Global submesoscale Transition Scale estimation using alongtrack
satellite altimetry
Abstract
The ocean’s sea surface height (SSH) field is a complex mix of motions
in geostrophic balance and high-frequency tides, internal tides and
internal gravity waves. The transition scale Lt, at which unbalanced
ageostrophic motions dominate balanced geostrophic motions, is
documented for the first-time using satellite altimetry. Lt is critical
to define the scales where surface geostrophic currents can be inferred
from SSH. We use a statistical approach based on the analysis of SSH
wavenumber spectra to obtain Lt. Small values of Lt are observed in
regions of energetic mesoscale activity, while large values are observed
in tropical latitudes and regions of low mesoscale activity. Seasonally,
larger Lt values are observed during summer than during winter,
following the seasonality of upper ocean dynamics. These results are
consistent with recent analyses of in situ observations and
high-resolution models. Limitations of our results and implications for
nadir and swath altimetric missions are discussed.