Marine Heatwaves
2023 JUL 13
Preliminary >
Disaster Management > Disasters > Disaster risk reduction
Why in news?
- The northern Bay of Bengal has been experiencing an intense Marine Heatwave since 28th June 2023, leading to India’s usually arid northwest receiving extreme rainfall.
What are Marine Heatwaves?
- Marine heatwaves are periods of extremely high temperatures in the ocean.
- These events are linked to coral bleaching, seagrass destruction, and loss of kelp forests, affecting the fisheries sector adversely.
- Study showed that 85% of the corals in the Gulf of Mannar near the Tamil Nadu coast got bleached after the marine heatwave in May 2020.
- The most common drivers of marine heatwaves include ocean currents which can build up areas of warm water and air-sea heat flux, or warming through the ocean surface from the atmosphere.
- Winds can enhance or suppress the warming in a marine heatwave, and climate modes like El Niño can change the likelihood of events occurring in certain regions.
What are the impacts of Marine Heatwaves?
- Affect ecosystem structure:
- Marine heat waves affect ecosystem structure, by supporting certain species and suppressing others.
- It has been associated with the mass mortality of marine invertebrates, and may force species to change behaviour in a way that puts wildlife at increased risk of harm.
- Change habitat ranges of certain species:
- Marine heatwaves can change the habitat ranges of certain species
- For example: Spiny sea urchin off southeastern Australia has been expanding southward into Tasmania at the expense of kelp forests which it feeds upon.
- Economic Losses:
- Marine heatwaves can cause economic losses through impacts on fisheries and aquaculture.
- Affect Biodiversity:
- Biodiversity can be drastically affected by marine heatwaves.
- In 2016, marine heatwaves across northern Australia led to severe bleaching of the Great Barrier Reef.
- Increase the risk of deoxygenation and acidification:
- Often they occur alongside other stressors such as ocean acidification, deoxygenation, and overfishing.
- In such cases, MHWs not only further damage habitats, but also increase the risk of deoxygenation and acidification.
Add ons:
- The Western Indian Ocean region experienced the largest increase in marine heatwaves at a rate of about 1.5 events per decade, followed by the north Bay of Bengal at a rate of 0.5 events per decade.
- From 1982 to 2018, the Western Indian Ocean had a total of 66 events, while the Bay of Bengal had 94 events.
PRACTICE QUESTION:
With reference to ‘Marine Heatwaves’, consider the following statements:
1. They are periods of extremely high temperatures in the ocean.
2. Marine heatwaves can change the habitat ranges of certain species
Which of the statements given above is/are correct?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer