Biogenic silica recycling in sea ice inferred from Si-isotopes: constraints from Arctic winter first-year sea ice

• Published in: Biogeochemistry
• Main Authors: Fripiat, F., Tison, J.-L., André, L., Notz, D, Delille, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2014
• Subjects: Antarctic; Arctic; Antarc*; greenlandic; Sea ice
• Online Access: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=247007

We report silicon isotopic composition (d 30 Si 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, d 30 Si of sea-ice brine similar to d 30 Si 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 d 30 Si: any d 30 Si 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 d 30 Si 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.