Diagnosing cross-scale kinetic energy exchanges from two submesoscale
permitting ocean models.
Abstract
The upper-ocean at fine-scales ($<$100\,km)
contributes significantly to energy exchanges and dissipation. However,
our knowledge of fine-scale motions (in terms of kinetic energy density
and transfer) in the real ocean is limited due to lack of sufficient
observational datasets at these scales. Kilometric resolving ocean
models have been developed in anticipation for the Surface Water and
Ocean Topography (SWOT) satellite mission. This mission would provide
unprecedented global coverage of energetic oceanic flows down to
10\,km. In this study, we investigate the distribution
and exchange of energy across different scales down to
10\,km based on two state-of-the-art realistic North
Atlantic basin simulations with horizontal resolution of
$\sim$\,1.5\,km. The
results show that ageostrophic motions have direct impacts on
cross-scale kinetic energy exchanges and that these exchanges undergo
both regional and seasonal variability. In particular, this seasonality
which is more pronounced at fine-scale is characterized by a significant
amount of direct KE cascade in wintertime. In general, we found the
forward cascade to be confined to the mixed layer depth while the
inverse cascade extends down to about 700m in the interior.