Lateral Mixing DRI: Turbulence-Resolving Simulations of Upper-Ocean Lateral Mixing

Abstract

Abstract : This study contributes to our long-term efforts toward understanding: Mixed layer dynamics; Processes that communicate atmospheric forcing; to the ocean interior Frontal dynamics, in particular the role of surface forcing in lateral mixing; and the interaction of finescale and submesoscale upper-ocean mixing at fronts. The focus of modeling in this study is to quantify relationships between surface fluxes of heat, energy and momentum, the available baroclinic potential energy, the resultant vertical mixing and geostrophic imbalance, and the ensuing dependence of lateral mixing at successively larger scales on atmospheric forcing. Large Eddy Simulations of 3D large-eddy turbulence in boundary layers of depth 10m< HML<100m have enabled model-data comparisons against measurements of turbulence and dispersion. Such comparisons can critically assess the role of mixed layer dynamics and surface-driven vertical mixing in the cascades of baroclinic potential energy into submesoscale lateral mixing processes. Large Eddy Simulations (LES) have been done in close collaboration with E. A. D'Asaro and C. M. Lee, whose AESOP field experiments measure upper ocean mixing processes in the strong lateral density gradients of the Kuroshio and in a weaker front of the California Current off Monterey, during periods of varying wind and wave forcing. Field experiments for the LatMix DRI will provide further basis for realistic modeling efforts. These simulations incorporate virtual Lagrangian Floats, gliders and drifters, to provide a basis for interpreting these small-scale mixing measurements. In addition to LES modeling and parameterization of observed and simulated frontal regimes, Harcourt has been participating extensively in the field component of the LatMix DRI by providing a steady stream of remote sensing and regional model data to scientists in the field through the information flow (INFLO) subgroup of the DRI.