2011 - tracing of water masses using a multi isotope approach in the southern indian ocean

8/11/2019 2011 - Tracing of Water Masses Using a Multi Isotope Approach in the Southern Indian Ocean

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Tracing of water masses using a multi isotope approach in the southern Indian Ocean

P.P. Povinec a,,1, R. Breier a, L. Coppola b,2, M. Groening c, C. Jeandel b, A.J.T. Jull d, W.E. Kieser e,3, S.-H. Lee f,1,L. Liong Wee Kwong g, U. Morgenstern h, Y.-H. Park i, Z. Top j

a Comenius University, Faculty of Mathematics, Physics and Informatics, Mlynska dolina F-1, SK-84248 Bratislava, Slovakiab CNRS/CNES/IRD/Universite de Toulouse, Laboratoire d'Etudes en Geophysique et Oceanographie Spatiales, Toulouse, Francec International Atomic Energy Agency, Isotope Hydrology Laboratory, Vienna, Austriad University of Arizona, Departments of Physics and Geosciences, Tucson, AZ 85712-1201, USAe University of Toronto, IsoTrace Laboratory, Toronto, M5S 1A7, Canadaf Korea Research Institute of Standards and Science, Daejeon, Republic of Koreag International Atomic Energy Agency, Marine Environment Laboratories, MC-98000 Monaco,h Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealandi

Musum National d'Histoire Naturelle, LOCEAN/DMPA, F-75231, Paris Francej University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami, USA

a b s t r a c ta r t i c l e i n f o

Article history:

Received 26 July 2010Received in revised form 13 November 2010Accepted 16 November 2010Available online 22 December 2010

Editor: P. DeMenocal

Keywords:

tritiumdeuteriumcarbon-14oxygen-18iodine-129seawaterANTARES IVCrozet BasinIndian Ocean

Anthropogenic radionuclides (3 H,14 C, and 129I) stemmed from nuclear weapons tests were found in 1999 tobe very abundant in the surface of the southern Indian Ocean, comparable to those in the subtropicalNorthwest Pacic Ocean. The observed radionuclide variations with latitude/longitude in the southern IndianOcean are not due to deposition patterns of global fallout, but due to transport of water masses from thewestern Pacic through the Indonesian seas, and different water fronts present in the Crozet Basin of theIndian Ocean. Highradionuclide concentrations observed in the latitudinal belt of 20-40S are associatedwiththe Indian Ocean Subtropical Gyre which acts as a reservoir of radionuclides, maintaining their highconcentrations on a time scale of several decades. 14 C data documents that the southern Indian Ocean is animportant for sink of anthropogenic carbon. The isotopic tracers reveal the evidence of the most intensesurface gradients and presence of several water masses in the southern Indian Ocean, which makes the regionone of the most dynamic places of the World Ocean.

2010 Elsevier B.V. All rights reserved.

1. Introduction

Global fallout radionuclides (e.g. tritium (3 H), radiocarbon (14 C),strontium-90 (90Sr), cesium-137 (137Cs), iodine-129 (129I), americium-241 (241Am), plutonium isotopes (238Pu, 239,240Pu ), etc.,) have beenfound as useful tracers for studyingthe heat and material transport andexchange processes occurring naturally both in the terrestrial (e.g.Houet al., 2009; Levin and Hesshaimer, 2000; Santschi and Schwehr, 2004)and marine environments (e.g. Livingston and Povinec, 2002; Schlosseret al., 1999). Concentrations of these radionuclides in the sea had risen

since 1945 and peaked in the Northern Hemisphere in 1963, after largescale atmospheric nuclear weapons tests carried out in 1961-1962 byformer Soviet Union at Novaya Zemlya (Livingston and Povinec, 2002).In the equatorial Pacic close in fallout from nuclear weapons testscarried out at Bikini and Enewetak Atolls contributed to radionuclideinventories in the Pacic Ocean as well. The major portion of globalfallout deposited in the mid-latitudes of the Northern Hemisphere(UNSCEAR, 2000), in particular, the North-western Pacic due to thecombined effect of higher precipitation and higher stratosphere-troposphere exchange of air(Aoyama et al., 2006). Some of the globalfallout radionuclides (e.g. 3 H, 14 C, 90Sr, 137Cs, 129I) are dissolved inseawater and becomes constituents of seawater, and suitable thereforefor studying transport of water masses in the ocean. On the other handAm and Pu isotopes are more particlereactive (LaRosa et al.,2005), andsuitable for investigation of processes in the water column andsediments. Signicant portions of these radionuclides in the worldocean have accumulated at the seaoor as bottom sediments (Bowenet al., 1980; Hong et al., 1999; Lee et al., 2005; Livingston et al., 2001).

Earth and Planetary Science Letters 302 (2011) 1426

Corresponding author. Tel.: +421 260 295 544; Fax: 421 265 425 882.E-mail address:[email protected](P.P. Povinec).

1 Formerly at the International Atomic Energy Agency, Marine EnvironmentLaboratories, Monaco.

2 Present address: Observatoire Oceanologique de Villefranche-sur-mer, La Darse BP08, 06238 Villefranche-sur-mer, France.

3 Present address: University of Ottawa, Ottawa K1N 6 N5, Canada.

0012-821X/$ see front matter 2010 Elsevier B.V. All rights reserved.

doi:10.1016/j.epsl.2010.11.026

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the Agulhas Front (AF), Subtropical Front (STF) and Subantarctic Front(SAF) converge into a narrow band of 100 to 200 km wide, with sharpacross-front changes in temperature, salinity and oxygen content(Belkin and Gordon, 1996; Park et al., 2002). Strong ocean currentsformed in this area characterizes the southern Indian Ocean as themost dynamic region of the World Ocean.

The dominant current system affecting the circulation in theCrozet Basin is the AF, characterized by warm and saline subtropicalwaters carried by the Agulhas Return Current (ARC). Extendingeastward into the basin, up to 60E, the AF re-circulates to the north,as a part of the southern limb of the anticyclonic IOSG (Park et al.,2002).

The STF forms a boundary between the subtropical surface waterand cooler, fresher subantarctic surface water (Pollard et al., 2002). Itrepresents the northernmost frontal jet that passes through DrakePassage and is generally regarded as circumpolar in extent.

