EGU2020-10767, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-10767
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The role of changing Southern Ocean circulation for the uptake and storage of CFC-12, anthropogenic CO2 and oxygen

Lavinia Patara, Jan Klaus Rieck, Toste Tanhua, Iris Kriest, and Claus Boening
Lavinia Patara et al.
  • GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Ocean Circulation and Climate Dynamics, Kiel, Germany (lpatara@geomar.de)

Recent studies highlighted an increase in the Southern Ocean ventilation since several decades and, at the same time, pronounced decadal fluctuations in its carbon sink. The role of changing ventilation for the anthropogenic CO2 uptake (and thus for the overall Southern Ocean carbon sink) and for oxygen concentrations of mode and intermediate waters (with possible impacts on low-oxygen regions downstream) are still poorly understood. The aim of this study is to assess the role of changing Southern Ocean ventilation for the uptake and storage of atmospheric gases such as CFC-12, CO2 and oxygen. A related question is whether CFC-12 can be used as a proxy of anthropogenic CO2 in the Southern Ocean, since CO2 equilibrates significantly more slowly in seawater than CFC-12 and, while the solubility of CFC-12 increases with decreasing temperature and salinity, the solubility of anthropogenic CO2 decreases. We developed a suite of global configurations based on the NEMO-LIM2 ocean sea ice model including the passive tracer CFC-12 and the biogeochemical model MOPS. The suite includes ORCA05 (1/2° resolution), ORCA025 (1/4° resolution) and ORION10 (featuring a 1/10° nest between 68°S and 30°S). Hindcast and sensitivity experiments performed with ORCA025 under the JRA-55-do atmospheric forcing are used to unravel the role of changing wind and buoyancy forcing on the gas uptake and storage. First results highlight that anthropogenic CO2 is taken up in lighter density classes than CFC-12, meaning that increased ventilation of lighter mode waters would be particularly effective in taking up anthropogenic CO2. This effect is more pronounced in the higher-resolution model ORION10, indicating that mesoscale eddies inject anthropogenic CO2 in lighter waters than lower-resolution models.

How to cite: Patara, L., Rieck, J. K., Tanhua, T., Kriest, I., and Boening, C.: The role of changing Southern Ocean circulation for the uptake and storage of CFC-12, anthropogenic CO2 and oxygen, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10767, https://doi.org/10.5194/egusphere-egu2020-10767, 2020

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Presentation version 1 – uploaded on 04 May 2020
  • CC1: Model vs obs seasonality of biological drawdown, Ivy Frenger, 14 May 2020

    Hi Lavinia,

    Thanks for the nice contribution!

    Models frequently have issues with reproducing the seasonality of SO air-sea carbon fluxes. How does your model compare to Lydia’s results of biological carbon drawdown?

    Best, Ivy