Manifestation of Upwellings in the Black Sea in Multisensor Remote Sensing Data

Abstract

Results of upwelling research in the Black Sea, namely in the northeastern part of the sea, near the Tendrovskaya Spit and western coast of Crimea, and off the coast of Turkey, are presented. The results are based on the use of Earth remote sensing data, in particular the data from color scanners (MODIS, VIIRS, OLCI-A, and OLCI-B), infrared radiometers (TIRS and AVHRR), and SAR images from synthetic aperture radars. An integrated approach using almost exclusively remote sensing data makes it possible to fully characterize the observed upwellings in the Black Sea. In the active phase, upwelling, in addition to sea surface temperature (SST), is usually reflected in both the chlorophyll a (Chl a) concentration field and sea surface roughness field. In our cases, the duration of upwellings varied from 6 to 10 days; the SST differences in the upwelling zone reached 3–8°C; and Chl a concentrations were 5–6 times higher than the background values, being 0.5–0.7 mg/m³. The maximum SST anomalies up to 8°C were observed off the Turkish coast. The analysis revealed a clear relationship between areas of reduced SST in the upwelling zone, sea surface roughness, and Chl a concentration. It is shown that, in the case of using a complete set of remote sensing data, observing, monitoring, and studying upwelling does not present any fundamental difficulties.