The effect of Ekman and geostrophic surface current on the distribution of SST variability over the Persian Gulf

Abstract

Ekman and geostrophic surface currents are often associated with mesoscale eddy activity and upwelling jets, due to their effect on the variability of SST, in the Persian Gulf. Therefore, understanding the distribution of geostrophic and Ekman surface currents and how they are related to SST variability is a vital step for understanding circulation dynamics in the Persian Gulf. This study aims to quantify the importance of components of current on the distribution of SST variability over the Persian Gulf. To this end, intra-annual variability of Ekman, geostrophic and total currents, and SST have been investigated based on the daily time series of 21 years (2000–2020). As well, a correlation analysis was done on the components of current and SST, the results indicated that Ekman current has more intensity in the winter months than the summer months due to the Winter Shamal events, and the maximum value of this current component is seen in the center of the Persian Gulf in all months. In addition, the direction of the Ekman surface currents is toward the sea in the northern region of the Persian Gulf so the Ekman current gives rise to the formation of coastal upwelling currents. The maximum value of the geostrophic component is seen in the northwestern part of the Persian Gulf (near the mouths of rivers) as well as the easternmost region of the Persian Gulf (Strait of Hormuz) in all months due to the difference in surface density in these areas and geostrophic component plays an important role in the formation of the total and main current in this region. The maximum value of total current is seen in the northwestern Persian Gulf in June. A negative (positive) correlation between Ekman (geostrophic) current and SST is found over the Persian Gulf (in the northern coastal regions) and certain parts of the northern Persian Gulf (about 52.5° E–53.5°), which have the strongest relationship between the components of current and SST, implying that there is a possibility of the upwelling and mesoscale eddy creation at the same time.