Deep Convection in the Ocean

SCIENTIFIC OBJECTIVES Issues specific to oceanic deep convection are the relatively strong role of rotation, such that convective Rossby numbers appropriate to the vertical motions may fall below unity; the highly intermittent nature of the forcing, with the strong impulses coming during the passage of atmospheric weather systems; the possible highly localized occurrence of deep convection; and the subsequent spatial redistribution and mixing of convected water by geostrophic mesoscale dynamics, which arise in part from instability of the localized convection regions. Our particular research projects are computational investigations intended to (1) quantify the extent to which penetrative mixing occurs at the base of a rotation convective layer, sharpening the pycnocline and entraining denser fluid from below; (2) determine how space/time intermittence in either the surface buoyancy flux or the pre-existing ocean stratification and circulation relate to the degree of localization of deep convection; and (3) explore the circumstances under which localized converted regions are persistent after the buoyancy forcing abates or undergo erosion through subsequent horizontal mixing and restratification of the gyre interior.