Deep Cycle Turbulence and Oceanic Heat Uptake in the Eastern Equatorial Pacific

The eastern Pacific cold tongue is a prime location for heat transfer into the ocean. The effect of this heat uptake on climate is determined in part by vertical transport: heat remaining near the surface can be returned to the atmosphere on a timescale of days, whereas heat transferred into the thermocline by turbulent mixing may not contact the surface again for centuries. Below the surface mixed layer, the so-called "deep cycle" turbulence dominates vertical transport. The mechanism of the deep cyce is not fully understood, but it depends on a combination of the stratified, parallel shear flow on the upper flank of the equatorial undercurrent and nonlocal forcing due to diurnally varying surface fluxes. In this presentation I will use data from the TOGA-TAO mooring array in combination with a new parameterization of deep cycle turbulence to estimate the strength of the turbulent heat flux over a period of 20 years and to show how it varies over diurnal, seasonal and ENSO cycles.