Variability of hydrophysical characteristics in the Gulf Stream

ISSN 0001�4370, Oceanology, 2013, Vol. 53, No. 4, pp. 401–409. © Pleiades Publishing, Inc., 2013.Original Russian Text © L.N. Karlin, V.N. Malinin, S.M. Gordeeva, 2013, published in Okeanologiya, 2013, Vol. 53, No. 4, pp. 454–462.

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INTRODUCTION

Recently, the interest in the circulation processes inthe North Atlantic has increased dramatically, notonly in a scientific but also social mileu due to numer�ous incompetent publications in the media and on theInternet concerning “the shutdown of the GulfStream and an impending new ice age, when the airtemperature in Europe in a short time will be reducedby 7–10°C.” The reason for this is called a “significantweakening, displacement of the Gulf Stream pathtowards Africa or even its extinction” because of fresh�ening of the cold Labrador Current as a result of melt�ing of the Arctic Ocean ice cover. Indeed, the ice coverarea was 8000000 km2 in 1980, but it dropped to5000000 km2 by 2009; i.e. the rate of ice cover shrink�ing was 100000 km2/yr [1]. Reduction of the total icecover continued in consequent years and the ice coverarea in the Arctic in 2012 reached its lowest value overthe whole period of observations. Naturally, thisshould result in a strengthening of the flow of waters oflesser salinity from the Arctic with the East GreenlandCurrent and through the straights of the CanadianArchipelago into the North Atlantic. In addition, astronger solid (iceberg) and liquid runoff from Green�land has been observed because of warming [6, 14, 17,27]. Eventually, both these processes are assumed tolead to an increased flow rate and desalination of thesurface Labrador Current and, as a result, to thereduced density of the latter. It is clear that this will notfail to affect the nature of interaction of the LabradorCurrent with the waters of the Gulf Stream.

In this context, we consider the two issues: evalua�tion of the interannual variability of the Gulf Streamintensity and statistical analysis of interannual fluctu�ations in parameters of seawater state in the GulfStream and the Labrador Current.

CIRCULATION VARIABILITY IN THE GULF STREAM

A rather detailed description of the Gulf Stream, asimplified diagram of which is shown in Fig. 1, is givenin [3, 4, 7, 9]. The study [10] is a source of prevailingopinion that the Gulf Stream’s runoff rate has consid�erably decreased in recent decades. The study exam�ines five hydrographical transects at 26.5° N and infersthat the meridional circulation of the ocean hasdecreased by 30% for the period of 1957–2004.

However, later it was discovered from the Argofloats that there are considerable seasonal and interan�nual fluctuations in the strength of Atlantic Meridi�onal Circulation (Atlantic Meridional OverturningCirculation, АМОС), whereby the trend calculatedfrom the five original transects cannot be consideredstatistically significant [13]. The idea of weakening ofthe Gulf Stream lacks support from more comprehen�sive recent calculations [25]. The latter were based onaltimetric observations of sea surface height and ontemperature, salinity, and current velocity dataobtained with the Argo floats and resulted in an esti�mate of the geostrophic meridional transport from thesurface down to a depth of 1130 m for the period of1993 to 2009 in two transects (70о–54о W and 15о–5о W)at 41о N. The first transect characterizes the GulfStream, while the second one describes the CanaryCurrent. It follows from [25] that no weakening ofmeridional circulation occurs. Moreover, a positivetrend, pointing to the strengthening of meridional cir�culation, has been observed since 2000. In addition, anincrease in variability of monthly mean circulationestimates as high as 70% of the long�term level wasestablished. However, earlier, Russian researchersnoted a quite considerable variability in the intensityof currents [3, 4]. For instance, G.I. Baryshevskaya [4]

Variability of Hydrophysical Characteristics in the Gulf StreamL. N. Karlin, V. N. Malinin, and S. M. Gordeeva

Russian State Hydrometeorological University, St. Petersburg, Russiae�mail: [email protected], [email protected], [email protected]

Received March 10, 2012; in final form, September 25, 2012

Abstract—We consider the interannual variability of the intensity of the Gulf Stream and interannual fluc�tuations of seawater parameters in the Gulf Stream and in the Labrador Current during intense climatewarming. We show that this intensity has increased during this period. The scales of fluctuations and theircontribution to variance in the initial time series was determined from wavelet analysis of the Gulf Streamnorth wall. We noted a considerable decrease in water density of the main branch of the Gulf Stream, causedby the increase in temperature due to global climate warming, and an absence of trends in water density ofthe main branch of the Labrador Current.

