to that in the Reanalysiswhen negative The component of the wind in thecross-shore direction was unchanged We note thatour correction is designed to account for theeffects of coastal terrain in an average sense theseeffects vary for individual storm eventsEnhancement of the low-level winds during

periods of positive along-shore flow is expecteddue to the prominent terrain along the GOA Thisphenomena is known as a barrier jet (eg Parish1982) The zone of stronger winds extendsoffshore approximately an atmospheric Rossby

radius (50ndash100 km for the GOA) The magnitudeof the enhancement found here is consistent withthe results of Overland and Bond (1995) andwith the wind algorithm used by Stabeno et al(1995a b) for forcing a numerical model forShelikof Strait These enhanced along-shore windsare present in the SAR data but not captured inthe Reanalysis because of the latterrsquos coarse (25

latitude) resolution relative to the Rossby radiusand its consequent inability to resolve the effects ofthe coastal terrain Inspection of individual casesfrom the Reanalysis also suggest that the directionof surface winds in the coastal zone are not parallelto the coast as is generally observedThe mean seasonal cycle in the coastal winds of

the GOA is illustrated in Fig 4 As mentionedearlier the GOA is stormy during the cool seasonand calmer during the warm season but there aresubstantial regional differences The seasonal cyclein storminess (as gauged by the wind speed cubedFig 4c) is more prominent at the western location(55N 160W near the Shumagin Islands) than atthe north-central and north-eastern locations Themean cross-shore wind is weak through much ofthe year (Fig 4a) although during early fall windsat the north-eastern location are slightly onshorewhile winds at the western location are moreoffshore The mean along-shore wind is morepositive at the north-eastern location than at thenorth-central and western locations throughoutthe year (Fig 4b) The north-eastern location alsoexperience a stronger seasonal signal in thiscomponent of the wind The annual cycle in thecoastal winds of the GOA has important con-sequences for the ACC (Royer 1998 Stabenoet al 1995a b) but the interannual variability inthe coastal forcing must also be consideredThe interannual variability in the seasonal mean

forcing is examined next focusing on the summer(JunendashAugust) with its intermittent upwelling-favorable winds and the cool season (OctoberndashMarch) with its systematic downwelling-favorablewinds The mean along-shore wind total upwel-ling and mean wind speed cubed during summerfor the years 1949 through 2000 at the same threecoastal locations is shown in Fig 5 We define thetotal upwelling to be the integrated along-shorewind stress (using the algorithm of Large and

ARTICLE IN PRESS

3 s- 3

55degN 160degW

59degN 140degW59degN 150degW

Fig 4 The annual cycle in winds at selected locations (a) the cross-shelf winds (b) the along-shore winds and (c) wind mixing (daily

mean wind speed cubed) The annual signal was created from daily averages over a 52-years period (1949ndash2000)

Pond 1982) considering only the periods ofnegative along-shore winds (ie upwelling favor-able winds) It is the along-shore component of thestress that is related to the cross-shelf Ekmantransport (eg Gill 1982) and because the stressis nearly proportional to the square of the windspeed this measure effectively accounts for the fewstrong events that produce most of the upwellingNote that while the mean summer along-shorewinds are only slightly more negative (B1m s1)at 55N 160W than at 59N 150W the totalupwelling at the former location tends to be aboutthree times greater A common characteristic ofthe time series shown in Fig 5 is the lack of anydiscernible decadal signals or long-term trendsThe year-to-year fluctuations are large howeverespecially at the three southern locations where

typical anomalies are roughly 50 as large as theirmeans Alternatively upwelling or mixing istypically three times greater in strong years relativeto weak years Such large interannual variabilitylikely have important implications for the supplyof nutrients to the euphotic zone over the shelf inthe summerNext we consider the interannual variability in

coastal wind forcing during the cool seasonDuring this time of year the wind mixing isusually vigorous and the surface heat fluxes to theatmosphere are substantial resulting in a relativelywell-mixed water column The most importantaspect of the coastal winds is their along-shorecomponent which regulates the transport of theACC (Stabeno et al 1995a b) We include timeseries of seasonal mean in the along-shore wind

ARTICLE IN PRESS

ed (10

3 s- 3

55degN 160degW

Fig 5 The summer (a) mean along-shore wind (b) total upwelling and (c) mean wind speed cubed for the years 1949 through 2000 at

the three coastal locations discussed in the paper

speed and the wind stress The former has oftenbeen compared to along-shore transports incoastal regions but the latter is related moredirectly to the cross-shore component of theEkman transport and hence the set-up responsiblefor the barotropic portion of the coastal flowThese two measures are obviously highly corre-lated but there are some interesting differencesNotably the average stress at the western mostlocation (55N 160W) is negative even thoughthe average along-shore wind is positive consis-tent with the tendency for stronger but lessfrequent winds to be from the west ratherthan from the east Also the winds in the north-eastern GOA are almost always more positivethan their counterparts in the north-central andwestern GOA

Similar to the summer winds the winter windsexhibit considerable interannual variability Inter-estingly any clear signature of the PDO (Mantuaet al 1997) and the regime shift in 1977 is lackingThere were largely negative seasonal mean windspeed and stress anomalies from the mid-1960s tomid-1970s and positive anomalies from the late1970s through 1980s especially in the easternGOA But on the whole the coastal winds do notreflect the PDO This can be explained by notingthat the winds relate to coastal SLP gradientswhich are sensitive to the position and intensity ofthe Aleutian low and the Aleutian low is impactedby factors other than the PDO (Overland et al1999a b) The year-to-year rather than decadalvariability in the coastal wind forcing in bothwinter and summer is substantial and this likely

ARTICLE IN PRESS

55degN 160degW

s-1) 8

Fig 6 The winter (a) mean along-shore wind and (b) mean

along-shore wind stress for the years 1949 through 2000 at the

three coastal locations discussed in the paper

has important implications for the year-to-yearvariability in the ACC (Figs 5 and 6)

23 Rainfall and runoff

Runoff is crucial to the baroclinic structure ofthe ACC We focus on the interannual variabilityin precipitation and air temperature which to-gether control the magnitude and timing of thefreshwater input to the ACC and concentrate onthe northern and eastern portions of the GOAwhere most of the freshwater for the ACCoriginates We use observations of precipitationand temperature from coastal weather stationsrather than the NCEP Reanalysis data set that wasused to estimate coastal winds The Reanalysislikely includes much greater errors in precipitationthan surface winds since the precipitation iseffectively a higher-derived quantity than the windand less constrained by observations Virtually nolong-term precipitation records are availableabove sea level in the GOArsquos watersheds so therecords presented below should be consideredindices rather than absolute measures of the

freshwater input As in the discussion of windswe consider the cool and warm seasons separatelyTime series of total precipitation and mean air

temperature at Ketchikan Yakutat and Sewardfor the warm seasons (defined as May throughOctober following Royer 1979) of 1950 through2000 are plotted in Fig 7 Apart from year-to-yearvariability little if any systematic signal isapparent in either precipitation or air temperatureOne exception is the relatively wet conditions atYakutat from the late 1980s through the early1990s but it is uncertain how important this issince the other two stations did not experiencesustained anomalies In the warm season theprecipitation lacks any significant systematicrelationship with air temperature and is at bestweakly related to the coastal winds with correla-tion coefficients less than 011 at all three stationsThe time series of precipitation and air tem-

perature during the cool season (Novemberthrough April) show greater interannual variabil-ity than that during the warm season and somedecadal signals (Fig 8) The major PDO regimeshift of 1977 was accompanied by a transition toslightly wetter conditions at Yakutat and Sewardand perhaps slightly drier conditions at KetchikanThe regime shift is even more evident in the airtemperature at Yakutat and Seward whichexperienced colder winters in the late 1960s andearly 1970s followed by warmer winters in the late1970s and 1980s As mentioned earlier it isuncertain how to quantify the causes of thisdecadal change because of the possible interactionsbetween the PDO and ENSO It is noteworthy thatthe El Ninos of 1977 1987 and 1998 all featuredwarmer wetter winters in the northern GOAUnlike the warm season precipitation and mean

air temperature during the cool season arepositively correlated in the northern GOA Thecorrelation coefficients between the along-shorewinds and the coastal precipitation are 029 028and 021 at Ketchikan Yakutat and Sewardrespectively While these values are modest theyare significantly different from zero at the 95confidence level The typical magnitude of thetemperature anomalies is 2C which correspondsto anomalies in the freezing level of B300mThis has important consequences for runoff Cool

ARTICLE IN PRESS

YakutatKetchikan

Seward

1950 1960 1970 1980 1990 2000

Fig 7 Time series of the average (a) total precipitation (b) mean air temperature at Ketchikan Yakutat and Seward during the warm

seasons of 1950 through 2000 The warm season is defined as May through October following Royer (1979) The average runoff for the

Gulf of Alaska for June through November (1950ndash2000) is shown (c)

winters may result in an enhanced snow pack andthus a possible increase in runoff during the warmseason Warm winters will tend to have signifi-cantly enhanced runoff not just because of greaterprecipitation but also because the snowice linewill be higher in elevation and farther north thanusual The technique used by Royer (1979) inwhich a constant fraction of the coastal precipita-tion in winter is assumed to be runoff may lead tosignificant errors There does not seem howeverto be any straightforward way to assess thistemperature effect since so few of the coastalGOA rivers are gauged The implication for theACC is that wet winters with their enhancedupper ocean baroclinicity also tend to include agreater wind forcing of the barotropic component

A strong seasonal signal exists in the freshwaterdischarge time series (Fig 3) that was developedby Royer (1982) which includes a factor based ontemperature Minimum runoff occurs during thecold winter months and maximum runoff occurs inearly fall when precipitation increases andtemperatures remain above freezing (Fig 3b) Wedivided the runoff into two parts high (JunendashNovember) and low (DecemberndashMay) which areshifted 1 month later than the monthly averagedprecipitation and temperature time series (Figs7ab and 8ab) During JunendashNovember runoff isapproximately double that during DecemberndashMay and the variability is slightly less (Fig 7cand 8c) Decadal variability is not clearly evidentin either time series although analysis by Royer

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

(c)Fig 8 Time series of average (a) total precipitation (b) mean air temperature at Ketchikan Yakutat and Seward during the cold

season of 1950 through 2000 The cold seasons is defined as November through April The runoff for the Gulf of Alaska for December

through May for each year (1950ndash2000) is also shown (c)

and Grosch (2000) shows that approximately aquarter of the variability is in a pair of bandscentered on 15 and 42 years As expected since thetime series of freshwater discharge is derived fromatmospheric variables years of high runoff duringwinter and spring (ie 1978) are associated withyears of above average temperatures during thecold season and high precipitation The weakerrunoffs during winterspring (ie 1972) areassociated with colder than average temperatureand not as sensitive to precipitation The summer-fall runoff is related predominately to rainfallwith temperatures warm enough to play little rolein variabilityIn addition to the flux of freshwater coastal runoff

contributes nutrients necessary for phytoplankton

production The riverine contribution may be espe-cially important in summer when runoff is near theseasonal maximum and surface concentrations ofnutrients over the shelf are otherwise depleted(discussed below) However as noted by Sugai andBurrell (1984) and Burrell (1987) nutrient levels likelyvary depending on the freshwater source (eg glacialvs non-glacial rivers with varying freshwater resi-dence times) In addition sediment discharge in fallcan dramatically reduce the photic zone and dampenfall blooms (Goering et al 1973 Burrell 1987)Riverine discharge adds significant iron and silicicacid to the ACC Dissolved iron and silicic acidconcentrations average about 3 and 100mM respec-tively for drainage basins throughout southernAlaska (Glass 1999 USGS Web Page Marc

ARTICLE IN PRESS

Kramer pers comm) During summer the ACC eastof Cook Inlet is about B8 fresher indicating acontribution of about 8mM silicic acid to the ACCfrom freshwater sources The flux of nitrate fromriverine sources is unclear Organically rich streamsmay be severely N limited such that any availableNO

