Sack Lunch Seminar (SLS)

Geography of baroclinic instability and eddy mixing in the ocean

Observations show that the ocean has a ubiquitous, energetic geostrophic eddy field on scales of order 100km. These eddies are thought to play an important role in many aspects of ocean circulation important to climate, including the strength of the meridional overturning circulation (MOC), the depth of the mixed layer, biogeochemical cycles and the nature and properties of abyssal water masses.

In this talk a mix of theory, modeling and observations will be used to discuss the intensity and scale of the ocean's eddy field. We argue that baroclinic instability generates eddies at spatial scales near the first Rossby radius of deformation. Once formed, eddies stir and mix biogeochemical tracers and potential vorticity. We show evidence that eddy mixing rates are enhanced at the steering level of baroclinic waves, inducing a vertical structure which peaks near zero crossings in potential vorticity gradients. Finally, we compare simulated mixing rates in the Southern Ocean against observations from the DIMES field experiment.