The Atmospheric Signature of Southern Ocean Carbon Fluxes

Matthew C Long1, Britton B Stephens2, Colm Sweeney3, Eric A Kort4, Ralph F Keeling5 and Kathryn McKain3, (1)National Center for Atmospheric Research, Climate and Global Dynamics Laboratory, Boulder, United States, (2)National Center for Atmospheric Research, Earth Observing Laboratory, Boulder, CO, United States, (3)NOAA, Global Monitoring Laboratory, Boulder, United States, (4)University of Michigan Ann Arbor, Climate and Space Sciences and Engineering, Ann Arbor, MI, United States, (5)Univ California San Diego, La Jolla, CA, United States
The Southern Ocean is a critical component of the global carbon cycle, but air-sea CO2 fluxes in the region are poorly constrained by observations and models. We present a comprehensive analysis of regional atmospheric CO2 observations from aircraft, ships, and surface monitoring stations; these data show a spatially coherent depletion of CO2 in the lower atmosphere over the Southern Ocean during the austral summer and an enhancement in winter. We demonstrate that this signal is directly attributable to Southern Ocean air-sea exchange and provides a metric to compare and validate with other estimates. The patterns revealed in these data suggest that the Southern Ocean is a strong CO2 sink during summer and the magnitude of this sink has strengthened over the past decade. Our analysis has important implications for quantifying and detecting changes in the Southern Ocean carbon sink.