Biogenic silica recycling in sea ice inferred from Si-isotopes: constraints from Arctic winter first-year sea ice |
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Authors: | François Fripiat Jean-Louis Tison Luc André Dirk Notz Bruno Delille |
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Institution: | 1. Department of Earth and Environmental Sciences, Université Libre de Bruxelles, 1050, Brussels, Belgium 5. Earth System Sciences & Analytical and Environmental Chemistry, Vrije Universiteit Brussel, Brussels, Belgium 2. Department of Earth Sciences, Royal Museum for Central Africa, Tervuren, Belgium 3. Max Planck Institute for Meteorology, Hamburg, Germany 4. Unité d’Océanographie Chimique, Interfacultary Center for Marine Research, Université de Liège, Liège, Belgium
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Abstract: | We report silicon isotopic composition (δ30Si vs. NBS28) in Arctic sea ice, based on sampling of silicic acid from both brine and seawater in a small Greenlandic bay in March 2010. Our measurements show that just before the productive period, δ30Si of sea-ice brine similar to δ30Si of the underlying seawater. Hence, there is no Si isotopic fractionation during sea-ice growth by physical processes such as brine convection. This finding brings credit and support to the conclusions of previous work on the impact of biogenic processes on sea ice δ30Si: any δ30Si change results from a combination of biogenic silica production and dissolution. We use this insight to interpret data from an earlier study of sea-ice δ30Si in Antarctic pack ice that show a large accumulation of biogenic silica. Based on these data, we estimate a significant contribution of biogenic silica dissolution (D) to production (P), with a D:P ratio between 0.4 and 0.9. This finding has significant implications for the understanding and parameterization of the sea ice Si-biogeochemical cycle, i.e. previous studies assumed little or no biogenic silica dissolution in sea ice. |
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