A Mysterious Ocean Shift in the Pacific Is Worrying NOAA Scientists

At the Southwest Fisheries Science Center, Andrew Leising spends his working days monitoring ocean temperatures on screens. He tracks what NOAA refers to as the California Current Marine Heatwave Tracker, a system that has been recording marine heat events off the West Coast since 2019 by gathering data from satellites, ships, and buoys. He is not someone who uses frightening language out of instinct or professional training. This is why it’s important to take note of his recent remarks. He stated earlier this year, “We are in uncharted conditions,” referring to a marine heatwave that has defied almost all of the predictions made by scientists. “This is not a situation that we have seen before.”

In Pacific oceanography, that phrase—a situation we have never seen before—is currently doing a lot of work. Because a number of events are occurring in the Pacific at the same time, not all of them are pointing in the same direction, and some of them still lack a satisfactory explanation. Only two other heatwaves in the entire observational record have managed to maintain their size and warmth throughout the winter months without the assistance of an El Niño, as is the case with the massive marine heatwave that is currently dominating the waters off the West Coast. In the mid-Pacific region between Hawaii and the continental United States, there is a persistent cold anomaly that is about a hundred miles wide. It should have disappeared months ago, but it hasn’t, indicating that something is sustaining it from below or from a change in wind patterns that scientists are still trying to pinpoint. All of this is overshadowed by an impending El Niño, which NOAA currently estimates has a 62 percent chance of occurring between June and August 2026. Forecasters anticipate that it will intensify into the fall.

Key Facts: Pacific Ocean Anomalies & NOAA Monitoring

The most obvious aspect of this is the heatwave. The northeast Pacific saw its highest average temperature ever recorded on September 9, 2025, at 20.6 degrees Celsius, or roughly 69 degrees Fahrenheit. Over an area about ten times the size of the Mediterranean, that is almost half a degree warmer than any previous peak. According to climate model projections, the BBC’s analysis of Copernicus climate data revealed that the likelihood of sea temperatures that high happening in any one year was less than 1%. Put more simply, this was not what the models anticipated. The Pacific was pushed far beyond what even warming-adjusted projections had predicted. The precise nature of that something—weaker trade winds that allow surface heat to build up without mixing downward, the elimination of aerosol cooling from cleaner shipping fuels since 2020, and decreased air pollution from Chinese cities—is still up for debate among scientists. Zeke Hausfather of Berkeley Earth stated, “There’s definitely something unusual going on in the north Pacific,” suggesting that all three may be interacting simultaneously in ways that are truly difficult to model. He was straightforward about what the data suggests, saying that the warmth is “quite remarkable” for such a vast area: “It certainly is not just natural variability.” There’s more going on here as well.” That is a noteworthy statement from a climate scientist who carefully selects words and works with numbers professionally.
If you know where to look, the ecological effects are already apparent. Last fall, a lot of tunas were caught in Alaska. This seems almost ridiculous until you consider that the temperature of the ocean has actually changed, making it harder for fish to survive. A deadly algal bloom that arrived early in 2025 and struck harder than previous blooms has been killing hundreds of sea lions, dolphins, and seabirds off the coast of Southern California. Along certain coastal areas, shellfish fisheries have been shut down. Additionally, because warmer waters tend to support less of the productive upwelling that feeds the prey salmon depend on, salmon—the fish that define a vast portion of Pacific Northwest culture, ecology, and economy—face declining ocean survival rates. In the coming months, Leising and his colleagues are keeping a close eye out for indications of how the heatwave this winter will affect the food chain.
It’s difficult to ignore how inconvenient the timing is in this situation. Decades of observational data describing a Pacific operating within specific patterns served as the foundation for NOAA’s long-range weather tools, fisheries management models, and ecosystem monitoring. These patterns are no longer trustworthy indicators. In a 2023 study, NOAA Fisheries admitted that “some models scientists use to estimate fishing impacts may no longer work well in this new ocean environment,” and the issue hasn’t improved since. If anything, the uncertainty has increased in 2025 and the first part of 2026. To be honest, Leising stated that the current situation is difficult to reconcile. Although La Niña is technically present and should be cooling coastal waters, the West Coast does not resemble a La Niña coast.
Climate scientists are treating the impending El Niño with genuine caution because it adds another variable. According to Norwegian climate scientist Tore Furevik of the Nansen Environmental and Remote Sensing Center, current conditions are similar to those of early 2023, which led to the record-warm year of 2024. The key distinction is that temperatures are now beginning from an even higher baseline. According to Furevik, “there is every reason to believe that we will see new heat records, perhaps as early as this year and most likely in 2027,” Science Illustrated reported. Global temperatures could rise to levels never seen in climate records if a powerful El Niño builds on the already high Pacific.
It’s still unclear if the unusual persistence of the heatwave, the cold bubble anomaly, and the impending El Niño are related phenomena that reflect a deeper structural shift in Pacific circulation or if they are independent events that happen to coincide at an uncomfortable time. To get a better picture, researchers are utilizing direct vessel surveys, deep-sea buoy networks, and satellite imagery. They are not treating this as normal in any conversation that has been made public. The largest ocean in the world is the Pacific. What occurs there doesn’t stay there; it affects drought and flood cycles from Australia to the American West, drives storm tracks, creates hurricane seasons, and shapes rainfall patterns across continents. Even though the data is still incomplete and the answers are still developing, scientists feel the weight of the ocean being so unsettled and so far outside of its historical patterns.