SGER: Turbulence Properties in the Mixed Layer/Thermocline Transition Layer

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Abstract OCE-0721168This study focuses on upper-ocean processes that impact the near-surface physics of the ocean and control the oceanic heat budget, which moderates global climate and the upper-ocean nutrient fluxes which moderate oceanic production and thus fisheries. The oceanic mixed layer is the uppermost portion of the ocean; it is a region of intense mixing where turbulence supplied by wind and waves homogenizes the vertical distribution of temperature and salinity down to depths of O(100m). Below this layer, in the upper layers of the stratified thermocline, turbulent Reynolds numbers are several orders of magnitude smaller. Although the transition between these two regimes is assumed to take place abruptly at the mixed-layer base, observations suggest that enhanced turbulence penetrates significantly into the stratified water just below the mixed layer. In this study, scientists at FSU will examine existing turbulence data collected during the past 20 years and low- and mid-latitude sites. These data allow for direct estimates of diffusivity and diapycnal flox occurring in the transition layer. The results will shed light on the suitability of parameterizations which are presently used to simulate upper ocean turbulence in numerical models of the global climate. Thus the study will have a broad impact on these models which are used in the prediction of issues that are important to society.