New Delhi: The Indian Space Research Organisation’s EOS-06, more popularly known as Oceansat-3, has captured a decline in marine productivity across the equatorial Pacific Ocean. The reason is warming oceans due to the ongoing El Niño—one of the worst warming events ever recorded in human history.
ISRO launched its Oceansat-3 satellite to monitor the atmosphere and observe biological and physical parameters of oceans in 2022. The satellite is equipped with three main instruments–a 13-band advanced ocean colour monitor, a Ku-band scatterometer, and a 2-channel sea surface temperature monitor.
ISRO’s National Remote Sensing Centre (NRSC) analysed observations of chlorophyll-a measurements from the Ocean Colour Monitor-3 (OCM-3) combined with ocean-surface wind vector observations from the EOS-06 Scatterometer across the tropical Pacific for April, May and June during 2023–2026. This was done to understand the evolution of El Niño as 2026 progresses.
El Niño, or the El Niño Southern Oscillation (ENSO), is a climate phenomenon in which trade winds and surface temperatures over the Pacific Ocean change course. It leads to large-scale disruptions in weather patterns across the world.
In Asia, including India, Indonesia, Sri Lanka, and even Australia, El Niño conditions are typically associated with weaker monsoons, and sometimes even droughts.
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Findings
The NRSC report explained that a comparison of the June 2024 and June 2025 composites, representing neutral ENSO conditions, with June 2026 observations during the developing El Niño reveals a notable reduction in surface chlorophyll-a. The green pigment used by microscopic ocean plants to absorb sunlight for photosynthesis.
This decline coincides with a reversal of ocean-surface winds, from easterlies—which blow from east to west—to westerlies, which blow from west to east.
“This weakening and reversal of the prevailing winds suppresses the normal equatorial upwelling across parts of the western and central equatorial Pacific. The resulting reduction in the supply of nutrient-rich subsurface waters is reflected in the observed decline in surface chlorophyll-a,” the report said.
ISRO said that the apparent contraction of the westward extent of the elevated-chlorophyll region between April and June 2026 supports the weakening of equatorial upwelling as the El Niño event developed.
The report also said that the synergistic application of multi-sensor data from both OCM-3 and scatterometer sensors of EOS-06 confirms the strong biophysical coupling in the equatorial Pacific Ocean during the ongoing El Nino event.
This means that if this El Niño intensifies further, as forecasted, the low-chlorophyll region may become more pronounced with time.
“This should be further inferred with concurrent estimates of anomalies in equatorial winds, sea-surface temperature, sea-level height, thermocline depth, and ocean circulation in the coming months,” the findings read.
The observations from ISRO’s Oceansat-3 also complement the World Meteorological Organisation (WMO) outlook.
In its June 2026 El Niño/La Niña update, the WMO estimated an approximately 80% probability of El Niño conditions developing during June–August 2026, with several forecast models indicating the possibility of a strong event.
The WMO forecast also said that by late July, El Niño conditions were intensifying and were expected to strengthen between August and October.
“Satellite observations from EOS-06/Oceansat-3 reveal a clear decline in marine productivity associated with the developing El Niño conditions across the equatorial Pacific Ocean,” ISRO said.
(Edited by Ratan Priya)