DOI: 10.1134/S0001437013040048

MARINEPHYSICS

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demonstrated that heat transport is subject to twofoldand eightfold variations in the cases of the Gulf Streamand the North Atlantic Current, respectively.

An indirect estimate of the Gulf Stream energyvariability can be obtained from analytical processingof the Gulf Stream index (Gulf Stream North Wall,GSNW) which characterizes the localization of thewell identifiable north boundary of the current. Thisindex, proposed by Taylor and Stephens in 1980 [21],is calculated at Plymouth Marine Laboratory (UnitedKingdom) and is used rather frequently by foreignresearchers to evaluate the variability of this current aswell as an indicator of climatic fluctuations in theNorth Atlantic [19, 20]. The monthly mean values ofthe GSNW index are available at http://www.pml�gulfstream.org.uk. To determine the GSNW, the lati�tude of the Gulf Stream “north wall” is retrieved frommaps at longitudes 79°, 75°, 72°, 70°, 67°, and 65° Wusing different sources. The long�term mean localiza�tion of the GSNW for the period 1966–2010 accord�ing to [22] is presented in Fig. 1. Taylor et al. [20] use

the principal components method to find the patternof the current energy variability. The first principalcomponent (PC) is taken as the GSNW index. Its pos�itive values indicate a northward shift of the current,while negative ones mean a southward displacementrelative to the current long�term average position. It isevident that the north wall estimates indirectly charac�terize the current intensity; the higher the latter, thefurther northward the current moves. As shown in[12], the GSNW and АМОС positively correlate oninterannual variability scales. The strengthening ofmeridional circulation occurs when the Gulf Streamshifts northwards.

Monthly and annual mean trends in GSNW indexvalues for 1966–2010 are given in Fig. 2. The irregularcharacter of fluctuations is quite evident. Neverthe�less, a positive trend of 0.03 yr–1, significant at a signif�icance level of α = 0.05, is quite clearly seen for yearlyestimates of the GSNW index. According to the esti�mates of determination coefficient, its contribution tovariance of the initial series is 15%. Thus, in total for

60°N

40°

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80° W 60° 40° 20° 0°

North

Gulf Stream

A T L A N T I C O C E A N

Africa

Europe

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South America

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North Atlantic Current

Labra

Irminger

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dor Current

Current

Fig. 1. Simplified pattern of surface circulation in North Atlantic. Circles mark areas involved in calculations of hydrophysicalcharacteristics. Triangles indicate long�term average localization of Gulf Stream north wall for 1966–2010 after [22].


VARIABILITY OF HYDROPHYSICAL CHARACTERISTICS IN THE GULF STREAM 403

the considered period, the northern boundary of theGulf Stream has shifted northwards. At the same time,it is possible to discriminate the time intervals whenopposite trends in GSNW changes occur on the back�ground of a general trend. These are the periods from1970 to 1994 when the northward shift of the GulfStream could be observed, and from 1994 to 2010when, on the contrary, it retreated to the south. Thesouthernmost Gulf Stream position occurred in 1971,and the northernmost, in 1994. As for 2010, the cur�rent boundary position was close to normal.

Fluctuations in the GSNW monthly mean valuesare irregular in character too. Even the annual cycle islacking since its contribution to the variance of the ini�tial series is only 3% and insignificant at α = 0.05according to the spectral analysis results. This is possi�bly caused by the random character of separation ofanticyclonic eddies (rings) at different longitudes fromthe main jet of the current. In addition, taking intoaccount the use of the first principal component todetermine only the GSNW, it is reasonable to assumethat a fraction of the intra�annual variance was redis�tributed among the other principal components.

