Particulate Trace Element Export in the North Atlantic (GEOTRACES GA01 Transect, GEOVIDE Cruise)

Nolwenn Lemaitre (1, 2, 3) , Hélène Planquette (2) , Frank Dehairs (3) , Frédéric Planchon (2) , Géraldine Sarthou (2) , Morgane Gallinari (2) , Stéphane Roig (2) , Catherine Jeandel (4) , Maxi Castrillejo (5)

1 Institute of Geochemistry and Petrology [ETH Zürich]
2 LEMAR - Laboratoire des Sciences de l'Environnement Marin (LEMAR)
3 Analytical, Environmental and Geo- Chemistry
4 LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
5 Ion Beam Physics [ETH Zürich]

Vertical export of particulate trace elements (pTEs) is a critically underconstrained aspect of their biogeochemistry. Here, we combine elemental analyses on large (>53 μm) particles and 234Th measurements to determine downward export fluxes from the upper layers (40-110 m) of pTEs (Al, Cd, Co, Cu, Fe, Mn, Ni, P, Ti, V, Zn) and mineral phases (lithogenic, Fe-and Mn-oxides, calcium carbonate, and opal) in the North Atlantic along the GEOVIDE transect (Portugal-Greenland-Canada; GEOTRACES GA01 cruise). The role of lithogenic particles in controlling TE fluxes is obvious at proximity of the Iberian margin where the highest pTE export fluxes were estimated (up to 3912 μg/m2/d for pFe). However, high lithogenic and pTE fluxes are also observed up to 1700 km off this margin in the west European and Icelandic basins (up to 931 μg/m2/d for pFe). The lowest pTE export fluxes are determined in the Labrador Sea (as low as 501 μg/m2/d for pFe). High Mn-and Fe-oxide fluxes are estimated at the open ocean stations, suggesting that authigenic particles are an important vector of pTEs. All along the transect, biogenic particles also drive the pTE export fluxes, as shown by the similar pTE/POC ratios between exports and phytoplankton quotas. The shortest residence times (dissolved + particulate) are generally observed where lithogenic particles control the pTE fluxes (as low as 2 days for Fe) whereas pTEs seem to be longer retained when the contribution of biogenic particles become greater (residence times up to 147 days for Fe).

Mots clés: multiple carrier phases; residence times; GEOTRACES; ACL; export fluxes; particulate trace elements

Domaines: Sciences de l'environnement; Biodiversité et Ecologie; Océan, Atmosphère

Nolwenn Lemaitre, Hélène Planquette, Frank Dehairs, Frédéric Planchon, Géraldine Sarthou, et al.. Particulate Trace Element Export in the North Atlantic (GEOTRACES GA01 Transect, GEOVIDE Cruise). ACS Earth and Space Chemistry, 2020, 4 (11), pp.2185-2204. ⟨10.1021/acsearthspacechem.0c00045⟩. ⟨hal-03030236⟩