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Climate change threatens Indian Ocean. Photo credit: iStock
A recent study suggests that the surface temperature of the Indian Ocean could surge by 1.7 to 3.8 degrees Celsius between 2020 and 2100, triggering a rise in marine heatwaves and extreme cyclones. These phenomena are poised to impact the monsoon patterns and sea levels.
The study, led by Roxy Mathew Cole, a climate scientist at the Indian Institute of Tropical Meteorology (IITM) in Pune, highlights alarming projections for the future of the Tropical Indian Ocean. It reveals a stark increase in oceanic heatwaves, with expected occurrences skyrocketing from an average of 20 days annually (during 1970–2000) to a staggering 220–250 days per year by the end of the 21st century. Consequently, the tropical Indian Ocean basin is anticipated to experience persistent heatwave conditions.
Heatwaves harm marine life, worsen cyclones
The ramifications of these prolonged heatwaves are dire, as they induce coral bleaching, devastate seagrass ecosystems, and negatively impact fisheries, as indicated by the study. Moreover, they intensify the severity of cyclones, compounding the risks posed by extreme weather events.
The escalating heat dynamics in the Indian Ocean extend beyond surface temperatures. The study underscores a significant increase in the ocean's heat content, with current trends showing a rise of 4.5 zeta-joules per decade up to a depth of 2,000 meters. Projections indicate a further acceleration to a rate of 16 to 22 zeta-joules per decade in the future.
To illustrate the gravity of these projections, the study draws a chilling comparison, likening the energy increase from future heatwaves to the detonation of a Hiroshima atomic bomb every second, continuously, for an entire decade.
As the oceans rapidly warm, changes in surface temperatures' seasonal patterns are expected to bring more extreme weather events to the Indo-Pacific region.
The study indicates that from 1980 to 2020, the Indian Ocean's average basin temperature stayed between 26°C and 28°C throughout the year. However, by the end of the 21st century, it's estimated to rise to between 28.5°C and 30.7°C under high emissions scenarios, setting a new baseline.
Ocean warming fuels cyclones, raises sea levels
Sea surface temperatures above 28°C typically foster deep convection and cyclone formation. The researchers note that extreme rainfall events and severe cyclones have already been on the rise since the 1950s and are anticipated to further increase with ocean temperature escalation.
The rising ocean temperatures are expected to contribute to a rise in sea levels. This thermal expansion accounts for over half of the sea level rise in the Indian Ocean, surpassing the effects of melting glaciers and sea ice.
Furthermore, changes are projected for the Indian Ocean Dipole, a phenomenon impacting monsoon and cyclone patterns. Extreme bipolar events are forecasted to increase by 66% by the century's end, while moderate events may decrease by 52%.
Additionally, researchers anticipate accelerated ocean acidification, with surface pH levels dropping from above 8.1 to below 7.7 by the end of the century. This shift is likely to lead to declines in surface chlorophyll levels and productivity, particularly pronounced in the western Arabian Sea.
The projected changes in pH could have severe consequences for marine ecosystems, especially for organisms like corals and shell-building organisms that are sensitive to ocean acidity changes. To put it into perspective, a mere 0.1 drop in human blood pH can lead to organ failure, highlighting the potential impact on marine life.
With its coastline touching 40 countries and hosting a third of the world's population, the Indian Ocean region faces significant social and economic challenges due to climate change. It has become the most vulnerable region globally to natural disasters, with coastal communities bearing the brunt of extreme weather events and climate impacts.
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