Response mechanism of the Oman coastal upwelling to El Niño-Southern Oscillation and Indian Ocean Dipole

Coastal upwelling brings low temperature, high nutrient and low dissolved oxygen water from deep ocean to the upper layers, significantly impacting local climate, ecological environments, and marine fisheries. Influenced by the summer Indian monsoon, the coastal regions of Oman and Somalia become one of the strongest upwelling zones in the world. To understand the relationship between this upwelling and the larger-scale events such as the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), this study investigated the response mechanism of the summer upwelling along the Oman coast to ENSO and IOD based on remote sensing data such as the sea surface temperature, wind and heat flux. Results indicate that during El Niño decaying years, the anomalous northeasterly winds in the Oman coastal upwelling zone weaken the prevailing southwesterly monsoon which is favorable for the upwelling, and finally result in a weakened upwelling. In contrast, during La Niña decaying years, the anomalous southwesterly winds strengthen the prevailing southwesterly monsoon, which result in an enhanced upwelling. Positive (negative) IOD events induce an anticyclonic (cyclonic) anomalous wind field north of the equatorial Indian Ocean. However, the wind anomalies induced by IOD events have little impact on the upwelling along the Oman coast, for the upwelling zone is not located within the main axis of the anomalous wind field area.