Impact of fine atmospheric scales on ocean eddies and deep convection in the Subpolar Northern Atlantic

Abstract

In this study we examine the sensitivity of the high-resolution regional ocean model solution to the atmospheric forcing of low (70 km - LoRes) and high (14 km - HiRes) spatial resolutions over the North Atlantic. To force the regional set up of NEMO ocean general circulation model (OGCM) we use the North Atlantic Atmospheric Downscaling (NAAD) product, which is the result of the Weather Research and Forecasting (WRF) atmospheric GCM with ERA-Interim as a boundary condition. Increase of the of the resolution of the atmospheric forcing and thus, representation of the surface turbulent heat and radiative fluxes in HiRes and LoRes atmospheric forcing, cause the 1.5° negative difference between sea surface temperature and -0.15 PSU in sea water salinity over the whole domain. The output of the OGCM forced by the high-resolution atmosphere is almost equal to the observational datasets. More intensive turbulent heat loss from the ocean surface and ventilation processes result in lower ocean heat content in the upper ocean (0-700 m) and at intermediate depth (700-1500 m) when the model is forced by HiRes. HiRes-driven experiment shows more intense coastal currents and less intensive large-scale currents. Ventilation processes are sensitive to the mesoscale atmospheric events representation: HiRes experiment provides deeper by 100 m mixed layer depths and its later in time deepening and restratification.