The SAF is located at the northern boundary of the Polar FrontalZone (PFZ), a transition region between the SAF and the Polar Front(PF). North of the SAF, there is a subsurface salinity minimum,associated with the subduction of Antarctic Intermediate Water(AAIW) (Park et al., 1993; Pollard et al., 2007). South of the SAF, thelowest salinity water is in the surface layer. Temperature dominatesthe stratication north of the SAF (Park et al., 1993). The PF is not apart of the ACC main core, but is very close to the Kerguelen Plateau(Fig. 1).

The distribution of tracers in the southern Indian Ocean is

therefore expected to be controlled by the banded structure of thefronts. It has been therefore a great challenge to collect water samplesin such a complex and dynamicregion,and touse isotopic tracers(3 H,14 C, 129I, and stable 2 H and 18O) to investigate movement of watermasses in the frontal zones.

The oceanographic cruise plan (Park et al., 2002) was designedwithin the framework of the French Southern Ocean Joint GlobalOcean Flux Study (SO-JGOFS) with the main objective to quantify thestocks and the export of biogenic particles in relation to the biologicalpump of atmospheric CO2in the Indian sector of the Southern Ocean.The sampling area, characterized with strong physical gradients, waslocated north of the Crozet Basin. This zone was chosen to studybiogeochemical processes in a mesoscale circulation pattern (Coppolaet al., 2006; Lee et al., 2009; Park et al., 2002). Radionuclide sampling

was carried out in subtropical waters inside the IOSG (Sts. 1, 2, 5 and

8), north of STF (St. 7), and south of SAF, (Sts. 3, 4 and 6) with the aimto study distribution of radionuclides within the water fronts.

3. Samples and methods

3.1. Water sampling

Ocean observation and water sampling (January-February 1999)wascarried out on boardof theR/V Marion Dufresne(CNRS) as a part oftheANTArctic RESearch(ANTARES) IV cruise (Coppolaet al.,2004;2006;Park et al., 2002) in the offshore of the northwest of Kerguelen Islandsand east of Crozet Islands between 32- 48S and 51- 70E, in the

conuencezoneoftheAF(Sts.1,2,5and8),STF(St.7),SAF(Sts.3and4)and close to the PF (St. 6) (Fig. 1). The observation on the watertemperature, salinity and dissolved oxygen was reported in Coppolaet al. (2006).

Surface samples for radionuclide analyses were collected about4 m below the sea level using a water pump. Water column samples(Sts. 3, 7 and 8) were collected at different depths using a Rosettesampling system equipped with 12 L Niskin bottles. One litter watersamples were stored separately for 3 H (and stable isotopes), 14 C(poisoned for preventing any biological activity by adding mercurychloride) and 129I analyses in well closed glass bottles. The bottles haddouble plugs to prevent a penetration of air into the water sampleduring storage, which was checked by storage and analysis of IAEAReference Materials, and no differences with time were observed.

Temperature and conductivity/salinity were measured using acommercial CTD mounted on the Rosette sampling system.

3.2. Isotope analyses

3 H was measured either by the 3He ingrowth method (Clarke et al.,1976; Top, 1999) at the University of Miami (USA) or by liquidscintillation spectrometry (after an electrolytic enrichment) at theInstitute of Geological and Nuclear Sciences (Lower Hutt, New Zealand;Morgenstern and Taylor, 2009), and at the Isotope HydrologyLaboratory of the International Atomic Energy Agency (Vienna, Austria;Groening et al., 2009). 3 H concentration is givenin Tritium Unit (1 TU isthe isotopic ratio of one 3 H atom to 1018 protium (1 H) atoms,equivalent to 118 mBq/L of water). The 3He ingrowth method can

measure3

H levels down to 0.01 TU (precision at 1 is around 0.005

Fig. 1.Sampling stations in the southern Indian Ocean during the ANTARES IV expedition. The main hydrographic fronts in the region: Agulhas Front (AF), Subtropical Front (STF),Subantarctic Front (SAF) and Polar Front (PF) are also shown (owing from the west to the east). While at Sts. 1, 2, 4 ,5 and 6 only surface water was collected, at Sts. 3, 7 and 8 full

water column was sampled.

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TU); the liquid scintillation spectrometry after double electrolyticenrichment and special calibration can reach 0.02 TU (Morgensternand Taylor, 2009; Povinec, 2004).

2analyses were done using H2O-Zn reduction (Coleman et al.,1982). 18analyses were performed using the CO2-H2O equilibra-tion procedure described in Epstein and Mayeda (1953). The stableisotopic compositions of hydrogen and oxygen are reported as "delta"() values in parts per thousand (denoted as ) enrichments or

depletions relative to a standard of known composition

Rsample=Rstandard1

103:

The isotopic results are reportedagainst the international standardVSMOW (Vienna Standard Mean Ocean Water) as dened byGonantini (1978). Typical uncertainties at 1 are1 for 2H,and0.1 for 18O. Analyses of H and O stable isotopes of seawaterwere carried out at the Lower Hutt and Vienna laboratories.

14 C was analyzed in dissolved inorganic carbon present inseawater using AMS. The samples were prepared either in theUniversity of Arizona or in IAEA-MEL following the proceduredescribed by Donahue et al. (1990) and Liong Wee Kwong et al.(2004). The CO2sample extracted from seawater was converted into

graphite, which was pressed into a sample target holder, and loadedinto the AMS machine ion source. The graphite sample wasbombarded with Cs+ ions under vacuum, and the sputtered C- ionswere accelerated and analyzed for isotopic composition (Jull et al.,2008). 14 C concentration is given as 14C in , relative to the NIST(National Institute of Standards and Technology, Gaithersburg, USA)14 C oxalic acid standard (Povinec et al., 2004b; Stuiver and Ostlund,1983)

14

C= Fm1 103

whereFm (a fraction of modern carbon)is themeasured AMS14 C/13 C

ratio in a sample normalised to 13CPBD=-25 , as dened byDonahue et al. (1990). The precision of AMS measurements was

around5. The AMS analyses were carried out at the University ofArizona (Jull et al., 2008).

Iodine samples were prepared either in the IsoTrace Laboratory or inIAEA-MELfollowing the procedure described by Povinec et al.(2000). NaIcarrier (2-10 mg)wasaddedto thesample, andafter several stepsAgI wasobtainedwhich was used as a targetfor AMS measurementscarried outinthe IsoTrace Laboratory. The AMS measurements were normalised withrespect to ISOT-2 reference material (129I/127I=(1.1740.022) 10-11).129I results are given in atom/L. The relative precision of AMS measure-ments was around 10 %.

