Langmuir Mixing Effects on Global Climate: Wavewatch III in CESM

Abstract:

Large-Eddy Simulations (LES) have shown the effects of surface wind waves in enhancing ocean boundary layer mixing, yet this Langmuir mixing process is missing in almost all the state-of-the-art climate models and may contribute to the shallow biases of mixed layer depth in the Southern Ocean and the Northern Atlantic in most climate models.

In this study a third generation wave model, WAVEWATCH III, has been incorporated as a component of the Community Earth System Model, version 1.2 (CESM1.2). In particular, the wave model is now coupled with the ocean model through a modified version of the K-Profile Parameterization (KPP) including the influence of Langmuir mixing. The misalignment of wind and waves and the effects of Stokes depth are considered in our implementation of Langmuir mixing in KPP.

Wave-ocean only tests show substantial improvements in the upper ocean simulation, including reductions in both the shallow biases of mixed layer depth and the low biases of pCFC-11 in the Southern Ocean. Ocean-Ice-Wave and Atmosphere-Ocean-Ice-Wave coupled tests confirm these improvements when other climate feedbacks are included. Progress toward a more computationally efficient data wave model will be summarized.