Quantifying Ice-Sheet Derived Lead (Pb) Fluxes to the Ocean; A Case Study at Nioghalvfjerdsbræ

• Published in: Geophysical Research Letters
• Main Authors: Krisch, Stephan, Huhn, Oliver, Al-Hashem, Ali, Hopwood, Mark J., Lodeiro, Pablo, Achterberg, Eric P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: John Wiley and Sons Inc. 2022
• Subjects: Arctic; GEOTRACES; Greenland ice sheet; Lead fluxes; Marine-terminating glacier; Nioghalvfjerdsbrae; Glaceres; Plom; Bergen; Colombo; Gerd; Greenland; Norway; Alfred Wegener Institute; glacier; Ice Sheet
• Online Access: http://hdl.handle.net/10459.1/84452; https://doi.org/10.1029/2022GL100296

Concentrations of the toxic element lead (Pb) are elevated in seawater due to historical emissions. While anthropogenic atmospheric emissions are the dominant source of dissolved Pb (dPb) to the Atlantic Ocean, evidence is emerging of a natural source associated with subglacial discharge into the ocean but this has yet to be constrained around Greenland. Here, we show subglacial discharge from the cavity underneath Nioghalvfjerdsbræ floating ice tongue, is a previously unrecognized source of dPb to the NE Greenland Shelf. Contrasting cavity-inflowing and cavity-outflowing waters, we constrain the associated net-dPb flux as 2.2 ± 1.4 Mg·yr−1, of which ∼90% originates from dissolution of glacial bedrock and cavity sediments. We propose that the retreat of the floating ice tongue, the ongoing retreat of many glaciers on Greenland, associated shifts in sediment dynamics, and enhanced meltwater discharges into shelf waters may result in pronounced changes, possibly increases, in net-dPb fluxes to coastal waters. The authors thank the captain and crew of the RV Polarstern GN05 cruise, operated by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). The authors also like to thank Michiel Rutgers van der Loeff (AWI) for his advice upon sampling and ship time management, Takamasa Tsubouchi (University of Bergen, Norway) for the CTD control and Martin Graeve and Kai‐Uwe Ludwichowski (both AWI) who performed the macronutrient analyses. The authors are grateful for the help received from Janin Schaffer (AWI), Florian Evers (GEOMAR), Eike Köhn (GEOMAR), Nat Wilson (Woods Hole Oceanographic Institution), and Gerd Rohardt (AWI) for CTD handling and processing, to Nicola Herzberg, Jaw Chuen Yong for assistance during sampling, and to Tim Steffens (all GEOMAR) for technical assistance during HR‐ICP‐MS analyses. Manuel Colombo (WHOI) is thanked for detailed feedback on this manuscript. Stephan Krisch was financed by GEOMAR and the German Research Foundation (DFG award number .