Impacts of Langmuir turbulence derived from a statistical wave model on the oceanic mean state in the North Atlantic

The study assesses impact of Langmuir turbulence on simulations in the North Atlantic using a climate system model. Instead of coupling a prognostic wave model online, we utilize a statistical wave model, which is implemented into a turbulent kinetic energy (TKE) closure scheme, to estimate Stokes drift aiming to reduce computational expenses. Another two parameterizations, including without Langmuir turbulence and Stokes drift directly estimated by wind stress, are also compared to explore the priority of the statistical wave model. Our findings indicate that enhanced turbulent mixing induced by Langmuir turbulence can mitigate cold sea surface temperature and fresh sea surface salinity biases in the North Atlantic, as well as shallow mixed-layer depth biases in the Labrador Sea. Additionally, simulation of the Atlantic Meridional Overturning Circulation (AMOC) is improved. This improvement is attributed to enhanced turbulent mixing due to Langmuir turbulence, which increases eddy vertical diffusivity and buoyancy loss, thereby weakening stratification in surface and thermocline layers. Consequently, reduced stratification enhances deep convection and the generation of North Atlantic Deep Water during boreal winter, ultimately strengthening the AMOC. Importantly, the parameterization that Stokes drift inferred from the statistical wave model outperforms the alternative method directly inferred from wind stress, providing the most compelling improvements in North Atlantic simulations within our fully coupled model.