Disentangling the Mesoscale Ocean-Atmosphere InteractionsDisentangling the Mesoscale Ocean-Atmosphere Interactions and How to Best Force an Ocean Model

Lionel Renault, University of California Los Angeles, Los Angeles, CA, United States, Sebastien Masson, Sorbonne Universités (UPMC, Univ Paris 06)-CNRS-IRD-MNHN, LOCEAN Laboratory, Paris, France, Vera Oerder, LOCEAN-IPSL, CNRS/IRD/UPMC, UMR7159, Paris cedex 05, France, Swen Jullien, IFREMER, France, Francois Colas, Univ Pierre and Marie Curie-Paris 6, Paris, France, Gurvan Madec, LOCEAN-IPSL, CNRS/IRD/MNHN/Sorbonne Université, Paris, France, James C McWilliams, University of California in Los Angeles, Los Angeles, United States and Arsouze Thomas, Barcelona Supercomputing Center, Barcelona, Spain
In the past decades, the use of scatterometer data allowed to demonstrate the global ubiquity of the Ocean Mesoscale Thermal FeedBack (TFB) and Current FeedBack (CFB) effects on surface winds and stress. Understanding those air-sea interactions is of uttermost importance as the induced atmospheric anomalies partly control the ocean circulation, and, thus, can influence the Earth Climate. Whether the TFB and CFB effects can be disentangled, and whether satellite scatterometers can properly reveal them, remain rather unclear. Here, using satellite observations and ocean-atmosphere coupled mesoscale simulations over 45\dg S-45\dg N, we show the CFB effect can be properly unraveled from that due to the TFB. We demonstrate that the TFB can be unambiguously characterized by its effect on the stress (and wind) divergence and magnitude. However, its effect on the wind curl is contaminated by the CFB. Finally, because scatterometers provide relative equivalent neutral stability winds to the oceanic currents, they cannot characterize adequately the CFB wind response and overestimate the TFB wind response by 25\%. Surface stress appears to be the more appropriate variable to consider from scatterometer data. We will also discuss the limitations of forcing an ocean model with scattterometers and how to best force an ocean model, mimicking the CFB.