IAEA reference materials (Irish Sea water (IAEA-381, Povinec et al.,2002; Mediterranean Sea water, IAEA-418,Pham et al., 2010) wereanalysed simultaneously with collected samples to ensure highquality of results. This is the rst time that such a suite of radioactive

(3 H, 14 C and 129I) and stable (2 H and 18O) isotope tracers have beenused in an oceanographic study.

4. Results

4.1. Radionuclides

Diagrams of potential temperature versus salinity, and potentialtemperature versus dissolved oxygen (Fig. 2) clearly show thepresence of different water masses in the sampling sites of the CrozetBasin (Fig. 1). Several water masses can be identied: saline NorthAtlantic Deep Water (NADW) was observed at all water prolestations (3, 7 and 8). Antarctic Bottom Water (AABW) occupies thebottom layers, below NADW. Antarctic Intermediate Water (AAIW)

situated above the NADW may be present at stations 7 and 8. Surface

waters are represented either by Subtropical Surface Water (STSW)(St. 7 and 8), or by SASW (St. 3). Further, the potential temperatureversus dissolved oxygen plot revealed another water mass of NorthIndian Deep Water (NIDW), whose oxygen concentration is around4 ml/L (Park et al., 1993).

The observed 3 H,14 C and 129I water proles (Fig. 3,Table 1) showtypical features the concentrations were highest at the surface (orsubsurface at 100-200 m), then gradually decreasing with depth withsharp decreases at 1000-2000 m water depths, and relativelyinvariable with depth in deep and bottom waters. 3 H concentrations(Fig. 3a) were below detection limit (0.02 TU) between 1000 and2500 m at Sts. 7 and 3, however, levels comparable to surface wereobserved at bottom waters at both stations. In contrast to this, St.8 shows by a factor of three higher 3 H levels for the surface waters.The 14 C proles (Fig. 3b) also show a downward transport of bombproduced 14 C to the depth of about 2000 m. The 129I water prolesshown inFig. 3c differ from the tritium ones due to a larger variabilityobserved both at surface and bottom waters.

We calculated the standing stocks of 3 H and 129I which best

represents global fallout radionuclides due to their direct input to the

Fig. 2.Diagrams of T-S and T-O2for Stations 3, 7 and 8 in the southern Indian Ocean(sampling sites as inFig. 1). Water masses: STSW - Subtropical Surface Water; SASW Subantarctic Surface Water; AASW Antarctic Surface Water; AABW AntarcticBottom Water; AAIW Antarctic intermediate water; NADW North Atlantic DeepWater; NIDW - North Indian Deep Water.

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sea. Thestanding stocks of3 H inthe upper 1 km3 of thewater columnin theIOSGW (St. 8) were 140 10 GBq, much higherthan in STSW ofSt. 7 (40 5 GBq) and in SASWof St. 3 (24 4 GBq). In the case of129Ithe standing stocks were much smaller, and the differences betweenthe stations were within the uncertainties: 112 kBq for St. 8, then9 2 kBq for St. 7 and 8 2 kBq for St. 3.

3 H, 14 C, and 129I concentrations observed in the western NorthPacic in 1997 during the IAEA97 expedition (Povinec et al., 2003a;

Povinec et al., 2010),andin the EastSea(theSeaof Japan)(Cooper et al.,2001) are comparable with the ANTARES IV data in the southern IndianOcean (Sts. 2,5 and 8, Fig. 3). The Pacic andIndian Ocean prolesshowsimilar features a surface (or subsurface at 100-200 m) maxima, asharpdecrease toward 1000 m, andnegligible levels in deepand bottomwaters.

4.2. Stable isotopes

In addition to physical oceanography parameters and radio-nuclides, also stable isotopes of water have been included in ouranalyses with the aim of better understanding the characteristics ofthe various water fronts present in the Crozet Basin. The subtropicalwaters inside the IOSG (Sts. 8, 1, 2, 5) appeared to be enriched with18O, with high salinity in thesurface andgradual depletion of18O withgradually freshening toward the depth. SASW (St.3) were mostdepleted with 18O and the most fresh among the water massespresent (Fig. 4a). Coefcient of determination, R2=0. 86 (P valueb0.0001), indicates that there is a strong correlation between 18Oand salinity.

While surface waters collected at Sts. 2, 5 and 8, located close to themain stream of the IOSG, were enriched in deuterium and oxygen,representing warmer and saltier subtropical waters, the southern St. 7(STF), and especially Sts. 3, 4 and 6 were depleted in both isotopes(Table 1), representing thus fresher, cooler and less saline PFZ watermasses (Fig. 4b). All experimental data are well below the GlobalMeteoric Water Line (GMWL) dened byCraig (1961), documentingheavy depletion of both isotopes in seawater. In the subtropical oceanthe evaporation dominates over precipitation, while at higher latitudes

the precipitation becomes higher than the evaporation (LeGrande andSchmidt, 2006). This effect is clearly visible in the 2H vs. 18O diagrampresented inFig. 4b which shows a typical correlation between thesetwo isotopes.

Tritium versus 18O, and 129I vs. dissolved oxygen diagramspresented inFig. 5also revealed presence of different water masses inthe Crozet Basin. Elevated3 H and 129I concentrations were observed atSt. 8 in surface, medium depth and bottom waters, while at Sts. 3 and 7only bottom waters showed higher concentrations.

5. Discussion

5.1. Radionuclide proles

Following the global atmospheric deposition, higher surface radio-nuclide concentrations are expected for the Northern Hemisphere thanin the Southern Hemisphere. The peak value in the SouthernHemisphere at 50S observed in 1965-1967 was only 4 % of thatobserved in 1963 for the same Northern Hemisphere latitude, withdecreasing values towards both the Equator and the South Pole (Weissand Roether, 1980). In 1998 the average 3 H value observed in thenorthern Indian Ocean at 20N was 1.0TU (Mulsow et al., 2003; Povinecet al., 2003b). Following the Weiss and Roether (1980) estimation of thedevelopment of the mean tritium concentration in the open ocean withtime, the expected value in 1998-1999 for the 40S latitude would be60% of that observed for 20N, it means only 0.6.

