NASA satellites detect early El Niño changes in Pacific

NASA's satellite observations have revealed early signs that El Niño is altering marine conditions in the Pacific Ocean, with potential implications for fish populations and fisheries along the West Coast of the United States and other regions. El Niño is a naturally recurring climate phenomenon characterized by warmer-than-normal waters in parts of the equatorial Pacific, along with shifts in atmospheric and ocean circulation. The National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center has indicated a greater than 90 percent chance of a very strong El Niño persisting into 2027, and a 69 percent chance of a historic event exceeding the strength of previous El Niños dating back to 1950.

NASA's satellites have already detected warmer sea surface temperatures, higher sea surface height, and changes in chlorophyll-a, a pigment used as an indicator of phytoplankton abundance. Specifically, NASA's PACE satellite observed substantially lower chlorophyll concentrations in parts of the central equatorial Pacific in June 2026 compared with neutral conditions in June 2025. Phytoplankton are microscopic organisms at the base of the marine food web, and their abundance is crucial for the entire marine ecosystem.

The reduction in chlorophyll is linked to warmer waters, which typically inhibit upwelling—the process that brings cold, nutrient-rich water from depth to the surface. Michael Jacox, a research oceanographer at NOAA's Southwest Fisheries Science Center, explained that the tropical Pacific is the center of action, but the eastern Pacific beyond the tropics, including the west coasts of North and South America, is also likely to be strongly affected due to teleconnections from the tropics through the ocean and atmosphere. Along the US West Coast, El Niño tends to limit productivity by reducing nutrient availability in surface waters. This can happen through weakened coastal upwelling, increased ocean stratification that makes it harder to lift nutrients from depth, and a deepening of the nutricline—the depth at which high nutrient concentrations are found.

The impacts on marine life are species-dependent. Cold water species may move north or to deeper waters, and generally experience lower growth and reproduction rates. However, not all effects are negative; some species may benefit, potentially leading to more fishing opportunities in certain areas. Leising, a researcher mentioned in the context, noted that warmer conditions can actually create more fishing opportunities for some species than in normal years.

Jacox cautioned that El Niño does not guarantee specific impacts, but the stronger the event, the more likely severe impacts become. Leising also warned against overinterpreting surface chlorophyll data alone, as satellites only see the top few meters of the ocean, while much of the phytoplankton can be deeper. Surface chlorophyll is often correlated with chlorophyll in the upper water column, but not always. Additionally, equatorial chlorophyll levels are normally low compared with coastal regions, so small changes can appear large in relative terms.

These early signs from NASA highlight the need for continued monitoring and research to understand the full extent of El Niño's effects on marine ecosystems and fisheries, which are vital for food security and economies worldwide.