3 is rapidly taken up and is undetectable (MKramer pers comm) Other studies found relativelyhigh nitrate concentrations near river inputs at PortValdez (15mM Goering et al 1973) and from severalrivers entering Smeaton Bay in southeast Alaska (2ndash6mM Sugai and Burrell 1984) Average lsquolsquonitrate plusnitritersquorsquo concentrations in USGS water quality studieswere about 13mM Hence given typical fresheningobserved in the ACC freshwater discharge only addsabout 1mM nitrate to surface waters of the ACC

3 Oceanography

In comparison to the meteorological dataoceanographic data for the GOA are limited Onlythrough combining historical data from hydro-graphic cruises instruments on moorings satellite-tracked drifters and satellite images have we beenable to develop a picture of ocean conditions in theGOA These data sets coupled with modelingresults permit the characterization of the currentsand water properties of the regionA coastal current with a marked freshwater core

is evident along the Alaska coast from Icy Point toUnimak Pass (Stabeno et al 2002 Schumacheret al 1982) Along its course it is modified byboth broad scale cross-shelf Ekman transport andepisodic entrainment from the slope as well as bytopographic steering at a variety of sites includingKayak Island Hinchinbrook Canyon and Ama-touli Trough The large freshwater discharge fromnumerous rivers and streams along the mountai-nous Alaska coastline is confined along the coastby downwelling favorable winds This combina-tion provides a strong baroclinic signal to theACC In response to variations of wind forcingand buoyancy flux maxima in along-shore trans-port can exceed 30 106m3 s1 (eg Stabenoet al 1995a b Stabeno and Hermann 1996 Bondand Stabeno 1998) and daily averaged speeds canexceed 100 cm s1 (Stabeno et al 1995a b Royer

1998) The transport in the ACC varies onseasonal time scales with maximum baroclinicflow occurring in October in conjunction withmaximum freshwater runoff maximum totaltransport (as measured from current meter moor-ings) is in the winter and associated with the strongwinter winds (Schumacher et al 1989)The complexity of the ACC over the shelf is

evident in a series of chlorophyll images taken inthe spring of 1997 1998 and 1999 (Fig 9)Detailed spatial structures are apparent in thechlorophyll-a distributions provided by SeaWiFsand ADIOS It is uncertain how much of thepatchiness in these chlorophyll distributions re-lates to physical processes such as localizedupwelling and eddies versus biological processessuch as grazing

31 Lagrangian measurements

Lagrangian devices or drifters provide informa-tion on the spatial characteristics (such as eddiesbifurcation and meanders) in the ACC locationsof onshelf flow and mean circulation Over 100satellite-tracked drifters have been deployed in theGOA during the last 15 years Most were deployedwest of Prince William Sound Typically thedrogues were at 35ndash45m so that direct effects ofwind and wind-wave generated currents weresmall and the ensuing trajectories provide adescription of the underlying oceanic currentstructure A description of data control andaccuracy of these instruments is found in Stabenoand Reed (1991)A general description of the flow in the ACC

from Kayak Island to Unimak Pass can be madeusing drifter trajectories Approximately a dozensatellite-tracked drifters were deployed betweenIcy Point and Kayak Island in 2001 and 2002While an organized flow is evident along the coastbetween Icy Point and Kayak Island duringsummer most of the drifters were diverted to theshelf break at Kayak Island (Fig 10a) Only onedrifter was advected into Prince William SoundDrifters deployed along the Seward Line(B149W Fig 10b) reveal episodic across shelfflow and a relatively unorganized ACC Thedrifters in Fig 10b were deployed in May 2001

ARTICLE IN PRESS

Fig 9 Satellite images of chlorophyll-a from (a) May 18ndash24 (ADEOS) (b) May 1998 (SeaWiFs) and (c) June 1999 (SeaWiFs) Both

the land and clouds are black Note the different scales for ADEOS and SeaWiFs (from Whitney and Welch 2001)

and the effects of weak winds that characterize thewarm season are evident in the trajectories As thedrifters approached Gore Point the current be-comes more organized The ACC bifurcates asindicated by drifter trajectories one drifter (green)entered Shelikof Strait through Kennedy Entranceand the other (dark blue) was advected along the

south-west side of Kodiak Island (Fig 10c) Suchflow patterns are relatively common in driftertrajectories (Fig 10d) The flow along the southside of Kodiak is relatively weak and variablewhile the flow in Shelikof Strait is stronger andlargely centered on the north side of the straitUpon exiting Shelikof Strait meanders once again

ARTICLE IN PRESS

(a)154degW 150degW 146degW 142degW

58degN

56degN

60degN

(d)(c)

Fig 10 Trajectories of satellite tracked drifters (depth of drogueB40m) The arrows indicate the direction of flow The small loopson the trajectories are tidal motion (a) Flow along the shelf Only one drifter deployed east of Kayak Island was advected in Prince

William Sound (b) Convoluted flow along the Kenai Peninsula (c) trajectories on each side of Kodiak Island with a retention area

over Portlock Banks and (d) drifters west of Shelikof Strait

became more prominent although not to theextent that was observed along the Kenai Penin-sula Eddies (diameter 20ndash30 km depth 200mgreen in Fig 10c) are also evident in the sea valleysouthwest of Kodiak Island and drifters haveremained trapped in such features for severalweeks (Bograd et al 1994 Schumacher et al1993) Most of the flow of the ACC continuesdown the sea valley (blue Fig 10d) althoughsome parallels the Alaska Peninsula (purple Fig10d) The transport in the sea valley exits the shelfand joins the Alaskan Stream or recirculates ontothe shallow shelf west of the sea valley The flowalong the peninsula continues westward through

or around the Shumagin Islands Some driftersenter the Bering Sea through Unimak Pass(Stabeno et al 2002) others join the AlaskanStream (Fig 10d) The exact percentage oftransport that goes with each path is not knownand would be best estimated from an array ofcurrent meter mooringsFlow along the shelf break and slope is more

organized than that on the shelf with the AlaskanStream evident in trajectories Of three driftersdeployed along the slope (water depths 1000ndash2000m) one (purple Fig 10b) was advected ontothe shelf A second drifter (red) was also advectedonto the shelf and followed the 200m isobath

ARTICLE IN PRESS

until rejoining the Alaskan Stream at the mouth ofthe Shelikof sea valley The third drifter (blue)remained in the Stream until it was advected intothe basin at about 158W Eddies in the stream arenot uncommon (eg Fig 10d blue)Results from a numerical model (details of

model can be found in Hermann et al 2002)show the complexity of current along the shelffrom east of Kayak Island to Shelikof Strait(Fig 11) The Alaska Current and Alaskan Streamare evident along the slope The narrowness of theshelf east of grid point 126 results in the AlaskaCurrent interacting with the shelf flow Unfortu-nately the coarseness of the model grid was suchthat Kayak Island was not resolved To the east ofPrince William Sound two eddies are apparentsuch eddies are also evident in some satellite-tracked drifter trajectories (Fig 10a) On shelf flowoccurs in the vicinity of the Seward line which isalso in agreement with the satellite-tracked driftertrajectories Finally the flow narrows at GorePoint and then passes through Kennedy EntranceIn general there is good agreement between thecurrents predicted by the model and those derivedfrom satellite-tracked drifter trajectories

Kenai Pen

Kodiak I

Fig 11 Depth integrated current velocities from a model (Hermann e

The red lines indicate bathymetry in meters Vectors are in m s1

32 Time series from moorings

Moorings have been deployed on the GOA shelfsince 1974 and these mooring sites can be dividedinto three general areas In the eastern region(Kayak) extends from Icy Bay west to KayakIsland moorings were deployed year around at tensites from 1974 through 1976 (Hayes 1979) Thesecond region (Kenai) extends along the KenaiPeninsula and into upper Shelikof Strait Moor-ings were deployed in a line across the shelf atGore Point in 1991 and 1994 and in Kennedy andStevens Entrances in 1991 (Stabeno et al1995a b) Moorings have been deployed as partof GLOBEC on the Seward Line but those dataare not yet available The third region (Shelikof)extends from the western exit of the Shelikof Straitwest to the Shumagin Islands Over 70 mooringshave been deployed in Shelikof sea valley and theshelf to the east since 1984 the majority of thesetime series are during spring and summer Un-fortunately there is little overlap in time betweenthe three regions All moorings were taut wiremoorings that recorded hourly or half-hourlydata Instrumentation and mooring designs can

02 m s-1

insula

Prince William Sound

t al 2002) The coast has been rotatedB45 counterclockwise

ARTICLE IN PRESS

Gore PtInshoreMiddleOffshore

InshoreMiddleOffshore

CapeKekurnoi

Kayak IInshoreMiddleOffshore

Fig 12 Time series of monthly mean near surface currents at

three locations (east of Kayak Island Gore Point and Cape

Kekurnoi) along the GOA coast Red dots are velocity

measured along the coast purple at mid shelf and blue at

outer shelf

be found in a variety of publications (Schumacheret al 1989 Stabeno et al 1995a Hayes 1979Hayes and Schumacher 1976)

321 Tidal currents

Tidal analysis of each of the time series providea map of the variability in strength and directionof the tidal constituents along the shelf Thedominant tidal component in each region is M2The axis of the tidal ellipses parallels the coast withsignificant spatial variability along the coastBeginning at Icy Bay the tidal constituents arerelatively weak with the amplitude of M2 approxi-mately 2ndash5 cm s1 To the west of Kayak Islandthe M2 tidal currents increase to 17 cm s

1 near theshore and B10 cm s1 at the shelf edge At GorePoint M2 has strengthened to 20ndash30 cm s

1 Thestrongest measured tidal currents are in KennedyEntrance where M2 is gt70 cm s

1 In the Shelikofregion tidal velocities (20ndash30 cm s1) are similar tothose at Gore Point

322 Low-frequency currents

The width speed and depth of the ACC varieswith location along the coast From Kayak Islandwest to Seward Line the ACC is convoluted withsignificant mesoscale activity likely due to thecomplex topography At Gore Point it narrows(B50 km wide) and flows westward parallel to thecoast with few reversals on daily time scales Thismore organized flow is likely a result of lesscomplex topography Gore Point lacks canyonscutting perpendicularly into the shelf which arecommon along the eastern half of the KenaiPeninsula In addition Gore Point is fartherremoved from eddies that influence on-shelftransport Farther down stream at Cape Kekur-noi the ACC narrows to B30 km wide and thenwidens again as it flows down the Shelikof SeavalleyUsing data from the moorings we examined the

currents at a depth of 20ndash35m at three locationsalong the continental shelf (Fig 12) The currentrecords were divided into three subsets near coastmid-shelf and outer shelf Examination of along-shore currents reveals a seasonal signal in velocitywith a tendency for weaker currents duringsummer (MayndashAugust) and stronger currents

during fall and winter especially at Gore PointEast of Kayak Island the current speed does notappear to be associated with cross-shelf position(Fig 12a) The strongest current was often nearthe middle of the shelf or even at the outer edgeAt Gore Point (Fig 12b) the highest speeds arenear the coast and decrease monotonically withdistance from the coast In Shelikof Strait (Fig12c) the strongest currents are along the AlaskaPeninsula where some individual monthly meansexceeded 50 cm s1 The currents are weaker nearthe middle of Shelikof Strait and along KodiakIsland where currents often reverse While aseasonal signal is not evident in the flow alongthe peninsula the speed nearest the center of thestrait appears weakest in the summer

ARTICLE IN PRESS

323 Relationship of currents to wind forcing

Correlations between winds and individualcurrent meter records are generally not significantdue to the temporal variability in the position ofthe ACC on the shelf and the presence of meandersand eddies Two locations where correlationsbetween winds and currents have been significantare to the east of Kayak Island (Hayes 1979Hayes and Schumacher 1976) and along theAlaska Peninsula in Shelikof Strait (Stabenoet al 1995a) The strong ageostrophic winds thataccelerate down Shelikof Strait result in a narrowcurrent confined along the coast (Lackmann andOverland 1989 Bond and Stabeno 1998 Stabenoet al 1995a b) A better indication of how windsrelate to the ACC is through an examination oftransport (derived from current meters) and windforcing During four different years (1984ndash19851989 1991 and 1996) there were sufficientmoorings deployed to measure total transport ofthe ACC across Shelikof Strait or across the seavalley (Stabeno et al 1995a Bograd et al 1994Schumacher et al 1989) The times series ofcurrents used here were all low pass filtered toremove the tidesDuring 1991 transport was calculated at Gore

