14.11.2022: online Ocean Circulation and Climate Dynamics Colloquium

Dr. Dafydd Gwyn Evans, National Oceanography Centre, Southampton, England: "Dissipation of mesoscale eddies at a western boundary via a direct energy cascade"

When?  Monday, November 14, 2022 at 11 am
Where?    ZOOM meeting room: https://geomar-de.zoom.us/j/7765120676?pwd=RVBGeDFBZldxc1pQSmN2VmhNSXltZz09

Meeting-ID: 776 512 0676
Kenncode: 530726


The fate of mesoscale eddy kinetic energy represents a large source of uncertainty in the global ocean energy budget. Satellite altimetry suggests that mesoscale eddies vanish at ocean western boundaries. However, the fate of the eddies’ kinetic energy remains poorly known. Here we show that the generation of small-scale turbulence as eddy flow impinges on the steep and corrugated slope of an ocean western boundary plays a dominant role in the regional decay of mesoscale eddy kinetic energy. We compare altimetry-based estimates of mesoscale eddy kinetic energy decline with measurements of turbulent dissipation. Mesoscale eddies are found to decay at a rate of 0.016 ± 0.012 GW and 0.023 ± 0.017 GW for anticyclonic and cyclonic eddies, respectively, similar to the observed turbulent dissipation rate of 0.020 ± 0.011 GW. This demonstrates that a major direct transfer of mesoscale eddy kinetic energy to small, dissipative scales can be effectively triggered by the eddies’ interaction with the western boundary topography.



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