It is clear that the observed3 H levels, combined with WOCE data(decay corrected to 1999), do not follow this pattern (Fig. 6a). As

there is not an additional sourceof3

H in the Indian Ocean (Livingston

Fig. 3. 3H (a), 14 C (b) and 129I (c) water proles atSts. 3.7 and 8 comparedwith nearestGEOSECS (stlund and Brescher, 1982; Stuiver and stlund, 1983) and WOCE (www.eWOCE.org) stations. 3 H, 14 C and 129I obtained for the NW Pacic (IAEA97 cruise;Povinec et al., 2004b; Povinec et al., 2010) are also shown. 3 H data were decaycorrected to January 1999 with half-life of 12.32 y. 3 H concentration is given in TritiumUnit (1 TU is the isotopic ratio of 1 3 H atom to1018 protium (1 H) atoms, equivalent to118 mBq/L of water). 14 C concentration is given as14C in , relative to the NIST 14 Cstandard (Stuiver and stlund, 1983). Relative precisions (at 1 ) are ~2 % for3 H, ~0.5% for 14 C and ~10 % for 129I. For positions of sampling stations seeFig. 1.

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and Povinec;Povinec et al., 2003b), high surface 3 H concentrationsobserved at Sts. 2, 5 and 8 (1.1 TU for the latitude belt 40S 43S,Table 1) should be associated with a radionuclide transport from thewestern Pacic Ocean, where high 3 H concentrations were observed(Povinec et al., 2010).

The average 3 H concentration observed in the top 200 m at St. 8 is1.3 TU, what is close to the value (1.6 TU, decay corrected 1999)observed in 1973 at GEOSECS stations 228 and 229 in the NW Pacic(stlund and Brescher, 1982). 3 H levels in subsurface maxima in the

NW Pacic, sampled in 1997 (Povinec et al., 2010), were between 1.3and 1.4 TU (Fig. 3a), again in very good agreement with datameasured for St. 8.

Some 107 m3/s of seawater ows from the western Pacic Oceanvia the Indonesian throughow into the Indian Ocean (Gordon et al.,2003). About 50% of it is transported to the Crozet Basin, and the restleaks to the South Atlantic (Speich et al., 2007). Using a simple massbalance approach we may estimate that the time needed to transportwaters from the western Pacic to the Crozet Basin is around 13 years,comparable with the 3 H half-life. A similar value has been obtainedfrom direct oat measurements (Davis, 2005). The oat data (Davis,2005) also indicate that about 10 years is needed to complete oneloop in the IOSG (Fig. 1). This would mean that 3 H decayed in theIOSG waters is renewed by fresh3 H water coming from the western

Pacic Ocean which acts as a tritium source for the Indian Ocean due

to higher fallout levels found in the western North Pacic Ocean(Aoyama et al., 2006; Povinec et al., 2010).

In general, the bulk of 3 H in the water column (Fig. 3a) shouldexist near surface due to the atmospheric input. Assuming no specicsources for 3 H in the study area, the existence of higher 3 Hconcentrations in the bottom layer could be related to an intrusionof surface water. In the study area, however, there is no informationabout sinking of surface water to the bottom due to strongthermohaline stratication. You (2000) reported that only a small

net transport of 0.5 Sv occurred across the lower intermediate layerdownward. The great difference (10 times more) in the watertransport across the upper layer than across the lower layer gives astrong implication for the advection of AABW to the region withelevated 3 H levels, as discussed later.

Radiocarbon water proles presented in Fig. 3b show featuresexpected for the southern Indian Ocean. Radiocarbon is behavingdifferently in the water column due to exchange processes with theatmosphere (Aramaki et al., 2001; Bard et al., 1988; Stuiver andOstlund, 1983). The 14 C proles shown inFig. 3b reect the differentpositionsof water fronts, similarly as it was in thecase of tritium. Peak14 C levels observed at St. 8 are comparable with those observed in theNW Pacic (IAEA97 Sts. 2 and 3;Povinec et al., 2004b), as well as atthe close-by GEOSECS (Stuiver and Ostlund, 1983) and WOCE stations

(Key et al., 2002).

Table 1

Oceanographic and isotope data of collected seawater samples in Crozet Basin (January-February 1999).

Station Position Depth Temperature Salinity 2H* 18O* 3 H 14 C* 129I

(m) (C) () () (TU) () (108 atom/L)

1 3242.19'S 7000.00'E 4 19.05 35.619 0.3 0.57 0.72 0.03 101.2 -2 4017.98'S 7000.00'E 4 17.01 35.177 0.3 0.34 0.93 0.03 108.3 -4 4551.32'S 5500.00'E 4 9.86 33.684 -5.8 -0.49 0.32 0.02 32.54 -5 4000.00'S 5157.27'E 4 19.55 35.533 0.2 0.47 1.10 0.03 110.5 -6 4800.00'S 6838.50'E 4 9.90 33.640 -6.1 -0.46 0.18 0.02 23.52 -3 4600.03'S 6303.58'E 6 9.53 33.6981 -5.2 -0.37 0.242 0.017 26.40 0.066 0.009

50 9.54 33.7001 -5.7 -0.57 0.197 0.019 43.60 0.058 0.008100 6.01 33.8346 -2.4 -0.37 0.279 0.023 31.30 0.062 0.009150 5.22 33.8800 -2.9 -0.30 0.227 0.022 -26.80 0.105 0.010300 5.00 34.2135 -3.1 -0.26 0.241 0.020 -60.20 0.061 0.009500 3.93 34.2484 -4.0 -0.21 0.178 0.010 -100.00 0.060 0.006

1000 2.95 34.4709 -4.5 -0.25 b0.02 -147.30 0.013 0.0081500 2.48 34.6666 -4.9 -0.24 b0.02 - 0.058 0.0082000 2.24 34.7527 -4.4 -0.26 b0.02 -145.20 0.053 0.0072500 1.84 34.7621 -4.6 -0.20 b0.02 .150.30 0.033 0.0063500 0.85 34.7080 -2.9 -0.17 0.289 0.022 - 0.062 0.0084300 0.47 34.6857 -2.7 -0.19 0.302 0.024 -162.00 0.050 0.005

7 4411.45'S 6324.45'E 6 14.30 34.3431 -3.3 -0.09 0.399 0.024 62.00 0.060 0.00750 13.53 34.3513 -3.8 0.08 0.433 0.022 - 0.077 0.009

