The signature of mesoscale eddies on sea surface temperature and its associated heat transport

This thesis aims at analysing the impact of oceanic turbulence and air-sea interactions on the sea surface temperature (SST) of the extra-tropical oceans on spatial scales of a few hundred kilometres (the so-called "mesoscale"). Using satellite-based measurements of SST and sea level, as well as surface tracks of mesoscale oceanic cyclones and anticyclones, it is shown that turbulence does not transport heat through systematic motions of cold cyclones and warm anticyclones, as was previously thought in regions of strong mean flows like the Gulf Stream. Rather, it is suggested that heat is transported as a result of the slight phase shift between temperature and pressure fluctuations developing on the mean flow. In addition, tentative estimates of the rate at which air-sea heat fluxes damp the SST signatures of cyclones and anticyclones are provided. The weak values obtained ( 20 W/m2K) contrast sharply with theoretical expectations, but are in agreement with the observed long-lived thermal heat content anomalies associated with the cyclones and anticyclones. These observations provide important benchmarks for high-resolution ocean models and may moreover guide the parametrization of subgrid-scale heat transport in climate models