El Niño could turn historic in 2026: ISRO satellite captures major changes in Pacific Ocean

India’s space agency has detected a visible biological signature of the strengthening 2026 El Niño in the tropical Pacific Ocean, with satellite observations showing a decline in surface chlorophyll-a and a shift in ocean winds.

ISRO said its EOS-06 (Oceansat-3) satellite detected a reduction in chlorophyll-a during June 2026, pointing to changes in phytoplankton — microscopic marine organisms that form the base of much of the ocean food web. The observations also captured a shift in surface winds compared with conditions seen in 2024 and 2025.

What ISRO’s satellite is seeing 

The observations were made using two instruments aboard EOS-06 — the Ocean Colour Monitor-3 (OCM-3) and the Scatterometer (SCAT-3).

ISRO’s National Remote Sensing Centre compared chlorophyll-a and ocean-surface wind observations for April, May and June across 2023-2026. The comparison of June 2024 and June 2025, when ENSO conditions were neutral, with June 2026 showed a marked reduction in surface chlorophyll-a.

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At the same time, the prevailing ocean-surface winds changed from easterlies, which generally blow from east to west, towards westerlies, which blow from west to east.

That matters because winds are closely linked to equatorial upwelling — the process that brings cold, nutrient-rich water from deeper layers of the ocean towards the surface.

During El Niño, weakened trade winds and a deeper thermocline can suppress this upwelling. With fewer nutrients reaching sunlit surface waters, phytoplankton growth can decline, resulting in lower chlorophyll-a concentrations.

In other words, 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.

Chlorophyll-a: why it matters 

Chlorophyll-a is a key pigment used by phytoplankton for photosynthesis. Satellite measurements of chlorophyll concentration therefore provide scientists with an important indicator of biological productivity in the ocean.

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EOS-06 was designed to monitor ocean colour, sea-surface temperature and wind vectors, among other parameters. Its OCM-3 instrument can measure ocean chlorophyll, while SCAT-3 provides information on ocean-surface wind speed and direction.

ISRO said the apparent contraction of the westward extent of the high-chlorophyll region between April and June 2026 further supports the weakening of equatorial upwelling as El Niño developed.

The agency cautioned that the evolution of this low-chlorophyll region will need to be assessed alongside changes in equatorial winds, sea-surface temperature, sea-level height, thermocline depth and ocean circulation.

El Niño is strengthening rapidly 

The satellite signal comes against an increasingly strong forecast from the US National Oceanic and Atmospheric Administration (NOAA).

In its latest ENSO diagnostic discussion issued on September 10, NOAA's Climate Prediction Center said El Niño had strengthened further over the previous month, with sea-surface temperature anomalies exceeding 3°C in the eastern equatorial Pacific.

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Subsurface temperatures were also significantly above average, with anomalies exceeding 10°C at depth in some areas. Westerly wind anomalies extended across the western to east-central Pacific, while enhanced rainfall and convection persisted over the central and eastern Pacific.

Taken together, NOAA said, these oceanic and atmospheric indicators point to a strengthening El Niño.

Could 2026 become a historic El Niño? 

NOAA now puts the probability of a very strong El Niño at more than 90% during the Northern Hemisphere fall and winter of 2026-27.

More strikingly, NOAA estimates a 75% chance that the October-December 2026 period could see a historic El Niño, exceeding the strength of previous events dating back to 1950. Such an event would correspond to a Relative Oceanic Niño Index (RONI) of at least +2.5°C over a three-month period.

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The probability does not mean that every region will necessarily experience extreme weather. NOAA stresses that a stronger El Niño increases the likelihood of characteristic impacts but does not guarantee their occurrence.

What it could mean for India 

El Niño is closely watched in India because changes in Pacific Ocean temperatures and atmospheric circulation can influence the Indian monsoon.

Historically, El Niño conditions have been associated with a higher likelihood of below-normal monsoon rainfall and warmer conditions over parts of India, although the relationship is not deterministic. Other oceanic and atmospheric factors can strengthen, weaken or even offset the influence of El Niño in a particular year.