INCOIS Warns of Marine Heatwaves in Indian Ocean
Why in News?
- The Indian National Centre for Ocean Information Services has warned of marine heatwaves across the Arabian Sea, the Bay of Bengal and nearby parts of the Indian Ocean, with sea surface temperatures up to 1°C above normal, coverage dated 5 to 7 November 2026 reported.
- The warning says the heat threatens coral reefs and fisheries and can feed cyclone intensification. One report listed affected coastal areas from Gujarat to the Andaman and Nicobar Islands.
- An earlier INCOIS El Niño bulletin said the event would peak between November 2026 and January 2027.
Key Terminologies
- Marine Heatwave
- A period of unusually high sea surface temperature that lasts for days. A common definition counts a heatwave when the temperature stays above the 90th percentile of the usual range for at least five days.
- INCOIS
- The Indian National Centre for Ocean Information Services, in Hyderabad, under the Ministry of Earth Sciences. It issues ocean state forecasts, tsunami warnings and marine heatwave advisories.
- Sea Surface Temperature
- The temperature of the top layer of the ocean. It controls evaporation, rainfall and the strength of cyclones.
- Cyclone Intensification
- Tropical cyclones draw energy from warm sea water, so a warmer sea surface can raise a storm's strength. The Bay of Bengal and the Arabian Sea see most Indian cyclones in October to December.
- Coral Bleaching
- When corals under heat stress expel the algae that give them colour and food. Repeated bleaching can kill reefs.
- El Niño
- A warming of the central and eastern equatorial Pacific that raises global temperatures and changes monsoon rainfall. A very strong event is under way in 2026.
Key Issues
- Wide Warning: INCOIS warned of marine heatwaves across the Arabian Sea, the Bay of Bengal and the wider Indian Ocean, with sea surface temperatures up to 1°C above normal.
- Levels of Alert: INCOIS grades heatwaves as Watch, Alert and Warning, and the Warning level means temperatures well above the 90th percentile of the daily norm.
- Earlier Spread: An August 2026 bulletin put 31 per cent of the Arabian Sea at Watch, 18 per cent at Alert and 1 per cent at Warning, and 23, 27 and 6 per cent of the Bay of Bengal at those levels.
- Peak Timing: INCOIS said in June that the El Niño effect would peak between November 2026 and January 2027, bringing marine heat stress and lower fish catch.
- Link to Cyclones: Warm water gives cyclones more energy, which matters in the post-monsoon cyclone season.
Key Implications
Positive/Pros/Merits
- Early Warning: Advisories let fishers, coastal managers and reef authorities prepare for heat stress.
- Scientific Capacity: INCOIS publishes regular marine heatwave bulletins for the Indian Ocean.
- Policy Input: Ocean warming data supports planning for fisheries and coastal protection.
- Public Awareness: Linking ocean heat to cyclones and fish catch explains why marine data matters, and it connects to the record warm October reported on 6 November.
Negative/Cons/Demerits
- Coral Damage: Heat stress can bleach corals in places such as the Gulf of Mannar, Lakshadweep and the Andaman and Nicobar Islands.
- Fisheries Loss: Warm water can push fish away from usual grounds and cut catch, hurting fishing communities.
- Stronger Cyclones: Higher sea temperatures can intensify cyclones, adding to coastal risk.
- Data Limits: The percentage area under each level in November was not available in the coverage reviewed, so the current extent is uncertain.
Key Initiatives
- INCOIS: It issued marine heatwave warnings for the Arabian Sea, Bay of Bengal and Indian Ocean, as reported 5 to 7 November 2026.
- INCOIS El Niño Bulletins: It launched specialised bulletins for maritime sectors, with a June 2026 outlook for a November to January peak.
- Ministry of Earth Sciences: It oversees INCOIS and ocean observation.
- Coastal States: States from Gujarat to the Andaman and Nicobar Islands are named as affected, according to one report.
The coverage was secondary and did not give November area percentages. The August figures are from an INCOIS bulletin, and the classification of levels is as described in the INCOIS bulletin.
Director's Perspective
Way Forward
- Define a marine heatwave using the 90th percentile and the five-day rule.
- Know INCOIS, its location and its parent ministry.
- Link ocean heat to El Niño, cyclone intensity and coral bleaching.
- Remember the Gulf of Mannar, Lakshadweep and Andaman reefs as vulnerable.
- In answers, link marine heatwaves to fisheries and the blue economy.
The INCOIS warning shows that the Indian Ocean is running warm during a strong El Niño, with risks to coral reefs, fisheries and cyclone strength. Early advisories help coastal communities, but they cannot stop the heating. In a Mains answer, define a marine heatwave, explain how El Niño and global warming combine to raise sea temperatures, and conclude that better ocean observation, reef protection and support for fishers are needed to cope with a warmer ocean.
GS Relevance
Frequently Asked Questions
What is a marine heatwave?
A marine heatwave is a period of unusually high sea surface temperature that lasts for days, commonly defined as temperature above the 90th percentile of the normal range for at least five days. INCOIS warned of such heatwaves in the Indian Ocean in early November 2026.
Which areas did INCOIS warn about?
INCOIS warned of marine heatwaves across the Arabian Sea, the Bay of Bengal and the wider Indian Ocean, with sea surface temperatures up to 1°C above normal. One report listed affected coasts from Gujarat to the Andaman and Nicobar Islands.
Why do marine heatwaves matter for India?
They can bleach corals, push fish away from usual grounds and give cyclones more energy. INCOIS said an El Niño effect would peak between November 2026 and January 2027, bringing marine heat stress and lower fish catch.
PYQ Practice — Statement Analysis
1 INCOIS functions under the Ministry of Earth Sciences.
It issued marine heatwave warnings for the Indian Ocean in November 2026.
2 A marine heatwave is defined only by air temperature on the coast.
It is defined by unusually high sea surface temperature lasting for days.
3 Coral bleaching is caused by heat stress that makes corals expel their algae.
Marine heatwaves are a major cause of bleaching.