Point Kennedy and Stevenson Entrance and at theexit to Shelikof Strait (Stabeno et al 1995a)Correlations among transports were all significantDuring periods of high transport most of the flowat Gore Point flows down Shelikof Strait but duringperiods of weak transport a significant portionflows south of Kodiak Island (Stabeno et al1995a) Mean transport in Shelikof Strait duringwinter (OctoberndashApril) was B1 106m3 s1 withtransport ranging from B35 106 to 05106m3 s1 (Fig 13) During summer both themean transport (o05 106m3 s1) and the varia-bility was less than during the winter

Fig 13 Transport (106m3 s1) measured using current meters at Ca

further down the sea valley (FebruaryndashJuly 1985 and 1989)

The high variability observed in the transportsappears related to the along-shore wind (6-hourlywinds from the NCEP Reanalysis at 59N150W) Using the four time series of transportin Shelikof Strait and sea valley we divided thetransports into three subsets (JanuaryndashAprilMayndashAugust and SeptemberndashDecember) to re-move the annual signal (Fig 14) For eachsubgroup the transport lags the wind by 12 hThe correlations range from r frac14 042 during thefall to r frac14 054 in the winter and early springLower correlations with the wind in the fall may bein part due to the large freshwater input whichmay modify transport The lower correlation inthe summer likely results from the weaker windforcing during this periodModel simulations (Hermann and Stabeno

1996) also show that while baroclinic structure isrelated to runoff the transport is largely deter-mined by winds Doubling the magnitudesof the winds results in an increase in transporthowever a doubling in the magnitude of therunoff does not result in a significant increasein transport Along-shore downwelling favor-able winds are necessary to confine the fresh-water discharge along the coast which thenresults in the ACC Without downwelling windsthe freshwater appears to pool at the fresh watersourceConclusions about the variability in transport

can be drawn from examination of along-shorewinds The year-to-year variability of the along-shore winds during winter in the northern GOA(Fig 6) is not particularly large and thus the year-to-year variability in transport during winter islikely not large Alternately during summer(Fig 5) there are years when the along-shorewinds would support a more vigorous ACCBiological productivity during the summer is

pe Kekurnoi (August 1984ndashJanuary 1985 1991 and 1996) and

ARTICLE IN PRESS

-20 -10 0 10 20Alongshore Wind (m s-1)

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

Fig 14 Scatter plot of along-shore winds along the Kenai

Peninsula versus transports shown in Fig 13 The maximum

correlations which occurred at 12 h lag are shown

dependent upon available nutrients and thevariability in transport of the ACC would likelyimpact the availability of nutrients

33 Hydrography

The cross-shelf hydrographic structure wasexamined at six locations during September andOctober and four locations during May (Fig 2Figs 15 and 16) Evident in each section is thefreshwater core of the ACC that is prominent infall and less so in the spring The easternmostlocation is at Icy Bay where measurements exten-ded into the bay In the September 1977 Icy Baysalinity was below 26 psu Even outside the baysalinities were less than 30 psu indicative of thestrong freshwater influence of the ACC At bothKayak Island and Gore Point autumn salinitiesbelow 30 psu occur Surface salinities beyondKennedy Entrance however increased to above31 psu and remained high into Shelikof Strait andthe sea valley Typically the less saline water wasconfined along the coast in the upper part of thewater column with salinities above 32 psu evidentbelow 100m Over the shelf the highest salinities(gt335 psu) were at Chirikof Island where waterdrawn from the slope flows up the sea valley in anestuarine flow along the east side (left on thefigure) of the sea valley This higher salinity wateris evident at Cape Kekurnoi (Reed and Bograd1995 Reed 1987) The salinity gradients duringspring were not as marked (Fig 16) Without thelarge freshwater input salinities were higher andmore uniform across the shelf but still the lowestsalinities are found along the coastWhile thousands of conductivity-temperature

and depth (CTD) casts have been made in theGOA only two sites (separated by B500 km) onthe shelf have sufficient data to evaluate a seasonalsignal The longest record exists at GAK1 (theinnermost station on the Seward Line) which hasbeen maintained by the University of Alaska since1970 The second site is at Cape Kekurnoi the exitof Shelikof Strait which has been maintained since1984 Both stations are near shore and thus areimpacted by the low salinity water of the ACCThe best data set is at the GAK1 site because thetime series is longer and the data are spreadthroughout the year In contrast measurements atCape Kekurnoi were most often in the springThe seasonal signal of depth averaged tempera-

tures and salinities at these two sites are similar

ARTICLE IN PRESS

C Kekurnoi 9 Oct 1978

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

Kennedy Entrance21 Oct 1978

Chirikof I8 Oct 1978

Fig 15 Across shelf structure of the salinity (psu) during September and October at six sites along the shelf shown in Fig 2 (1) Icy

Bay (2) Kayak Island (3) Gore Point (4) Kennedy-Stevenson Entrances (5) Cape Kekurnoi at the exit of Shelikof Strait and (6) line

between Chirikof Island and Semidii Islands The Alaska coast is to the right in panels 1ndash5 In panel 6 Chirikof Island is to the right

The shaded areas represent salinities o30 psu

ARTICLE IN PRESS

Fig 16 Across shelf structure of salinity during May or early June at four sites along the shelf (1) Kayak Island (2) Gore Point and

(3) Cape Kekurnoi (4) line between Chirikof Island and Semidii Islands Once again the Alaskan coast is at the right of each panel

(Fig 17) At GAK1 there is a spread of almost1 psu in the data and a distinct seasonal signal inthe salinity with the higher salinities occurringin late springearly summer and lowest salinities in

the fall As expected this is in phase with the timeseries of freshwater runoff which also reaches amaximum in the fall The seasonal temperaturesignal includes a broad minimum in March and a

ARTICLE IN PRESS

10GAK 1Shelikof Strait

GAK 1Shelikof Strait

330(a)

Fig 17 Depth averaged (a) temperature and (b) salinity

measured from CTD at GAK1 and Cape Kekurnoi The blue

circles indicate measurements at GAK1 and the red squares

indicate measurements at a site near Cape Kekurnoi Data are

from 1976 to the present

GAK1Shelikof Strait

1985 1990 1995 2000

Fig 18 Interannual time series of the depth integrated (a)

temperature and (b) salinity at GAK1 and Cape Kekurnoi

during May All measurements were made using CTDs

broad maximum in September The lack of datacollected during fall and early winter make itdifficult to quantify a seasonal signal at CapeKekurnoi although trends in the sparse dataappear similar to GAK1The best hydrographic data to examine the

interannual variability on the GOA shelf are fromMay at GAK1 and Cape Kekurnoi (Fig 18) Dataexist for most years since 1985 with data at bothsites for 12 of those years The correlation betweentemperature at the two sites is r frac14 080 andbetween salinity is r frac14 056 As in the atmospherictime series there is much year-to-year variabilityin the signals The 1986ndash7 and the 1997ndash8 El Ninosare characterized by warm less saline water in1987 and 1998 respectively In contrast during the1989 and 1999 La Ninas the water column wascooler and more saline This is expected as ElNino events are associated with warmer winter-time air temperatures and greater precipitationwith the reverse true for La Nina periods Theshortness of the record precludes the ability to

examine decadal variability however there was anincrease in temperature and decrease in salinity atthe outer end of the Seward line after 1977(Overland et al 1999b) which is generallyrecognized when there was well-defined regimeshift in the North PacificThe annual cycle of near surface temperatures at

GAK1 has a distinct seasonal signal with amaximum in August and minimum in March(Fig 19 top) The cooling in the winter is largelydue to the local surface heat fluxes The lens offreshwater near the surface stabilizes the watercolumn permitting surface temperatures to oftenbe colder than near-bottom temperatures Theannual temperature signal at depth is much weakerthan that at the surface with an indication ofslightly warmer temperature in January The dataat Cape Kekurnoi (Fig 19 bottom) are sparserand have been augmented with time series fromcurrent moorings (open circles and squares) Thedepth of the shallowest temperature sensor onmost moorings was at 25ndash35m and thus well

ARTICLE IN PRESS

Shelikof Strait

Fig 19 Near surface (blue) and near bottom (red) temperature

at (a) GAK1 and (b) Cape Kekurnoi The open circles and

squares are from current meter moorings one point every 2

weeks The bottom current meter was 10ndash15m off the bottom

and the top current meter was located 25ndash40m from the

surface

Near SurfaceBottom GAK 1

Near SurfaceBottom Shelikof Strait

Fig 20 Near surface (blue) and near bottom (red) salinity at

(a) GAK1 and (b) Cape Kekurnoi See Fig 19

below the surface During winter this is not aproblem since the surface mixed layer is typicallygreater than 35m During summer however themixed layer can be shallower than 25m Ingeneral the surface temperature signal at CapeKekurnoi is similar to that at GAK1 Thetemperature at depth however is colder at CapeKekurnoi than at GAK1 during February throughApril This can be explained by mixing inKennedy-Stevenson Entrances that results fromthe strong tidal currents thereA strong seasonal signal in salinity exists at the

Seward Line near the surface (Fig 20a) As runoffincreases and reaches its maximum in late summerand early fall (Fig 3b) the ocean salinity at thesurface decreases During winter runoff decreasesand the surface salinity increases while the verticalmixing and downwelling of the fresher surfacewater by strong winter storms reduces the salinityat depth During summer the salinity near the

bottom increases once again likely a result of anonshelf flux of slope water in response to relaxa-tion of downwelling favorable winds The seasonalcycle in near-surface salinity at Cape Kekurnoi(Fig 20b) is much weaker than that at GAK1 Inparticular near surface salinity during the summeris B3 psu greater than at GAK1 (the range insalinity from the current moorings is similar tothat of the CTD casts) This supports thehypothesis that strong mixing occurs at Kenne-dy-Stevenson Entrance where the fresher surfacewater is vertically mixed Such an increase insurface salinity downstream of Kennedy Entrancewas observed in 1978 (Fig 3 in Schumacher andReed 1980) Vertical shear in Kennedy Entrancewas calculated using data from a 150 kHz acousticDoppler current profiler that was deployed inKennedy Entrance in 1991 (Stabeno et al1995a b) Bands of increased shear occur onfortnightly time scales likely a result of tidalmodulation (Fig 21) The strongest vertical shearsoccurred at and above 100m This provides theenergy necessary to mix the water column as theACC flow through Kennedy Entrance and likely

ARTICLE IN PRESS

Fig 21 Vertical shear (s1) at Kennedy Entrance as measured

from 150 kHz ADCP Bin depth was 4m

provides a pathway for the nutrients from thebottom of the water column to be exported intothe euphotic zone

