As the threat of climate change looms large, a new study shows that the Indo-Pacific Ocean is warming at a rapid rate and the changes are impacting rainfall patterns across the globe.
In India, it could lead to reduced rainfall over northern parts of the country from November to April and trigger cyclone activity in the North Indian Ocean during post-monsoon period.
The study was conducted as part of Indo-US collaboration, between the ministry of earth sciences (India) and the US national oceanic and atmospheric administration (NOAA) and published in peer-reviewed journal Nature.
The findings show that the Indo-Pacific warm pool, a region of warm ocean between the western Pacific Ocean and eastern Indian Ocean has expanded two-fold between 1981 and 2018, due to consistent warming.
It has expanded on average by 2.3 × 105 km2, equivalent to the size of Washington State every year during 1900–2018 and at an accelerated average rate of 4 × 105 km2 per year during 1981–2018, which is an area equal to the size of California.
This rapid warming has altered a major mode of weather system called the Madden Julian Oscillation (MJO), which is responsible for 55% of the weather variability over the tropics. The phase and strength of MJO at a given location impacts activity of tropical cyclones, the monsoons, and the El Niño cycle and triggers extreme weather events.
“Most cyclones in the pre- or post- monsoon period over Bay of Bengal are triggered by MJO activity in the Indian Ocean. Even when MJO occurs in the West Pacific, the remnants of those systems can pass over to Bay of Bengal and get activated,” said lead author Dr. Roxy Mathew Koll from Indian Institute of Tropical Meteorology, Pune.
The findings raise concern over increased vulnerability of the coastal population, which faces the impact of extreme weather events. “While changes in MJO impact rainfall patterns across the globe, the impact is more keenly felt in the tropics, which consist of mostly low- and middle-income countries, which are in need of a strong early-earning weather system,” he said.
India with its vast coastline has been facing increased cyclone activity and intensity over the North Indian Ocean in recent times. In 2019 so far, seven cyclones have impacted the country, with the latest being Cyclone Bulbul in the Bay of Bengal.