Note also that the annual cycle in the intensity ofthe Gulf Stream is generally weak. In particular, amore detailed assessment of the annual cycle can bederived from data on daily water consumption of theFlorida Current for 1982–2011 at the zonal transect at27° N which are freely available on the website ofNASA Atlantic Oceanographic and MeteorologicalLaboratory (http://www.aoml.noaa.gov/phod/flon�dacurrent/data_access.php). We averaged the dataover the calendar month, and filled the insignificant

gaps with estimates of a linear trend for 1982–2011.We obtained the time dependence of water dischargerate, shown in Fig. 3. It is easy to see that there are nowell�expressed patterns in variations of this rate in theFlorida Current. The negative linear trend describesonly 1% of the variance of the series and is statisticallyinsignificant at α = 0.05.

To examine the internal (frequency) structure oftime series for the Florida Current, the wavelet analy�sis was used. It has significant advantages over conven�tional spectral analysis, since there are no stationaritylimitations and, moreover, it makes it possible toinvestigate all aspects of fluctuations (intensity, varia�tion of the period, localization in time) with necessaryand sufficient resolution. Therefore, wavelet trans�form is also called spectral analysis of local distur�bances [2]. The Morlet wavelet is preferable as basisfunctions when solving hydrometeorological problems[5, 8].

Wavelet expansion of the monthly mean dischargerates of waters of the Florida Current (Fig. 4) showsthe presence of two significant periodicities (one yearand six months), whose contribution to the varianceare 10 and 8%, respectively. Their periods are notstrictly constant, and the amplitude of both periodici�ties substantially decreases after 1995. A close estimateof the annual cycle of water discharge of the FloridaCurrent was obtained in [16], where the contributionto the initial variance of the time series over a 16�yearperiod was less than 10%. In addition, the interannualfluctuations involved well�marked quasi�two�year�and four� to five�year�long cycles whose periods arenot constant; in addition, the cycles are observed for a

GSNW = 0.027t – 0.62R2 = 0.15

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x G

SN

W

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Fig. 2. Time dependence of monthly mean and annual mean values of GSNW index for 1966–2010. The trend is shown with abroken line. Dots indicate values of index in May–June, 2010, during incident in Gulf of Mexico.

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short time. Our estimates of fluctuation significance,obtained from comparison of the global spectrum ofwavelet expansion with a red noise intensity at a 95%confidence level using the methodology from [23, 24],revealed that the semiannual and annual periodicitiesexceed the red noise level, but the quasi�two�year andfour� to five�year cycles are insignificant because ofinsufficient length of the series.

Note that no substantial changes in fluctuations ofthe water discharge rate in the Florida Current werefound since the incident on April 27, 2010, in the Gulfof Mexico. These rates were higher and lower thannormal for 50 and 158 days of the 614 day period sincethe incident, respectively. Thus, the water dischargerates turned were slightly lower than the normal levelsince May 2010. However, comparison of the meanrates before and after April 27, 2010 demonstrates sta�tistical insignificance of their difference according toStudent’s t�test at α = 0.05. It can therefore be confi�dent enough to believe that the accident on the rig inthe Gulf of Mexico did not have a significant effect onthe intensity of the Florida Current.

We turn now to Fig. 5, showing the coefficients ofwavelet transform of time series of the Gulf Streammonthly mean indices for 1966–2010 based on theMorlet wavelet. It is easy to see that the eight� to ten�year fluctuation is the most powerful in amplitude.Since the 1980s, there has been a four�year cycle, theperiod of which has gradually increased to six years.Finally, a 23�year�long fluctuation could be observedduring the whole period under review. It was found

that only eight� to nine�year and five�year cyclesexceed the red noise level by a 95% confidence leveland that their contribution to the variance of the initialseries is 20 and 18%, respectively. In this case, a morepronounced 23�year cycle is insignificant due to insuf�ficient length of the sample.

Thus, the total proportion of variance of the deter�ministic components (trend and cyclic fluctuations) ofannual values of the Gulf Stream index is Ddet = 0.15 +0.20 + 0.18 = 0.53. The residual fraction of the vari�ance (Dres = 0.47) is already due to random fluctua�tions.

