Generation of lee waves and submesoscale vortices in the wake of the Charleston Bump

Jonathan Gula, Université de Bretagne Occidentale, Laboratoire d'Océanographie Physique et Spatiale (UBO, CNRS, Ifremer, IRD), Plouzané, France, Charly de Marez, Laboratoire d'Océanographie Physique et Spatiale, Plouzané, France, Noe Lahaye, LOPS, IUEM, University of Brest, Brest, France, Tanya M Blacic, Montclair State Univ, Montclair, NJ, United States and Robert E Todd, Woods Hole Oceanographic Institution, Physical Oceanography, Woods Hole, MA, United States
Surface signatures of internal waves are observed in satellite sun-glitter images where the Gulf Stream flows along the U.S. seaboard, in particular above a deep topographic feature called the Charleston Bump. Deep, lens-shaped submesoscale features are also captured in seismic images and glider sections of the Gulf Stream front in the lee of the Bump. These are typical signatures of anticyclonic submesoscale coherent vortices (SCVs). The generation of lee waves and SCVs is studied using submesoscale resolving realistic simulations. The model reproduces the observed signature of the lee waves at the surface and SCVs at depth. The SCVs are generated primarily where the Gulf Stream meets the Charleston Bump due to the frictional effects and intense mixing in the wake of the topography. The waves are generated by the interaction of the Gulf Stream with small scale topographic features. These waves are shown to match with the linear theory describing topographically-generated internal waves. Finally, small scale topographic features are shown to have a significant impact on the mean flow in this region of the Gulf Stream.