El Niño Transforms Ocean Colors, NASA Satellite Data Reveals

Super El Niño is altering the coloration of the world's oceans, according to new analysis of NASA satellite imagery. Data indicates that the equatorial Pacific has become "measurably more blue" in recent months as rising ocean temperatures impact marine life.

Time-lapse images illustrate a shrinking band of green along the equator, replaced by a bright blue wave correlating with increased ocean temperatures. In contrast, satellite data from 2025 shows this region maintained its typical green hue throughout the year.

The dramatic color shift is attributed to the decline of photosynthesizing plankton. While plankton can exhibit various colors, areas rich in these organisms typically appear emerald green. However, El Niño disrupts ocean currents that normally bring cold, nutrient-rich water to the surface. This lack of essential nutrients has led to plankton starvation in the equatorial Pacific, resulting in a return of a deep blue hue to the ocean.

El Niño is part of the El Niño Southern Oscillation (ENSO), a natural climate cycle that occurs every two to seven years, alternating between a hot El Niño phase and a cooler La Niña phase. During El Niño, warm waters accumulate in the equatorial Pacific off the coast of South America, elevating average temperatures and influencing global weather patterns.

Scientists suggest the current period is in the early stages of a significant El Niño cycle, with potential for widespread effects throughout 2027. The National Oceanic and Atmospheric Administration (NOAA) predicted an 83 percent chance in October that this El Niño would be the strongest on record since 1950.

NASA's satellite measurements show sea surface temperatures in the eastern Pacific are currently 1.7°C (3°F) above the long-term average, with potential for further increases. This warm water band has expanded across millions of square miles, stretching from the South American coast into the central Pacific.

This marks the first El Niño year since NASA launched the PACE (Plankton, Aerosol, Cloud, Ocean Ecosystem) satellite in 2024, providing unprecedented observational capabilities. The PACE satellite's Ocean Colour instrument measures ocean color across hyperspectral wavelengths.

"Some people think of water as being just blue, but it's amazing the multitude of colours the ocean can be," said Dr. Matthew Kehrli, a lead research scientist at NASA’s Goddard Space Flight Center. "During El Niño, the trade winds... weaken or even reverse. This reduces the upwelling of nutrient-rich waters from deeper parts of the ocean, leading to a decline in algae numbers and bluer waters."

The decline in phytoplankton can trigger cascading effects throughout the marine ecosystem, potentially forcing other animals to relocate in search of food.

Scientists first detected signs of a major El Niño year in January through sea level measurements from satellites. These instruments observed a Kelvin Wave building near Micronesia. Kelvin Waves are large pulses of water that transport heat eastward across the Pacific, influencing air pressure and weakening trade winds, thereby initiating the El Niño chain reaction.

By early April, satellites confirmed the Kelvin wave had reached the eastern Pacific, contributing to rising sea surface temperatures. As warm water expands, it also causes sea levels to rise. In critical El Niño regions, sea levels increased by as much as 1.3 feet (40cm) near South America and California, while levels dropped by up to eight inches (20cm) near Indonesia and Australia.

"El Niño touches almost all of us in some way every time it occurs," said Dr. Josh Willis, project scientist for sea level missions at NASA’s Jet Propulsion Laboratory. "While many have seen what it can do, we look to the ocean to understand why."