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The Arctic CrossroadsThe Influence of the Mendeleev Ridge and the

Chukchi Borderland on the Large-scale Circulation ofthe Arctic Ocean

Rebecca Woodgate and Knut Aagaard, University of WashingtonJim Swift, Scripps Institution of Oceanography

Bill Smethie, Lamont-Doherty Earth ObservatoryKelly Falkner, Oregon State University

Ed Carmack and Fiona McLaughlin, Institute of Ocean Sciences, B.C.

Rebecca A Woodgate, M.A., D.Phil.Research Assistant Professor

Applied Physics Laboratory/School of OceanographyUniversity of Washington, Seattle

Dr Rebecca Woodgate

B.A. Hons (First Class) and M.A.Physics and Theoretical PhysicsUniversity of Cambridge, United Kingdom

D.Phil. Physical OceanographyUniversity of Oxford, United Kingdom- researching use of satellite data to improvecomputer models of ocean circulation

Post-doctoral StudiesAlfred-Wegener-Institute of Polar and MarineResearch, Bremerhaven, Germany- Arctic and Antarctic physical oceanographicresearch, especially the Greenland Sea, theFram Strait and the Weddell Sea- ship-based observations in collaboration withGermany, Norway, U.S.A. and U.K.

Current Research CareerResearch Assistant ProfessorApplied Physics Laboratory/Department of OceanographyUniversity of Washington, Seattle, U.S.A.- Arctic physical oceanographic research- observational projects in the high Arctic, at the North Pole, in the ChukchiSea and in the Bering Strait- teaching of physical oceanography to University of Washington under-graduate students

Motivation- an understanding of the physical Arctic system, from large-scale circula-tion to regional oceanography, the processes and implications of climate

change in the Arctic and its feedback into World Ocean circulation(http://psc.apl.washington.edu/HLD)

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Lomonosov Ridge

Atlantic waters Pacific waters

Transfer out into the deep basin?

Barrow

Large-Scale Arctic Ocean Circulation

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1. A boundary current, followingthe depth contours, carries

warm Atlantic waters into theChukchi Borderland region

3. Some of the boundary cur-rent, and some of the Pacificwaters are diverted into the

deep Arctic Ocean

2. The nutrient-richPacific waters enter theArctic via the Chukchi

Sea.

The fate of the Atlantic and Pacific waters is determined bythe interplay of topography, wind, currents and ice motion

in the region of the Chukchi Borderland

4. Some of the boundarycurrent and some of thePacific waters continuealong the north coast of

Alaska

Mendeleev Ridge

ChukchiBorderland

The Role of the Arctic Crossroads

Barrow

Why do we care?

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1. The “warm” Atlanticlayer carries heat. Itsfate can influence ice

thickness.

2. The Pacific waters carry nutrients.The fate of these waters in the Arcticcan affect the biological productivity.

3. The interplay of Atlantic andPacific waters may be affected bythe changes in Arctic oceanic and

atmospheric circulation we seeover the last decade (or longer).

4. A better understanding of theArctic Ocean Boundary Current

and the interaction of Atlantic andPacific waters in this region will

improve computer models of Arc-tic circulation and Arctic climate

change.

How can the Atlantic waters affect theice?

Temperature SalinityDepth

ca.50m

ca.300m

ca.200m

Warm (0 to 2 deg C)Atlantic Layer

Cold, saltier “Cold Halocline”layer insulates the surface icefrom the deeper warm Atlantic

Layer

The Atlantic waters carry heat into the region.

The “cold halocline” waters, which insulate the ice from the underlyingwarm Atlantic waters, come from the Arctic shelves and the Pacific

waters.

The combination of the pathways of these waters determines howmuch heat can escape upwards to melt ice.

?

?

?

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Pathways of nutrient-rich Pacific waters?

The Pacific waters are the mostnutrient-rich waters in the

Arctic.

They enter the Arctic in threemain flows,

- though Barrow Canyon,- through Herald Canyon- between the Herald and

Hanna Shoals.