34 Seasonal dynamics of nutrients and primary

production

Seasonal variations of nutrients and productionin the ACC are extreme Aspects of seasonalprimary production and nutrient distributions forthe northern GOA have been reviewed with focusmainly on the central Gulf and coastal regions(Sambrotto and Lorenzen 1987) and in ShelikofStrait (Napp et al 1996) There is little publisheddata on the shelves east of Cook Inlet Chlor-ophyll-a concentrations varied from o1 mg ll inwinter to gt30 mg ll during the spring bloom whensurface nutrients are rapidly depleted (Napp et al1996) Annual C14 based production on the shelf isB300 gCm2 compared to 48 gCm2 at OceanStation Papa (Sambrotto and Lorenzen 1987)In winter cooling and storm winds weaken

stratification deepen the upper mixed layer andentrain high concentrations of nutrients intosurface waters Deeper mixing of phytoplanktona low solar angle shorter photoperiod andpersistent cloud cover all limit irradiance toprimary producers and hence limit primaryproduction in winter In MarchndashMay lengtheningdays a higher solar angle and high nutrientconcentrations lead to successional spring blooms

of primary and secondary producers There issignificant interannual variability in the magnitudeand timing of these blooms which are dependenton factors such as the extent of cloud cover theintensity of stratification and grazing (Napp et al1996) Variability in the timing of spring produc-tion could disrupt predatorprey interactions andinfluence larval survival and recruitment (Nappet al 1996 Freeland et al 1997)As phytoplankton growth is initially light-

limited in spring timing of the spring bloom overthe entire shelf may be related to the extent ofcloud cover (Napp et al 1996 Townsend et al1994) Napp et al (1996) examined the percentageof Total Opaque Sky Cover (TOSC) in Aprilabove Kodiak Alaska from 1952ndash1991 TOSCis non-transparent cloud cover which has thegreatest attenuation on photosynthetically avail-able radiation (PAR) For example a 30 changein TOSC was related to a 25 change in meandaily PAR The mean TOSC above Kodiak inApril varied from about 55ndash95 with significantinterannual variability in the mean TOSC and inattenuation of PAR Napp et al (1996) argue thatthe spring bloom might be significantly delayedduring years with the greatest cloud attenuation ofPAR While the extent of cloud cover mightinfluence timing of spring production over largeportions of the shelf the influence of other factorssuch as riverine flow and stratification are morespecific to the ACCDespite increased irradiance in early spring

stratification across the shelf remains weak Thereis very little warming of surface waters fromMarch through May (1ndash15 warming of surfacewaters relative to 150m was observed in mooringsalong the Seward line not shown) and freshwaterdischarge is near the seasonal minimum (Fig 3b)The limited runoff generates weak salinity gradi-ents in the ACC (Fig 16 see also Reeburgh andKipphut 1987) causing the ACC to be slightlymore stratified than other shelf waters Napp et al(1996) hypothesized that phytoplankton within theACC are confined to a shallower mixed layer andexposed to greater solar irradiation than otherplankton on the shelf and therefore might beexpected to bloom earlier Yet such generalities aredifficult to apply in early spring due to significant

ARTICLE IN PRESS

mesoscale spatial variability and small gradients inphysical parameters on the shelf For example in1998 relatively high fluorescence was observed notonly in the ACC but also in surface waters at theshelf break (Fig 9)Nitrate data are too sparse to examine the

hypothesis that the shelf bloom initiates in theACC Surface maps of nitrate data in the ACCshow relatively high concentrations in early springand depleted concentrations in mid-to-late sum-mer (Fig 22) but adequate spring and summerhydrographic sections across the ACC are not yetavailable to address this questionIn late spring and early summer (MayndashJune)

intense chlorophyll blooms and low surfacenutrients are observed across the shelf Compositesof satellite ocean color from May 1997 1998 and1999 show intense and patchy blooms throughoutthe coastal GOA (Fig 9) The satellite imagesreveal a sharp contrast between the highly

Fig 22 Surface nitrate maps (a) MarchndashMay (b) Junendash

September These are data from NODC several FOCI cruises

and a GLOBEC cruise in May 2001

productive iron-rich and spatially variable watersof the shelf compared to the moderate and moreuniform production of the iron limited centralGOA (Martin et al 1989) Exchange betweencoastal waters rich in chlorophyll with centralGOA waters rich in macro-nutrients during 1997ndash1999 is evident in the form of swirls eddies andfilaments of high chlorophyll extending into thecentral GOA and regions of low chlorophyllimpinging on the coastSections of nitrate at Gore Point and at the

Seward line in May 2001 show low surfaceconcentrations with strong vertical structure(Fig 23) At Gore Point the highest nitrateconcentrations in the surface waters were alongthe coast At Seward concentrations in the surfacewaters near the coast were very low (o2 mM)while at each of the other stations concentrationswere typically above 10 mM The highest concen-trations were at the slope below 100m withintrusions of the nitrate rich water evident onshelf below B120mIn summer there is strong stratification across

the shelf These months of increasing riverinedischarge result in the fresher waters of the ACC

200 150 100 50 0

Distance Along Section (km)

Fig 23 Concentrations of nitrate at two locations along the

Kenai Peninsula (a) Gore Point and (b) Seward line Data was

collected in May 2001 Dots indicate location of data points

The coast is at the right in each plot

ARTICLE IN PRESS

confined near the coast and an intense thermo-cline atB25m extending over the remaining shelfIn these stratified surface waters nutrients aredepleted with concentrations increasing below thepycnocline (not shown) Measurements of ironover the shelf are sparse However what dataexists support the hypothesis that iron and nitratehave similar distribution over the shelf in summerConcentrations are depleted at the surface andincrease below the pycnocline (Martin et al 1989)except in fresher waters of the ACC where riverinedischarge may supply ample ironA sub-surface chlorophyll-a maximum is often

associated with a strongly stratified surface layerdepleted in nutrients Pigment concentrations arehighest at the base of the euphotic zone wherenutrients are supplied from the pool nutrientsbelow the pycnocline through diffusion diapycnaland tidal mixing (Whitney et al 1998 Sharpleset al 2001) Along the Seward Line such anintense sub-surface fluorescence maximum wasobserved above thermocline The seasonal distri-bution of nutrients and chlorophyll-a near theSeward Line evolved from spring conditions (afluorescence maximum in the ACC and stronghorizontal gradients) to mid summer conditions(depleted nutrients at the surface a subsurfacechlorophyll-a maximum independent of the ACCand intense vertical gradients associated with thepycnocline)To examine the spatial patterns of surface

chlorophyll-a during summer a composite chlor-ophyll-a image was created using SeaWifsL1A data We averaged non-cloudy pixels fromsummer (June 15ndashAugust 30) images collected in1998ndash2002 Pixels at high zenith angles (gt60) orwithin two pixels of land or clouds were excludedWe did not exclude pixels where turbidity washigh The SeaDas level-2 processing flaggedturbidity in the near coastal (ie orange area eastof Prince William Sound) and in Cook Inlet butrarely elsewhere High turbidity can either mask orenhance chlorophyllThere is a marked difference between chloro-

phyll-a concentrations east of the Gore Point line(Fig 2) and west of it Summer surface chlorophyllproduction in the GOA was concentrated alongthe shallower banks south of Kodiak Island the

region northwest of Kodiak Island and inShelikof Strait Concentrations along the KenaiPeninsula are markedly less than those observedfarther west indicating there was not a persistentinfusion of nutrients into the surface mixed layerduring summer The higher concentrations ofchlorophyll in Shelikof Strait support the conclu-sion that mixing in Kennedy Entrance suppliesnutrients into the euphotic zone A large portion(B25ndash50 km wide) of the shelf east and south ofKodiak Island is shallow (o50m) and may besusceptible to significant tidal mixing The extentof stratification and surface nutrient depletionacross this shallow shelf in summer are uncertainDrifter tracks do show a highly convolutedflow with sufficient energy to widely distributeany surface waters enriched in nutrients andchlorophyll-aIn lower Cook Inlet high nitrate concentrations

are observed all summer (Larrance and Chester1979 Sambrotto and Lorenzen 1987) In mid-to-late summer concentrations of 5ndash10 mM areobserved in southeastern Cook Inlet in contrastto undetectable to 2 mM concentrations along theshelf to the east (Fig 22) Drifter studies indicatedthat the ACC enters Cook Inlet to the east andundergoes only a slight excursion northwardMixing that occurs in Kennedy Entrance maycontribute to the nutrient supply at the exit ofCook Inlet Certainly high concentrations(gt14 mM) of nitrate existed at a depth of 50m atboth the Seward line and at Gore Point (Fig 23) inMay 2001 Measurements of vertical shear atKennedy Entrance (Fig 21) indicated mixing togreater than 50m These observations suggest thattidally driven (persistent) deep mixing in KennedyEntrance and likely in southeast Cook Inletcontinually supplies nutrients to the surface Thissteady nutrient supply to surface waters sustainshigh production rates even in mid-to-late summer(Larrance et al 1977) making lower Cook Inletone of the most productive high-latitude shelfregions in the world (Sambrotto and Lorenzen1987)Transport of surface pigments and nutrients by

the ACC from Cook Inlet through Shelikof Straitmight contribute to the high chlorophyll-a concen-trations observed in the northern strait (Fig 24)

ARTICLE IN PRESS

54deg156deg 152deg 148deg 144deg 140deg 136deg 132deg

Fig 24 The average concentrations of chlorophyll-a during June 15ndashAugust 30 (1998ndash2002) as measured from SeaWiFs The method

of averaging is described in the text The 100m and 1000m isobaths are shown The high concentrations of chlorophyll-a along the

coast (o100m) from Icy Point to Prince William Sound may not be reliable due to high turbidity

however off Cape Kekurnoi nitrate depletion hasbeen observed as early as May on the peninsula(northern) side of the sea valley (Napp et al 1996)Resident times of phytoplankton from CapeDouglas (58160 153160) to Cape Kekurnoi areestimated at 7ndash18 days given production estimatesof 100ndash300 gCm2 yr1 over 180d and 50m ofwater this equals the consumption of 1ndash8mMnitrate within Shelikof Strait values similar to theobserved concentrations in lower Cook Inlet Thiscalculation suggests that additional nutrient intro-duced through vertical mixing support high pig-ment concentrations during summer observed insouthern Shelikof Strait (Fig 24)Another possible source of nutrients is the

estuarine inflow in the Shelikof sea valley Thereis significant interannual variability of ACCtransport through Shelikof Strait Years withstrong ACC flow can induce an estuarine-likedeep return flow up the sea valley This return flowis concentrated on the Kodiak Island side (south-ern) of the sea valley (Napp et al 1996) and isthought to entrain nutrients into the upper layerdue to intense horizontal sheer and turbulenceHence the southern extent of high chlorophyll-ain Shelikof Strait appears to be a function of thecontinuity of flow through the strait the supply ofnutrients upstream and phytoplankton grazing

4 Mechanisms for cross-shelf fluxes

Major questions remain on how nutrients andzooplankton are advected onto the shelf in thishighly productive predominantly downwellingregime Several mechanisms exist which result incross-shelf fluxes of nutrient rich waters from thedeep basin although many are transient in natureand thus difficult to detect We next examinesome likely mechanisms supported (or refuted) bythe data

41 Episodic upwelling

Even though this is predominantly a down-welling regime during summer winds relax andperiods of upwelling occur which result in in-creased salinity at depth as observed at SewardLine (Fig 20) As there is a significant correlationbetween salinity and nutrients (Mordy et alsubmitted) increased salinity during the summermonths at the bottom of the water column implies asource of nutrient rich water However our analysisof wind data suggests that upwelling events are rareto the east of the Shumagin Islands Hence thismechanism is unlikely to provide a consistentsource of nutrients in the observed areas of highproduction During the summer the relaxation of

ARTICLE IN PRESS

the strong downwelling winds and the resultingdepression of the pycnocline can result in increasedsalinity and nutrients near the bottom

42 Surface flux in the Ekman layer

The central GOA is characterized as a highnutrient-low chlorophyll (HNLC) region Upwel-ling in the central gyre supplies an abundance ofmacro-nutrients to the surface through winterentrainment across a deep and weakly stratifiedmixed layer (Whitney et al 1998) In summerchlorophyll-a concentrations remain relatively lowdespite abundant nutrients warmer temperaturesstronger stratification and increased irradianceThis is presumed due to a combination of factors(1) the predominance of small zooplankton whichcontinually graze phytoplankton and hence pre-vent large blooms from depleting the nitrate(Frost 1991) (2) the absence of sufficient iron tosupport such blooms (Martin and Gordon 1988Martin et al 1989) Whatever the cause theobserved high values of nutrients could provide asignificant source of nitrate to the coastal areasthrough simple Ekman flux driven by the down-welling favorable winds The high productivity ofthe CGOA may be fundamentally due to theconvergence of the offshore waters rich in nitratewith the coastal waters rich in iron Indeed someSeaWiFs chlorophyll imagery suggests highestproductivity at the interface between the coastaland offshore watersNumerical simulations of circulation can be

used to help infer patterns of onshelf transport inthe CGOA To investigate cross-shelf transportwe have seeded numerical floats in a regionalmodel of the area (Hermann et al 2002) Floatswere uniformly seeded over areas with bathymetryin the range of 1000ndash3000m (Fig 25a) These weretracked at two different fixed depths (5 and 40m)using a 2-month series of model hindcast dailymean horizontal velocities for late fall 1996 Manyof the floats tracked at the shallow depth movevigorously across isobaths from the slope onto theshelf (Fig 25b) Preferred sites for onshore move-ment include areas to the east and south of PrinceWilliam Sound whereas onshore flux is weakacross the Alaska Stream and in the vicinity of the

