Role of marine heatwave in fuelling the super cyclone Amphan

The anthropogenic warming of the oceans and atmosphere facilitates the generation and intensification of extreme events such as MHWs and tropical cyclones.

Mechanism behind generation of Marine heat waves

• Greenhouse gas emissions: it is the primary factor for anthropogenic (human-induced) climate change.
• The increase in carbon dioxide concentration can trap the radiation into the atmosphere and not let it go into space.
• This trapping of the extra energy increases the average surface air temperature and warms the climate that we know as global warming.
• As the capacity of the atmosphere to absorb the heat is very less, more than 90% of the extra heat that has been trapped in the climate system has been absorbed by the oceans since 1970
• Due to this, oceans are warming globally from the surface to deeper depths.
• Consequences of warming of oceans : it has severe consequences such as increasing intensity and frequency of extreme events, rising sea levels, melting glaciers, and changing the weather pattern across the globe.

Faster warming & Generation of Marine heat waves

• Due to global warming, the tropical Indian Ocean, at the surface, is warming at a faster rate as compared to the rest of the global ocean.
• The high sea surface temperatures are more susceptible to generating extreme temperature conditions that persist over days to months and are termed as Marine Heatwaves (MHWs).
• Impact : it has severe socio-economic consequences such as fish mortality, and coral bleaching, and also has the potential to interact and modify other extreme events such as tropical cyclones.

Recent study regarding Bay of Bengal & tropical cyclones

• The Bay of Bengal exhibits high sea surface temperatures (about 28°C) throughout the year and is more prone to tropical cyclones.
• The Bay of Bengal is home to about 5-7% of the total number of tropical cyclones occurring globally each year
• It makes the North Indian Ocean vulnerable to the highest number of fatalities globally.
• Amphan was the first super cyclone in the Bay of Bengal in the last 21 years and intensified from category 1 (cyclonic storm) to category 5 (super cyclone) in less than 24 hours.

Causes behind the supercyclone

• The presence of a strong MHW beneath the track of the cyclone with an extremely high anomalous sea surface temperature of more than 2.5°C coincided with the cyclone track and facilitated its rapid intensification in a short period.
• Other factors responsible for it: ocean stratification and warming below the surface also play a crucial role during this phenomenon of compound extreme events.

Future forecasts regarding such events

• Such compound or individual extreme events are going to increase in the future due to global warming and the Indian Ocean will witness the increased intensity and frequency of such climate extremes.

Significance of the study

• It provides new perspectives on the interactions between different extreme events that could aid in improving the current understanding of compound extreme events that have severe socio-economic consequences in affected countries.
• It will be very helpful for the political and scientific authorities to make better disaster management and mitigation planning for vulnerable coastal communities from such extreme events.

Exam Track

Prelims takeaway

• Cyclone Amphaan
• Global warming
• Greenhouse gases
• Super cyclone
• Bay of Bengal   Mains Track

Q Explain the role of the marine heat waves in fuelling Super cyclones like Amphaan.How the recent study done on it can be helpful in mitigating such cyclones.