Do Altimeter Wavenumber Spectra Agree with the Interior or Surface Quasigeostrophic Theory?

Abstract

Abstract In high-eddy-energy regions, it is generally assumed that sea level wavenumber spectra compare well with quasigeostrophic (QG) turbulence models and that spectral slopes are close to the expected k−5 law. This issue is revisited here. Sea level wavenumber spectra in the Gulf Stream, Kuroshio, and Agulhas regions are estimated using the most recent altimeter datasets [the Ocean Topography Experiment (TOPEX)/Poseidon, Jason-1, the Environmental Satellite (Envisat), and the Geosat Follow-On]. The authors show that spectral slopes in the mesoscale band are significantly different from a k−5 law, in disagreement with the QG turbulence theory. However, they very closely follow a k−11/3 slope, which indicates that the surface quasigeostrophic theory (SQG) is a much better dynamical framework than the QG turbulence theory to describe the ocean surface dynamics. Because of the specific properties of the SQG theory, these results offer new perspectives for the analysis and interpretation of satellite data.