Ocean responses to Shaheen, the first cyclone to hit the north coast of Oman in 2021

Abstract

On October 3rd, 2021, cyclone Shaheen made landfall on the northeast coast of Oman as a first-category cyclone after crossing the Sea of Oman. It is the first time in more than 130 years that a storm has made such extraordinary landfall on the northeast coast of Oman. This study intends to examine the effects of cyclone Shaheen on ocean cooling and biological response in the Sea of Oman (SO) and the the Arabian Sea (AS) using satellite remote sensing data, an Argo float, and the HYCOM model. The validation analysis of the HYCOM model and the Argo float showed strong correlations between vertical temperature profiles (R = 0.99) and vertical salinity profiles (R = 0.89). Furthermore, winds during the cyclone caused mixing and upwelling leading to Sea Surface Temperatures (SST) dropping 2.5 °C along southern Iranian coastlines, decreasing 5 °C along northern Oman's coastlines, and rising 1 °C across the Arabian Sea. As a result of the exitance of the cyclonic eddies in the Sea of Oman, a significant drop of 5 °C in SST was observed along the coastline of Oman caused by cold upwelled water from southern Iranian coastlines. Cyclone Shaheen's heavy rainfall caused the Sea Surface Salinity (SSS) in the Sea of Oman to drop from 36.7 to 36.8 psu. According to the results, Ekman pumping and upwelling processes predominated along the southern Iranian coast resulting in nutrient uplift and phytoplankton blooms (3 mg/m³). In contrast, strong stratification near the coast of Oman prevented nutrient uplift and led to low Chl-a concentrations. Due to the unique nature of cyclone Shaheen, it is essential to examine the complex dynamic and interaction between the ocean and atmosphere in the Sea of Oman and the Arabian Sea.