Evolution of the Arabian Sea Upwelling from the Last Millennium to the Future as Simulated by Earth System Models

Abstract

Arabian Sea upwelling in the past has been generally studied based on the sediment records. We apply two earth system models and analyze the simulated water vertical velocity to investigate coastal upwelling in the western Arabian Sea over the last millennium. In addition, two models with slightly different configurations are also employed to study the upwelling in the 21st century under the strongest and the weakest greenhouse gas emission scenarios. With a negative long-term trend caused by the orbital forcing of the models, the upwelling over the last millennium is found to be closely correlated with the sea surface temperature, the Indian summer Monsoon and the sediment records. The future upwelling under the Representative Concentration Pathway (RCP) 8.5 scenario reveals a negative trend, in contrast with the positive trend displayed by the upwelling favorable along-shore winds. Therefore, it is likely that other factors, like water stratification in the upper ocean layers caused by the stronger surface warming, overrides the effect from the upwelling favorable wind. No significant trend is found for the upwelling under the RCP2.6 scenario, which is likely due to a compensation between the opposing effects of the increase in upwelling favorable winds and the water stratification.

Robust Estimates of the Total Alkalinity From Satellite Oceanographic Data in the Global Ocean

“…The magnitudes of TA are high in Arabian Sea waters due to the upwelling process and low in Bay of Bengal waters due to the freshwater inputs [26], [27]. The surface ocean TA ranged from 2250 to 2500 µmol kg −1 in Atlantic Ocean waters, 2100 to 2400 µmol kg −1 in Pacific Ocean waters, and 2200 to 2380 µmol kg −1 in Southern and Indian Ocean waters (Fig.…”