The 79°N Glacier cavity modulates subglacial iron export to the NE Greenland Shelf

• Published in: Nature Communications
• Main Authors: Krisch, Stephan, Hopwood, Mark J., Schaffer, Janin, Al-Hashem, Ali, Höfer, Juan, van der Loeff, Michiel M. Rutgers, Conway, Tim M., Summers, Brent A., Lodeiro, Pablo, Ardiningsih, Indah, Steffens, Tim, Achterberg, Eric P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Research 2021
• Subjects: Antarctic; Gerd; Greenland; Hanno; Antarc*; Antarctica; glacier; Ice Shelf; Swiss Polar Institute
• Online Access: http://hdl.handle.net/10459.1/72075; https://doi.org/10.1038/s41467-021-23093-0

Approximately half of the freshwater discharged from the Greenland and Antarctic Ice Sheets enters the ocean subsurface as a result of basal ice melt, or runoff draining via the grounding line of a deep ice shelf or marine-terminating glacier. Around Antarctica and parts of northern Greenland, this freshwater then experiences prolonged residence times in large cavities beneath floating ice tongues. Due to the inaccessibility of these cavities, it is unclear how they moderate the freshwater associated supply of nutrients such as iron (Fe) to the ocean. Here, we show that subglacial dissolved Fe export from Nioghalvfjerdsbrae (the ‘79°N Glacier’) is decoupled from particulate inputs including freshwater Fe supply, likely due to the prolonged ~162-day residence time of Atlantic water beneath Greenland’s largest floating ice-tongue. Our findings indicate that the overturning rate and particle-dissolved phase exchanges in ice cavities exert a dominant control on subglacial nutrient supply to shelf regions. The authors thank Captain Schwarze and the crew of the RV Polarstern (GN05 cruise); chief scientist Torsten Kanzow (AWI); Nicola Herzberg and Jaw Chuen Yong (GEOMAR) for assistance with sample collection; Takamasa Tsubouchi (AWI), Eike Köhn (GEOMAR) and Nat Wilson (Woods Hole Oceanographic Institution) for CTD handling; Gerd Rohardt (AWI) for CTD data processing; Christian Schlosser and Shao-Min Chen (GEOMAR) for assistance during trace element analyses; Martin Graeve and KaiUwe Ludwichowski (AWI) for macronutrient analysis; and Hanno Meyer (AWI) for the analyses of oxygen isotopes. S.K. was financed by GEOMAR and the German Research Foundation (DFG award number AC 217/1-1 to E.A.). M.H. received support from the DFG (award number HO 6321/1-1) and the GLACE project, organized by the Swiss Polar Institute and supported by the Swiss Polar Foundation. J.S. acknowledges support from the German Federal Ministry of Education and Research (BMBF) within the GROCE project (grant 03F0778A).