Presenter: Cal LeDoux (University of Chicago)

Description:
Thermobaric convection, or convection that results from the increasing thermal expansivity as pressure increases, likely contributes substantially to high-latitude ocean convection and associated deep-water formation. However, the effects of thermobaric convection remain poorly constrained. To evaluate the role of thermobaric convection in the Southern Ocean (and, therefore, the role of thermobaracity in the formation of Antarctic Bottom Water), Ocean Convective Available Potential Energy (OCAPE), the potential energy arising from thermobaracity within a conditionally stable ocean column, is diagnosed in simulations using the MITgcm coupled ice-ocean model. As found in other models, and consistent with some observational evidence, Antarctic Bottom Water formation in these simulations is highly variable, showing oscillatory behavior at multiple frequencies.  We find that OCAPE in the Southern Ocean is high while convective activity is lowest while being depleted rapidly once deep convection sets in. The build-up of OCAPE seems to arise due to the advection of anomalously salty and warm water at depth. Hence, OCAPE accumulation appears to play an important role in the variability of bottom water formation and provides a potential predictor of when deep convection will occur.