Near-shore Frontal Systems in the Patagonian Shelf Using High and Low Resolution Temperature Data

JUAN P. PISONI; GABRIELA N. WILLIAMS; RICARDO O. AMOROSO; DOMINGO A. GAGLIARDINI

Puerto Madryn, Chubut. Argentina

Workshop; 4th Aquarius/SAC-D Science Workshop; 2008

Comisión Nacional de Actividades Espaciales (CONAE)

The Argentine Patagonian coastal zone is highly productive, constituting an outstanding foraging and breeding area for many species of birds, marine mammals and various species of great importance to fisheries. The high biodiversity observed in this area can be ascribed to the particular conditions generated by the presence of spatially and temporally persistent frontal systems. Even the presence of fronts of different length-scale is well documented, their main dynamic features are not well understood due to the incompleteness and scarcity of oceanographic field data at the near-shore. Although a large amount of remote sensed data is available, it is provided for satellite systems of diverse spatial and temporal resolution. While NOAA-AVHRR sensor’s radiometric features allow an accurate calculus of SST and have high revisit frequency, their spatial resolution (1100 m) is not enough to study in detail processes taking place in very-coastal areas. By contrast, LANDSAT sensors (TM and ETM+) provide data at an appropriate spatial scale (120 m and 60 m resolution for TM and ETM+, respectively) for the near-shore zones, but their radiometric and revisit frequency limitations inhibit a multi-temporal monitoring of SST evolution. The complementary use of temperature maps allows exploiting the spatial resolution of LANDSAT satellites to monitor the processes taking place at small scale, and the accuracy, broad spatial coverage and high temporal resolution of the NOAA-AVHRR sensors. A set of LANDSAT and NOAA-AVHRR images was used to characterize different frontal systems by temperature gradients in the nearby of continental Patagonia: the Valdés Front, over the continental shelf; the San Matías Front, over the San Matías Gulf mouth; the San José Front, inside a small semi-enclosed basin and the San Jorge Front, located in the south of the gulf’s mouth. LANDSAT images were used to perform a detailed mapping of surface temperature distribution and its spatial variability. Even some of these features were hard to detect by NOAA images, once identified by LANDSAT images, their temporal SST evolution could be effectively tracked, resulting in a characterization of dynamic processes taking place at different spatial scales in this sensible region.