INCOIS warns of Marine Heat Wave, issues swell surge alert for east and west coasts

A marine heat wave is an extended period when ocean temperatures are unusually warmer than the normal range for that place and time. It differs from ordinary seasonal warming because seasonal changes follow a recurring pattern. A heat wave is an unusual temperature anomaly that can place extra stress on marine life.

In this warning, sea surface temperatures may be up to 1 degree Celsius above normal. That extra heat can affect coral reefs, seagrass meadows, seaweed ecosystems and fisheries. Scientists are assessing whether the warming could reduce biodiversity or change where species live.

The current warning covers the Arabian Sea, the Indian Ocean and the Bay of Bengal, among other basins. INCOIS has classified most conditions as ‘Watch’ or ‘Alert’. If unusual warming continues, it could contribute to long-term ecological changes linked to climate change, although the article does not give a forecast for how long these conditions will last.

The warning is geographically broad. INCOIS’s study area is divided into six ocean basins and 14 sectors along the Indian coastline. This arrangement allows scientists to assess regional differences instead of treating the entire ocean area as one uniform zone.

The listed basins include the Persian Gulf, Red Sea, Southern Indian Ocean and South China Sea. The wider warning also covers the Arabian Sea, the Indian Ocean and the Bay of Bengal. Along India, the service provides detailed analysis for 14 coastal sectors.

This scale matters because marine conditions can vary between neighbouring regions. The warning identifies warming across a large ocean area, while the coastal sectors support closer monitoring. The article does not list all 14 sectors individually, but it shows that the assessment includes both broad ocean basins and detailed Indian coastal regions.

In the INCOIS warning system, ‘Watch’ and ‘Alert’ are categories used to describe the intensity of marine heat waves. The article presents them as warning levels for conditions that require attention and continued assessment. It does not provide separate temperature thresholds for the two categories.

Most of the marine heat waves have been placed in these categories. Their sea surface temperature anomalies can reach up to 1 degree Celsius above normal. An anomaly is the difference between the observed temperature and the usual temperature for that area and period.

The categories matter because unusually warm seas can affect living systems even when the temperature increase appears modest. INCOIS is assessing possible effects on coral reefs, seagrass, seaweed, fisheries and biodiversity. The article links possible longer-term ecological changes to climate change, but gives no further category definitions or duration forecast.

A swell surge is a coastal period when long, powerful ocean waves become higher or more persistent than usual. Unlike a single small wave, a surge of swell can repeatedly push water toward the shore. The article reports that INCOIS issued this warning for both India’s east and west coasts and the Andaman and Nicobar Islands.

Waves of one metre or higher are expected to affect Gujarat, Goa, Maharashtra, Karnataka, Kerala, Odisha, Andhra Pradesh, Lakshadweep, Puducherry, Tamil Nadu and West Bengal. Such waves can make coastal waters hazardous and increase risks for people, boats and shoreline activities. The article gives no detailed damage forecast.

The warning applies for the next two days from November 4, 2026. Car Nicobar Island received a danger alert. By identifying affected coastlines in advance, the bulletin gives communities and authorities time to take precautions around exposed shores and marine operations.

Prolonged marine warming can place sustained stress on ecosystems that depend on stable temperature conditions. The article warns that coral reefs, seagrass meadows and seaweed ecosystems may be affected. Coastal biodiversity and overall marine productivity could also decline if the unusual warmth continues.

The key mechanism is ecological stress from temperatures above normal. Sensitive organisms may struggle, while other species may move into newly suitable waters. The article specifically identifies possible biodiversity loss and shifts in species distribution. Fisheries may also be affected because changes in habitats and species locations can alter where marine life is found.

Scientists are assessing these possible impacts rather than reporting confirmed losses from this warning. The current conditions could contribute to long-term ecological changes linked to climate change. The article does not quantify effects on catches, reef area or particular species, so those outcomes remain under evaluation.

INCOIS is a research organisation under India’s Ministry of Earth Sciences. In this report, it monitors ocean conditions and issues warnings about marine heat waves and swell surges. Its service divides the study area into six ocean basins and 14 Indian coastal sectors for regional analysis.

This monitoring combines broad ocean coverage with more detailed coastal assessment. INCOIS identified sea surface temperature anomalies of up to 1 degree Celsius above normal and classified most heat waves as ‘Watch’ or ‘Alert’. It also forecast waves of one metre or higher along several coastal states and territories, with a danger alert for Car Nicobar Island.

These warnings can help authorities, fishers and coastal communities prepare for hazardous sea conditions and possible ecological effects. The article does not describe specific response measures. It shows that early information supports attention to exposed coastlines, fisheries and vulnerable marine ecosystems.

The ocean absorbs much of the heat added to the climate system and redistributes it through currents, winds and large-scale circulation. This movement can carry warm water into new regions. Marine heat waves occur when local sea temperatures remain unusually high compared with normal conditions.

A persistent change in winds, currents, cloud cover or ocean mixing can help keep heat near the surface. Climate change increases the ocean’s overall heat content, leaving less room for unusual weather or circulation patterns to produce extreme temperatures. These mechanisms are established scientific context; the article itself mainly reports the warning and links possible ecological changes to climate change.

The current warning covers the Arabian Sea, Indian Ocean and Bay of Bengal, among other basins. Scientists are assessing effects on reefs, seagrass, seaweed and fisheries. The article does not quantify how much climate change contributed to this specific event.