West-east near-surface current trend between 1993-2022. The blue colors show increased westward currents; red colors show increased eastward currents. The largest trends are observed in the central tropical Pacific Ocean (black box). Current velocity data from three equatorial moored buoys (yellow diamonds) provide a subsurface view on long-term upper-ocean current velocity trends.
A study published October 31, 2024, in the Journal of Geophysical Research: Oceans has revealed significant acceleration in the upper-ocean circulation of the equatorial Pacific over the past 30 years. This acceleration is primarily driven by intensified atmospheric winds, leading to increased oceanic currents that are both stronger and shallower, with potential impacts on regional and global climate patterns, including the frequency and intensity of El Niño and La Niña events. The study provides a spatial view of these long-term trends from observations, adding at least another decade of data from previous studies.
The research team, led by Franz Philip Tuchen, a postdoctoral scientist at the University of Miami Rosenstiel School’s NOAA Cooperative Institute for Marine and Atmospheric Studies (CIMAS), in collaboration with NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML), synthesized thirty years of long-term ocean and atmosphere observations from satellites, mooring buoys, and ocean surface drifters. By integrating the reanalysis of wind data and satellite altimetry into a high-resolution, gridded time series of near-surface ocean currents, this study presents a new and comprehensive view to date of the changes in the Pacific upper-ocean circulation.
The research findings indicate that stronger winds across the equatorial Pacific have caused a notable acceleration of westward near-surface currents by approximately 20 percent in the central equatorial Pacific. Poleward currents north and south of the equator have also accelerated, with increases of 60 percent and 20 percent, respectively.
“The equatorial thermocline—a critical ocean layer for El Niño–Southern Oscillation (ENSO) dynamics—has steepened significantly,” said Tuchen. “This steepening trend could reduce ENSO amplitude in the eastern Pacific and favor more frequent central Pacific El Niño events, potentially altering regional and global climate patterns associated with ENSO.”
The researchers indicate the study offers a benchmark for climate models, which have had limited success to accurately represent Pacific circulation and sea surface temperature trends. The researchers suggest the findings could help improve the predictability of ENSO events and related weather patterns, especially for regions like the United States, which experience significant climate variability from ENSO-driven changes.
Funding for this study was provided by NOAA’s Global Ocean Monitoring and Observing (GOMO) programs, including the Global Tropical Moored Buoy Array (GTMBA), the Global Drifter Program (GDP), and the Tropical Atmosphere Ocean (TAO) program.
The study, titled Strengthening of the equatorial Pacific upper-ocean circulation over the past three decades was published in the Journal of Geophysical Research: Oceans, on October 31, 2024. The authors include Franz Philip Tuchen1,2 Renellys C. Perez 2, Gregory R. Foltz2, Michael J. McPhaden3 and Rick Lumpkin2
1. Cooperative Institute for Marine and Atmospheric Studies, Rosenstiel School of Marine,
Atmospheric, and Earth Science, University of Miami, Miami, FL, USA
2. NOAA Atlantic Oceanographic and Meteorological Laboratory, Miami, FL, USA
3. NOAA Pacific Marine Environmental Laboratory, Seattle, WA, USA
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