100 12.37 34.9364 -2.7 0.20 0.534 0.025 - 0.080 0.009150 11.49 34.8774 -3.3 0.26 0.524 0.022 51.30 0.114 0.009300 10.50 34.7880 -4.4 -0.09 0.493 0.023 25.10 0.059 0.007

500 8.38 34.5982 -3.8 -0.12 0.158 0.010 -26.70 0.058 0.0081000 3.73 34.3584 -4.5 -0.20 b0.02 -149.30 0.026 0.0061500 2.82 34.5739 -4.8 -0.27 b0.02 -150.90 0.042 0.0092500 2.14 34.7600 -4.9 -0.20 b0.02 -144.90 0.046 0.0123500 1.22 34.7260 - - - -150.16 0.039 0.0094300 0.49 34.6850 -2.5 -0.15 0.302 0.024 -156.40 0.042 0.022

8 4308.03'S 6231.42'E 6 17.40 35.5319 2.7 0.56 1.23 0.03 - 0.079 0.01250 17.53 35.5244 -0.1 0.33 1.25 0.03 - 0.082 0.008

100 15.69 35.4892 -1.2 0.20 1.42 0.03 101.20 0.0790.008200 14.77 35.4557 1.2 0.22 1.35 0.03 98.50 0.152 0.014500 13.14 35.2852 -1.3 0.10 1.29 0.02 10.70 0.055 0.007

1000 7.34 34.5270 -2.0 -0.18 0.75 0.02 -100.300 0.033 0.0051500 3.55 34.4122 -3.0 -0.20 0.64 0.02 -125.000 0.075 0.0082000 2.72 34.6225 -3.3 -0.27 0.28 0.01 -150.100 0.045 0.0062500 2.44 34.7330 -2.9 -0.20 0.54 0.01 - 0.077 0.0083000 2.09 34.7612 - - - - 0.081 0.0094000 1.12 34.7184 -2.7 -0.17 0.37 0.03 -162.200 0.034 0.008

5000 0.44 34.6786 -2.6 -0.15 0.39 0.03 - 0.055 0.006* Uncertainty at 1is1 for 2H, 0.1 for 18O and 5 for 14 C.



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Iodine-129 water proles shown inFig. 3c have minima at 1000 mwater depth at all ANTARES IV samples which may be associated withthe presence of NADW carrying low 129I levels. An interesting featureis that 129I levels in the top 1000 m are by about a factor of two lowerin the IOSGW (St. 8) than in the NW Pacic samples (Sts. 2 and 3 inFig. 3c). Thiscan bedue tothe factthat the Pacic stations were under

the inuence of the Kuroshio Current, which carried higher 129I levelsreleased from the Tokai-mura reprocessing facility (Livingston andPovinec, 2000; Povinec et al., 2010), while the IOSG St. 8 show globalfallout 129I concentrations.

The differences between the 3 H and 129I levels observed in theIOSGW and in NW Pacic waters may indicate that a source of theseradionuclides need not be only NW Pacic. Surface Tasman watersmay ow northward along the Australian coast (Ridgway and Dunn,2007), and supply IOSGW via the Indonesian Throughow withelevated 3 H levels (around 1.2 TU) observed in the Tasman Sea(www.eWOCE.org). A similar connection has been observed betweenthe SHOTS (Southern Hemisphere Ocean Tracer Study) 137Cs datacollected along 20S in the Indian Ocean (Povinec et al., submitted forpublication), and along 30S in the Pacic Ocean (Aoyama et al.,

submitted for publication). However, the observed3

H concentrations

in the Tasman Sea are only of global fallout origin (unfortunately no129I data are available), which have been accumulating in the westernpart of the Pacic Ocean Subtropica Gyre (Mittelstaedt et al., 1999;Nakano and Povinec, 2003). Therefore the 129I levels in the IOSGWshould be lower than in NW Pacic waters, where they wereinuenced by radioactive waste discharges from the Tokai-murareprocessing plant.

5.2. Spatial distribution of radionuclides

5.2.1. Tritium

Surface water samples collected in 1998 as a part of the IndianOcean transect (Povinec et al., 2003b) also showed higher 3 H levelsaround 30S, comparable with those presented inFig. 6a. High surface3 H levels (0.6-0.7 TU, decay corrected to 1999) were also measured at34S, 57- 62E during the WOCE project. This is consistent with 3 Hconcentration observed at St. 1 (0.720.03 TU at 3242S, 7000E;Table 1), located inside the loop formed by the IOSG. High surface 3 Hlevels (1.1-1.2 TU), observed at Sts. 2, 5 and 8 (located between 40and43S),suggestthatthese stationswereclose to the main stream ofthe IOSG. It is evident that the gyre ow is strongest at 40-43S, west

of 65E, where highest 3

H levels were observed. This is a clear

33.0 33.5 34.0 34.5 35.0 35.5 36.0-0.6

-0.4

-0.2

-0.0

0.2

0.4

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St. 8

St. 7

St. 3

St. 1

St. 2

St. 6

St. 4

St. 5

Salinity

181

/

188(

/)

/

-0.9 -0.7 -0.5 -0.3 -0.1 0.1 0.3 0.5-7

-5

-3

-1

1

3

5

7

9

11

St. 8

St. 7

St. 3

St. 1

St. 2

St. 6

St. 4

St. 5

GMWL

a

b

Fig. 4. 18O vs.salinity (a)and 2H vs. 18O (b)plots for allstationsvisited. 2Hand 18Oare expressed in per mill relative to VSMOW (Vienna Standard Mean Ocean Water).

Relative precisions (at 1 ) are 1 for 2H, and 0.1 for 18O. Coefcient ofdetermination, R2=0. 86 (P valueb0.0001), indicates that there is a strong correlationbetween18O and salinity. All experimental data are well below the Global MeteoricWater Line (GMWL) dened byCraig (1961), documenting heavy depletion of bothisotopes in seawater. Sts 1, 2, 4, 5 and 6 are surface water samples, at Sts. 3, 7 and 8 fullwater column was sampled. For positions of sampling stations seeFig. 1.