Some fraction continues east-ward along the north coast of

Alaska

Some appears to head off intothe deep Arctic basin

The depth these waters reach inthe Arctic depends on their den-sity (i.e. their temperature and

salinity).Measurements from theBeringStrait show these properties to

be changing over the lastdecade.

What causes these changes andhow will they affect Arctic eco-

systems?

Arctic Climate Change?

>1.0>

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‘98‘95

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‘96Tmax

/oC

Maximum temperatures in the Atlantic core from the Scicex and AOSexpeditions. Note the warming of the core in the Chukchi Borderlandregion between 1993 and 1998, and the excursion of warm water into

the deep Arctic basin (1996 and 1997, ca.79N)

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Chukchi Borderland Cruise 2002

A single cruise oceanographic surveyof the Chukchi Borderland and

Mendeleev Ridge region, aboard theUSCGC Polar Star in autumn 2002.

CTD sections

3 oceanographic moorings, inplace for the ca. 1 month duration ofthe cruise.

Barrow200 nm

SBE-16 S/Nwith pressure

________

Depth _______

MOORING ID: __________CBL-B

CHUKCHI

BORDERLAND

02

RCM-7 S/N ________Depth _______m.

Double 17in. Glass Float

Double 17in. Glass Float

SBE-16 S/Nwith pressure

________

Depth _______

RCM-7 S/N ________Depth _______m.

EG&G 8242S/N: ______

EG&G 8242S/N: ______

RCM-7 S/N ________Depth _______

5/16“ Kevlar_______m.

5/16“ Kevlar_______m.

5/16“ Kevlar_______m.

5/16“ Kevlar_______m.

5/16“ Kevlar_______m.

5/16“ Kevlar_______m.

100

101m.

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351m.

800m.

3

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100+144

3

5

Double 17in. Glass Float

5/16“ Kevlar_______m.3

97

Double 17in. Glass Float

5/16“ Kevlar_______m.100+91

2m. Chain (Long Link)

AnchorDry Wt. = _______lbs.

BottomDepth: _______m.1000 1400

30“ Steel Float

Pieps

XT-6000 S/N ______Depth ____m.

2m. Chain (Long Link)

Chukchi Borderland Moorings 2002

Three moorings- deployed across the boundary current,- in place for ca.1 month- hourly measurements of temperature,salinity and water velocity in the mainwater layers of the Arctic Ocean

This will provide information on- the physical structure, transport andvariability of the boundary current- the variability of the interactionsbetween Pacific and Atlantic waters

Moorings will be recovered at the end ofthe cruise

A series of CTD (Conductivity and Temperature with Depth) stationswill measure the temperature and salinity of the Arctic (Atlantic and

Pacific) waters in a set of 12 sections in the Chukchi Borderland/Men-deleev Ridge regions.

Teams from Scripps, LDEO and OSU will take water samples for chem-ical analysis of oxygen, nutrients, and tracers of Atlantic, Pacific and

river waters.

Example of CTD Rosettesystem from RV Alpha Helix(Photos from NPMR, UAF)

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Chukchi Borderland CTD Work 2002

The combination ofthese data tell us thepathways and origins

of the waters, andcomparison with

older data indicateshow the system is

changing

The floating classroom

Ms Gail Grimes, a High School sci-ence teacher from Washington

State, and her classes, from LakeStevens High School, will also takepart in the cruise. Ms Grimes will

sail on the Polar Star and send backdaily reports and photos to a public

website, both for her classes andfor others interested in following the

cruiseMs Gail Grimesand her class

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The Influence of the Mendeleev Ridge and the ChukchiBorderland on the Large-scale Circulation of the Arctic

Ocean

R. Woodgate, K. Aagaard, J. Swift, B. Smethie, K. Falknerin collaboration with E. Carmack, F. McLaughlin

= delineate the pathway of theArctic Ocean Boundary Current,past the Mendeleev Ridge and

through the Chukchi Borderland

= assess the input from the boundarycurrent and the shelves to the

deep Arctic Ocean

= understand and quantify the pathways and transformations

of the Pacific waters

= describe thehorizontal and

vertical structure ofthe boundary current,

and estimateits transport

= quantify temporal change,by combining this survey

with historic data

Mendeleev Ridge

ChukchiBorderland