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GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L09606, doi:10.1029/2008GL033407, 2008

Global energy dissipation rate of deep-ocean low-frequency flows by quadratic bottom boundary layer drag: Computations from current-meter data

Ayon Sen

Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, USA
Westwood High School, Austin, Texas, USA


Robert B. Scott

Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, USA


Brian K. Arbic

Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, USA


Abstract

The global energy dissipation rate of deep-ocean low-frequency flows by quadratic bottom boundary layer drag is estimated in three ways. First, an average over the dissipations computed from the near-bottom velocities recorded by 290 moored current meters is multiplied by the World Ocean area. Second, near-global maps of surface velocities derived from satellite altimetry data are used to estimate the bias due to the sparse spatial coverage of the moorings. Third, a relationship between bottom and surface flows, computed over the mooring locations, is used to estimate global maps of bottom flows from the surface data. All three methods suggest that at least 0.2 TW of the wind-power input into geostrophic flows is dissipated in deep water by quadratic bottom drag. Implications for the oceanic overturning circulation, and for oceanic mesoscale eddy dynamics, are briefly discussed.

Received 24 January 2008; accepted 1 April 2008; published 9 May 2008.

Keywords: quadratic bottom drag; dissipation; ocean energy budget.

Index Terms: 4520 Oceanography: Physical: Eddies and mesoscale processes; 4512 Oceanography: Physical: Currents; 4532 Oceanography: Physical: General circulation (1218, 1222); 4576 Oceanography: Physical: Western boundary currents.

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Citation: Sen, A., R. B. Scott, and B. K. Arbic (2008), Global energy dissipation rate of deep-ocean low-frequency flows by quadratic bottom boundary layer drag: Computations from current-meter data, Geophys. Res. Lett., 35, L09606, doi:10.1029/2008GL033407.