California beach communities are expected to see rising sea levels in the coming weeks as El Ni\u00f1o continues to strengthen, with more sand erosion and damage possible, according to new data.<\/p>\n
Another El Ni\u00f1o-influenced phenomenon \u2014 a \u201ccoastally trapped Kelvin wave\u201d \u2014 is moving up the coast of Mexico and will soon hit the U.S. West Coast.<\/p>\n
This isn\u2019t a surfable wave, and it wouldn\u2019t be overtly noticeable to swimmers or boaters either. But it is expected to increase the sea level off the California coast by another 6 inches or so, and its effects could last months, according to Dillon Amaya, an expert on coastally trapped waves and an assistant professor at North Carolina State University\u2019s Department of Marine, Earth and Atmospheric Sciences. <\/p>\n
It might not sound like much, but another 6 inches of sea level rise could further bludgeon the already battered California coast, especially if combined with the effects from a storm. <\/p>\n
\u201cWe saw why that\u2019s important recently, with houses across Southern California getting battered, especially at those high tides. We had hurricane-generated swells and high tides, and the combination was extremely damaging to these homes,\u201d said Jonathan Warrick, research geologist with the U.S. Geological Survey. \u201cWhen the water level is extra high, a foot or more higher than we expect it to be, then it can really wreak havoc.\u201d<\/p>\n
As it stands, the Golden State has already experienced about a foot of sea level rise over the past 125 years from human-caused global warming and the melting of the polar ice caps. And lately, the state has also seen abnormally high tides. <\/p>\n
The California coast has also been dealing with a long-lasting marine heat wave unrelated to El Ni\u00f1o, which can also raise the sea level. <\/p>\n
\u201cThe combination of the wave and El Ni\u00f1o and marine heatwave, all of these factors are contributing essentially another foot of sea level rise \u2014 in addition to what we\u2019ve experienced from climate change,\u201d said Amaya, who got his doctorate in oceanography at the Scripps Institution of Oceanography at UC San Diego. <\/p>\n
Until recently, Kelvin waves were a pretty obscure concept. But they\u2019re fundamentally at the heart of El Ni\u00f1o: a climate pattern in which the ocean waters in the central and eastern equatorial Pacific heat up and spur changes in the atmosphere that can affect weather around the world. <\/p>\n
As El Ni\u00f1o develops, the typical east-to-west trade winds along the equator weaken or even reverse, \u201cwhich allows a lot of really hot water and high sea surface heights to slosh back from the far western equatorial Pacific, where they typically sit, all the way to the east,\u201d Amaya said. <\/p>\n
That means typically warmer water, like around Indonesia, moves east to a normally cooler part of the Pacific, near Peru \u2014 pushed along by Kelvin waves. <\/p>\n
Upon hitting South America, the Kelvin wave splits into two, one heading north, toward California. <\/p>\n
In the Northern Hemisphere, these Kelvin waves become \u201ccoastally trapped,\u201d meaning they have to follow a coastal boundary, with the shoreline to their right, said Michael Jacox, research oceanographer with the National Oceanic and Atmospheric Administration\u2019s Fisheries\u2019 Ecosystem Science Division. <\/p>\n
\u201cAlong the coast, these waves elevate sea levels, increase ocean temperatures, and push cold, nutrient-rich waters deeper below the surface,\u201d Jacox said.<\/p>\n
As they travel, Kelvin waves can raise sea levels by as much as 6 to 12 inches \u2014 potentially for months.<\/p>\n
\u201cThose elevated sea levels, when combined with passing weather or storms, can substantially increase flood risk and risk for things like beach erosion,\u201d Amaya said. <\/p>\n
The coastally trapped Kelvin wave is currently on the west coast of Mexico, perhaps south of Puerto Vallarta. Amaya said he expects the wave to enter the Gulf of California on or around Sept. 19. Once there, it\u2019ll take about 11 days for the wave to hug the gulf\u2019s U-shaped coast and, from there, another seven days for it to travel from the southernmost tip of the Baja California peninsula \u2014 Cabo San Lucas \u2014 to San Diego. <\/p>\n
It\u2019ll then take about two to three days to reach L.A., another two to three more to get to San Francisco. <\/p>\n
That would put the wave\u2019s arrival in Southern California in early October, although the exact timing remains uncertain.<\/p>\n
\u201cThey\u2019re pretty epic. They travel something like 25,000 kilometers [15,500 miles] all the way from the western equatorial Pacific up … to the Gulf of Alaska, and it takes about 120 days,\u201d Amaya said. <\/p>\n