-0.6 -0.5 -0.4 -0.3 -0.2 -0.1 -0.0 0.1 0.2 0.3 0.4 0.5 0.60.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

St. 8

St. 7

St. 3

St. 1

St. 2

St. 6

St. 4

St. 5

AAIWNADW

AABWSASW

STSW

IOSGW

NIDW

3

H(TU)

3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.00.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

St. 8

St. 7

St. 3

6

50

1500

3000

100

2500

200

5000

500

10004000

2000

300

150

6 10050500 6

50

150

100

300500

IOSGW

STSWSASW

1000

150043002500

1000

3500

4300

AABW

2500

20001500

AAIW

NIDW+NADW

Oxygen (mL/L)

129I(108a

tom/L)

188

(

/

)

a

b

Fig. 5. 3H vs. 18O (a) and 129I vs. dissolved oxygen (b) plots for collected samplesshowing different water masses in the region. IOSGW- Indian Ocean Subtropical GyreWater, STSW Subtropical Surface Water, SASW- Subantarctic Surface Water, AAIWAntarctic Intermediate Water, NADW North Atlantic Deep Water; NIDW NorthIndian Deep Water, AABW Antarctic Bottom Water. Water depths in meters are alsoshown in the plot (b). Sts 1, 2, 4, 5 and 6 are surface water samples, and at Sts. 3, 7 and8 full water column was sampled. For positions of sampling stations seeFig. 1.

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inuence of the IOSG on the downstream radionuclide transport fromits western boundary associated with the Agulhas Retroection

(Ridgway and Dunn, 2007).

The atmospheric deposition of global fallout tritium in the SouthernHemisphere was highest during the late sixties in the latitude belt 40-

50S (International Atomic Energy, 2005; Weiss and Roether, 1980).

Fig. 6. Spatial distribution of3 H in surface waters (a) and deep waters (along 60E) (b) at Sts. 1- 8 (x-signs), combined with nearest WOCE stations (dots) (www.eWOCE.org), decaycorrected to January 1999. Higher 3 H concentrations were observed atthe main stream of the Indian Ocean Subtropical Gyre at ~40S (as well as at ~20S, as indicated by the WOCEdata). Downward tritium transport around 40S can be seen as well. Higher 3 H levels observed below 3000 m are associated with Antarctic Bottom Water (AABW).

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However, 3 H water proles across the basin (Fig. 6b), combined withWOCE data(www.eWOCE.org) south of 34S (decay correctedto 1999),show higher surface and subsurface 3 H levels at 20S and 40S latitude

belts. This indicates an accumulation of tritium within the IOSG on atime scale of several decades. The gyre acts as a reservoir, maintaininghigher radionuclide concentrations in the region. Simultaneously,

Fig. 7. Spatial distribution of14 C in surface waters(a) anddeepwaters (along60E)(b) at Sts. 1- 8 (x-signs),combined with nearest WOCE stations (dots) (www.eWOCE.org). Higher14 C concentrations were observed at the main stream of the Indian Ocean Subtropical Gyre at ~40S (as well as at ~20S, as indicated by the WOCE data). Downward 14 C transport

around 40S can be seen as well.

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higher tritium levels can be seen in thetransectaround 40S and60Eatwater depths below 3000 m which should be due the advection ofAABW.

5.2.2. RadiocarbonCombining the 14 C data presented in this work together with

WOCE data (www.eWOCE.org) we constructed a 14 C distributionmap for the southern Indian Ocean (Fig. 7a). We can see high 14 C

concentrations observed along the subtropical gyre (20 - 40S) at thetop 500 m, and sharp decrease south of 40S, as conrmed by 3 H dataas well (Figs. 3 and 6).

14 C water prole data (WOCE and ANTARES IV) presented inFig. 7b show a clear penetration of bomb14 C around 40S (transect at60E) down to almost 5000 m (similarly as we could see it in the caseof tritium,Fig 6b).Fig. 7documents that the southern Indian Ocean isimportant for sink of anthropogenic carbon. The high phytoplanktonbiomass in the region of the Kerguelen Plateau and the Crozet Islandsand Plateau was found to be fueled by the natural iron inputs fromshallow topography close to islands (Pollard et al., 2009).

5.3. Water masses

The isotopic observations (Fig. 3and especiallyFigs. 5, 6 and 7)show the presence of different water masses in the Crozet Basin moreclearly than the conventional water mass tracers of potentialtemperature and salinity/dissolved oxygen presented in Fig. 2. 3 Hconcentrations largely decrease below the 1000 m water depth atwhich CDW (Circumpolar Deep Water) appears, formed by the deep-water circulation and ventilation south of 40S (Fine, 1993; You,2000). The depletion of 3 H in the CDW in the STF and SAF fronts(Stations 3 and 7, water depth 1000 2500 m) may be related to theintrusion of NADW especially to LCDW (Lower CDW), characterizedby salinity maximum (Fig. 2a). NADW injects its water into the CDWin the south Atlantic by mixing and entrainment, and then ows intothe southwest Indian Ocean, south of Africa between 35S and 40S.One branch of NADW then moves to the Southwest Indian Ridge(Toole and Warren,1993). Considering very low 3 H concentrations (5

to 24 mTU) observed in the South Atlantic bottom water (Jenkinset al., 1983), which is predominantly affected by the NADW, andtaking into account the replenishment of the CDW by lateral transportof the NADW from the South Atlantic to the South Indian Ocean on atime scale of 4-10 years, the contribution of the NADW to the CDWmay explain the observed 3 H minima.

Except for the AF, STF and SAF, which control radionuclidedistribution in surface and subsurface waters, several other watermasses can be identied in the basin using isotopes (Fig. 5a, b). Theintermediate layer (300-500 m) with relatively low 3 H levelsrepresent AAIW, which is best characterized by a minimum in salinity(Fig. 2a). There are differences in AAIW depths because the stationsare distributed across the ACC whose strong currents make theisopycnals inclined vertically due to geostrophic equilibrium princi-

pal. In the southern Indian Ocean, the isopycnals along which watermasses move become deeper when going to the equator, butshallower when going to the pole (Park et al., 1993). So, theshallowest depth of AAIW at St. 3 (300 m) and the deepest depth atSt. 8 (500 m) are entirely consistent with the geostropic dynamics.

However, the elevated 3 H levels observed at St. 8 at water depths1500 and 2500 m (Fig. 3a) indicate the presence of other watermasses (Fig. 5a). It is known that the NIDW, which is characterized bya deep oxygen minimum (Fig. 2b), exists in the Crozet Basin (Parket al., 1993). This would explain higher 3 H concentrations observed indeep waters at St. 8, as the NIDW originates from the northern IndianOcean where comparable 3 H levels were observed (Mulsow et al.,2003; Povinec et al., 2003b). There may also be at St. 8 a contributionfrom the advection via the Agulhas Current system of the deep water

coming from the Indonesian Throughow region, where deep tidal

mixing could incorporate the tritium-rich Pacic water. Lower 3 Hlevels found at 2000 m water depth may be due to intrusion of NADWcarrying low radionuclide concentrations.

