New regional SMOS Sea Surface Salinity maps in the Black Sea from the EO4SIBS project

Abstract

he monitoring of the Sea Surface Salinity (SSS) in semi-enclosed seas has a significant impact in the study of climate change. In those basins the oceanographic processes occur at shorter temporal scales than in the open ocean, and therefore, trends and anomalies can be detected before. In the Black Sea, river run-off and precipitation exceed evaporation making the typical salinity values much lower than in the global ocean (17-18 psu versus 32-38 psu). Moreover, unlike other large estuarine basins, the Black Sea is a deep basin (maximum depth of ~2200 m) with a large North-Western shelf. A distinct vertical layering is created between the surface waters in the upper 100m and the deep graphic conditions maintained by strong stratification resulting from river runoffs flowing at the surface and the entrance of saline Bosporus waters at depths. The geophysical characteristics of the basin hinder the satellite SSS acquisition: 1) the dielectric models have some limitations in this range of low salinity values; 2) the strong stratification limits the use of in situ data to calibrate or validate the satellite acquisitions; 3) the sensitivity to potential trends requires a robust stable time series of measurements. Besides there are some already known acquisition issues in the region: 1) Strong land sea contamination; 2) Strong contamination from very close Radio Frequency Interference sources. In the framework of the ESA regional initiative project An Earth Observation Data for Science and Innovation in the Black Sea (EO4SIBS), we have developed new algorithms to deal with these issues. Here we present the enhanced methods used in the generation of the first regional SSS products in the Black Sea and the quality assessment of their performance. The products consists of: a) Daily level 2 maps at 0.25ºx0.25º with an accuracy of 1.5 psu; b) 9-day level 3 maps at 0.25ºx0.25º with an accuracy of 0.5 psu, and; c) daily level 4 at 0.05ºx0.0505º with an accuracy of 0.4 psu