Complementary use of SAR and thermal IR observations in the Brazil-Malvinas confluence region

The Western South Atlantic Ocean is characterized by the confluence of the Brazil Current and the Malvinas (Falkland) Current. along the western margin of the Argentine Basin. The so-called Brazil-Malvinas Confluence occurs near the entrance of the La Plata River estuary; roughly between 35 degrees S and 40 degrees S. A significant number of papers related to different oceanographic and biological aspects of the confluence has been published with many based on thermal infrared (IR) and/or visible satellite imagery. The NOAA-AVHRR sensor, which has been most commonly used, observes this area four or five times per day in the visible and IR bands. However: this frequency, is often insufficient, given the high probability of cloud cover in the region. In contrast, an active sensor such as the synthetic aperture radar (SAR) can be used day and night and under cloudy conditions to observe a variety of sea surface signatures. A GlobeSAR-2 project was carried out during 1997-1998 to monitor the confluence using ScanSAR Wide Beam Mode RADARSAT-1 images. The project aimed at determining the possibility of using these data to provide complementary information to AVHRR and defining their capability, to detect ocean dynamic patterns in the region. RADARSAT-1 images were acquired during 1997 and 1998. Two 1998 images corresponding to July 19 and September 5 are presented here. Complex patterns associated with the ocean surface circulation, biological productivity; and atmospheric conditions were analyzed The results show that tinder adequate wind speed conditions SAR can be used in a complementary way with NOAA-AVHRR, and provide details about different aspects of the dynamics of the region, such as fronts,,filaments and eddies. The observations suggest that SAR imagery may, also be able to provide a useful link between physical oceanography, information derived from thermal sensors and biological information from visible sensors like SeaWiFS and MODIS.