Seasonal variability of hydrography off the east coast of Qatar, central Arabian Gulf

Abstract

Seasonal variability of hydrography along a nearshore-offshore transect in the eastern part of the EEZ of Qatar has been analyzed using in situ measurements carried out during 5 different months. The study reveals distinct features in temperature, salinity, density, dissolved oxygen (DO), and chlorophyll fluorescence. The sea surface temperature (SST) varies from nearshore to offshore with a positive gradient during January, June, and August, of the order of 1.0–2.0 °C, and with a negative gradient during October and April, of the order of 1.0 °C. Thermal stratification began in June, reached a well-defined thermocline with a vertical difference in temperature of about 10 °C during August, and started to de-stratify during October. The low salinity and low-density inflow of IOSW is evident in the surface layer of the middle of the transect during August, which has enriched the DO in the surface layer up to 20 m depth, while hypoxia prevailed below 50 m depth. The lowest chlorophyll fluorescence was measured in April 2013 (~ 1.0 μg l−1), moderate in June 2013 (~ 1.5 μg l−1), and relatively high in August 2013 (~ 6.0 μg l−1).