Measurable 3 H concentrations were also observed in bottomwaters at Sts. 3, 7 and 8 (Fig. 3a), as well as at the WOCE stations at34S (www.eWOCE.org). As sinking of surface water to the bottom atmid-latitudes is impossible due to strong thermohaline stratication(You, 2000), an injection of AABW might be considered as the most

plausible source of

3

H (and low levels of

129

I, Fig. 3c) in bottomwaters. In fact, below the CDW, the salinity and temperaturedecrease,but oxygen increases sharply to the bottom,indicating the presence ofthe AABW (Park et al., 1993). A major formation area of the AABW isthe Weddell Sea, where it is produced by sinking of cold, dense shelfwaters (Rahmstorf, 2002). The AABW then ows around the ConradRise and enters the Crozet Basin through the Crozet-Kerguelen Gap(Park et al., 1993). Weddell Sea waters showed in 1975-76 3 H levelsof 1 TU for surface and 0.5-0.7 TU for bottom waters ( Michel, 1978).This is in agreement with our recent analysis of 3 H in seawatersamples collected in 2003 at depths of 100-200 m in the Weddell andRoss Seas (0.4-0.5 TU). The transit time of surface water from theWeddell Sea to deep waters in the Crozet-Kerguelen Gap wasestimated using CFCs as 23 5 years (Haine et al., 1998). Hence, 1TU observed in 1975-76 in Weddell Sea surface water may become0.27 TU in 1999 in deep waters in the southern Indian Ocean, which isconsistent with 3 H levels found in bottom waters at Sts. 3, 7 and 8. Asthe NADW has very low 3 H concentrations, and the NIDW is locatedwell above the bottom layer, the only plausible explanation for higher3 H levels found in bottom waters is the presence of the AABW. This isalso supported by the stable isotope data as the AABW should bedepleted both in 2 H and 18O in comparison with surface waters, asshown inFig. 4b.

The 129I data (Fig. 3c) have also been used for the identication ofwatermasses present in the Crozet Basin. The results plotted in Fig. 5basthe 129I concentration vs. dissolved oxygen showthe presence of allwater masses as identied inFig. 5a with 3 H data. The surface watersrepresenting fronts (AF, STF and SAF) have highest 129I concentra-tions. The intermediate waters, represented by AAIW, show very

similar 129I concentrations, thus eliminating the differences observedin the surface layer. The same is true for the deep and bottom waters.Higher 129I levels observed at St. 8 at 1500 and 2500 m water depthsare probablydue to the presenceof NIDW. Thelowest129I levels foundat 1000 m water depth may be due to intrusion of NADW carrying lowradionuclide concentrations. The separation of NIDW from NADW is,however, not so clear as it was presented in the case of3 H(Fig. 5a).Low, but measurable 129I levels were found at bottom waters whichcould be attributed to AABW.

5.4. Radionuclide inventories

The inventory of a radionuclide in a seawater column is calculatedby interpolating the radionuclide concentration measured at each

depth:

IR=12

N

i = 1Wi +1 + Wi

di +1di

+ 2W1d1+ 2WN dBdN

( );

whereIRis the inventory of the radionuclideRin the seawater column(Bq/m2), N is the number of sampling depths, Wi is the radionuclideconcentration in seawater at depth i, di is the i-th sampling depth ofseawater, and dB is the totalwaterdepth to the bottom. The inventoriesaregiven in Bq/m2 (for 3 H:1 TU= 0.118 kBq/m3,andfor 129I:106 atom/L=1.4 Bq/m3).

Under normal conditions the radionuclide water column inven-tories should primarily depend on the geographical position of the

sampling station, especially on its latitude. In this case the dominant

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factor affecting the radionuclide water column inventories wouldbe global fallout. However, in the subtropical part of the IndianOcean a continuous transport of global fallout radionuclides fromthe central western Pacic via the Indonesian Seas, and its accu-mulation in the subtropical gyre should increase their inventoriesin the gyre. We shall focus on the evaluation of 3 H and 129I watercolumn inventories as these radionuclides have had similar inputfunctions to the ocean, as well as very similar behavior in the

water column, and at least for

3

H the data can be compared withGEOSECS and WOCE results. These radionuclides could be thereforeuseful for characterization of water masses and their transport inthe region.

The highesttotal 3 H inventory (330 30 kBq/m2) was observed atSt. 8 (430S; 6232E), situated close to the southern gyre stream. Incontrast, the Sts. 3 and 7 situated more south showed lower 3 Hinventories (around 60 kBq/m2). This difference in the 3 H inventoriesis mainly caused by differences in water fronts present in the region.The 3 H inventories in top 500 m for SASW (St. 3) and STSW (St. 7)were 13 1 kBq/m2 and 25 2 kBq/m2, respectively, when comparedwith 78 8 kBq/m2 observed forIOSGW (St. 8). A similar trendcan bealso seen for AAIW: at Sts. 3 and 7 the 3 H inventories were 101 kBq/m2 and 12 1 kBq/m2, respectively, while the inventory at St.8 was 591 kBq/m2. The bottom waters at all three stations wereunder the inuence of AABW showing similar 3 H inventories: 141 kBq/m2 for St. 3 and 7, and 182 kBq/m2 for St. 8.

The 3 H inventories estimated for the Crozet Basin can becompared with WOCE (www.eWOCE.org) and GEOSECS (stlundand Brescher, 1982) data, although their sampling sites were not closeto theANTARES IV ones.The WOCEtransect I5P in the southern IndianOcean (1998) with sampling St. 35 (33S, 48E), St. 39 (34S, 53E), St.44 (34S, 57E) and St. 50 (34S, 62E) showed 3 H inventories byabout a factor of 2 lower than that observed at St. 8. This is areasonable result as all WOCE stations were inside the IOSG loop,similarly as St. 1, which showed the surface 3 H concentrationcomparable with the WOCE stations. The GEOSECS (1978) samplingSt. 428 (38S, 58E; 1300 m water depth) located inside the IOSG loop(the closest station to St. 8) showed 3 H inventory of 556 kBq/m2

(data were decay corrected to 1999), what is lower than the inventoryobserved at St. 8 (for the same water depth), situated, however, at43S on the main IOSG loop.

