Abstract
The energy sources for convection and the general circulation are revisited through an analysis of the compressible equations of motion, rather than the Boussinesq equations. We are motivated in this endeavor by a more straightforward connection in the compressible equations between thermodynamics and dynamics, and the continuing debate in the field regarding the suggestion, made first in the form of Sandström’s theorem, that surface buoyancy fluxes can not drive the overturning circulation. While ultimately supporting the Sandström position, the analysis leads to some new insights into ocean energetics and surface energy fluxes. We argue the ultimate role of buoyancy fluxes are to damp the circulation and that ocean energy cycles between internal and kinetic energy. Ocean heating due to the general circulation, geothermal heat flux and the biosphere are evaluated for their roles and we suggest the latter two provide energy to the overturning much more effectively than surface forcing. All three also contribute significantly to net ocean surface energy flux, an effect that influences the interpretation of ocean heat content imbalances.
Keywords:
Energetics; Turbulence