Climatology and Variability of Sea Surface Temperature in the Region of Turkish Straits System, 1982-2021

This study focuses on spatio-temporal climatology and long-term variability of sea surface temperature (SST) in the region of Turkish Straits System for the period 1980-2021. For this purpose, daily SST data from the Advanced Very High-Resolution Radiometer (AVHRR) version 5.3 were used. From this dataset, 40 years of monthly, seasonal, and yearly mean SST time series and spatial fields and their descriptive statistics were calculated. In addition, daily air temperature and sea temperature data that obtained from the Turkish State Meteorological Service (TSMS) for the period 1980-2021 were analysed and compared with AVHRR SST data. Interannual and interdecadal variability of the SST was investigated by using linear trend analysis. The results of this study showed that all regions are experiencing a steady warming trend. In comparison to the north Aegean Sea (0.050 °C.yr^-1) and the western Black Sea (0.060 °C.yr^-1), the Sea of Marmara shows the largest positive SST annual mean trend (0.064 °C.yr^-1). The basin-averaged yearly mean SST anomalies exhibits a similar variability and pattern across all regions: From 1982 to 1998, negative anomalies dominant, from 1999 to 2006, anomalies generally fluctuate around normal, and from 2007 onward, positive anomalies predominant. The seasonal cycle is strong for all regions, with lower SST values in the winter months (January, February, and March) and higher SST values in the summer (July, August and September). From one decade to the next, the SST values in the seasonal cycle gradually increasing. According to the monthly mean climatic SST fields, due to the seasonal upwelling, the eastern Aegean Sea coast experiences lower SST values in the summer compared to all other regions. These findings imply that, over the 40-year study period, the SST values have consistently increased for all regions.