The impact of climate change on submesoscale instabilities in the surface ocean

Anthropogenic climate change is projected to influence ocean mixed layer depths with the potential for significant changes in submesoscale dynamics. The implications of such physical changes on ocean heat fluxes and biogeochemical cycling are unclear. Here, we present results from a submesoscale-resolving regional model of an open-ocean region in the eastern North Atlantic, where submesoscale-resolving observations are available for model validation. We investigate the effects of the resolved spatial scale on the resulting submesoscale activity in a present-day scenario, and then we consider how the submesoscale activity changes by the end of the 21st century in the RCP8.5 emissions scenario. This future scenario produces a clear reduction in the depth of the mixed layer and submesoscale activity during the winter/spring. Conditions that are unstable at the submesoscale are identified using the balanced Richardson number, and the spatial and seasonal variation of instability types will be presented. The analysis highlights how anthropogenic climate change may impact the type, frequency and seasonal cycle of submesoscale instabilities. Particular focus is on the projected changes in the vertical component of velocity and the implications for mixing in the surface ocean, ocean heat fluxes and biogeochemical cycles.