NASA’s visualization of El Niño’s effect on the Pacific. Image: NASA Earth Observatory image by Lauren Dauphin, using modified Copernicus Sentinel data (2023) processed by the European Space Agency and further processed by Josh Willis, Severin Fournier, and Kevin Marlis/NASA/JPL-Caltech
El Niño is currently upon us. It’s warming up Pacific water temperatures after a few straight years of La Niña called a “Triple Dip“, and NASA has put together an image that shows exactly where it’s happening.
Real quick, here’s why El Niño and La Niña matter so much to the entire planet. The El Niño-Southern Oscillation (ENSO) cycle is an ongoing pattern of climate fluctuations in the Pacific. Depending on the year, we’ll have El Niño or La Niña. El Niño is the warmer phase, while La Niña is the colder one. In an El Niño year, winds swirling around the equator aren’t as strong. Warmer water moves east towards the west coast of the Americas, which means the cold water that cools the surface of the Pacific doesn’t affect temperatures as much. Once sea temperatures in the tropical eastern Pacific rise 0.5°C (0.9°F) above the long-term average, scientists declare an El Niño year.
La Niña, obviously, is the opposite. Ocean temperatures are colder. Since ocean temperatures are one of the primary drivers of weather and climate (remember, weather is short term while climate is long term trends), El Niño and La Niña years have drastic effects on weather patterns around the world. The warmer the water, the more intense the storms. Hurricanes are more powerful, rain fall is heavier, and wind is… well, windier.
For those of us who reside in North America, El Niño generally means more rain and more snow along the coast, but drier conditions in places like the Midwest. In places like Australia, however, El Niño means less rainfall, which leads to many things. The most worrisome for the Aussies, though, is wildfire risk.
The data NASA used in the graphic was taken from two satellites, the Sentinel-6 Michael Freilich and Sentinel-3B. Researchers at NASA’s Jet Propulsion Laboratory compiled it all and created an easy-to-understand map, which was nice of them considering we’re not all researchers at NASA’s Jet Propulsion Laboratory.
The data shows that rising sea temperatures have caused the sea surface height in the tropical Pacific to raise nearly five inches higher than average in the first few days of June. That’s because warmer water expands in a process fittingly called Thermal Expansion, which NASA explains in detail here. “Thermal expansion happens when water gets warmer,” researchers wrote, “which causes the volume of the water to increase. About half of the measured global sea level rise on Earth is from warming waters and thermal expansion.”
