India's space agency, ISRO, has observed visible biological signatures in the tropical Pacific Ocean suggesting the rapid strengthening of the 2026 El Niño. Data from the EOS-06 (Oceansat-3) satellite revealed a notable reduction in surface chlorophyll-a concentrations and a change in ocean wind patterns during June 2026.
ISRO's Satellite Observations
Using its Ocean Colour Monitor-3 (OCM-3) and Scatterometer (SCAT-3) instruments, ISRO's National Remote Sensing Centre compared observations from June 2026 with neutral ENSO conditions in June 2024 and 2025. The findings showed a marked decrease in chlorophyll-a, a vital pigment for phytoplankton photosynthesis. Phytoplankton, microscopic marine organisms, form the base of the ocean's food web, making their decline a significant indicator of environmental shifts.
Furthermore, the satellite detected a shift in prevailing ocean-surface winds, transitioning from easterlies (east to west) to westerlies (west to east). This alteration in wind patterns is crucial because winds are directly linked to equatorial upwelling, a process that brings cold, nutrient-rich water from deeper ocean layers to the surface.
During El Niño, weakened trade winds and a deeper thermocline suppress this upwelling. With fewer nutrients reaching sunlit surface waters, phytoplankton growth declines, resulting in lower chlorophyll-a concentrations. The change detected from space is not simply a change in ocean colour; it is an indication of a larger physical and biological shift taking place in the Pacific.
NOAA Forecasts a Potentially Historic Event
ISRO's observations align with increasingly strong forecasts from the U.S. National Oceanic and Atmospheric Administration (NOAA). NOAA's Climate Prediction Center, in its September 10 diagnostic discussion, reported that El Niño has intensified significantly over the past month. Sea-surface temperature anomalies in the eastern equatorial Pacific now exceed 3°C, with subsurface temperatures in some areas showing anomalies greater than 10°C.
These oceanic and atmospheric indicators collectively point to a rapidly strengthening El Niño. NOAA places the probability of a very strong El Niño at over 90% for the Northern Hemisphere fall and winter of 2026-27. More strikingly, there is a 75% chance that the October-December 2026 period could see a historic El Niño, potentially exceeding the strength of all previous events recorded since 1950. Such an event would correspond to a Relative Oceanic Niño Index (RONI) of at least +2.5°C over a three-month period.
Implications for Global Weather, Including India
A historic El Niño could have widespread implications for global weather patterns. In India, El Niño is closely monitored due to its potential influence on the Indian monsoon. Historically, El Niño conditions have been associated with a higher likelihood of below-normal monsoon rainfall and warmer conditions in parts of the country. However, this relationship is not deterministic, as other oceanic and atmospheric factors can modify or even offset El Niño's impact in any given year.
Scientists will continue to assess the evolution of this low-chlorophyll region alongside changes in equatorial winds, sea-surface temperature, sea-level height, thermocline depth, and ocean circulation to fully understand the unfolding event.