Pacific shows 9,000-mile warm anomaly

A large pool of unusually warm water is moving beneath the surface of the tropical Pacific, and forecasters are watching whether that heat reaches the surface strongly enough to reinforce El Niño later in 2026. Weatherzone reported on May 19 that subsurface temperatures in parts of the tropical Pacific were running more than 6 degrees Celsius above the long-term average, with the warm water starting to emerge in the eastern Pacific. The concern is not only the ocean signal itself. The Global Ocean Observing System, or GOOS, said in its 2025 status report that the observing network used to track ocean temperatures, currents, sea level and related variables remains uneven and financially fragile. UNESCO’s Intergovernmental Oceanographic Commission and the World Meteorological Organization said the system is still “subcritical” despite recent gains in some autonomous networks. (weatherzone.com.au) ### What exactly is moving under the Pacific? Weatherzone described the feature as a large mass of abnormally warm water sitting below the surface in the top few hundred meters of the tropical Pacific. The outlet said that in recent weeks the warm subsurface water had begun spreading toward the surface in the eastern tropical Pacific, helping lift sea-surface temperature anomalies in the Niño3 region. (ioc.unesco.org) The Met Office said on April 15 that warming across the central and eastern equatorial Pacific had already crossed important thresholds used internationally to identify El Niño conditions. It added that rising sea level in the region was another sign that additional heat was building in the ocean. ### Why do scientists care about water that is still below the surface? The Australian Bureau of Meteorology, as cited by Weatherzone, says warmer-than-average subsurface water in the central and eastern tropical Pacific can be a sign of El Niño development. (weatherzone.com.au) That matters because subsurface heat often appears before the full surface expression that affects the atmosphere and, eventually, weather patterns around the world. (metoffice.gov.uk) The Met Office said stronger El Niño events tend to have more widespread global effects, and that current model projections point to continued warming through the summer and toward the end of the year. It said El Niño events often peak between November and February. ### Why does the observing network matter here? GOOS said its networks provide sustained observations of essential ocean variables including sea temperature, salinity, sea level, currents and sea ice. (weatherzone.com.au) Emma Heslop, an IOC program specialist and GOOS lead for the Statement of Guidance for Oceanic Applications, said the new guidance should help agencies and policymakers address “critical gaps” across weather, climate, operational oceanography and hazard warnings. (metoffice.gov.uk) The WMO said in November 2025 that the “eyes” of thousands of observing platforms feed weather forecasts, early warnings and climate prediction. WMO Secretary-General Celeste Saulo said robust data are necessary for better forecasts and decision-making, while IOC Executive Secretary Vidar Helgesen said that without a resilient, coordinated observing system, the information people rely on every day becomes more uncertain. (goosocean.org) ### Where are the weak points in that system? The GOOS Status Report 2025 said in situ observing networks had expanded over the prior two years, driven mainly by growth in autonomous systems such as Argo profiling floats. But it also said that increase had only partly offset declines in drifting buoys and ship-based oceanographic observations, which are facing budget constraints and can reduce long-term reference data. GOOS and its sponsors said the system also relies heavily on a small number of contributors, leaving coverage uneven across regions and platforms. (public.wmo.int) That makes continuity a practical issue, not only a scientific one, when forecasters are trying to detect changes in ocean heat content and refine climate projections. ### What happens next? GOOS said it will hold an official webinar on May 26, 2026, to present the latest Statements of Guidance for atmospheric, oceanic and cryospheric applications. (ocean-ops.org) In the Pacific, forecasters will keep watching whether the current subsurface warmth continues surfacing in the Niño3 and Niño3.4 regions as the year moves toward the period when El Niño typically peaks. (goosocean.org) (ioc.unesco.org)