Sun glitter as a "tool" for monitoring the Ocean from Space Alexander Myasoedov Satellite Oceanography Laboratory Russian State Hydrometeorological University St. Petersburg, Russia mag@rshu.ru Vladimir Kudryavtsev Satellite Oceanography Laboratory Russian State Hydrometeorological University St. Petersburg, Russia kudr@rshu.ru Bertrand Chapron Department of Oceanography and Ecosystem Dynamics IFREMER Brest, France Bertrand.Chapron@ifremer.fr Johnny A. Johannessen Nansen Environmental and Remote Sensing Center Bergen, Norway johnny.johannessen@nersc.no Fabrice Collard Direction of Radar Applications CLS Plouzané, France dr.fab@cls.fr Abstract- A method for retrieval of the spatial variations of the sea surface mean square slope (MSS) in sun glitter imagery is proposed. Observed sun glitter brightness anomalies are converted to the MSS anomalies with use of a transfer function determined from the smoothed shape of the sun glitter brightness. The method is applied to MODIS and MERIS sun glitter imagery of natural oil seeps and the catastrophic Deep- water Horizon oil spill in the Gulf of Mexico. The results clearly demonstrate a highly feasible approach for investigation of surface signatures of the oil slicks, as well as other ocean phenomena. Keywords- Sun-glitter; Mean square slope;Surface slicks; Oil spills; optical imagery I. INTRODUCTION In general, the main oceanographic applications of satellite optical data (e.g. from MODIS and MERIS instruments) are associated with ocean color studies. In such cases the sunlight reflected from the sea surface is a major part of upward radiation and possess significant difficulties for ocean color retrieval algorithms. On the other hand, sun glitter contain valuable information on statistical properties of the sea surface roughness, its mean square slope (MSS), skewness and kurtosis, as demonstrated by Cox and Munk [1] and more recently by Bréon and Henriot [2]. Most ocean surface phenomena, e.g. biogenic and oil slicks, internal waves, ship wakes, spiral eddies, are locally affecting sea surface roughness to become visible in optical data. Numerous satellite observations of surface slicks in sun glitter were reported, e.g. by Adamo et al. [3], Chust and Sagarminaga [4], and Hu et al. [5]. Hennings et al. [6] presented observations of the surface manifestation of shallow water bottom topography in sun glitter brightness. Other authors also observed and studied non-linear internal waves in sun glitter imagery. Evidently, sun glitter signatures are caused by spatial variation of short scale sea surface roughness tracing surface manifestation of an ocean phenomenon. The magnitude of the contrasts is connected to the type of surface slick, e.g. biogenic, oil, and possibly thickness of the oil spill producing the slick. Retrieval and quantitative interpretation of these sun glitter brightness contrasts can thus help to better understand damping mechanisms. Unlike determination of the background statistical properties of the sea surface slopes, to the best of our knowledge, satellite sun glitter imagery has never been specifically used for quantitative estimates of MSS anomalies of the surface roughness. Complexity arises from the fact that the sun glitter brightness and the MSS contrasts depend on the viewing and sun illumination geometries. Contrasts of MSS can then either be visible as dark/bright or bright/dark brightness signatures (see e.g. Hu et al. [5] for the oil slicks). This property is quite straightforward, and as shown recently by Jackson and Alpers [7], is a simple consequence of different viewing distance Funding for this research was provided by the Mega-grant of the Russian Federation Government to support scientific research under the supervision of leading scientist at RSHU, No. 11.G34.31.0078 978-1-4673-0875-5/12/$31.00 ©2012 IEEE