Joe LaCasce (University of Oslo)
The vertical structure of ocean eddies
Satellite observations capture diverse oceanic phenomena over much of the globe. However, it remains to understand how surface fields, like sea surface height, reflect the motion occurring at depth. The vertical structure of ocean eddies is usually expressed in terms of flat bottom baroclinic modes. Bathymetry alters the modes though, weakening the bottom velocities. We show that with realistic bathymetry and/or bottom friction, the bottom velocities are nearly zero. The resulting "surface modes" should thus be ubiquitous. This would explain the dominant mode of variability obtained from globally-distributed current meters, and is consistent with energy spectra derived from sea surface height data. The results yield a simple way to infer subsurface velocities from satellite data, and suggest ocean analyses should probably be made in terms of surface modes and topographic waves.