Abstract:
The Oden Southern Ocean 2008-2009 expedition (OSO08), which was an international collaborative research project, took place between November 2008 and January 2009 and traveled across the poorly studied south Pacific sector of the Antarctic between Montevideo, Uruguay and McMurdo Station, Antarctica. Although sea-ice biota have been studied for decades, the Oden cruise afforded a unique
... opportunity to study their impact on climate-sensitive biogeochemistry. The Antarctic transect covered more than 3000 miles of the ice-covered Pacific sector, allowing us to sample a large range of sea-ice conditions and types, normally unavailable within a single expedition. Our measurements should provide insight to relationships between climate-active gas fluxes, microbial activity, and physical variables potentially measurable by satellite. We collected sea ice (cores), brine (from sackholes), and under-ice seawater from 16 stations between 70°S, 107°W and 76°S, 151°W in the Amundsen Sea and measured concentrations of inorganic and organic carbon and nitrogen, along with microbiological biomass and rate measurements. The Yager group measured concentrations of total inorganic carbon, bacterial abundance, bacterial community structure, bacterial production and respiration, as well as bacterial incorporation and respiration of model organic carbon substrates such as amino acids and methyl bromide. 
Purpose:
Polar regions are changing rapidly in response to human activities. Although the total extent of Antarctic seasonal sea ice has not yet changed significantly as a result of climate change, regional reductions or growth can be extensive and coupled to global cycles such as ENSO and the Southern Annular Mode. Future reductions are predicted by climate models. Changes in sea ice extent and
... thickness will have profound implications for productivity, food webs and carbon fluxes at high latitudes, since sea ice biota are a significant source of biogenic matter. While sea ice is often thought to be a barrier to gas exchange between the ocean and the atmosphere, it more likely functions as a source or sink for climate-active gases such as carbon dioxide and ozone-depleting organohalogens. Since controls on the production and destruction of these gases are very likely coupled to the extent and type of microorganisms living at or near this critical interface, changes in both the extent and type of sea ice will have a profound effect on the balance between the marine environment and the biosphere. Understanding critical feedbacks between climate and the marine biosphere becomes increasingly urgent as we project rates of change into the future. This project brings together experienced US and Swedish investigators to investigate the controls by sea-ice biota on the production and degradation of key climate-active gases in the Pacific sector of the Southern Ocean.
