Scientists warn a slow-moving Kelvin wave triggered by a very strong El Niño could raise California coastal sea levels by up to about 30 cm, roughly a foot, for months. The planetary-scale pulse forms when trade winds weaken or reverse and propels warm western Pacific water east along the equator, then north and south when it reaches the coast, Severine Fournier of NASA’s Jet Propulsion Laboratory said. One Kelvin wave struck the northern tip of South America in late August and has begun moving north toward the US west coast, and researchers say it could reach California within days. Nate Mantua of NOAA’s Southwest Fisheries Science Center said the elevated water is expected to linger through the winter and into early next year as El Niño traps warm water along the shore. Sea levels have already risen about 8 inches over the last century, meaning the Kelvin wave will add on top of that baseline and raise the floor for tides. Mike Jacox of the Southwest Fisheries Science Center noted higher tides around Thanksgiving and Christmas, and warned that higher baseline sea levels will amplify storm surge, flooding and coastal erosion during storms. California officials are already taking preparatory steps for a potentially severe coastal impacts season.
David Ho3
Stephen Smith1
HydrologyNL1
