Variability of submesoscale dynamics in the North Atlantic from a 1/60° ocean model simulation.

Several processes contribute to energize oceanic flows at scales smaller than the first baroclinic Rossby radius (frontogenesis, mixed-layer instabilities, current-topography interactions...). But the relative strength of these processes and their impact on energy cascades at basin scale is still poorly quantified. Likewise, little is known regarding how submesoscale dynamics actually affects larger scale flows at basin and global scales. Here, we use several years of an unprecedented sub-mesoscale-permitting, North Atlantic ocean/sea-ice model simulation performed at 1/60° resolution with 300 vertical levels. We describe the spatio-temporal variability of dynamical regimes at scales <100km at mid and high latitudes in the North Atlantic. Statistical properties of submesoscale dynamics across the basin are described in terms of wavenumber spectra and probability distributions of surface variables and discussed in the light of recent information collected during field experiments at submesoscales. Our results show in particular how the seasonal cycle of surface stratification in the subpolar gyre leads to a strong seasonal modulation of submesoscale activity at high latitudes. We finally discuss how the future wide-swath altimetric missions (SWOT) will sample these dynamical regimes.