Eddies and circulation: Lessons from oceans and the GFD lab

Abstract

This is a discussion of aspects of the energy-dominant eddies/waves of the global ocean emphasizing their finite-amplitude dynamics in the upper levels of the ocean and their reshaping of the deep branches of the general circulation. We rely heavily on observations which, only in the past few years have achieved the status of a global quasi-synoptic observing system, making possible an increasingly complete understanding of the time-dependent oceans. In stratified oceans and atmospheres a significant fraction of the baroclinic energy is captured in mesoscale structures which resist the classic cascades of geostrophic turbulence toward barotropic (depth-independent) states and thence to larger horizontal scale. Eddies both stir the deep ocean, shape its PV field, transfer surface momentum downward to drive large recirculation gyres, and greatly alter the western boundary currents. In effect, eddies redefine the general circulation. © 2010 Springer Science+Business Media B.V.