Sitka eddy This broad pattern of cross-shelftransport is consistent with the spatial pattern ofobserved climatological surface nitrate (Conkrightet al 1998) which exhibits a tongue of highnitrate waters penetrating onto the shelf to thesoutheast of Prince William Sound Floats trackedat a deeper (40m) depth (not shown) exhibitsubstantially weaker onshelf flux instead theyfollowed the isobaths with none entering onto theshelf The time-averaged wind stress used for thesesimulations is typical of the fall season This resultsupports that an Ekman flux from the basin can bea source of nutrientsA simple calculation indicates that sufficient

nutrients can be supplied via this mechanism toaccount for the observed primary productionEstimates of downwelling and runoff-driven pro-duction on the shelf may be made as followsassume that 100ndash300 gCm2 (83ndash25molCm2)of new production is generated each year on theshelf Given a standard Redfield ratio for theelemental composition of new production

C N P Fe frac14 106 16 1 001

annual nitrogen and iron requirements would be13ndash38molNm2 and 78ndash24 104mol Fem2For a productive area of 50ndash250 km wide a km ofcoastline would require 6ndash94 107molNyr1 and4ndash59 104mol Fe yr1Nitrate concentrations in the upper 100m over

the deep basin of the GOA range from 10 to20 mmol l1 or 001 to 002molNm3 A surfacelayer 40m thick moving towards the coast at0025m s1 would supply roughly 16ndash32107molN along each km of coastline during 6months of strong downwelling conditions Thisrepresents sufficient nitrogen for highly productivenarrow shelves but insufficient to sustain thehighest production over wide shelves (Thechosen value of 0025m s1 over 40m is in factsensible for a typical wind stress of 01Nm2

and a Coriolis force of B10 104 s1 at 45Nthe total Ekman flux is 1000 kgm1 s1 or1m3m1 s1)Royerrsquos discharge values suggest an average

discharge of 2 104m3 s1 along the length of theCGOA coastline in spring and early summer Ifthese waters contain 3mmol l1 of Fe then

ARTICLE IN PRESS

Fig 25 Locations of floats (a) seeded into model velocity field at a depth of 5m and (b) position of the floats after 50 days

60molFe s1 would be added to the shelf ie 19108molFe yr1 If the runoff is assumed distributedover a 1000km section of coastline this correspondsto 190 104molFe yr1 in excess of the requiredvalue This is not the only possible source of FeWinds blowing off land may deposit Fe over theshelf In addition strong currents may resuspend

sediments and perhaps be a source of Fe to theeuphotic zone There is insufficient data to identifywhich of these are the most important sourcesObviously the above argument uses very crude

estimates However it suggests that even as muchas 200ndash300 gCm2 yr1 production could besupported on the shelf through the combination

ARTICLE IN PRESS

of downwelling-supplied surface nitrate from thedeep basin and runoff-supplied iron at the coastHowever near-surface nutrient concentrations inthe central GOA are highly variable and may bedecreasing (Freeland et al 1997) So while thismechanism may replenish nutrients to the shelfduring winter and early spring it is not a reliablesource during summer

43 Upwelling seaward of a coastal wind jet

The steep and prominent terrain surroundingthe GOA causes systematic spatial patterns in thewinds which can produce important variations inthe surface Ekman transports discussed in theprevious section In particular the coastal terrainof the GOA forces a phenomena known as abarrier jet (Parish 1982) in which enhancedalong-shore winds occur in the nearshore regionrelative to farther offshore In conditions ofcyclonic atmospheric flow over the GOA thecross-shelf gradients in the winds can result insubstantial positive wind stress curl and hencelocal upwelling off the coast but typically inshoreof the shelf break (Fig 26)

Fig 26 Schematic of the coastal wind jet and its effects on the upper

into the plane of the figure the cross-shore gradient in these winds p

arrows indicate the cross-shore component of the wind-driven ocean

Barrier jets tend to occur when the cross-shorecomponent of the large-scale low-level flow isdirected onshore the along-shore component iswith the terrain on the right (in the NorthernHemisphere) and the static stability from thesurface to mountain crest level is moderate (Over-land and Bond 1995) Barrier jets are expected tooccur in the eastern and northern GOA duringsoutherly and southeasterly flow respectivelywhich is a common occurrence during fall throughspring The potential enhancement of wind speedsassociated with barrier jets scales linearly with theheight of the coastal terrain (Overland and Bond1995) this mechanism therefore includes signifi-cant along-coast variations in magnitude Thebarrier jet extends approximately one Rossbyradius offshore (B50ndash100 km for the GOA) Thepositive wind stress curl at this location tends to beconcentrated over a narrow (o20 km) band due tofrontogenetical stretching within the atmosphericboundary layerWe do not know the full implications of a

barrier jet for the mixed layer over the shelf of thenorthern GOA but rough estimates of its fre-quency and magnitude suggest that it could be

mixed layer The circled Xrsquos indicate the strength of the winds

roduces a region of strong positive wind stress curl The open

circulation in these conditions

ARTICLE IN PRESS

Fig 27 Since 1984 a number of moorings have been deployed

in troughs and canyons along the GOA coast The bold arrows

represent the mean flow at B15m off the bottom

important Conditions favorable for the develop-ment of barrier jets appear to occur approximatelyone-third of the time during the cool season basedon our perusal of SAR-derived winds during 1999ndash2000 Following Overland and Bond (1995) andDoyle and Bond (2001) and based on ourexperience in analysis of the weather of the regionwe assume that barrier jets typically result in near-shore wind speeds of 14ms off-shore speeds of10ms and that the cross-shore gradient of theresulting wind stress is distributed over a width of20 km These values combined with a frequency ofoccurrence of one-third yields an average Ekmanpumping velocity of approximately 10m per dayThis vertical velocity is comparable to that foundby Munchow (2000) for the region off PtConception California where topographical ef-fects cause similar spatial gradients in the windsIts magnitude suggests that local upwelling overthe shelf in conditions of downwelling favorablewinds in the immediate vicinity of the coast couldplay an important role in nutrient supply to theshelf in the GOA especially during late fallthrough spring During summer the winds areweaker and this mechanism probably is not asignificant source of nutrients to the shelf

44 Topographic steering

Coastal flows are strongly steered by bathyme-try and the region from Icy Bay to the ShumaginIslands is rich in large bathymetric features such asHinchenbrook Canyon Amatouli Trough and theShelikof sea valley in addition to many smallertroughs Given the right circumstances topo-graphic features interact with currents in manyways that result in on shelf fluxes of slope water(Allen et al 2001) For instance the ACC flowsparallel to the axis of the Shelikof sea valley whichresults in an estuarine-like inflow (Reed et al1987 Stabeno and Hermann 1996) This intrusionof slope water extends past Cape Kekurnoi and isentrained in the strong ACC providing nutrientsto surface waters Neither Hinchenbrook Canyonnor Amatouli Trough however appear to haveestuarine flow although onshelf flux is evident inthe model result at Amatouli Trough (Fig 11) Anexamination of mean flow at a number of mooring

sites located in canyons or troughs reveal aconsistent pattern There is flow into the troughon the east side and outflow on the west side in thebottom 50m (Fig 27)Klinck (1988) proposed that inertial overshoot

of an along-shore flow intruding into a canyoncould lead to significant onshelf flux of deeperwaters However he demonstrated how suchonshelf transport is stronger when the shallowbathymetry is to the left of the direction of thealong-shore flow in the Northern Hemisphere andmuch weaker when the bathymetry is to the rightof the flow In the GOA the coast is typically tothe right hence the inertial overshoot mechanismis less importantA third mechanism describes the interaction of

downwelling and canyons In a downwellingregime water accumulates at the surface within aRossby radius of the coastline and the subsurfacepycnocline and nutricline are depressed Thesurface pressure gradient acts in the offshoredirection whereas (for a two-layer flow at least)the subsurface pressure gradient acts in theonshore direction Along a straight coastline thesepressure gradients are mainly balanced by theCoriolis force Narrow canyons which cut acrossan otherwise straight shelf have weak flows at

ARTICLE IN PRESS

depth and so any cross-shelf pressure gradientsmay push the deeper nutrient-rich waters onto theshelf We cannot presently quantify the magnitudeof this source to the shallow GOA but furthermodel studies at fine (B1 km) resolution can beused to address this issueThe interplay of canyons and shallow banks can

provide a steady although localized supply ofnutrients to the euphotic zone over the shelfNutrient rich slope waters transported up canyonscan upwell onto banks Strong tidal mixing on thebanks can introduce nutrients into the upper watercolumn The complexity of bathymetry in theGOA and the higher primary production at thesurface in the vicinity of Kodiak Island (Fig 24)support this as a possible mechanism for theintroduction of nutrients onto the shelf andeventually into the euphotic zone not only duringwinter but throughout the year

45 Eddies

Large (B200 km) eddy features most dramati-cally illustrated by AVHRR imagery reported inThompson and Gower (1998) may play asignificant role in cross-shelf exchange Whenthese large eddies impinge on the slope in thenorthern CGOA they may advect deep nitrate-rich waters onto the shelf Model results suggest asignificant flux of waters off the shelf in the vicinityof the large semi-permanent eddy near SitkaAlaska (Hermann et al 2002) This cross-shelfexchange may serve to mix the iron rich nitratepoor shelf waters (summer) with the nitrate richiron poor basin surface waters It has beensuggested (Paul Harrison personal communica-tion) that eddies containing iron-rich shelf watermight account for observed periods of higherproductivity at Ocean Station PAn example of interaction of an eddy with shelf

occurred in 2001 (Fig 28) A large eddy wasevident in the basin seaward of Prince WilliamSound in May It slowly migrated along the slopeand eventually in late July could be found off theKenai Peninsula where it remained largely sta-tionary for approximately a month with a secondweaker eddy persisting slightly to the northeast Anumber of satellite tracked drifters were deployed

in May and July between Kayak Island and GorePoint Trajectories of three of the drifters show thecomplexity of flow that resulted from the closeproximity of the eddy One drifter (dark blue) wasdrawn off the shelf between the two eddies whileanother drifter (light blue) left the shelf nearKayak Island A third drifter (black) was drawnoff the shelf moved eastward along the slope andreturned to the shelf near Hinchinbrook CanyonOther drifters further on the shelf show noresponse to the eddy Eddies like topographicsteering can increase onoff shelf exchange yearround but the impact is localized to outer portionsof the shelf In contrast the on shelf flow due toEkman fluxes impacts broad areas but theprimary effect is during the cold season Theproductivity of the shelf is likely dependent not ona single mechanism but rather on a variety ofsources

5 Discussion

Our purpose in this section is to summarizeknowledge and gaps in our understanding of thecoastal meteorology and oceanography of theGOA especially as it pertains to the forcing ofthe ACC We first discuss the nature of thetemporal variability on scales from decadal tosub-seasonal and then outline issues related to thedownscaling of the large-scale atmospheric circu-lation to the coastal conditions Finally we discussthe effects of physical forcing on the nutrientsupply of the shelfThe 50-year record of GOA coastal weather

permits consideration of decadal scale variationsWith regard to winter it is instructive to compareour time series with the leading mode of variabilityfor the North Pacific as a whole the PDO Asevident in Figs 6 and 8 the relationship betweenthe PDO and GOA coastal weather is actuallyquite weak There are tendencies for relativelywarm winters in the northern GOA and anom-alous southerly winds in the eastern GOA duringpositive phases of the PDO (and vice versa) butfor the most part the fraction of the variabilitythat occurs on decadal time scales is much greaterfor the PDO than for the coastal weather of the

