Indian Ocean to See ‘Rapid and Strong’ Increase in Heat Waves Unless CO2 Emissions ‘Substantially Cut’

New research has found that the tropical Indian Ocean is warming at an unprecedented rate that could speed up this century if human-produced greenhouse gas (GHG) emissions are not reduced right away.

The accelerated temperature increase could have significant impacts on biodiversity — particularly coral reefs — as well as have wide-ranging socioeconomic effects.

“The future increase in heat content is equivalent to adding the energy of one Hiroshima atomic bomb detonation every second, all day, every day, for a decade,” Dr. Roxy Mathew Koll, the study’s lead author and an Indian Institute of Tropical Meteorology climate scientist, told Down To Earth.

According to the study, the temperature of the planet’s third-largest ocean experienced a basin-wide warming increase from 1871 to 2020. The average sea surface temperature in the 1870s was 79.6 degrees Fahrenheit, but had increased to 81 degrees Fahrenheit by the 2010s.

Ocean surface warming in the Indian Ocean — coupled with heat built up in the first 6,561.7 feet below — can have substantial effects on the region’s monsoon season, reported Down to Earth. The weather pattern brings roughly 70 percent of India’s yearly rainfall while affecting climate in other South Asian nations.

The increased warming could also cause more intense and frequent extreme weather like flooding and tropical cyclones, in addition to sea level rise from thermal expansion in the 40 countries that border the Indian Ocean. Koll pointed out that thermal expansion is responsible for more than 50 percent of sea level rise, exceeding that caused by sea ice and glacial melt.

“Marine heatwaves are projected to increase from 20 days per year (during 1970–2000) to 220–250 days per year, pushing the tropical Indian Ocean into a basin-wide nearpermanent heatwave state by the end of the 21st century,” the study said.

Marine heat waves can lead to coral bleaching, kelp forest degradation and seagrass loss. They can also contribute to the rapid intensification of tropical cyclones.

“These prolonged marine heatwaves will not only intensify cyclones but also affect fish migration, coral reefs, phytoplanktons and marine biodiversity,” Koll told Mongabay India.

The researchers looked at the ocean’s surface temperature warming and found it had increased at a rate of 0.12 degrees Celsius each decade from 1950 to 2020.

The most marked warming occurred in the northwest portion of the ocean, which includes the Arabian Sea, while the least warming was seen off the Java and Sumatra coasts, Down to Earth reported.

Warming in the Indian Ocean is also predicted to cause a decrease in the water’s pH levels from roughly 8.1 to 7.7 by 2100.

“The projected changes in pH may be detrimental to the marine ecosystem since many marine organisms — particularly corals and organisms that depend on calcification to build and maintain their shells — are sensitive to the change in ocean acidity,” Koll told Down to Earth.

The study said the most effective plan of action to mitigate current and future warming impacts is to build infrastructure that is climate resilient and reduce GHG emissions.

“The Indian Ocean, a climate change hotspot, faces rapid and strong increases in marine heatwave frequency and intensity unless global CO2 emissions are substantially cut,” said co-author of the study Thomas Frölicher, a University of Bern climate scientist, as reported by Down to Earth.