Internal Wave Interactions with Equatorial Deep Jets. Part II: Acceleration of the Jets

Abstract

Abstract What drives the equatorial deep jets is a puzzle because of their isolation from surface forcing by the intervening main pycnocline and the Equatorial Undercurrent, and from lateral boundaries by distances of tens of thousands of kilometers. It would take decades for energy to propagate to the jets’ midbasin location from boundary sources. Their persistence points to some mechanism maintaining them in situ. The authors hypothesize that the ambient internal wave field deposits momentum fluxes at critical layers within the deep jets and, using calculated momentum- and energy-flux divergences as forcing, estimate acceleration of the mean zonal flow in the deep jets. Internal wave momentum-flux divergences are more than sufficient to sustain the jets, acting to sharpen the shear between the jets on timescales of months to years. Predicted energy-flux divergences produce turbulent dissipation rates compatible with those observed.