[A-OS11] Ocean Mixing Frontiers

[AOS11-07] Enhanced turbulent mixing in the equatorial thermocline

*Kelvin John Richards¹, Andrei Natarov¹, Yanli Jia¹ (1.International Pacific Research Center, School of Ocean and Earth Science Technology, University of Hawaii)

Keywords:Ocean turbulence, Ocean/atmosphere interaction

Enhanced mixing caused by small vertical scale features (SVSs) in the equatorial thermocline is known to impact the state of the ocean and its interaction with the atmosphere, in particular the sea temperature of the Pacific cold tongue and ENSO variability. The SVSs are produced by wind variability and instabilities. The good news is that with enough resolution these features can be captured in both observations and models. From observations we show that the vertical distribution of turbulent activity in the thermocline is very dependent on the turbulent length scale. From models we show that inertial and parametric subharmonic instability play a role and that wind driven inertia-gravity waves lead to an enhancement in mixing by a combination of three factors: a stronger super-inertial component of the wind forcing close to the equator, wave action convergence at turning latitudes for equatorially trapped waves, and nonlinear wave-wave interactions between equatorially trapped waves. Using a combination of ideal models and an OGCM we investigate the properties of SVS activity and its impact on mixing. Of particular interest is the dependency on stratification, the spatial and temporal variability of wind forcing and model resolution (both vertical and horizontal). The impact of the spatially and temporally varying mixing on the seasonal and inter-annual variability of the Pacific with be discussed. Such knowledge is invaluable in the planning of future observational studies and the design of the next generation climate models.