Altimetry sea level anomalies have been showing an elevation all along the Equator in the Pacific for the past four months.

Longitude-time diagram over 2021-2023, showing sea level anomalies averaged of 2°S-2°N across the whole equatorial Pacific.(data EU Copernicus Marine service, from all available altimeters on any day). Kelvin waves can be seen as elevations propagating from west to east of the basin. (data EU Copernicus Marine Service, figure Aviso)

Altimetry sea level anomalies have been showing an elevation all along the Equator in the Pacific for the past four months.

These positive anomalies across the Equatorial Pacific are among the early warning signs of an upcoming El Niño. Altimetry enables to monitor the phenomena at global scale, and thus add information to the in situ array installed there (TAO). The elevation reached the coasts of Equator in March, but has just triggered a reaction from the atmosphere, which is the actual El Niño.

Models show a high probability of an El Niño developing in the second half of 2023. It is a bit early to assert its magnitude, though, since some west wind gusts can still dampen the phenomenon, but it seems more than likely that there will be an El Niño this Christmas. The Equatorial Pacific will be closely monitored in the coming months for this.

From the first El Niño monitored by Topex/Poseidon in 1994, the altimetry satellites have brought knowledge and foresight to help in mitigating the impacts of the phenomenon in a large part of the world.

• Animation Sep. 2022-Jun 2023 https://youtu.be/Wl_HxwUNFSM
• https://www.aviso.altimetry.fr/enso
• Applications: ENSO