This year's El Niño could be "historically strong", and may lead to intense flooding across the U.S. West Coast, including cities like Seattle and San Diego.
There is a 35 percent chance of an "historically strong" El Niño between November and January, with a greater than 55 percent chance of at least a "strong" El Niño persisting through January to March 2024, a U.S. Climate Prediction Center (CPC) forecast predicts.
El Niño is a climate pattern that happens in the Pacific Ocean every two to seven years, which leads to lessening trade winds and warmer ocean waters being pushed towards the western coast of the U.S.
This can result in the Pacific jet stream shifting southwards, leading to unusual and disruptive weather across the U.S. "Strong" El Niños are defined as seeing an average water temperature anomaly of at least 1.5 degrees Celsius [2.7 degrees Fahrenheit], while "historically strong" events see a 2 degree Celsius [3.6 degrees Fahrenheit] average rise.
This "historically strong" event could lead to increased high-tide flooding along the U.S. West Coast, according to an analysis by NASA's sea level change science team, with the possibility of up to five "10-year flood events" occurring in places like Seattle and San Diego.
Ten-year flood events are floods so large that they have a one in 10 chance of occurring in a given year, and are therefore a measure of how high local sea levels have become.
"I'm a little surprised that the analysis found these 10-year events could become commonplace so quickly," Phil Thompson, an oceanographer at the University of Hawaii and a member of NASA's sea level change science team, said in a NASA statement. "I would have thought maybe by the 2040s or 2050s.
Ten-year floods can lead to water flowing into towns and cities, possibly flooding roads and buildings. They usually aren't seen along the U.S. West Coast unless an El Niño is occurring, but this may change in the coming years with the effects of climate change.
As climate change's impacts cause glaciers and ice sheets, such as the Greenland ice sheet and the Antarctic ice sheet—the largest ice sheets in the Northern Hemisphere and in the world, respectively—around the world to melt, this will also increase the sea levels around the world, exacerbating the effects of El Niño-driven flooding.
"The Greenland ice sheet is by far the largest ice mass in the Northern Hemisphere. It contains about 12 percent of the world's ice which is equivalent to about 7 m [23 feet] of sea level [rise]," Joel Hirschi, associate head of marine systems modeling at the U.K.'s National Oceanography Centre, told Newsweek. "Recent work has shown that we can expect an extra contribution of about 27 cm [10.6 inches] from the Greenland ice sheet to global sea level rise by 2100. This is about twice as much as previously expected."
During the strongest El Niño years by the 2030s, up to 10 of these 10-year flood events could be seen on the U.S. West Coast, and this could spike to 40 events during strong El Niño years by the 2050s.
"As climate change accelerates, some cities will see flooding five to 10 times more often. SWOT will keep watch on these changes to ensure coastal communities are not caught off guard," Nadya Vinogradova Shiffer, SWOT (Surface Water and Ocean Topography) program scientist and director of the ocean physics program at NASA headquarters in Washington, said in the NASA statement.
El Niño and its counterpart La Niña usually only last between nine and 12 months, but can occasionally last for years, depending on how strong they are. The NOAA forecast estimates that this year, El Niño may last into spring, with a 62 percent chance of persisting until April-June next year.
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About the writer
Jess Thomson is a Newsweek Science Reporter based in London UK. Her focus is reporting on science, technology and healthcare. ... Read more
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