Joint Seminar: Available Potential Energy and the general circulation: Partitioning wind, buoyancy forcing, and diapycnal mixing

A new definition of Available Potential Energy (APE) is used to partition the adiabatic component of the ocean circulation from diapycnal mixing. The energy cycle is applied to results from the ECCO2 eddy-permitting ocean state estimate (using the MITgcm) and observed surface heat fluxes from the WHOI OAFlux project. Compared with the traditional Lorenz Energy Cycle this framework provides a more accurate estimate of the background potential energy of the global oceans and the surface generation and interior fluxes of APE. The analysis suggest that the adiabatic portion of the general circulation is maintained by a balance between the mean wind-driven upwelling which increases APE and eddies, which release APE. The analysis also demonstrates clearly that surface buoyancy fluxes generate APE at a rate comparable to the mean winds. The energy cycle also provides an estimate of the global rate of diapycnal mixing, which must balance the surface APE generation. This estimate (0.46 TW) is consistent with previous estimates of the diapycnal fluxes associated with maintaining deep stratification \citep{Munk1998} and a global diapycnal diffusivity of O($1\times10^{-4}$ m$^2$s$^{-1}$). The analysis suggests a method for monitoring the global rate of diapycnal mixing rate using measurable surface properties such as SST and heat flux.

Datum

03.06.2015

Uhrzeit

13:30 Uhr

Ort

Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg

ReferentIn

Brian White, Marine Sciences, University of North Carolina

Chair

Jin-Song von Storch

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