Inventories of anthropogenic carbon and their variability in the Atlantic sector of the Southern Ocean, 1984-2010

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The Atlantic sector of the Southern Ocean is a key area for the formation of bottom, deep and intermediate water. It is, hence, an important component of the Meridional Overturning Circulation and a significant sink for atmospheric gases. Climate relevant anthropogenic carbon (Cant) is taken up at the atmospheric interface and exported from the atmosphere during Antarctic Bottom Water (AABW) and Antarctic Intermediate Water (AAIW) formation. In turn, formation of these waters are influenced by climate change. Despite their importance, Cant inventories and related formation rates of AABW and AAIW in that area are not well known, and estimates of the temporal variability are quite uncertain. The major aims of this proposal are 1. to determine the Cant inventories in the Atlantic Southern Ocean, especially in AABW and AAIW, based on transient tracer (CFC) data from a closed box (2008-2010), and to compare the results with inventory estimates from tracer data starting in 1984. 2. compare the Cant inventories calculated with the CFC based methods with Cant inventories based on “classical” methods (ΔC*, linear regression, etc.). 3. to calculate formation rates of AABW and AAIW in the Atlantic Southern Ocean (closed box data, 2008-2010) and their changes (since 1984) and to quantify export rates into the South Atlantic, into Drake Passage, and towards the east across the Prime Meridian. 4. to apply a newly developed method of maximum entropy inversion to determine the spatial origin and the transit time scales of AABW and AAIW and the related Cant inventories and to compare the results with “classical” transient tracer methods.