Processes Driving Carbon and Oxygen Fluxes in the High Latitude Southern Ocean Determined from Biogeochemical-Argo Floats

The Southern Ocean plays a significant role in the global carbon and oxygen cycles. Around 40% of the global oceanic uptake of anthropogenic carbon dioxide occurs in the waters south of 35˚S. Substantial oxygenation of upwelled waters also takes place in the Southern Ocean. Historically, observational datasets for this isolated region have been strongly biased towards summer and limited in spatial coverage. Recent analysis of data obtained using autonomous biogeochemical floats deployed by the Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project showed greater than expected wintertime outgassing of carbon dioxide in the high-latitude Southern Ocean (Gray et al., 2018) as well as strong uptake of oxygen in the seasonal ice zone (Bushinsky et al., 2017). The mechanisms explaining these unanticipated air-sea fluxes are undetermined at this time. Here, we use a mixed layer budget and 5 years of data from SOCCOM profiling floats, complemented with atmospheric reanalysis and satellite-based observations of sea ice and winds, to investigate the processes that determine the seasonal cycle of carbon and oxygen fluxes in the Southern Ocean, including the role of net community production and biogenic carbon export. In particular, we examine the coupling of carbon dioxide and oxygen fluxes in different regions delimited by well-known Southern Ocean fronts and the effect of sea ice on this coupling in the seasonal ice zone and adjacent regions.