Physical drivers of the Southern Ocean carbon sink in a changing climate

• Applicant: Dr. Lavinia Patara
• Subject Area: Oceanography ; Biochemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 454049236

The Southern Ocean, currently the largest oceanic sink of anthropogenic CO2, will play an important role in modulating the pace of climate change in the 21st century. There is intense debate regarding the response of the Southern Ocean carbon sink to projected changes in Southern Hemisphere winds and temperatures. In this project, the physical drivers of the Southern Ocean carbon sink over the next decades will be assessed. The method of ocean dynamical downscaling of a projection performed under the SSP5 scenario of the IPCC will be applied onto a hierarchy of global ocean biogeochemistry models at increasing horizontal resolution (from 1/2° to 1/10°). Earth System Model projections offer limited confidence as they typically do not resolve ocean mesoscale dynamics, which is thought to significantly affect the response of the Southern Ocean to climate change. In contrast, the high-resolution ocean model used here resolves ocean mesoscale dynamics by embedding a regionally refined ocean grid at 1/10˚ in the Southern Ocean (30˚-77˚S) within a global 1/2° ocean grid. A series of perturbation experiments through 2060 will disentangle the role of different physical factors on the future Southern Ocean CO2 uptake. The project will thereby address key unresolved questions such as: 1) will rising CO2 emissions and associated changes in ocean circulation and hydrography reduce the Southern Ocean carbon sink in the next decades? and 2) will a strengthened mesoscale eddy activity in response to increasing winds counteract the stalling of the Southern Ocean carbon uptake projected by several Earth System Models? The results of the high-resolution experiments will provide a benchmark for the reliability of non-eddy resolving Earth System Models and will thereby contribute to the development of modelling strategies for the prediction of the 21st century ocean carbon sink under rising CO2 emissions.

• DFG Programme: Research Grants