VARIABILITY OF SEAWATER STATE PARAMETERS IN THE GULF STREAM

AND LABRADOR CURRENT

As it is generally known, the cold surface LabradorCurrent, which originates from waters of the WestGreenland Current and the Canadian ArchipelagoCurrent, meets the Gulf Stream at its delta. The dis�charge rate of the Labrador Current is close to 5 Sv(Sverdrups). Simultaneously, the Labrador Currentdivides into two branches. The coastal branch pene�trates southwards and, after passing by Newfound�land, turns west and extends along the coast of NorthAmerica. The main stream of the Labrador Currentinvolves the upper 300�m�thick layer and features adischarge rate of about 3.5 Sv. The Labrador Currentinteracts with the northern and, particularly, the cen�tral branches of the North Atlantic Current, whichresults in the formation of two stationary (permanent)

FT = –0.0024t + 32.36R2 = 0.01

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Fig. 3. Time course of average monthly discharge rate of water of Florida Current (F) in sverdrups for 1982–2011 in zonal transectat 27° N. The bold line designates the 13�month running average.



frontal zones where intensive mixing processes occur.Typically, the frontal zones are many tens of kilome�ters wide. Exactly here does the surface Labrador Cur�rent end its existence and cooler and less saline trans�

formed waters of the North Atlantic Current continuemoving.

Statistical analysis of interannual fluctuations inthe seawater state parameters involves deep�water

8

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2

1985 1990 1995 2000 2005 2010

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8

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0

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Fig. 4. Coefficients of wavelet expansion of time series of monthly discharge rate of water in Florida Current for 1982–2011 basedon Morlet wavelets. The zero isoline is highlighted.

25

1985 1990 1995 2000 2005 2010

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–2

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198019751970

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le,

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Fig. 5. Coefficients of wavelet expansion of time series of annual values of Gulf Stream index for 1966–2010 based on Morletwavelet. The zero isoline is highlighted.

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data from the CARTON�GIESE SODA archive(http://iridl.ldeo.columbia.edU/SOURCES/.CAR�TON�GIESE/.SODA/. v2pOp2�4), which containsinformation on the monthly mean values of temper�ature, salinity, and zonal, meridional, and verticalcomponents of currents at 40 depth levels from thesurface down to 5374 m from 1958 to 2007 at thenodes of a half�degree grid.

The estimates of the current velocities in thisarchive were obtained from a numerical simulationmodel of general ocean circulation using actual winddata [18] and assimilating deep�water and surfaceobservational data on temperature, salinity, and oceanlevel acquired by shipborne, buoy, and satellite stations[11]. In general, high reliability of current velocities inthis archive is hardly possible, but temperature andsalinity estimates are quite accurate, particularly inareas of multiple oceanographic observations. In ourstudy we chose values of temperature (T) and salinity(S) down to a depth of 293 m for six half�degreesquares (Fig. 1) from January 1958 to December 2007.As it can be seen from Fig. 1, the Gulf Stream, theLabrador Current, and the North Atlantic Currenthave two squares each. The second square mostlycharacterizes the alongshore flow of the LabradorCurrent, while the first does the same for the entireLabrador Current.

Next, we calculated the vertically weighted valuesof ТL and SL, which were the basis for calculating thedensity values ρL using equation of state US�80. Theinterannual trend in density is shown in Fig. 6. As one

would expect, the Labrador Current exhibits a higherdensity in the northern square. Its long�term meanvalue is 1027.0 kg/m3. In this square, the mean tem�perature slightly exceeds the zero level (0.8°C) andsalinity is rather low (33.73‰).

The southward coastal flow of the Labrador Cur�rent is already warmer (6.8°C), thus its densitydecreases. There is no density trend in the main flowof the Labrador Current, which exhibits mostly ran�dom fluctuations. In contrast, a well�expressed nega�tive trend of about 0.003 kg/(m3 yr), which describes26% of the variance of the initial series (Table 1) ischaracteristic of the alongshore flow. Origination ofthis trend relates mainly to temperature growth (thetrend is as high as 0.036°C/yr, R2 = 0.17).

