Indirect Oceanic Current Feedback on Atmospheric Dynamics over Western Boundary Currents and Adjacent Continents
A set of two Global coupled Ocean-Atmosphere experiments has been carried out using the EC-Earth 3.2 model, with both atmospheric and oceanic models at ~10-15km degree of horizontal resolution over a 25 years period. They only differ by taking account or not the ocean current feedback in the calculation of wind stress (CFB – Current FeedBack and NOCFB).
The WBCs paths rectification along with the reduction of EKE cause large difference of Sea Surface Temperature (SST, more than 2 degrees) over the core of WBCs (i.e., Gulf Stream, Kuroshio, Agulhas Brazil and the East Australian currents) between CFB and NOCFB. These SST differences lead to a significant changes in heat fluxes at the air-sea interface. The resulting convection cells and cloud formation processes are then modified between CFB and NOCFB and induce +/- 10% of seasonal rainfall difference over the WBCs, but also, over subtropical gyres and adjacent continents. A significant difference are then found in extratropical storms tracks in both Northern and Southern parts of Atlantic and Pacific oceans, linking the local mesoscale dynamical air-sea interactions with larger atmospheric dynamics and, notably, the strength, the extremes and the variability of extratropical atmospheric jets.