Friday 26 August 2005

P2
1550-1710 hours

513
Control of large-scale ocean transport by small-scale mixing
Cessi, Paola¹, Polton, Jeff¹, Young, William¹
1 Scripps Institution Of Oceanography, UCSD, CA, USA
Author email: pcessi@ucsd.edu
We prove that the ocean heat transport is strongly constrained by small-scale mixing. The implications of these constraints are analyzed in the context of two eddy-resolving, rapidly rotating primitive-equation models driven by specified surface temperature and wind-stress, with isotropic diffusion and bottom-drag. The statistical equilibrium is characterized by several quantities, for which we propose scaling-laws as a function of the external parameters. The mean stratification, measured by the depth of the thermocline, is independent of the diapycnal mixing to leading order, but depends on the bottom drag. This dependence arises because the mean stratification is due to a balance between the large-scale wind-driven heat transport and the heat transport due to baroclinic eddies. The latter equilibrate at an amplitude which depends to leading order on the bottom-drag. The net poleward heat transport instead depends to leading order on the diapycnal mixing, and it is very small when observed values of diapycnal mixing are used. The implications of these results on the stability of the thermohaline circulation are discussed.

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