The absence of density trend in waters of the mainflow of the Labrador Current is due to local coolingthat occurred in the 20th century [15], which has lev�eled weak desalination. Additional comparison ofwater density and temperature for periods of weakcooling in the Northern Hemisphere (1958–1975)and intensive warming (1976–2007) based on t�test�ing at α = 0.05 demonstrated the absence of meaning�ful discrepancies of their average values. In addition,the lack of salinity trend (Table 2) means that flowintensification of waters with lesser salinity from theArctic and increased liquid runoff from Greenlandproduce no appreciable effect on desalination atpresent.

As for the Gulf Stream and the North Atlantic Cur�rent, there are no salinization (desalinization) trends

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Fig. 6. Interannual variations of seawater density within the 5� to 293�m layer for a number of half�degree squares of the NorthAtlantic. (1) Labrador Current (sq. 1); (2) Labrador Current (sq. 2); (3) Gulf Stream (sq. 3); (4) Gulf Stream (sq. 4); (5) NorthAtlantic Current (sq. 5); (6) North Atlantic Current (sq. 6).



in interannual salinity fluctuations. At the same time,there is evidence of a strong positive trend in tempera�ture of the Gulf Stream waters (Table 2), apparentlydue to warming during recent decades. This results ina negative trend occurring in fluctuations of the GulfStream water density. However, the trend disappears inthe source of the North Atlantic Current where theGulf Stream waters mix with cooler and desalinatedwaters of the Labrador Current. Evidently, therein liesthe “historical” role of the impact of the LabradorCurrent on the Gulf Stream.

It should be noted that the water temperature vari�ability in the surface layer of the ocean is rather fre�quently identified as temperature changes within awater column from the surface to a depth level H andis attributed to current activity. However, according tothe heat balance equation for the ocean, the temporalchanges in ocean water temperature are determined bythe two main factors: components of external heat bal�ance and horizontal transport (advection) of heat withcurrents. Therefore, we calculated the correlation ofannual mean temperature values in the sea surfacelayer (depth 5 m) with the integral temperature from 0to 293 m, whose changes are already conditioned bythe heat advection with current. The results of calcu�

lations are presented in Fig. 7. The correlation is r =0.60–0.68 for the Gulf Stream and is as low as r =0.41–0.43 for the Labrador Current. In the first case,only 36–46% of water temperature variability isexplained by action of currents and 54–64% of thesame variability relate to processes of heat interactionin the ocean�atmosphere system. Proportion of exter�

Table 1. Statistical density characteristics within the 5� to 293�m layer for individual half�degree squares in the North At�lantic for 1958–2007

No. sq. Current Latitude N

Longitude W

Mean, kg/m3

Standard deviation, kg/m3

Trend kg/(m3 year) R2

1 Labrador 53 53 1027.03 0.14 –0.001 0.018

2 Labrador 45 56 1026.51 0.08 –0.003 0.259

3 Gulf Stream 36 70 1025.29 0.15 –0.006 0.287

4 Gulf Stream 40 49 1025.69 0.14 –0.003 0.096

5 North Atlantic Current 45 45 1026.59 0.13 –0.001 0.001

6 North Atlantic Current 50 30 1026.73 0.11 –0.001 0.020

Note: Boldface highlights significant estimates of a linear trend at critical magnitude of coefficient of determination (5%) = 0.07.Rcr2

Table 2. Statistical characteristics of the trend of interannual fluctuations in temperature and salinity of water within the 5�to 293�m layer for individual half�degree squares in the North Atlantic for 1958–2007

No. sq. CurrentWater temperature of Salinity

trend, °C/year R2 trend, ‰/year R2

1 Labrador –0.010 0.021 –0.002 0.0112 Labrador 0.036 0.173 0.003 0.0583 Gulf Stream 0.023 0.295 0.001 0.0334 Gulf Stream 0.018 0.066 0.000 0.0005 North Atlantic Current –0.010 0.007 –0.002 0.0186 North Atlantic Current 0.007 0.024 0.001 0.008

Note: Boldface highlights significant estimates of a linear trend at critical magnitude of coefficient of determination (5%) = 0.07.Rcr2

1.00.90.80.70.60.50.40.30.20.1

01 2 3 4 5 6

1 2 Square number

Cor

rela

tion

coe

ffic

ien

t

Fig. 7. Correlation coefficient of weighted water tempera�ture within the 0� to 293�m layer with water temperature atdepth levels of 5 m (1) and 112 m (2) in squares presentedin Fig. 1.