The estimated 3 H inventories in the southern Indian Ocean arehigher at least bya factor of threethanexpected from globalfallout forsimilar latitude belts. They are also higher than 3 H inventoriesestimated for the northern Indian Ocean (Mulsow et al., 2003), andcomparable (for the normalized water depth of 1000 m) with 3 Hinventories in the western Pacic (Povinec et al., 2010). The 3 Hinventories conrm again our hypothesis that there must be anadditional source of tritium (as documented by ANTARES IV andWOCE data), which keeps its inventory in IOSGW high.

129I inventories in thewater column of theCrozet Basin show similarfeaturesas the3 H inventories,i.e.a higherinventoryat St.8 (0.42 0.08

mBq/m2), and smaller inventories at Sts. 3 and 7 (0.300.06 mBq/m2and 0.310.06 mBq/m2, respectively). Unfortunately, there are nomore data available for 129I in the water column of the southern IndianOcean. Therefore, the only comparison we can do is with129I data fromthe IAEA97 cruise in the NW Pacic Ocean(Povinec et al., 2010). The129I inventories at Sts. 2 and 3 in the NW Pacic Ocean (38 4 mBq/m2

and 515 mBq/m2, respectively) are about two orders of magnitudehigher than the inventory at St. 8. The difference is, as we alreadypointedout,dueto 129I releasesfrom theTokai-mura reprocessing plant.

The estimated radionuclide inventories conrm the unique role ofthe IOSG accumulating high inventories of radionuclides in thesouthern Indian Ocean. We can expect that the same is true forother radionuclides (e.g. for cesium (Povinec et al., submitted forpublication), heavy metals and organic compounds which are

dissolved in seawater and behave similarly as iodine.

5.5. Isotope activity ratios

We shall compare isotope activity ratios of3 Hand 129I inthe watercolumn. As these radionuclides have similar input functions to theocean, and similar behavior in the water column (however, verydifferent half-lives - 12.32 y vs. 15.7 My), their activity ratios shouldhelp to differentiate between water masses present in the region.

3 H/129I activity ratios in surface waters (b100 m) of Sts. 3, 7 and

8 are (3.2 0.5)10

6

, (5.30.8)x10

6

and (13.7 2.1)10

6

, respectively,documenting a presence of different water fronts in the region (SAF,STF and AF, respectively). While at 1000 m water depth of Sts. 3 and 7we could report only limits (b0.8x106), St. 8 shows the highest ratio(193)106, associated with 129I minimum. Waters in the depthinterval of 1500-2500 shows measurable 3 H/129I ratio (61)106 onlyat St. 8, associated with NIDW, while for Sts. 3 and 7 we can reportonly limit (b0.3x106), associated with NADW. Bottom watersassociated with AABW show comparable ratios from (41)106 (forSt. 3) to (6 1)106 (for St. 8).

We can also compare 3 H/90Sr activity ratios in surface waters ofthe Crozet Basin where 90Sr (half-life 28.78 y) data are available (Leeet al., 2009). While IOSG Sts. 2, 5 and 8 show comparable activityratios (13020, 110 15, and 130 20, respectively), St. 1 locatedinthe IOSG loop shows a lower ratio (749). The STF St. 7 gives theratio of 8913 and Sts. 3, 4 and 6 of SAF show the ratios of 18030,290 50 and 300 140, respectively. The differences are mainly dueto lower 90Sr concentrations observed at the SAF stations, however,they are not signicant as the precision of 90Sr measurements waslower (Lee et al., 2009) than of the 3 H measurements.

6. Conclusions

Several observations have been made in this study which can besummarized as follows:

(i) By comparing observed radionuclide (3 H, 14 C, and 129I) levelsin the southern Indian Ocean with those found in the westernPacic Ocean it has been found that they are of common origin

due to the transport of water masses from the western Paci

cvia the Indonesian Seas to the southern Indian Ocean.(ii) The radionuclide variations with latitude observed in the Indian

Ocean are not due to the latitudinal atmospheric depositionpatterns of global fallout, but due to the redistribution ofradionuclides by ocean currents and mixing and spatial con-straints given by different water masses present in the region.

(iii) High radionuclide concentrations observedin theIndian Ocean inthe latitudinal belt of 20-40S are associated with Indian OceanSubtropical Gyre which acts as a reservoir of radionuclides.

(iv) High 14 C levels observed in bottom waters for transect around40S and 60E document that the southern Indian Ocean isimportant for sink of anthropogenic carbon.

(v) While latitudinal (32 - 48S) variations of anthropogenicradionuclides in surface waters (b300 m deep) are attributableto different fronts tightly concentrated in the Crozet Basin, theintermediate layer (300-1000 m) is inuenced by the AAIW,the deep waters (1000-3000 m) by the NADW and NIDW, andthe bottom waters (N3000 m) by the AABW. As a consequence,the AAIW, NADW, NIDW and AABW eliminate the differencesobserved in the surface layer characterized by the AF, STF andSAF.

The southern Indian Ocean appears to have been acting on a timescale of several decades as a nal reservoir of contaminantstransported from the northern Indian Ocean and central westernPacic Ocean. This has strong environmental consequences for theprotection of the marine environment against a contamination fromthe land-based sources. The observed distribution of isotopic tracers

in the Crozet Basin reects the complex dynamics and advection of

http://www.ewoce.org/http://www.ewoce.org/


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different water masses, which makes the basin one of the mostinteresting oceanographic places in the World Ocean.

Acknowledgments

Colleagues participating in water sampling, and the Captain andthe crew of the R/V Marion Dufresne are acknowledged for theirassistance during the ANTARES IV expedition. The authors thank

Isabelle Durand for the frontal analysis, as well as the Editor and twoanonymous reviewers for constructive comments. This work wascarried out in the framework of the IAEA international projectWorldwide Marine Radioactivity Studies (WOMARS). The Interna-tional Atomic Energy Agency is grateful to the Government of thePrincipality of Monaco for support provided to its Marine Environ-ment Laboratories. PPP acknowledges support provided by the SlovakScientic Agency VEGA (grant No. 1/108/08) and the EU Research &Development Operational Program funded by the ERDF (project No.26240220004).

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