NASA satellites are tracking a potentially powerful El Niño developing across the Pacific Ocean in 2026 revealing changes in sea surface temperatures ocean height and marine ecosystems that could influence weather patterns around the world.
In October, the US National Oceanic and Atmospheric Administration (NOAA) estimated an 83 per cent chance that the event would become the strongest El Niño since 1950. The outcome remains uncertain, but satellite observations are providing scientists with detailed information about the changing ocean conditions.
El Niño is a naturally occurring climate pattern that typically develops every two to seven years. It is characterised by unusually warm surface waters in the central and eastern equatorial Pacific and changes in atmospheric circulation that can influence rainfall, temperature and storm patterns across different regions.
The 2026 event is being monitored through several satellite missions allowing researchers to observe changes in ocean height, surface temperatures and colour.
Ocean height reveals the movement of heat
One early sign of the developing El Niño appeared in January 2026 when scientists detected a Kelvin wave near Micronesia in the western Pacific.
Kelvin waves are large slow moving pulses of warm water that travel across the ocean. They transport heat from the western Pacific towards the east and can help initiate the ocean atmosphere changes associated with El Niño.
As warm water moves eastward it heats the air above the ocean, influencing atmospheric pressure and weakening the trade winds that normally blow from the Americas towards Asia. These changes can further warm the eastern Pacific and raise sea levels in parts of the region.
By early April the Kelvin waves had reached the eastern Pacific, where sea surface temperatures began rising. Satellite measurements showed local sea levels increasing by approximately 30-40 centimetres in some areas. In contrast, sea levels around Indonesia and northern Australia were 15-20 centimetres below normal.
NASA’s Sentinel-6 satellites measure ocean height using radar altimetry, surveying vast areas of the sea and detecting changes of just fractions of an inch. The observations help scientists track the movement of warm water and monitor the development of El Niño.
Josh Willis project scientist for sea-level missions at NASA’s Jet Propulsion Laboratory, described Kelvin waves as a key indicator of the phenomenon, with satellite measurements allowing researchers to follow their movement across the Pacific.
Scientists have used satellite altimetry to monitor ocean height continuously since 1993. The Sentinel-6 missions continue this record, complementing measurements from ocean buoys, ships and other monitoring systems.
Pacific temperatures rise above average
Satellite instruments buoys and ship-based sensors show that sea surface temperatures in the eastern Pacific are approximately 1.7 degrees Celsius above the long-term average.
These unusually warm waters are central to El Niño’s development. Heat and moisture from the ocean enter the atmosphere, influencing cloud formation, rainfall and atmospheric circulation far beyond the Pacific.
The geographical extent and intensity of the warming are important indicators of how the event may evolve. However, the eventual strength of El Niño and its regional effects depend on interactions between ocean temperatures, winds and atmospheric conditions.
The consequences can vary widely. Some regions may experience increased rainfall and flooding, while others may face reduced rainfall drought or higher temperatures. The precise effects depend on the strength of the event, the season and other climate patterns operating at the same time.
Ocean colour reveals changes in marine life
NASA’s observations are also revealing changes in the colour of the Pacific Ocean providing clues about the biological effects of El Niño.
Measurements from the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite show that parts of the equatorial Pacific have become bluer in recent months. This change is associated with declining concentrations of phytoplankton, microscopic organisms that form the foundation of the marine food web.
Phytoplankton often thrive in cool nutrient rich surface waters. Under normal conditions, trade winds help drive the upwelling of deeper water, bringing nutrients towards the ocean surface.
During El Niño weaker trade winds reduce this upwelling in parts of the equatorial Pacific. With fewer nutrients available, phytoplankton populations can decline changing the ocean’s colour and potentially affecting marine food webs.
These organisms provide food for a wide range of marine species. A reduction in their abundance can therefore affect the distribution and feeding opportunities of other organisms, including fish.
The PACE satellite launched in 2024, is observing its first El Niño event. Its Ocean Color Instrument measures light across hundreds of wavelengths including visible, near infrared and ultraviolet bands. These observations allow scientists to monitor phytoplankton and other changes in ocean colour.
Researchers use a measurement called apparent visible wavelength to summarise the ocean’s observed colour. Changes in this measure can help identify shifts in the composition and abundance of material in surface waters including phytoplankton.
Matthew Kehrli a lead research scientist on the PACE satellite team at NASA’s Goddard Space Flight Center said the new observations allow scientists to see how expected changes associated with El Niño are unfolding in real time.
Monitoring a global climate influence
NASA scientists will continue to use satellite observations to track the event as it develops. By combining sea level measurements, temperature maps and ocean colour data, researchers can examine different aspects of the same climate phenomenon.
These observations are important because El Niño influences the distribution of heat across the ocean and atmosphere affecting seasonal weather patterns in many parts of the world. Farmers, emergency planners and coastal communities can face very different risks depending on how the event develops and interacts with regional climate conditions.
Although El Niño is a natural climate phenomenon, its impacts occur against a backdrop of long term global warming. Understanding how ocean conditions evolve can help scientists distinguish the effects of natural climate variability from longer-term changes and improve assessments of potential risks.
The strength of the 2026 event will become clearer as more observations become available. For now, satellite data are providing an unusually detailed view of the changing Pacific, from shifting sea levels and warmer surface waters to changes in the microscopic organisms that sustain marine ecosystems.
As NASA’s observations demonstrate tracking the ocean can provide critical insights into a climate pattern whose effects extend far beyond the region where it begins.