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nal factors in water temperature variability in the sur�face layer plays a key role and achieves 82–83% in theLabrador Current waters.

CONCLUSIONS

Comprehensive processing of the GSNW index,which represents the localization of the northernboundary of the current, indicated that fluctuations inthe monthly mean values of the index are random incharacter for the period of 1966–2010. Even theannual cycle is absent, since its contribution to thevariance of the initial series is as low as 3%. However,the weak annual cycle in intensity is a characteristicfeature of the Gulf Stream. This is corroborated by theestimates of the annual component of water dischargerate for the Florida Current, whose contribution to theinitial variance is less than 10%. It can be stated with suf�ficient confidence that the accident of April 27, 2010, onthe rig in the Gulf of Mexico did not have a significanteffect on the intensity of the Florida Current.

The annual course of values of the GSNW indexclearly exhibits a significant positive trend of 0.03 yr–1

and contributes about 15% to the variance of the initialseries. This points to a northward shift of the GulfStream for the specified period. This trend is superim�posed by fluctuations, the most powerful of which is aquasi�nine�year oscillation contributing about 20% tothe initial variance of the series. Since 1980s, a quasi�five�year cycle with a slightly reduced power (contri�bution of 18%) can be observed.

There was no density trend of the main branch ofthe Labrador Current from 1958 to 2007. Hence, flowintensification of desalinated waters from the Arcticand strengthening of solid (iceberg) and liquid runoffoff Greenland do not lead as yet to a significant reduc�tion in the density of the Labrador Current. At thesame time, the Gulf Stream exhibits an evident ten�dency toward density reduction caused by waterwarming due to global climatic warming. However, thetrend disappears in the source of the North AtlanticCurrent, where the freshened Labrador Currentwaters mix with the Gulf Stream. Certainly, thereinlies the main impact of the Labrador Current on theGulf Stream at present.

Thus, a characteristic feature of the second half ofthe 20th and the beginning of the 21st centuries is thediminishing density of the Gulf Stream due to thewarming of its waters in recent decades and theabsence of a density trend of waters of the main branchof the Labrador Current. In this regard, there is no rea�son to believe that even in the foreseeable future couldthe Labrador Current become equal to the GulfStream in water density.

REFERENCES

1. G. V. Alekseev, B. F. Radionov, E. I. Aleksandrov, et al.,“Climatic changes in Arctic and Northern Polarregion,” Probl. Arkt. Antarkt., No. 1, 67–80 (2011).

2. N. M. Astaf’eva, “Wavelet analysis: basic theory andsome applications,” Fiz. Usp. 39, 1085–1108 (1996).

3. E. I. Baranov, Water Structure and Dynamics of the GulfStream (Gidrometeoizdat, Moscow, 1988) [in Rus�sian].

4. G. I. Baryshevskaya, The Gulf Stream System Currentsand Thermal Regime of the Northern Atlantic (Gidrom�eteoizdat, Moscow, 1990) [in Russian].

5. T. V. Belonenko, The North�Western Part of the PacificOcean. A Study of the Variability of Sea Level in theWater System of the Kuroshio�Oyashio Based on SatelliteAltimetric Information (Lambert Academic Publishing,2010) [in Russian].

6. V. N. Malinin, “Variations of global water exchangeunder changing climate,” Wat. Resour. 36 (1), 12–25(2009).

7. V. N. Malinin, “The Gulf Stream and Climate ofEurope,” O�vo, Sreda, Razvit. (Terra Humana), No. 1,214–220 (2012).

8. V. N. Malinin and S. M. Gordeeva, “About currentglobal air temperature changes,” O�vo, Sreda, Razvit.(Terra Humana), No. 2, 215–221 (2011).

