Coastal upwelling by wind-driven forcing in the Caspian Sea: A numerical analysis

Abstract

In this study, wind-driven coastal upwelling in the Caspian Sea was investigated using a developed three-dimensional hydrodynamic numerical model based on the Princeton Ocean Model (POM). The model was forced with wind fields and atmospheric fluxes from the ECMWF database and it considers freshwater inflows from the Volga, Kura and Ural Rivers. This model was implemented for 10 years (2008–2018). Findings indicated that the upwelling in the Caspian Sea was due to effects of wind and bottom topography, often occurring from May to September. In June and July, in the eastern part of the middle and sometimes southern basins, up to 3°C water temperature difference occurs between coastal and offshore areas. The vertical temperature gradient in the middle basin was larger than that in the southern basin. Upwelling in August in the eastern coasts of the middle basin within 25 km of coast from the depth of 15 m to the surface was shown, which was due to the effects of wind and bottom topography. In the middle basin, the highest vertical velocities caused by upwelling in June, July and August were 12, 13.82, and 10.36 m/day, respectively.