FN Archimer Export Format PT J TI Tracing water masses with 129I and 236U in the subpolar North Atlantic along the GEOTRACES GA01 section BT AF CASTRILLEJO, Maxi CASACUBERTA, Nuria CHRISTL, Marcus VOCKENHUBER, Christof SYNAL, Hans-Arno GARCIA-IBANEZ, Maribel LHERMINIER, Pascale SARTHOU, Geraldine GARCIA-ORELLANA, Jordi MASQUE, Pere AS 1:1,2;2:1,3;3:1;4:1;5:1;6:4,5;7:6;8:7;9:2,8;10:2,8,9; FF 1:;2:;3:;4:;5:;6:;7:PDG-ODE-LOPS-OH;8:;9:;10:; C1 Swiss Fed Inst Technol, Lab Ion Beam Phys, Otto Stern Weg 5, CH-8093 Zurich, Switzerland. Univ Autonoma Barcelona, Inst Ciencia & Tecnol Ambientals, Bellaterra 08193, Spain. Swiss Fed Inst Technol, Environm Phys, Inst Biogeochem & Pollutant Dynam, Univ Str 16, CH-8092 Zurich, Switzerland. Bjerknes Ctr Climate Res, Uni Res Climate, N-5008 Bergen, Norway. CSIC, IIM, Eduardo Cabello 6, Vigo 36208, Spain. Univ Brest, IFREMER, Lab Oceanog Phys & Spatiale, CNRS,IRD,IUEM, Plouzane, France. IFREMER, IUEM, Lab Sci Environm Marin LEMAR, UBO,IRD,CNRS,UMR 6539, Technopole Brest Iroise, F-29280 Plouzane, France. Univ Autonoma Barcelona, Dept Fis, Bellaterra 08193, Spain. Edith Cowan Univ, Sch Sci, Ctr Marine Ecosyst Res, Joondalup, WA 6027, Australia. C2 ETH ZURICH, SWITZERLAND UNIV AUTONOMA BARCELONA, SPAIN ETH ZURICH, SWITZERLAND BCCR, NORWAY CSIC, SPAIN UBO, FRANCE IFREMER, FRANCE UNIV AUTONOMA BARCELONA, SPAIN UNIV EDITH COWAN, AUSTRALIA SI BREST SE PDG-ODE-LOPS-OH UM LOPS LEMAR IN WOS Ifremer jusqu'en 2018 DOAJ copubli-france copubli-europe copubli-univ-france copubli-int-hors-europe IF 3.951 TC 19 UR https://archimer.ifremer.fr/doc/00457/56873/58725.pdf https://archimer.ifremer.fr/doc/00457/56873/58726.pdf https://archimer.ifremer.fr/doc/00457/56873/58727.xlsx https://archimer.ifremer.fr/doc/00457/56873/58728.pdf https://archimer.ifremer.fr/doc/00457/56873/58729.pdf https://archimer.ifremer.fr/doc/00457/56873/58730.pdf LA English DT Article CR GEOVIDE BO Pourquoi pas ? AB Pathways and timescales of water mass transport in the subpolar North Atlantic Ocean (SPNA) have been investigated by many studies due to their importance for the meridional overturning circulation and thus for the global ocean. In this sense, observational data on geochemical tracers provide complementary information to improve the current understanding of the circulation in the SPNA. To this end, we present the first simultaneous distribution of artificial 129I and 236U in 14 depth profiles and in surface waters along the GEOVIDE section covering a zonal transect through the SPNA in spring 2014. Our results show that the two tracers are distributed following the water mass structure and that their presence is largely influenced by the global fallout (GF) and liquid effluents discharged to north-western European coastal waters by the Sellafield and La Hague nuclear reprocessing plants (NRPs). As a result, 129I concentrations and 236U∕238U atom ratios and 129I∕236U atom ratios display a wide range of values: (0.2–256) × 107atkg−1 (40–2350) × 10−12 and 0.5–200, respectively. The signal from NRPs, which is characterised by higher 129I concentrations and 129I∕236U atom ratios compared to GF, is transported by Atlantic Waters (AWs) into the SPNA, notably by the East Greenland Current (EGC)/Labrador Current (LC) at the surface and by waters overflowing the Greenland–Scotland passage at greater depths. Nevertheless, our results show that the effluents from NRPs may also directly enter the surface of the eastern SPNA through the Iceland–Scotland passage or the English Channel/Irish Sea. The use of the 236U∕238U and 129I∕236U dual tracer approach further serves to discern Polar Intermediate Water (PIW) of Canadian origin from that of Atlantic origin, which carries comparably higher tracer levels due to NRPs (particularly 129I). The cascading of these waters appears to modify the water mass composition in the bottom of the Irminger and Labrador seas, which are dominated by Denmark Strait Overflow Water (DSOW). Indeed, PIW–Atlantic, which has a high level of 129I compared to 236U, appears to contribute to the deep Irminger Sea increasing the 129I concentrations in the realm of DSOW. A similar observation can be made for 236U for PIW entering through the Canadian Archipelago into the Labrador Sea. Several depth profiles also show an increase in 129I concentrations in near bottom waters in the Iceland and the West European basins that are very likely associated with the transport of the NRP signal by the Iceland–Scotland Overflow Water (ISOW). This novel result would support current modelling studies indicating the transport of ISOW into the eastern SPNA. Finally, our tracer data from 2014 are combined with published 129I data for the deep central Labrador Sea between 1993 and 2013. The results obtained from comparing simulated and measured 129I concentrations support the previously suggested two major transport pathways for the AWs in the SPNA, i.e. a short loop through the Nordic seas into the SPNA and a longer loop, which includes recirculation of the AWs in the Arctic Ocean before it enters the western SPNA. PY 2018 PD SEP SO Biogeosciences SN 1726-4170 PU Copernicus Gesellschaft Mbh VL 15 IS 18 UT 000444986100002 BP 5545 EP 5564 DI 10.5194/bg-15-5545-2018 ID 56873 ER EF