The impact of Southern Ocean mesoscale eddies on the uptake and transport of CO2 and CFC-12

Jan Klaus Rieck and Lavinia Patara, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
The Southern Ocean is a key area for the oceanic uptake of CO2, but the mechanisms in present climate conditions and its possible future changes are uncertain. One contributor to this uncertainty is the coarse resolution of most models used for biogeochemical simulations and climate projections, not allowing for the explicit simulation of oceanic mesoscale eddies. This study focuses on the direct effects of mesoscale eddies on the Southern Ocean CO2 uptake in the framework of a changing climate. To this end, we developed a new ocean-sea ice model configuration (ORION10-MOPS) with a global horizontal resolution of 1/2°, refined to 1/10° between 68°S-30°S. The ocean model includes CFC-12 and a biogeochemical model containing the inorganic carbon dynamics. This model is initialized with a 300-year spin-up performed at lower resolution and is integrated under the JRA55-do atmospheric forcing from 1958 to 2018. Companion simulations at 1/2° and 1/4° resolution are also performed. With this model configuration, the effects of the mesoscale on the uptake and transport of CO2 in the Southern Ocean are investigated. An inventory of individual mesoscale eddies is build and the eddies are tracked to investigate their property changes during the eddies' lifetime. The eddies are categorized based on their source region, as well as their dynamical, physical and biogeochemical properties and their effects on the air-sea fluxes of total CO2 and anthropogenic CO2 are evaluated. Analogously, the same processes and mechanisms are investigated for CFC-12 to assess the potential role of CFC-12 as a proxy for CO2. This analysis, performed in different decades, will shed light onto the direct effect of eddies for the uptake and transport of CO2 in changing climate conditions. We will then contrast the role of eddies in ORION10-MOPS to a companion 1/4° resolution simulation, with the aim of assessing its ability to simulate the impact of the mesoscale on the uptake and transport of CO2.