ARTICLE IN PRESS

Fig 28 Trajectories of satellite tracked drifters (drogue depth 40m) overlayed on TOPEX and ERS-2 altimeter data based on 10 days

of TOPEX (August 4ndash14 2001) and 17 days of ERS-2 (July 27ndashAugust 14 2001) Maps were provided courtesy of Colorado Center for

Astrodynamics Research on their Global Near Real-Time Sea Surface Height Data Viewer web page The drifter trajectories are

approximately 1 month long

GOA The lack of a significant PDO signature inthe coastal GOA can be attributed to three factors(1) the PDO itself accounts for only about a thirdof the variance in SST during winter over theNorth Pacific (Hare 1996 Overland et al1999a b) (2) the PDO largely reflects the state ofthe atmospherendashocean climate system in the west-central North Pacific and the GOA is only weaklyout of phase with this region and (3) the large-scale pressure anomalies driving the weather of thecoastal GOA are poorly correlated with the SSTanomalies While the coastal weather of the GOAdoes not appear to be tightly coupled to the PDOthe wind forcing of the central portion of the basinmight be At least the 1977 regime shift of the PDO

seems to be well represented in the sequence ofcentral GOA dynamic height anomalies documen-ted by Lagerloef (1995) We consider it an openquestion whether decadal variability in the deepbasin of the GOA presumably through itsmodulation of the Alaskan Stream influences theACC The lack of long-term oceanographic datahowever makes it difficult to resolve the relation-ship A better understanding of the linkagesbetween the atmosphere and ocean and betweenthe basin and the shelf is being pursued throughthe observational and modeling work for thenorthern GOA undertaken as part of GLOBECWe also examined a 50-year record of summer-

time conditions in the coastal GOA and the

ARTICLE IN PRESS

decadal variability for this time of year is alsorelatively weak We had expected to find systema-tic summertime weather anomalies in the 1990sdifferent from those in the 1980s because the twoleading modes of springsummer climate variabil-ity for the North Pacific were of opposite sign inthe two periods (Overland et al 2001) The resultsfound here (Figs 5 and 7) suggest that the coastalweather of the GOA is more sensitive to localrather than to basin-scale atmospheric circulationanomaliesPart of the variability of the coastal GOA on

2ndash7 year time scales is linked to ENSO Herethe principal impacts are on wintertime precipita-tion and hence runoff including the timing ofrunoff since precipitation and air temperatureare positively correlated in coastal GOA water-sheds (eg Bitz and Battisti 1999) The coastalwinds do not seem to be sensitive to ENSOand so changes in sea level in the ACC inassociation with ENSO may be caused more bycoastally trapped Kelvin waves emanating fromthe tropical Pacific (Enfield and Allen 1980Chelton and Davis 1982) than by anomalouslocal forcing In spring there was a response toENSO in the salinity and temperature at GAK1and Cape Kekurnoi which is likely a combinationof propagation of coastal signal and response tolocal forcing Changes in transport of the ACC arenot expected because the coastal winds are notvery sensitive to ENSOSince the atmospheric basic state is much

different in the summer than in the winter theatmospheric response in the eastern North Pacificto ENSO is different for the two times of year Inparticular Overland et al (2001) showed thatanomalously high pressures occur over the GOAduring El Ninos in the summertime whileanomalously low pressures are found in thewintertime Based on our examination of coastalweather records we conclude that this difference ismanifested more in the central GOA than in itscoastal marginsWe have concentrated on the interannual

fluctuations in coastal GOA weather in this paperbut for completeness we now briefly discuss itssub-seasonal variability The weekly to monthlyvariability during the winter serves to modulate

the frequency intensity and nature of theindividual storms that determine the transport ofACC The preponderance of one or the other ofthe two most important sub-seasonal weatherregimes that is high-amplitude ridges or troughsat geopotential heights at 500 hPa over the NorthPacific is linked to large-scale long-term circula-tion anomalies associated with the PDO and PNA(eg Renwick and Wallace 1996) The summer-time sub-seasonal variability has received lessattention but from our experience the GOA ismarked by swings between cyclonic regimes whichfeature more downwelling favorable coastal windsand enhanced coastal rainfall and anticyclonicregimes with weakly upwelling favorable windsand suppressed rainfall The timing of the transi-tions between these summer weather regimes isimportant to the ACC and its marine ecosystemPeriods of weak winds result in a lack of transportdown Shelikof Strait This decrease results in adecrease in the estuarine flow up the Shelikof seavalley and a reduction in nutrients available to thewest of Kodiak Island In addition a lack oforganizing winds result in a more convoluted flowalong the Kenai Peninsula which also may impactthe replenishment of nutrients to this part of theshelf although whether to decrease or increase it isnot known Certainly reduced transport throughKennedy Entrance will both reduce the nutrientsthat are mixed in Kennedy Entrance and theiradvection down stream in Shelikof Strait Notingthis we suspect that short-term events such as theoccasional strong storm or periods of upwellingare relatively more important to the ACC inthe summer than in the winter when winds arestronger There is some evidence that the incidenceof such events has a weak relation to the slowmanifold of climate variability (Minobe andMantua 1999)In summary we find most of the variability in

atmospheric forcing and ocean response to be onseasonal or shorter time scales In terms of thecoastal meteorology and oceanography decadalsignals are relatively weak However while itappears that much of the GOA ecology is adaptedto this seasonal variability the biology appears tobe responsive to the weak decadal signals (Hareand Mantua 2000) The pathways that determine

ARTICLE IN PRESS

this connection are not known but some relation-ships have been hypothesized (Gargett 1997Francis and Hare 1994)Decreased winter convection and nutrient en-

trainment in the central gyre are predicted to be aconsequence of long-term global warming (Woodsand Barkmann 1993) Indeed over the pastseveral decades central GOA surface waters havewarmed and freshened Long-term records of SSTand salinities at Ocean Station Papa (OSP) and atcoastal stations in British Columbia reveal a 04ndash10 century1 decrease in salinity and a 1ndash2Ccentury1 increase in temperature (Freelandet al 1997 Whitney et al 1999) As predictedthis region has experienced increased stratificationthinning of the mixed layer and reduced winterentrainment of nutrients (Freeland et al 1997)Along Line-P south of the GOA the extent ofseasonal nutrient depletion was more widespreadin the 1990s relative to historic (1970s) observa-tions (Whitney et al 1998) It has been estimatedthat associated with lower nitrate concentrationsalong Line-P chlorophyll concentrations areabout half of historic levels (Whitney et al 1999)The 1997ndash98 ENSO event had a similar impact

to that predicted for secular warming on thenitrate and chlorophyll-a fields With both PDOand ENSO in the warm phase extremely large SSTanomalies (gt3C) were observed all along thewest coast of North America Warmer watersincreased buoyancy of the winter mixed layersuppressing winter entrainment and coastal upwel-ling Along Line-P nutrient concentrations wereabout half as large as observed in the 1970s withnutrient depletion occurring 1 month earlier thanin previous years (Whitney et al 1999) In May1998 chlorophyll-a concentrations were low overthe entire GOA shelf presumably from a reducedsupply of nutrients (Fig 9 Whitney and Welch2002)One approach to better understand the extent of

upwelling in the central GOA and coastal down-welling is through analysis of pCO2 which is asensitive measure of vertical fluxes A number ofpapers have examined the North Pacific CO2based on large-scale survey cruises (eg Landrumet al 1996 Murphy et al 1998) ship-of-opportunity data between the US and Asia (eg

Takahashi et al 1993 Stephens et al 1995Murphy et al 2001) and from time-series cruisesalong Line-P (eg Wong and Chan 1991) Ingeneral the northeastern subarctic Pacific isthought to be a small sink for atmospheric CO2(Landrum et al 1996) Conditions in the northernGOA however are likely to be very different Theconditions shoreward of the Alaska CurrentAlaska Stream are much more variable than thoseseaward None of these carbon programs hassampled the GOA region sufficiently to describethe nutrientcarbon dynamics in this region Theextensive ship-of-opportunity work that has oc-curred in this area only cuts across the southernboundary of the GOA between Victoria andUnimak Pass Perhaps the best indication thatconditions in the northern GOA are very differentfrom the generalized assessment of the north-eastern subarctic Pacific can be derived fromrecent high-resolution ship-of-opportunity data(Y Nojiri personal communication httpwwwmircjhaorjpminnanoCGER NIESskau-granindexhtml) The pCO2 variability observedas the ship transects through Unimak Pass isamong the largest observed anywhere in the world(175ndash185 ppm)mdashsuggesting the importance of lo-calized upwelling events A proper assessment ofthis variability can provide valuable informationon the physical and biological mechanisms oper-ating in this areaWe close the discussion with consideration of

unresolved issues for GOA coastal meteorologyand oceanography First our results provide someinformation on along-coast variability Using theinterannual variations from the various locationsas a guide (Figs 5ndash8) it is apparent that thecoherence in the weather along the coast is greaterin winter than in summer especially in terms of thewinds In general the coherence between thevarious stations is greatest in the wind time seriesand least in the precipitation time series Thisresult is no surprise in that precipitation has moreinherent small-scale variability and hence moresensitivity to local effects than does the windEven so there are certainly systematic small-scalevariations in GOA coastal winds especially neargaps in the terrain (as shown by Macklin et al1988 1990) It is uncertain how sensitive the ACC

ARTICLE IN PRESS

is to these kinds of variations on scales ofB100 km but because the variations are lockedto the terrain they tend to be persistentTransport from Gore Point through the Sheli-

kof Sea Valley appears to be coherent but thecontinuity of flow from the region east of KayakIsland to the Kenai Peninsula is not knownSatellite-tracked drifters (Fig 10a) indicate thatthere likely is an interruption of flow at KayakIsland and a reorganization along the KenaiPeninsula In particular what role this flow playsin supply of nutrients to ACC downstream fromthe Seward line has only been hypothesizedthrough models In addition the ACC is greatlymodified by the topography from Kayak Islandthrough Shelikof Strait The currents on theshallow shelves to the east of the KodiakIsland and the east of the Semidii Islands appearto be more dominated by local processes Cross-shelf advection is critical to this ecosystem Tounderstand the mechanisms that control onshelfflux requires focused research on mesoscaleprocesses particularly those involving canyonsand eddiesIn general we have an incomplete understand-

ing of how the coastal weather relates to the large-scale atmospheric circulation The response of thelow-level flow to the coastal terrain depends onfactors such as wind speed and static stability asencapsulated in scaling parameters such as theFroude number but this response is complicatednot just by terrain variations but also time-dependent effects and non-conservative (diabaticand friction) processes Progress here requireshigh-resolution numerical weather predictionmodel experiments (present models do seemcapable of accurately accounting for terraineffects) with sufficient observations for validationThe transport in the ACC is apparently largelycontrolled by winds knowledge how spatialvariability in wind forcing impacts transport andthe confinement of the low salinity water along theshelf is critical in understanding this ecosystemIn addition our knowledge of the runoff into

the GOA is meager The hydrology of the region isgreatly complicated by factors related to variationsin precipitation type (snow or rain) as a functionof altitude and location and freezemelt cycles on

land Present hydrological models are not up tothe task of characterizing the runoff into theGOA and past and present monitoring of riversdraining into the GOA is poor If the detailsof this runoff are important to the ACC which islikely a major increase in our hydrologicalcapabilities is required for monitoring let alonepredicting the freshwater input to the ACC Itmust be noted that runoff contributes to micro-nutrient supply to this marine ecosystem Quiteobviously measurements of nutrients and sedi-ments provided by rivers should be expandedFinally an understanding temporal changes in theclimate (interannual decadal and long-term timescales) and how these changes impact the ecosys-tem is criticalFrom a bottom up perspective the ultimate

control of the complicated ecosystem found in theGOA lies in how the meteorological forcingcontrols the ocean physics that in turn governsthe availability of nutrients and hence food withinthe lowest trophic levels If conditions of runoffadvection physical mixing nutrient and lightavailability change primary production its timingor the composition of the primary producers theentire food web structure can be affected (Nappet al 1996) with perhaps deleterious impacts onthe highest trophic levels

