Mercury distribution and transport in the North Atlantic Ocean along the GEOTRACES-GA01 transect

Type Article
Date 2018-04
Language English
Author(s) Cossa Daniel1, Heimburger Lars-Eric2, Perez Fiz F3, Garcia-Ibanez Maria Isabel3, 4, Sonke Jeroen E.5, Planquette Helene6, Lherminier PascaleORCID7, Boutorh Julia6, Cheize Marie6, Barraqueta Jan Lukas Menzel8, Shelley Rachel6, Sarthou Geraldine6
Affiliation(s) 1 : Univ Grenoble Alpes, ISTerre, CS 40700, F-38058 Grenoble 9, France.
2 : Aix Marseille Univ, Univ Toulon, CNRS INSU, MIO,UM 110,IRD, Marseille, France.
3 : CSIC, Inst Invest Marinas, Eduardo Cabello 6, Vigo 36208, Spain.
4 : Bjerknes Ctr Climate Res, Uni Res Climate, N-5008 Bergen, Norway.
5 : CNRS, GET OMP, 14 Ave E Belin, F-31240 Toulouse, France.
6 : Univ Bretagne Occidentale, LEMAR, F-29280 Plouzane, France.
7 : IFREMER, Brittany Ctr, LPO, BP 70, F-29280 Plouzane, France.
8 : Helmholtz Ctr Ocean Res, GEOMAR, D-24148 Kiel, Germany.
Source Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2018-04 , Vol. 15 , N. 8 , P. 2309-2323
DOI 10.5194/bg-15-2309-2018
WOS© Times Cited 13
Note Special issue GEOVIDE, an international GEOTRACES study along the OVIDE section in the North Atlantic and in the Labrador Sea (GA01) Editor(s): G. Henderson, M. Lohan, L. Bopp, C. Jeandel, and G. Reverdin
Abstract

We report here the results of total mercury (HgT) determinations along the 2014 GEOTRACES GEOVIDE cruise (GA01 transect) in the North Atlantic Ocean (NA) from Lisbon (Portugal) to the Labrador coast (Canada). Ninety-seven percent of the HgT concentrations of unfiltered samples (HgTUNF) ranged between 0.16 and 1.00 pmol L−1. The geometric mean was 0.51 pmol L−1 for the 535 samples analysed. The dissolved fraction (< 0.45 μm) of HgT, determined on 141 samples, averaged 78 % of the HgTUNF for the whole water column. HgTUNF concentrations increased eastwards and with depth from Greenland to Europe and from sub-surface to bottom waters, respectively. The Hg distribution mirrored that of dissolved oxygen concentration, with highest HgTUNF levels associated with oxygen-depleted zones. The statistically significant (p <  0.01) relationship between HgTF (filtered samples) and the apparent oxygen utilization confirms the nutrient-like behavior of Hg in the NA. An extended Optimum Multiparameter Analysis allowed us to characterize HgTUNF concentrations in the different Source Water Types (SWTs) present along the transect. Mean HgTUNF concentrations ranged from 0.26 ± 0.03 pmol L−1 in the Irminger Subpolar Mode Water to 1.02 ± 0.02 pmol L−1 in the lower North East Atlantic Deep Water. Anthropogenic Hg-enriched SWTs were found in the upper oceanic layers (i.e., East North Atlantic Central Water and Subarctic Intermediate Water). The change in anthropogenic Hg concentrations in the Labrador Sea Water, during its eastward journey, suggests a continuous decrease of Hg content in this water mass over the last decades. Calculation of the water transport driven by the Atlantic Meridional Overturning Circulation across the Portugal-Greenland transect indicates a northward Hg transport within the upper limb, and a southward Hg transport within the lower limb, with a resulting net transport from low latitudes to the polar zones of about 111 kmol yr−1.

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Cossa Daniel, Heimburger Lars-Eric, Perez Fiz F, Garcia-Ibanez Maria Isabel, Sonke Jeroen E., Planquette Helene, Lherminier Pascale, Boutorh Julia, Cheize Marie, Barraqueta Jan Lukas Menzel, Shelley Rachel, Sarthou Geraldine (2018). Mercury distribution and transport in the North Atlantic Ocean along the GEOTRACES-GA01 transect. Biogeosciences, 15(8), 2309-2323. Publisher's official version : https://doi.org/10.5194/bg-15-2309-2018 , Open Access version : https://archimer.ifremer.fr/doc/00412/52303/