On long term assessement of improved ocean/wave coupling in the Southern Ocean and Marginal Ice Zone

The Southern Ocean is strongly affected by uncertainties on the surface wind, and consequently the fluxes exchanged between the atmosphere and the ocean include fairly strong biases. The assimilation of directional wave spectra from wave scatterometer SWIM of CFOSAT has demonstrated the improvement of the prediction of the different scales of waves from the wind-waves to the swell. As a result, the estimation of momentum and heat fluxes are positively affected, particularly in the western boundary current regions. This work presents long term validation of key ocean parameters (temperature, current and salinity) in the Southern Ocean from coupled experiments of the MFWAM and NEMO models over a long period of 4 years. Simulations with and without the assimilation of SWIM spectra are compared to estimate the impact on ocean circulation.

The ocean model outputs have been validated with the available level 3 & 4 in situ and satellite observations over the Southern Ocean. A comparison was made with climatologies for some parameters such as the ocean mixed layer. The results indicate a significant impact on the heat content at 300 m depth in the Southern Ocean, particularly in the marginal ice zone. The analysis of temperature and salinity profiles over specific locations in the MIZ shows good consistency of variability with the coupled simulation using CFOSAT assimilation. In this work we investigated the impact of using wave/ice interaction in the coupling. We also examined the use of Eddy diffusivity Mass fluxes (EDMF) convection scheme in NEMO model and evaluate the impact on ocean circulation in the southern ocean. Further comments and conclusions will be reported in the final presentation.