Acknowledgements

We thank D Kachel for data analysis and SSalo for providing satellite images E Dobbinsdeveloped the algorithms used for model floattracking experiments C Sabine provided discus-sion on carbon in the North Pacific We thank twoanonymous reviewers and C Mooers for theircareful reading and comments on this manuscriptK Birchfield provided graphics work and RWhitney did the technical editing (all at PMEL)We thank Dr T Royer for supplying the run-offtime series and UAF for the GAK1 time seriesThis research was funded by the Coastal OceanProcesses Program at ONR This is contributionFOCI-0452 to the Fisheries OceanographyCoordinated Investigations 849 to Joint Institutefor the Study of Atmosphere and Ocean

ARTICLE IN PRESS

University of Washington 2343 to PMEL and348 to USGLOBEC

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Bitz CC Battisti DS 1999 Interannual to decadal

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Bograd SJ Stabeno PJ Schumacher JD 1994 A census

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Bond NA Stabeno PJ 1998 Analysis of surface winds in

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Burrell DC 1987 Interaction between silled fjords and

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Chelton DB Davis RE 1982 Monthly mean sea level

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Doyle JD Bond NA 2001 Research aircraft observations

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Enfield DB Allen JS 1980 On the structure and dynamics

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Francis RC Hare SR 1994 Decadal-scale regime shifts

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Freeland H Denman K Wong CS Whitney F Jacques

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Frost BW 1991 The role of grazing in nutrient-rich areas of

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Gargett AE 1997 The optimum stability window a

mechanism underlying decadal fluctuations in North Pacific

salmon stocks Fisheries Oceanography 6 109ndash117

Gill AE 1982 Atmosphere-Ocean Dynamics Academic

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Glass RL 1999 Water-quality assessment of the Cook Inlet

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Goering JJ Patten CJ Shiels WE 1973 Nutrient cycles

In Hood DW Shiels WE Kelley EJ (Eds) Environ-

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Occasional Pub No 3 University of Alaska Fairbanks

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Hare SR 1996 Low frequency climate variability and salmon

production PhD Dissertation University of Washington

School of Fisheries 306pp

Hare SR Mantua NJ 2000 Empirical evidence for North

Pacific regime shifts in 1977 and 1989 Progress in

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Hayes SP 1979 Variability of current and bottom pressure

across the continental shelf in the Northeast Gulf of Alaska

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Hayes SP Schumacher JD 1976 Description of wind

current and bottom pressure variations on the continental

shelf in the Northeast Gulf of Alaska from FebruaryndashMay

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Hermann AJ Stabeno PJ 1996 An eddy-resolving model

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development and sensitivity analyses Journal of Geophy-

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Hermann AJ Hinckley S Megrey BA Stabeno PJ

1996 Interannual variability of the early life history of

walleye Pollock near Shelikof strait as inferred from a

spatially explicit individual-based model Fisheries Ocea-

nography 5 (Suppl 1) 39ndash57

Hermann AJ Haidvogel DB Dobbins EL Stabeno PJ

2002 Coupling global and regional circulation models in the

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Ingraham Jr WJ Ebbesmeyer CC Hinrichsen RA 1998

Imminent climate and circulation shift in North Pacific

Ocean could have major impact on marine resources

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Kalnay E Kanamitsu M Kistler R Collins W

Deaven D Gandin L Iredell M Saha S White G

Woollen J Zhu Y Leetmaa A Reynolds B Chelliah

M Ebisuzaki W Higgins W Janowiak J Mo KC

Ropelewski C Wang J Jenne R Joseph D 1996 The

NCEPNCAR 40-year reanalysis project Bulletin of the

American Meteorological Society 77 437ndash471

Klinck J 1988 The influence of a narrow transverse canyon

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Lackmann GM Overland JE 1989 Atmospheric structure

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Lagerloef GSE 1995 Interdecadal variations in the

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Landrum LL Gammon RH Feely RA Murphy PP

Kelly KC Cosca CE Weiss RF 1996 North Pacific

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1985ndash1989 Journal of Geophysical Research 101 (C12)

28539ndash28555

Large WG Pond S 1982 Sensible and latent heat

measurements over the ocean Journal of Physical Oceano-

Larrance JD Chester AJ 1979 Source composition and

flux of organic detritus in lower cook inlet Outer

Continental Shelf Environmental Assessment Program

Final Reports of Principal Investigators 46 1ndash71

Larrance JD Tennant DA Chester AJ Ruffio PA

1977 Phytoplankton and primary production in the

northeast Gulf of Alaska and lower Cook Inlet Final

Report Research Unit 425 Environmental Assessment of

the Alaskan Continental Shelf Annual Reports of

Principal Investigators for the Year Ending March 1977

10 1ndash136

Macklin SA Lackmann GM Gray J 1988 Offshore-

directed winds in the vicinity of prince William Sound

Alaska Monthly Weather Review 116 (6) 1289ndash1301

Macklin SA Bond NA Walker JP 1990 Structure of a

low-level jet over lower Cook Inlet Alaska Monthly

Weather Review 118 (12) 2568ndash2578

Mantua NJ Hare SR Zhang Y Wallace JM Francis

RC 1997 A pacific interdecadal climate oscillation with

impacts on salmon production Bulletin of the American

Meteorological Society 78 1069ndash1079

Martin JH Gordon RM 1988 Northeast pacific iron

distributions in relation to primary productivity Deep-Sea

Martin JH Gordon RM Fitzwater S Broenkow WW

1989 VERTEX phytoplanktoniron studies in the Gulf of

Alaska Deep-Sea Research 36 649ndash680

Minobe S Mantua N 1999 Interdecadal modulation of

interannual atmospheric and ocean variability over the

North Pacific Progress in Oceanography 43 163ndash192

Munchow A 2000 Wind stress curl forcing of the coastal

ocean near Point Conception California Journal of

Physical Oceanography 30 1265ndash1280

Murphy PP Feely RA Wanninkhof R 1998 On

obtaining high-precision measurements of oceanic pCO2using infrared analyzers Marine Chemistry 62 (1ndash2)

103ndash115

Murphy PP Nojiri Y Harrison DE Larkin NK

2001 Scales of spatial variability for surface ocean

pCO2 in the Gulf of Alaska and Bering Sea toward

a sampling strategy Geophysical Research Letters 28

1047ndash1050

Napp JM Incze LS Ortner PB Siefert DLW Britt L

1996 The plankton of Shelikof Strait Alaska standing

stock production mesoscale variability and their relevance

to larval fish survival Fisheries Oceanography 5 (Suppl 1)

19ndash38

Norris JR Zhang Y Wallace JM 1998 Role of low

clouds in summertime atmospherendashocean interactions over

the North Pacific Journal of Climate 11 2473ndash2481

Overland JE Bond NA 1995 Observations and scale

analysis of coastal wind jets Monthly Weather Review 123

(10) 2934ndash2941

Overland JE Adams JM Bond NA 1999a Decadal

variability in the Aleutian low and its relation to

high-latitude circulation Journal of Climate 12 (5)

1542ndash1548

Overland JE Salo S Adams JM 1999b Salinity signature

of the Pacific Decadal Oscillation Geophysical Research

Letters 26 (9) 1337ndash1340

Overland JE Bond NA Adams JM 2001 North Pacific

atmospheric and SST anomalies in 1997 links to ENSO

Fisheries Oceanography 10 69ndash80

Overland JE Bond NA Adams JM 2002 The relation of

surface forcing of the Bering Sea to large-scale climate

patterns Deep-Sea Research II Topical Studies in Oceano-

graphy 49 (26) 5855ndash5868

Parish TR 1982 Barrier wind along the Sierra Nevada

Mountains Journal of Applied Meteorology 21 925ndash930

Reeburgh WS Kipphut GW 1987 Chemical distributions

and signals in the Gulf of Alaska its coastal margins

and estuaries In Hood DW Zimmerman ST (Eds)

The Gulf of Alaska US Dept of Commerce USA

pp 77ndash91

Reed RK 1984 Flow of the Alaskan Stream and its

variations Deep-Sea Research 31 (4) 369ndash386

Reed RK 1987 Salinity characteristics and flow of the

Alaska Coastal Current Continental Shelf Research 7

573ndash576

Reed RK Schumacher JD 1986 Physical Oceanography

In Hood DW Zimmerman ST (Eds) The Gulf of

Alaska Physical Environment and Biological Resources

Ocean Assessment Division NOAA USA pp 57ndash75

Reed RK Stabeno PJ 1989 Recent observations of

variability in the path and vertical structure of the

Alaskan Stream Journal of Physical Oceanography 19

(10) 1634ndash1642

Reed RK Bograd SJ 1995 Transport in Shelikof Strait

Alaska an update Continental Shelf Research 15 (23)

213ndash218

Reed RK Schumacher JD Incze LS 1987 Circulation in

Shelikof Strait Alaska Journal of Physical Oceanography

17 (9) 1546ndash1554

Renwick JA Wallace JM 1996 Relationships between

North Pacific wintertime blocking El Nino and the PNA

pattern Monthly Weather Review 124 2071ndash2076

Royer TC 1979 On the effect of precipitation and runoff on

coastal circulation in the Gulf of Alaska Journal of Physical

ARTICLE IN PRESS

Royer TC 1982 Coastal fresh water discharge in the

northeast Pacific Journal of Geophysical Research 87

2017ndash2021

Royer TC 1981 Baroclinic transport in the Gulf of Alaska

Part II Fresh water driven coastal current Journal of

Marine Research 39 251ndash266

Royer TC 1998 Coastal Processes in the northern North

Pacific In Robinson AR Brink KH (Eds) The Sea

Vol 11 Wiley New York pp 395ndash413

Royer TC Grosch CE 2000 Analysis of low frequency

signals in the northeast Pacific coastal freshwater discharge

salinity temperature an salmon production using wavelet

techniques presented at the Ninth Annual Pices Meeting

Hakodate Japan 24 October 2000

Sambrotto RN Lorenzen CJ 1987 Phytoplankton and

Primary Production In Hood DW Zimmerman ST

(Eds) The Gulf of Alaska US Department of Commerce

USA pp 249ndash282

Schumacher JD Reed RK 1980 Coastal flow in the

northwest Gulf of Alaska the Kenai Current Journal of

Geophysical Research 85 (C11) 6680ndash6688

Schumacher JD Pearson CA Overland JE 1982 On

exchange of water between the Gulf of Alaska and the

Bering Sea through Unimak Pass Journal of Geophysical

Research 87 (C7) 5785ndash5795

Schumacher JD Stabeno PJ Roach AT 1989 Volume

transport in the Alaska Coastal Current Continental Shelf

Research 9 (12) 1071ndash1083

Schumacher JD Stabeno PJ Bograd SJ 1993 Char-

acteristics of an eddy over a continental shelf Shelikof

Strait Alaska Journal of Geophysical Research 98

98395ndash98404

Sharples J Moore CM Rippeth TP Holligan PM

Fisher DJ Simpson JH 2001 Phytoplankton distribu-

tion and survival in the thermocline Limnology and

Spencer RW 1993 Global oceanic precipitation from the

MSU during 1979ndash1991 and comparisons to other climatol-

ogies Journal of Climate 6 1301ndash1326

Stabeno PJ Reed RK 1991 Recent Lagrangian measure-

ments along the Alaskan Stream Deep-Sea Research 38 (3)

