Abstract/Summary

The exchange of heat and momentum between the oceanic mesoscale and the atmosphere, and its impact on the local and large-scale ocean and atmosphere, presents a relatively new field. Its explicit representation or parameterization remain absent in most of the current generation of CMIP6 climate models. Using a state-of-the-art coupled climate model, it is shown that 1/12◦ and 1/4◦ resolution oceans generate 63% and 40% of the eddies found in observations respectively. Improvements in 1/12◦ are likely to be due to a better representation of the mean state in eddy-energetic regions with many more, smaller eddies being represented. However, eddy survival rates are biased high in the 1/12◦ , especially in the Southern Ocean. The first estimate of the turbulent heat flux feedback over coherent mesoscale eddies is provided, using a high-resolution coupled model. However, the ocean-to-atmosphere regridding of sea surface temperature (SST) may underestimate the feedback by between 20 to 80%. Importantly, the underestimate increases for models with larger ratios between atmospheric and ocean resolutions, implying that eddy SST anomalies are not dampened enough in such setups. Finally, by parameterizing the mesoscale heat flux feedback and SST-wind stress feedback in an ocean-only model, I was able to isolate and compare their effects. It is shown that the two feedbacks drive opposite meridional shifts of the western boundary current separation, suggesting they could partially cancel one another in the real ocean. The results of this thesis hold implications for future model development, highlight biases in the current observational altimeter dataset and guide the future parameterization of mesoscale air-sea feedbacks in climate models. Both the ocean and atmospheric resolutions are critical to represent the oceanic mesoscale and its interaction with the atmosphere, with uncoordinated increase in the ocean and atmosphere resolutions having a potential detrimental impact on the quality of the solutions.