Langmuir Mixing Affects Global Climate

The effects of Langmuir turbulence on the surface ocean mixing and thereby the global climate are assessed in the CESM earth system model by adding a parameterization of Langmuir mixing to the K-Profile Parameterization (KPP). A global wave field is needed by this Langmuir mixing parameterization to provide the Stokes drift that drives Langmuir mixing. Both a prognostic wave model, WAVEWATCH III, and a climatological data wave model have been coupled with CESM and tested. Nearly identical and substantial improvements in the simulated mixed layer depth and intermediate water ventilation are found in both cases when Langmuir mixing is included. The greatest improvement occurs in the Southern Ocean. A climatological data wave model, which responds to simulated winds, but with fixed wind-wave relationships, can therefore reproduce the primary improvements of Langmuir mixing, but with much less computational cost than even a coarse-resolution prognostic wave model. Progress toward an improved wave-induced entrainment through the bottom of ocean surface boundary layer will also be discussed.