Intense deformation field at oceanic front inferred from directional sea surface roughness observations
|Copyright||2017. American Geophysical Union. All Rights Reserved.|
|Author(s)||Rascle Nicolas3, Molemaker Jeroen1, Marie Louis1, Nouguier Frederic1, 2, Chapron Bertrand1, Lund Bjorn2, Mouche Alexis1|
|Affiliation(s)||1 : Univ Brest, CNRS, IRD, LOPS,IUEM,Ifremer, Brest, France.
2 : Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Dept Ocean Sci, 4600 Rickenbacker Causeway, Miami, FL 33149 USA.
|Source||Geophysical Research Letters (0094-8276) (Amer Geophysical Union), 2017-06 , Vol. 44 , N. 11 , P. 5599-5608|
|Keyword(s)||sea surface roughness, surface current, remote sensing, Sun glitter, high resolution, oceanic fronts|
Fine scale current gradients at the ocean surface can be observed by sea surface roughness. More specifically, directional surface roughness anomalies are related to the different horizontal current gradient components. This paper reports results from a dedicated experiment during the LASER (LAgrangian Submesoscale ExpeRiment) drifter deployment. A very sharp front, 50 m wide, is detected simultaneously in drifter trajectories, sea surface temperature and sea surface roughness. A new observational method is applied, using sun glitter reflections during multiple airplane passes to reconstruct the multi-angle roughness anomaly. This multi-angle anomaly is consistent with wave-current interactions over a front, including both cross-front convergence and along-front shear with cyclonic vorticity. Qualitatively, results agree with drifters and X-band radar observations. Quantitatively, the sharpness of roughness anomaly suggests intense current gradients, 0.3 m s−1 over the 50 m wide front. This work opens new perspectives for monitoring intense oceanic fronts using drones or satellite constellations.