Recent changes in the CO2 sink of the Southern Ocean inferred from ocean state estiamates
Manfredi Manizza, Univ of California--SIO, Geosciences Research Division, La Jolla, CA, United States, Cynthia D Nevison, INSTAAR/University of Colorado, Boulder, CO, United States, Mati Kahru, Univ of California--SIO, La Jolla, CA, United States, Dimitris Menemenlis, NASA Jet Propulsion Laboratory, Pasadena, CA, United States, Ralph F Keeling, University of California-San Diego, Scripps Institution of Oceanography, La Jolla, CA, United States and Brian Greg Mitchell, Scripps Institution of Oceanography, UCSD, La Jolla, CA, United States
Abstract:
The Southern Ocean represents a key area of the global ocean for the uptake of the anthropogenic carbon (AC) due to fossil fuels emissions. In these waters, cold temperatures combined with high rates of biological productions drive the uptake of CO
2 while wind-driven upwelling of carbon-rich waters counteract the carbon uptake. Combined prognostic models and atmospheric inversions suggested that after since 1980s the sink of AC in the Southern Ocean has significantly slowed down due to increased wind intensity upwelling more carbon-rich waters. However, a more recent study mainly based on surface ocean pCO
2 dataset, has shown that since year 2000 the capacity of the Southern Ocean of taking up AC has increased again due to notable changes in the phase of the Southern Annular Mode (SAM). In order to investigate these changes using a mechanistic approach we propose to use an eddy-permitting global ocean model coupled to a interactive sea-ice model that can generate data-constrained ocean physical estimates of the Southern Ocean for the 1996-2014 period.
These physical estimates will be used to force an ocean biogeochemical model (ECCO2-Darwin) that will compute the uptake of AC for each year. The physical model, forced with optimized atmospheric forcing, aims to realistically simulate inter-annual ocean climate variability that drives changes in both physical and biogeochemical processes ultimately impacting the carbon uptake of the Southern Ocean, especially in response to SAM variations. Although in this study great emphasis is given to the role of physical climate variations at driving the carbon uptake of these polar waters, we will integrate model results with estimates of carbon export production based on remote sensing techniques to also track the inter-annual variations of the biological carbon pump and highlight which areas of the Southern Ocean also show a strong link between the biological carbon pump and ocean climate variability.
