EGU21-2155
https://doi.org/10.5194/egusphere-egu21-2155
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Zonal asymmetry of Southern Ocean air-sea carbon fluxes

Channing Prend1, Alison Gray2, Lynne Talley1, Sarah Gille1, Alexander Haumann3,4, Kenneth Johnson5, Stephen Riser2, Isabella Rosso1, Jade Sauvé2, and Jorge Sarmiento3
Channing Prend et al.
  • 1University of California San Diego, Scripps Institution of Oceanography, La Jolla, USA
  • 2School of Oceanography, University of Washington, Seattle, USA
  • 3Atmospheric and Oceanic Sciences, Princeton University, Princeton, USA
  • 4British Antarctic Survey, Cambridge, UK
  • 5Monterey Bay Aquarium Research Institute, Moss Landing, USA

The Southern Ocean modulates the climate system by exchanging heat and carbon dioxide (CO2) between the atmosphere and deep ocean. While this region plays an outsized role in the global oceanic anthropogenic carbon uptake, CO2 is released into the atmosphere across large swaths of the Antarctic Circumpolar Current (ACC). Southern Ocean outgassing has long been attributed to remineralized carbon from upwelled deep water, but the precise mechanisms by which this water reaches the surface are not well known. Using data from a novel array of autonomous biogeochemical profiling floats, we estimate Southern Ocean air-sea CO2 fluxes at unprecedented spatial resolution and determine the pathways that transfer carbon from the ocean interior into the mixed layer where air-sea exchange occurs. Float-based flux estimates suggest that carbon outgassing occurs predominantly in the Indo-Pacific sector of the ACC due to variations in the mean surface ocean partial pressure of CO2 (pCO2). Within the Polar Frontal Zone and Antarctic Southern Zone of the ACC, the annual mean pCO2 difference between the Indo-Pacific and Atlantic is 40.1 ± 12.9 μatm and 17.9 ± 12.4 μatm, respectively. We show that this zonal asymmetry in surface pCO2 and consequently air-sea carbon fluxes stems from regional variability in the mixed-layer entrainment of carbon-rich deep water. These results suggest that long-term trends of the Southern Ocean carbon sink inferred from sparse shipboard data may depend on the fraction of measurements from each basin in a given year. Furthermore, sampling these different air-sea flux regimes is necessary to monitor future changes in oceanic carbon release and uptake.

How to cite: Prend, C., Gray, A., Talley, L., Gille, S., Haumann, A., Johnson, K., Riser, S., Rosso, I., Sauvé, J., and Sarmiento, J.: Zonal asymmetry of Southern Ocean air-sea carbon fluxes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2155, https://doi.org/10.5194/egusphere-egu21-2155, 2021.

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