BIoGeochemical cycles in the SOUTHern Ocean: Role within the Earth System

The BIGSOUTH project (Biogeochemical cycles in the Southern Ocean: role within the Earth system) aims at achieving a detailed understanding of the processes controlling functioning and strength of the oceanic biological pump for representative key areas of the Southern Ocean, including open ocean and sea-ice covered areas, in order to upgrade present day assessments of the carbon sequestration capacity and nutrient cycling in the Southern Ocean and possible impacts on the global ocean. Therefore, we apply a unique combination of stable isotope (natural and spiked isotopic abundances), geochemical tracers, trace element and modeling tools to study the relevant biogeochemical processes and control factors (including Fe) acting on the fluxes of carbon and the two major macronutrients N and Si in the open and seasonally sea-ice covered water column.
Since the start of the project we have applied this combination of tools during 3 major Southern Ocean studies, being: (1) KEOPS 2 (Kerguelen Ocean and Plateau compared Study; Oct. 6 to Nov. 30, 2011): understanding the impact of natural iron fertilization from plateau sediments on the efficacy of the biological pump in the vicinity of Kerguelen Island; (2) YROSIAE, (Oct. 2011 – Dec. 2012): multi-year survey of air-sea, ice-ocean fluxes of carbon, nutrients, trace metal and climate gases together with sea ice biogeochemistry, including primary production and N, Si uptake in McMurdo Sound; (3) SIPEX 2 (Sea Ice Physics and Ecosystem eXperiment; Oct.-Nov. 2012; Australian Antarctic Basin): study of the sea ice biogeochemistry in an early season situation, with focus on primary production and nutrient (N, Si) uptake. Analysis and data interpretation are ongoing. A further ongoing expedition in which we participate is AWECS (Antarctic Winter Ecosystem Climate Study) in the Weddell Sea (Jul.-Aug. 2013), which is devoted to sea ice biogeochemistry (trace metal, nutrients and climate gases).