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

Abstract

The global energy dissipation rate of deep-ocean lowfrequency 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 windpower 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.