What are marine heat waves?
Marine heat waves are defined as sharp rise of anomalously warm temperature that last at least five days, although many persist for weeks or months.
Is there an increase in marine heatwaves in the Indian Ocean?
Marine heat waves used to be rare in the tropical Indian Ocean, but now they have become an annual affair.
The western Indian Ocean region experienced the largest increase in marine heatwaves at a rate of about 1.5 events per decade (four-fold rise), followed by the north Bay of Bengal at a rate of 0.5 events per decade (two-to-three fold rise).
During 1982–2018, the western Indian Ocean had a total of 66 events while the Bay of Bengal had 94 events.
Is there any link between marine heatwaves and atmospheric circulation?
There is a close link between marine heatwaves and atmospheric circulation and rainfall.
What are the impacts of marine heat waves on Indian monsoon?
The marine heatwaves in the western Indian Ocean and the Bay of Bengal are found to result in dry conditions over the central Indian subcontinent.
At the same time, there is a significant increase in rainfall over south peninsular India in response to the heatwaves in the north Bay of Bengal.
These changes are in response to the modulation of the monsoon winds by the heatwaves.
What are the impacts of marine heat waves on tropical cyclones?
Higher ocean temperatures, which are associated with marine heat waves, can make storms like tropical cyclones stronger.
With warmer temperatures, the rate of evaporation escalates and so does the transfer of heat from the oceans to the air.
When storms travel across hot oceans, they gather more water vapour and heat. This results in more powerful winds, heavier rainfall and more flooding when storms reach the land — meaning heightened devastation for humans.
Do factors like El Nino and positive Indian Ocean Dipole have any influence on marine heat waves?
Other than rapid ocean warming, the co-occurrence of either an El Nino, positive Indian Ocean Dipole (IOD), or the negative North Atlantic Oscillation (NAO) can trigger and intensify the marine heatwaves.
What are the future challenges associated with marine heat waves in the Indian Ocean?
Climate model projections suggest further warming of the Indian Ocean in the future, which will very likely intensify the marine heatwaves and their impact on the monsoon rainfall.
Since the frequency, intensity, and area covered by the marine heatwaves are increasing, we need to enhance our ocean observational arrays to monitor these events accurately and update our weather models to skillfully predict the challenges presented by a warming world.
Must read: What is a Heat Dome?
External link: https://m.thewire.in/article/environment/indian-ocean-headed-for-a-near-permanent-state-of-marine-heatwave
