KOCHI: The Arabian Sea is warming at an alarming rate and will spin more intense cyclones in the coming years, said oceanographer and former director of the National Institute of Oceanography, Dr S Prasannakumar, on Thursday. Prasannakumar, who made a presentation on the rapid warming of the Arabian Sea and modulation of upwelling and winter convection along the eastern boundary at the national workshop on climate change organised by NIO in Kochi on Thursday, told TNIE that the warming of the upper 300 m of the North Arabian Sea has been very steep and the impact will be visible within the next two or three years.
“The Arabian Sea is going to witness much more intense cyclones and the change will be visible in the next two to three years. The destruction it will bring to the west coast will be enormous. The coastal states should gear up to manage the situation. The ratio of cyclones between the Bay of Bengal and the Arabian Sea was 4:1, but now it has changed to 2:1 and the situation is scary,” said Dr Prasannakumar.
The surface temperature in the Arabian Sea has been rising at an alarming rate since 1995. The Arabian Sea has two mechanisms to cool — upwelling and winter convection. This cooling system was sufficient to offset the excess heat in the Arabian Sea till 1995. But now the sea is trapping excess heat which has led to rapid warming of the water up to a depth of 300m. The excess heat trapped in the sea is the primary mechanism that stirs up cyclones. It will intensify evaporation. Warming of the atmosphere will increase the moisture-holding capacity. When there is excess moisture in the air, a cooling system can trigger intense rainfall like a cloud burst in a small area which can trigger floods, he said.
Dr Prasannakumar has conducted research, analysing data regarding heat content in the Arabian Sea and cyclones from 1960 to 2022, which helped him decode the impact of sea surface heating. “The Arabian Sea is warming at the rate of 0.18 degree Celsius per decade which is much higher than the warming of the Pacific Ocean and Atlantic Ocean. The surface sea temperature of the Bay of Bengal is higher than the Arabian Sea which is the reason for frequent cyclones there. But that situation is changing. Cyclone is a natural mechanism for the ocean to cool down the excess heat. It will churn and cool down the water column up to a depth of 200m,” he said.
Dr Prasannakumar said the warming of the Indian Ocean can adversely affect the monsoon current. “If the thermal contrast between the land and the ocean changes on the Madagascar coast, it can reduce the wind speed. Already the northern part of the Arabian Sea is witnessing a reduction in wind speed,” he said.