Biological carbon uptake and trace gas emissions in the polar oceans under a changing climate

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The high latitude oceans of both the Northern and Southern hemispheres play a large role in controlling atmospheric concentrations of climate-active trace gases. These regions contribute disproportionately to oceanic CO2 uptake and exhibit large sea-air fluxes of dimethylsulfide (DMS), a biogenic gas which influences cloud formation and impacts the atmospheric radiation budget. Global modeling studies suggest that polar ocean CO2 and DMS cycles are likely to change significantly over the coming century in response to climate-dependent changes in sea ice cover, circulation patterns and biological productivity. However, the magnitude of these potential climate-dependent changes is very poorly constrained by direct observations. The proposed research program will collect fundamental data on biological carbon cycling in Antarctic and Arctic marine waters, and on the production of various climate-active gases (e.g. DMS, methane and nitrous oxide). The principle research objectives are to: 1) examine the influence of increasing sea surface temperature and pCO2 on primary productivity and phytoplankton species assemblage composition in Antarctic and Arctic marine waters; 2) quantify the spatial and temporal variability of biological oxygen saturation, pCO2 and DMS concentrations in Arctic and Antarctic polynyas over a range of hydrographic and sea ice conditions; 3) use isotope tracer experiments to quantify key production and consumption terms in the high latitude DMS cycle, and 4) measure methane (CH4) and nitrous oxide (N2O) concentrations and production rates in Arctic shelf waters in relation to surface water productivity and sea ice cover. Field surveys will be used to map the surface distribution of trace gases in the Southern Ocean and Arctic Ocean using membrane inlet mass spectrometry (MIMS) for high spatial resolution analysis, combined with GC-MS for high sensitivity analysis of discrete depth profile samples. Isotope tracer experiments using 13C and 2H labelled compounds will be used to follow the production and consumption of DMS through various metabolic pathways, while phytoplankton sensitivity to temperature and CO2 variability will be assessed using controlled field-based incubation experiments.