Acceleration of Pacific Ocean circulation is impacting global weather

Significant acceleration in the upper-ocean circulation of the equatorial Pacific Ocean over the past 30 years is impacting global weather patterns, according to a new study.

The acceleration is driven by strengthening atmospheric winds. The oceanic currents are becoming stronger and shallower. Among the effects are increased frequency and intensity of El Niño and La Niña events.

The study is published in the Journal of Geophysical Research: Oceans.

Researchers used data collected between 1993–2022 from satellites, mooring buoys and ocean surface drifters.

They reanalysed wind data and satellite altitude measurements to create a high-resolution gridded map of ocean currents over time.

Among the findings is the roughly 20% acceleration of westward near-surface currents in the central equatorial Pacific.

North and south of the equator, currents going toward the poles have also accelerated. Currents going to the north pole have intensified by 57%, and the currents heading southward have increased 20%.

“The equatorial thermocline – a critical ocean layer for El Niño–Southern Oscillation (ENSO) dynamics – has steepened significantly,” says first author Franz Phillip Tuchen, a postdoctoral researcher at the University of Miami’s Ronenstiel School of Marine Atmospheric and Earth Science.

“This steepening trend could reduce ENSO amplitude in the eastern Pacific and favour more frequent central Pacific El Niño events, potentially altering regional and global climate patterns associated with ENSO.”

The new and comprehensive study provides a benchmark for climate models which have had limited success in accurately representing Pacific circulation and sea surface temperature trends.

The research helps explain why, for example, global mean sea surface temperatures have risen but parts of the tropical South Pacific have seen a cooling trend of more than –0.5°C over the past 3 decades.