289ndash296

Stabeno PJ Hermann AJ 1996 An eddy circulation model

for the western Gulf of Alaska shelf II Comparison of

results to oceanographic observations Journal of Geophy-

sical Research 101 1151ndash1161

Stabeno PJ Reed RK Schumacher JD 1995a The

Alaska Coastal Current continuity of transport and

forcing Journal of Geophysical Research 100 2477ndash2485

Stabeno PJ Hermann AJ Bond NA Bograd SJ 1995b

Modeling the impact of climate variability on the advection

of larval walleye pollock (Theragra chalcogramma) in the

Gulf of Alaska In Beamish RJ (Ed) Climate Change

and Northern Fish Populations Can Spec Publ Fish

Aquat Sci 121 719ndash727

Stabeno PJ Schumacher JD Bailey KM Brodeur RD

Cokelet ED 1996 Observed patches of walleye pollock

eggs and larvae in Shelikof Strait Alaska their character-

istics formations and persistence Fisheries Oceanography 5

(Suppl 1) 81ndash91

Stabeno PJ Reed RK Napp JM 2002 Transport

through Unimak Pass Alaska Deep-Sea Research II

Topical Studies in Oceanography 49 (26) 5931ndash5943

Stephens MP Samuels G Olson DB Fine RA

Takahashi T 1995 Sea-air flux of CO2 in the North

Pacific using shipboard and satellite data Journal of

Sugai SF Burrell DC 1984 Transport of dissolved organic

carbon nutrients and trace metals from the Wilson and

Blossom Rivers to Smeaton Bay Southeast Alaska

Canadian Journal of Fisheries and Aquatic Sciences 41

180ndash190

Takahashi T Olafsson J Goddard J Chipman DW

Sutherland SC 1993 Seasonal variation of CO2 and

nutrients in the high latitude surface oceans a comparative

study Global Biogeochemical Cycles 7 843ndash878

Thompson RE Gower JFR 1998 A basin-scale oceanic

instability event in the Gulf of Alaska Journal of

Geophysical Research 103 3033ndash3040

Townsend DW Cammen LM Holligan PM Campbell

DE Pettigrew NR 1994 Causes and consequences of

variability in the timing of spring phytoplankton blooms

Deep Sea Research 41 747ndash765

USGS Web Page httpwwwwaterdatausgsgovaknwis

qwdata

US Navy Marine Climatic Atlas 1969

Wallace JM 2000 North Atlantic OscillationAnnular Mode

Two paradigms One Phenomenon Quarterly Journal of

the Royal Meteorological Society 126 791ndash805

Wallace JM Gutzler DS 1981 Teleconnections in

the geopotential height field during the Northern

Hemisphere winter Monthly Weather Review 109

784ndash812

Wallace JM Smith C Bretherton CS 1992 Singular

value decomposition of wintertime sea surface temperature

and 500-mb height anomalies Journal of Climate 5

561ndash576

Whitney FA Welch DW 2002 Impact of the 1997ndash8

El Nino and 1999 La Nina on the nutrient supply

in the Gulf of Alaska Progress in Oceanography 54

405ndash421

Whitney FA Wong CS Boyd PW 1998 Interannual

variability in nitrate supply to surface waters of the

Northeast Pacific Ocean Marine Ecology Progress Series

170 15ndash23

Whitney FA Mackas DL Welch D Robert M 1999

Impact of the 1990rsquos El Ninos on nutrient supply and

productivity of Gulf of Alaska waters In Proceedings of

the 1998 Science Board Symposium on the Impacts of the

199798 El Nino Event on the North Pacific Ocean

and its Marginal Seas Pices Scientific Report No 10

pp 59ndash62

Wilson JG Overland JE 1986 Meteorology of the north-

ern Gulf of Alaska In Hood DW Zimmerman ST

ARTICLE IN PRESS

(Eds) The Gulf of Alaska Physical Environment and

Biological Resources DOCNOAA DOI pp 31ndash54

Wong CS Chan YH 1991 Temporal variations in the

partial pressure and flux of CO2 at ocean station P in the

subarctic Northeast Pacific Ocean Tellus 43B 206ndash223

Woods J Barkmann W 1993 The plankton multipliermdash

positive feedback in the greenhouse Journal of Plankton

Zhang Y Wallace JM Battisti DS 1997 ENSO-like

interdecadal variability Journal of Climate 10 1004ndash1020

Meteorology and oceanography of the Northern Gulf of Alaska

Introduction

The atmosphere

Interannual to decadal scales

Winds

Rainfall and runoff

Oceanography

Lagrangian measurements

Time series from moorings

Tidal currents

Low-frequency currents

Relationship of currents to wind forcing

Hydrography

Seasonal dynamics of nutrients and primary production

Mechanisms for cross-shelf fluxes

Episodic upwelling

Surface flux in the Ekman layer

Upwelling seaward of a coastal wind jet

Topographic steering

Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

W e s t W i n d D r i f t

Alaska Current

Alaska

Peninsu

Kodiak I

Bering Sea

Peninsula

Current

Pr inceWi l l iamSound

YakutatBay

Kayak I

Coastal

Akaska

UnimakPass

A l a s k a n S t r e a mShumagin

SamalgaPass

60degN

QueenCharlotte Is

170degW

140degW150deg160deg 130degW170deg

Fig 1 Map of the Gulf of Alaska The flow of the Alaska Coastal Current and subarctic gyre are indicated as are several geographic

place names (After Reed and Schumacher 1986)

divides as it approaches the west coast of NorthAmerica into the southward flowing CaliforniaCurrent and the northward flowing Alaska Cur-rent The Alaska Current is a typical easternboundary current rich with eddies and meandersAt the head of the GOA it turns southwestwardfollowing the isobaths This is the beginning of theAlaskan Stream the western boundary current ofthe eastern subarctic gyre Near the southwesternedge of Kodiak Island (B155W) the AlaskanStream is a narrow (B50 km) high speed(gt50 cm s1) current that flows southwestwardalong the slope of the Alaska Peninsula andAleutian Islands to 180W where the AleutianArc turns northwestward (Reed and Stabeno1989 Reed 1984)The ACC driven by winds and freshwater

runoff dominates circulation of the shelf andcontrols the transport of dissolved substances andplanktonic material (Stabeno et al 1995a bRoyer 1981) While much is known throughdrifter trajectories and current meter mooringsabout the continuity seasonal variability andmean flow of the ACC from the Seward Line(B149W) westward less is known in the regionsouth and east of PrinceWilliam Sound Observations

from Icy Point (B137W Fig 2) to Kayak Islandreveal a baroclinic current with a strong seasonalsignal in the freshwater core typical of the ACCfarther west (Hayes and Schumacher 1976) TheACC flows westward along the Kenai Peninsula andbifurcates at Kennedy-Stevenson Entrance with themajority of annual transport continuing downShelikof Strait (Stabeno et al 1995ab Schumacheret al 1989) Approximately 70 of the transportcontinues down the Shelikof Sea Valley with less thanhalf joining the Alaskan Stream the remainder flowsalong Alaska Peninsula to Unimak Pass andSamalga Pass the western terminus of the ACC(Schumacher et al 1989)The continental shelf of the GOA supports a

productive ecosystem which includes numerousspecies of fishes marine mammals and sea birdsThe larvae of many species of vertebrates andinvertebrates occur in surface waters For manylarvae the ACC is their main path of dispersalCoastal waters also provide a conduit for youngsalmon upon entering the oceanic environment Atfirst impression such high productivity is surpris-ing because GOA coastal winds are downwellingfavorable However other mechanisms such aseddies and advection in canyons may replenish

ARTICLE IN PRESS

Icy Bay

Kayak I

Chirikof I

Shelik

of Str

GorePt

CKekurnoi

a l le

SewardLine

SemidiiIs

Prince WilliamSound

HinchinbrookCanyon

AmatouliTrough

ARTICLE IN PRESS

Yakutat

Ketchikan

Seward

2 The atmosphere

ARTICLE IN PRESS

22 Winds

ARTICLE IN PRESS

3 s- 3

55degN 160degW

ARTICLE IN PRESS

ed (10

3 s- 3

55degN 160degW

ARTICLE IN PRESS

55degN 160degW

s-1) 8

ARTICLE IN PRESS

YakutatKetchikan

Seward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Icy Bay

Kayak I

Chirikof I

Shelik

of Str

GorePt

CKekurnoi

a l le

SewardLine

SemidiiIs

Prince WilliamSound

HinchinbrookCanyon

AmatouliTrough

ARTICLE IN PRESS

Yakutat

Ketchikan

Seward

2 The atmosphere

ARTICLE IN PRESS

22 Winds

ARTICLE IN PRESS

3 s- 3

55degN 160degW

ARTICLE IN PRESS

ed (10

3 s- 3

55degN 160degW

ARTICLE IN PRESS

55degN 160degW

s-1) 8

ARTICLE IN PRESS

YakutatKetchikan

Seward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Yakutat

Ketchikan

Seward

2 The atmosphere

ARTICLE IN PRESS

22 Winds

ARTICLE IN PRESS

3 s- 3

55degN 160degW

ARTICLE IN PRESS

ed (10

3 s- 3

55degN 160degW

ARTICLE IN PRESS

55degN 160degW

s-1) 8

ARTICLE IN PRESS

YakutatKetchikan

Seward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

22 Winds

ARTICLE IN PRESS

3 s- 3

55degN 160degW

ARTICLE IN PRESS

ed (10

3 s- 3

55degN 160degW

ARTICLE IN PRESS

55degN 160degW

s-1) 8

ARTICLE IN PRESS

YakutatKetchikan

Seward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

22 Winds

ARTICLE IN PRESS

3 s- 3

55degN 160degW

ARTICLE IN PRESS

ed (10

3 s- 3

55degN 160degW

ARTICLE IN PRESS

55degN 160degW

s-1) 8

ARTICLE IN PRESS

YakutatKetchikan

Seward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

3 s- 3

55degN 160degW

ARTICLE IN PRESS

ed (10

3 s- 3

55degN 160degW

ARTICLE IN PRESS

55degN 160degW

s-1) 8

ARTICLE IN PRESS

YakutatKetchikan

Seward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

ed (10

3 s- 3

55degN 160degW

ARTICLE IN PRESS

55degN 160degW

s-1) 8

ARTICLE IN PRESS

YakutatKetchikan

Seward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

55degN 160degW

s-1) 8

ARTICLE IN PRESS

YakutatKetchikan

Seward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

YakutatKetchikan

Seward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

400Yakutat

KetchikanSeward

1950 1960 1970 1980 1990 2000

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

3 Oceanography

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

58degN

56degN

60degN

(d)(c)

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Kenai Pen

Kodiak I

02 m s-1

insula

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

CapeKekurnoi

outer shelf

321 Tidal currents

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Sep-Dec

6 m3 s

May-Aug

6 m3 s

4Jan-Apr

6 m3 s

33 Hydrography

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Gore Pt10 Oct 1978

Icy Bay13 Sep 1977

Kayak I27 Sep 1978

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

330(a)

GAK1Shelikof Strait

1985 1990 1995 2000

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Shelikof Strait

surface

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

production

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

200 150 100 50 0

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

C N P Fe frac14 106 16 1 001

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

45 Eddies

5 Discussion

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Acknowledgements

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

References

58 671ndash684

18243ndash18254

DC 245pp

75ndash84

978ndash998

279ndash291

2117ndash2129

335ndash367

197ndash201

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

1817ndash1833

2242ndash2258

28539ndash28555

10 1ndash136

103ndash115

1047ndash1050

19ndash38

(10) 2934ndash2941

1542ndash1548

graphy 49 (26) 5855ndash5868

pp 77ndash91

573ndash576

(10) 1634ndash1642

213ndash218

17 (9) 1546ndash1554

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

2017ndash2021

USA pp 249ndash282

98395ndash98404

289ndash296

(Suppl 1) 81ndash91

180ndash190

qwdata

784ndash812

561ndash576

405ndash421

170 15ndash23

pp 59ndash62

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

ARTICLE IN PRESS

Introduction

The atmosphere


Winds

Rainfall and runoff

Oceanography



Tidal currents



Hydrography



Episodic upwelling




Eddies

Discussion

Acknowledgements

References

Documents

MeteorologyandoceanographyoftheNorthernGulf ofAlaskadepts.washington.edu/fish437/resources/Week 2/stab goa.pdf · rent. The Alaska Current is a typical eastern boundarycurrent,richwitheddiesandmeanders