RESOLVING THE LEDGER
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Add as preferred source As of June 2026, El Niño has officially arrived . This naturally recurring phenomenon is characterized by warmer-than-normal water temperatures in parts of the equatorial Pacific, along with changes to atmospheric and oceanic circulation patterns. Its regional effects range from desert floods to delayed monsoons to shifts in where tropical cyclones are more likely to form.
NOAA's Climate Prediction Center expects the current El Niño to continue strengthening through the end of 2026, with a 97% chance of lasting through early Northern Hemisphere spring 2027. Even during El Niño's early stages, satellites have observed characteristic changes along the equatorial Pacific, such as warmer-than-normal sea surface temperatures and higher-than-normal sea surface height.
Among the first ecological downstream effects are changes to the marine food web. The maps above show chlorophyll-a concentrations—the pigment present in most phytoplankton—as observed by the OCI (Ocean Color Instrument) on NASA's PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) satellite. In June 2025 (left), conditions were neutral, while in June 2026 (right), El Niño was strengthening.
The most noticeable difference appears in the central Pacific, around the equator, due north of New Zealand: Chlorophyll concentrations, an indication of phytoplankton abundance, are substantially lower in 2026. This change is expected, said Matthew Kehrli and Graham Trolley, oceanographers in the Ocean Ecology Laboratory at NASA's Goddard Space Flight Center. That's because during an El Niño, easterly equatorial trade winds weaken, the warm surface layer of the ocean extends deeper, and the upwelling of cool, nutrient-rich water that typically fuels phytoplankton growth is suppressed.
As the El Niño progresses, the scientists anticipate the differences in the central Pacific will become more pronounced. "This may manifest as a greater difference in values across the current region, as a broader region of reduced surface chlorophyll-a concentration, or both, depending on the behavior of the equatorial trade winds," they said.
Reductions in phytoplankton have ripple effects through the marine food web, including in coastal regions. Less food is available for zooplankton, as well as for fish, seabirds and marine mammals. Peru's anchovy fisheries have seen profound declines in catch during past El Niños, driven similarly by warmer surface waters, reduced upwelling and lower phytoplankton abundance.
In 2026, Peru's Ministry of Production repeatedly suspended the fishery to safeguard the country's main fishing resource. Pelicans have been seen venturing into Peruvian ports and urban areas in search of food.
Although the disruptions to marine life can be severe, a post-El Niño "chlorophyll rebound," with higher-than-normal concentrations in the equatorial Pacific, can occur.
Research published in Geophysical Research Letters suggests that higher iron concentrations delivered in ocean currents, as well as dust arriving from drier land in parts of Central and South America, help fuel the resurgence—a rebound that doesn't require a follow-on La Niña.
La Niña, which often follows El Niño events, can also produce elevated chlorophyll concentrations. A strong La Niña in 1998–1999 set off a large phytoplankton bloom in the eastern Pacific and a dramatic increase in fish populations.
Scientists have new tools available for studying this sort of variability. The PACE mission launched in February 2024, making this the first complete El Niño event for which the satellite will gather global, near-daily hyperspectral measurements. "The scientific community will be able to observe the 2026 El Niño with data across more wavelengths of light than ever before," Kehrli and Trolley said.
To better understand effects on life in the ocean, researchers hope to use PACE data to gauge the responses of specific phytoplankton communities to El Niño. The possibilities extend beyond the marine realm, the scientists note. PACE's sensors can measure plant pigment composition on land and clouds and aerosols in the atmosphere, all of which are influenced by El Niño.
Hyung‐Gyu Lim et al, Oceanic and Atmospheric Drivers of Post‐El‐Niño Chlorophyll Rebound in the Equatorial Pacific, Geophysical Research Letters (2022). DOI: 10.1029/2021gl096113
Journal information: Geophysical Research Letters
Swati Mestri holds a bachelor's degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space. Full profile →
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