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Polynya dynamics drive primary production in the Larsen A and B embayments following ice shelf collapse

TitlePolynya dynamics drive primary production in the Larsen A and B embayments following ice shelf collapse
Publication TypeJournal Article
Year of Publication2014
AuthorsCape M.R, Vernet M, Kahru M, Spreen G.
JournalJournal of Geophysical Research-Oceans
Date Published2014/01
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000331879100041
Keywordsamundsen sea; antarctica; climate-change; fuels; hemisphere annular mode; Larsen; mcmurdo dry valleys; melting glaciers; phytoplankton; phytoplankton biomass; polynya; primary production; ross sea; sea ice; sea-ice; southern-ocean; western antarctic peninsula

The climate-driven collapses of the Larsen A and B ice shelves have opened up new regions of the coastal Antarctic to the influence of sea ice resulting in increases in seasonal primary production. In this study, passive microwave remote sensing of sea ice concentration and satellite imagery of ocean color are employed to quantify the magnitude of and variability in open water area and net primary productivity (NPP) in the Larsen embayments between 1997 and 2011. Numerical model output provides context to analyze atmospheric forcing on the coastal ocean. Following ice shelf disintegration the embayments function as coastal, sensible heat polynyas. The Larsen A and B are as productive as other Antarctic shelf regions, with seasonally averaged daily NPP rates reaching 1232 and 1127 mg C m(-2) d(-1) and annual rates reaching 200 and 184 g C m(-2) yr(-1), respectively. A persistent cross-shelf gradient in NPP is present with higher productivity rates offshore, contrasting with patterns observed along the West Antarctic Peninsula. Embayment productivity is intimately tied to sea ice dynamics, with large interannual variability in NPP rates driven by open water area and the timing of embayment opening. Opening of the embayment is linked to periods of positive Southern Annular Mode and stronger westerlies, which lead to the vertical deflection of warm, maritime air over the peninsula and down the leeward side causing increases in surface air temperature and wind velocity. High productivity in these new polynyas is likely to have ramifications for organic matter export and marine ecosystem evolution.

Short TitleJ Geophys Res-Oceans

The embayments previously covered by the Larsen ice shelf have quickly become productive regions, some years contributing more to total net primary productivity (NPP) than their spatial share of the NW Weddell Sea surface area. While the absolute magnitude of this new carbon pool is too low to contribute to carbon sequestration on a global scale and the interannual variability in production is extreme, the presence of this new organic matter in the water column and its sedimentation to the benthos are likely to lead to extensive changes in the regional marine ecosystem of the NW Weddell Sea.

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