Biogeochemical impact of snow cover and cyclonic intrusions on the winter Weddell Sea ice pack

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Tison, Jean-Louis, Schwegmann, S., Dieckmann, Gerhard S., Rintala, Janne-Markus, Meyer, H., Moreau, Sébastien, Vancoppenolle, Martin, Nomura, Daiki, Engberg, S., Blomster, J., Hendricks, Stefan, Uhlig, C., Luhtanen, A.-M., de Jong, J., Janssens, Jan, Carnat, Gauthier, Zhou, J., Delille, Bruno
• Other Authors: Laboratoire de Glaciologie Bruxelles, Université libre de Bruxelles (ULB), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine (AWI), Helmholtz-Gemeinschaft = Helmholtz Association, Helsingin yliopisto = Helsingfors universitet = University of Helsinki, Institute for Marine and Antarctic Studies Hobart (IMAS), University of Tasmania Hobart (UTAS), Faculty of Fisheries Sciences Hakodate, Hokkaido University Sapporo, Japan, Finnish Environment Institute (SYKE), Université de Liège, Australian Research Council's Special Research Initiative for Antarctic Gateway Partnership . Grant Number: SR140300001JSPS KAKENHI . Grant Numbers: 12J04175 , 17H04715, European Project: 262922,EC:FP7:SPA,FP7-SPACE-2010-1,SIDARUS(2011)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: sea ice; Weddell Sea; Antarctica; biogeochemistry; winter; [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; Antarctic; Southern Ocean; Weddell; Antarc*; ice pack; Sea ice
• Online Access: https://hal.science/hal-01832196; https://hal.science/hal-01832196v1/document; https://hal.science/hal-01832196v1/file/JGR%20Oceans%20-%202017%20-%20Tison%20-%20Biogeochemical%20Impact%20of%20Snow%20Cover%20and%20Cyclonic%20Intrusions%20on%20the%20Winter%20Weddell%20Sea%20Ice%20Pack.pdf; https://doi.org/10.1002/2017jc013288

International audience Sea ice is a dynamic biogeochemical reactor and a double interface actively interacting with both the atmosphere and the ocean. However, proper understanding of its annual impact on exchanges, and therefore potentially on the climate, notably suffer from the paucity of autumnal and winter data sets. Here we present the results of physical and biogeochemical investigations on winter Antarctic pack ice in the Weddell Sea (R. V. Polarstern AWECS cruise, June–August 2013) which are compared with those from two similar studies conducted in the area in 1986 and 1992. The winter 2013 was characterized by a warm sea ice cover due to the combined effects of deep snow and frequent warm cyclones events penetrating southward from the open Southern Ocean. These conditions were favorable to high ice permeability and cyclic events of brine movements within the sea ice cover (brine tubes), favoring relatively high chlorophyll‐a (Chl‐a) concentrations. We discuss the timing of this algal activity showing that arguments can be presented in favor of continued activity during the winter due to the specific physical conditions. Large‐scale sea ice model simulations also suggest a context of increasingly deep snow, warm ice, and large brine fractions across the three observational years, despite the fact that the model is forced with a snowfall climatology. This lends support to the claim that more severe Antarctic sea ice conditions, characterized by a longer ice season, thicker, and more concentrated ice are sufficient to increase the snow depth and, somehow counterintuitively, to warm the ice.