9. H. Stommel, The Gulf Stream: A Physical and Dynami�cal Description (Univ. of California Press, Berkeley,1958).

10. H. L. Bryden, H. R. Longworth, and S. A. Cunning�ham, “Slowing of the Atlantic meridian overturningcirculation at 25° N,” Nature, No. 438, 655–657(2005). doi:10.1038/nature04385.

11. J. A. Carton, B. S. Giese, and S. A. Grodsky, “Sea levelrise and the warming of the oceans in the Simple OceanData Assimilation (SODA) ocean reanalysis,” J. Geo�phys. Res. 110 (9), C09006 (2005).doi:10.1029/2004JC002817.

12. G. de Coëtlogon, C. Frankignoul, M. Bentsen,C. Delon, H. Haak, S. Masina, and A. Pardaens, “Gulfstream variability in five oceanic general circulationmodels,” J. Phys. Oceanogr., No. 36, 2119–2135(2006).

13. S. A. Cunningham, T. Kanzow, D. A. Rayner, et al.,“Temporal variability of the Atlantic Meridional over�turning circulation at 26.5° N,” Science, No. 317, 935(2007). doi:10.1126/science.1141304.

14. H. Hanna, P. Huybrechts, I. Janssens, et al., “Runoffand mass balance of the Greenland ice sheet: 1958–2003,” J. Geophys. Res. 110 (13), D13108 (2005).

15. IPCC. Climate Change 2007: The Physical Science Basis.Intergovernmental Panel on Climate Change FourthAssessment Report Climate Change 2007, Eds. byL. Bernstein, et al. (Cambridge University Press, NewYork, 2007).

16. C. S. Meinen, M. O. Baringer, and R. F. Garcia, “Flor�ida Current transport variability: An analysis of annualand longer period signals,” Deep�Sea Res., Part I 57(7), 835–846 (2010).



17. E. Rignot and P. Kanagaratnam, “Changes in thevelocity structure of the Greenland ice sheet,” Science,No. 311, 986–990 (2006). doi:10.1126/science.

18. R. D. Smith, J. K. Dukowicz, and R. C. Malone, “Par�allel ocean general circulation modeling,” Phys. D(Amsterdam, Neth.), No. 60, 38–61 (1992).

19. A. H. Taylor, Monthly and Annual Means of the 1stPrincipal Component of the Position of the North Wallof the Gulf Stream 1966–2010, Plymouth Marine Lab�oratory, United Kingdom. http://www.pml�gulf�stream.org.uk/2010/Web2010.pdf

20. A. H. Taylor and A. Gangopadhyay, “A simple modelof interannual displacements of the Gulf Stream,” J.Geophys. Res. 106 No. C7, 13849–13860 (2001).

21. A. H. Taylor and J. A. Stephens, “Latitudinal displace�ments of the Gulf Stream and their relation to changesin temperature and zooplankton abundance in the NEAtlantic,” Oceanol. Acta, No. 3, 145–149 (1980).

22. A. H. Taylor and J. A. Stephens, “The North Atlanticoscillation and the latitude of the Gulf Stream,” Tellus,No. 50A, 134–142 (1998).

23. C. Torrence and G. P. Compo, “A practical guide towavelet analysis,” Bull. Am. Meteorol. Soc., No. 79,61–78 (1998).

24. Wavelet Software, University of Colorado, USA. http://paos.colorado.edu/research/wavelets/software.html

25. J. K. Willis, Can in situ floats and satellite altimetersdetect long�term changes in Atlantic Ocean overturn�ing?” Geophys. Res. Lett. 37 (6), L06602 (2010).doi:10.1029/2010GL042372.

26. B. Wouters, D. Chambers, and E. J. O. Schrama,“GRACE observes small�scale mass loss in Green�land,” Geophys. Res. Lett. 35 (20), L20501 (2008).doi:10.1029/2008GL034816.

Translated by G. Karabashev

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Variability of hydrophysical characteristics in the Gulf Stream