NASA has identified the precursor of El Niño from space. One of its satellites recorded the movement of warm water from the Pacific Ocean as it shifts eastward towards the western coast of South America. Data from the Sentinel-6 satellite, which monitors sea level, showed Kelvin waves moving across the Pacific.
These long oceanic waves are only 5-10 centimeters high but are hundreds of kilometers wide. They are clear signals of El Niño when they manifest at the equator, indicating the simple displacement of the upper layer of warm water in the western Pacific. “We will be watching this El Niño like hawks. If it’s big, the globe will see a record warming” said (ref.) Josh Willis, a scientist from the Sentinel-6 project at the Jet Propulsion Laboratory (JPL), in a statement.
How often does El Niño occur?
El Niño is part of the El Niño-Southern Oscillation (ENSO) climate cycle. Normally, prevailing easterly winds along the equator, known as trade winds, blow surface water westward in the Pacific, moving it from South America towards Asia. As the warm water moves, cold water rises to replace it.
The phenomenon has a significant impact on weather patterns worldwide. For the United States, it means wetter climate in southern parts and warmer climate in northwestern areas. Its counterpart, La Niña, has the opposite effect, with strong trade winds pushing warm water westward.
El Niño typically occurs once every three to five years, but its frequency can vary greatly and has been increasing in recent decades. The last recorded El Niño occurred in 2019 and lasted six months, from February to August of that year.
Is it an El Niño year?
On May 11th, representatives from the National Atmospheric and Oceanic Administration (NOAA) stated that there was a 90% chance of El Niño occurring this year, persisting into the winter of the Northern Hemisphere (ref.). According to NOAA’s predictions, there is an 80% chance of a moderate El Niño, with surface ocean temperatures increasing by 1°C. At the same time, there is a 55% chance of a strong El Niño, with temperature increases of 1.5°C, as reported by NOAA.
A statement from JPL released on May 12th (ref.) states that images captured by the Sentinel-6 satellite between early March and late April show Kelvin waves moving warm water eastward, starting off the coasts of Colombia, Ecuador, and Peru. The red and white parts of the animation represent warmer water and higher sea level.
“Ocean waves spread heat around the planet, bringing warmth and moisture to our shores and changing our weather” said Nadya Vinogradova Shiffer, a scientist in NASA’s program and manager of Sentinel-6. NOAA and NASA will continue to monitor the precursor signal in the Pacific in the coming months to determine if and when El Niño will strike and how strong it might be. “Here in the southwestern United States, we could see another wet winter, right on the heels of the soaking we had last winter” Willis said.
Grim predictions
In April, scientists recorded the highest-ever temperatures on the ocean surface, with a global average of 21.1°C. This record reflects the impact of climate change. “Now that La Niña is over, the tropical Pacific, which is a huge expanding ocean, is warming up” said Michael McPhaden, an oceanographer at NOAA’s Pacific Marine Environmental Laboratory.
Willis himself stated in the journal Nature that the combination of El Niño and increasingly high ocean temperatures could mean a “series of record highs over the next 12 months, with the coming year resembling an unchecked temperature sprint if El Niño takes off for real”.