Arctic rivers are discharging organic matter enriched in mercury to the Labrador Sea

Science Highlights

9 April 2018

In the framework of GEOVIDE-GEOTRACES GA01 cruise (spring 2014), Cossa and co-workers (see reference below) measured the first high-resolution mercury (Hg) distribution pattern along a transect from Greenland to Labrador coasts. An interesting feature is the observation of Hg enrichment originating from fluvial sources in the Canadian Arctic Archipelago waters. This excess Hg is transferred southward, in surface waters with the Labrador Current, and at depth with the lower limb of the Atlantic Meridional Overturning Circulation via the Deep Western Boundary Current. The authors underline that global warming could accelerate permafrost thawing in a near future, increasing the Hg discharge by the Arctic rivers.

18 CossaFigure: (a) Total mercury (HgT) concentratons in Labrador Sea waters ranged from 0.25 to 0.67 pmol L-1; (b) Anthropogenic Hg concentrations (Hganth) represents 36 % of the HgT present with the highest fraction (> 80%) in sub-surface and lowest fraction (< 15 %) near the bottom; (c) Hg enriched waters were identified in desalted waters originating from the Canadian Arctic Archipelago. Please click here to view the image larger.

Reference:

Cossa, D., Heimbürger, L. E., Sonke, J. E., Planquette, H., Lherminier, P., García-Ibáñez, M. I. Pérez, F.F., Sarthou, G. (2018). Sources, cycling and transfer of mercury in the Labrador Sea (Geotraces-Geovide cruise). Marine Chemistry, 198, 64–69. http://doi.org/10.1016/J.MARCHEM.2017.11.006

Latest highlights

East-West contrasting fate and anthropogenic inputs for dissolved trace metals in the Subarctic Pacific Ocean

Chan and co-authors report the full-depth distribution of dissolved nickel, copper, zinc, and cadmium in the North Pacific Ocean.

Comprehensive quantification of the rare earth element cycle in the northwest Pacific Ocean

Cao and co-authors investigate dissolved rare earth elements and the factors controlling their distributions in the northwest Pacific Ocean.

Iron and zinc isotopes disentangle the anthropogenic, natural and wildfire sources of aerosols over the North and Equatorial Pacific Ocean

Bunnell and co-authors analysed aerosol iron and zinc isotopic compositions along the North Pacific GEOTRACES GP15 section (Alaska-Tahiti).

Contribution of sandy beaches to the oceanic silica cycle

This paper calls into question the commonly accepted idea of an oceanic silicon cycle in equilibrium.

Rechercher