TRR 181 Seminar "High-resolution simulations of submesoscale processes in the Baltic Sea: The role of storm events" by Evridiki Chrysagi (IOW)

The TRR 181 seminar is held byEvridiki Chrysagi(IOW) on November 26, 11am.

High-resolution simulations of submesoscale processes in the Baltic Sea: The role of storm events

Abstract

Recently discovered, submesoscales have drawn the attention due to their ability to change the upper ocean stratification and induce high vertical velocities, both being instrumental for marine biogeochemistry, but also due to their potential role on the downscale cascade of energy. This study investigates the effect of submesoscale fronts and filaments on the restratification process and mixing efficiency during the lifetime of storms, thereby extending previous idealized simulations towards real-ocean applications. A realistic high-resolution numerical simulation is analyzed focusing on the central basin of the Baltic Sea, an area where available observations from a field campaign confirm that features persistent lateral density gradients and rich submesoscale activity, hence forming an ideal natural laboratory for this study. The simulation reveals a strong thermal frontal structure that persists during autumn and has not been reported previously. Cold submesoscale filaments with sharp lateral buoyancy gradients, strong surface convergence and high vertical velocities arise from this front. Highly heterogeneous Mixed Layer Depth (MLD) patterns appear, with the shallowest MLDs found in the vicinity of submesoscale features. As it turns out, submesoscales are able to maintain shallow MLDs during storms and induce vigorous and rapid restratification when the wind subsides, creating significant temporal MLD variability. The interaction of strong near-surface turbulence and submesoscale restratification results in highly efficient mixing inside submesoscale fronts.