Diagnosing cross-scale kinetic energy exchanges from two submesoscale permitting ocean models.

• Main Authors: Ajayi, Adekunle, Le Sommer, Julien, Chassignet, Eric, Molines, Jean-Marc, Xu, Xiaobiao, Albert, Aurelie, Dewar, William
• Other Authors: Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)
• Format: Report
• Language: English
• Published: HAL CCSD 2020
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; North Atlantic
• Online Access: https://hal.science/hal-03084219; https://doi.org/10.1002/essoar.10501077.1

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.