El Niño Likely to Persist Until April 2027, Threatening Marine Ecosystems: INCOIS

El Niño conditions are expected to remain dominant until at least April 2027, with probabilities ranging between 80% and 100%, according to scientists at the Indian National Centre for Ocean Information Services (INCOIS). The prolonged warm phase of the El Niño-Southern Oscillation (ENSO) is likely to adversely affect the marine ecosystem, they said.

El Niño refers to the warming of sea surface temperatures in the central and eastern equatorial Pacific Ocean. Such conditions are known to weaken the Indian summer monsoon, often altering rainfall patterns and, in turn, affecting the country's agriculture and economy.

Beyond rainfall, El Niño can trigger stronger and longer-lasting marine heatwaves across the northern Indian Ocean, disrupting marine ecosystems, damaging coral reefs and impacting fisheries. La Niña, characterised by unusually cool waters in the equatorial Pacific, generally supports stronger monsoon conditions over India.

Scientists say El Niño has strengthened and is expected to remain strong through the August 2026-March 2027 period. Its persistence is likely to influence ocean conditions across the North Indian Ocean, leading to higher sea surface temperatures, increased upper-ocean heat content, stronger water-column stratification and widespread marine heatwaves.

Marine heatwave conditions are already widespread across the northern Indian Ocean, with moderate to extreme events affecting large parts of the Arabian Sea and the Bay of Bengal. The area impacted by marine heatwaves has expanded in 2026 compared with 2025.

The ongoing El Niño has also caused a significant reduction in coastal upwelling along India's west coast — a process that brings nutrient-rich waters to the surface and is crucial for sustaining marine productivity. Reduced upwelling, coupled with marine heatwaves, may adversely affect fish habitats and productivity.

P.A. Francis, senior scientist and head of the Ocean Modelling & Data Assimilation Centre (OMDA), said historical analyses of fishery landings since 1950 show that marine fish catches across the Indian Ocean region generally tend to decline during El Niño phases, although the impact varies by region.

Studies using data from the Central Marine Fisheries Research Institute (CMFRI) for 1985-2023 indicate that El Niño-induced warming has negatively affected the maturation and recruitment success of key small pelagic species, such as the Indian oil sardine and Indian mackerel, in Kerala and Karnataka.

Climate variability can also push fish populations towards their physiological limits, forcing them into deeper waters or higher latitudes. Mr. Francis said El Niño also influences extreme wave conditions, leading to higher significant wave heights in the Bay of Bengal and reduced wave activity in the Arabian Sea, largely because the South Asian monsoon weakens.