The 39th meeting of the Sandbox Series will be on:
The power of the small: how submesoscale motions shape the ocean’s kinetic energy cycle
Abstract: Mesoscale eddies contain the bulk of the ocean’s kinetic energy (KE), but fundamental questions remain on the cross-scale KE transfers linking eddy generation and dissipation. The role of submesoscale flows represents a key point of discussion, with contrasting views of submesoscales as either a source or a sink of mesoscale KE.
Here, the annual cycle of the KE transfer between mesoscale and submesoscale motions is assessed in the upper layers of a typical open-ocean region, by analysing a unique set of in situ observations. The cross-scale KE transfer is shown to exhibit two distinct stages, whereby submesoscales energise mesoscales in winter and drain mesoscales in spring. An exploration of the dynamics governing mesoscale-submesoscale KE exchanges suggests that the upscale KE transfer in winter is underpinned by mixed-layer baroclinic instabilities, and that the downscale KE transfer in spring is associated with submesoscale frontogenesis. Our results are compatible with recent high-resolution (submesoscale-permitting) modelling investigations that place the headwaters of the inverse KE cascade at the submesoscale, and that rationalise the seasonality of mesoscale KE as an inverse cascade-mediated response to the generation of submesoscales in winter. However, our findings challenge many of those investigations by suggesting that submesoscale frontogenesis can substantially dampen the mesoscale – a process that is poorly represented in most high-resolution models. The dynamics of such submesoscale frontogenesis, and the reasons for their misrepresentation in models, will be assessed and discussed.
Schedule
1200-1245: Alberto Naveira Garabato
1245-1315: Discussion
1315-1330: Break
1330-1345: Mini-talk 1 – Maneesh Kumar Singh (Imperial College London)
1345-1400: Mini-talk 2 – TBC
1400-1430: Discussion & close