Communities across California are rushing to prepare for the imminent arrival of the so-called “Kelvin wave”, a massive underwater band of warm water threatening to inundate swaths of the vast North American shoreline. The wave is nearing southern California and expected to reach the San Francisco Bay Area by early October, as it crawls toward Alaska. Waters could rise by a foot along the California coast, according to scientists, who have warned that this could dramatically double the 8-12in rise in sea levels already caused by climate change over the last century.
The Kelvin wave doesn’t climb and crash like a typical ocean wave; rather, it swells the tides from beneath the surface. It’s effectively a massive slosh of warm water, driven by El Niño conditions, that moves across the Pacific before colliding with the South American coastline and surging north. It also won’t transport water in the way a tsunami might, but creates conditions that enable higher sea levels to linger.
On their own, Kelvin waves aren’t always hazardous, according to Mike Jacox, a research oceanographer with the National Marine Fisheries Service, though they can reduce the growth of phytoplankton that form the base of the marine food web. If the rising waters coincide with other climatic events, such as rainstorms and high tides, the phenomenon could swallow beaches, chew away bluffs and coastlines, and submerge streets, homes and businesses. Together, Warrick said, the systems will pack a far bigger punch.
But a “super” El Niño that’s brewing in the Pacific – which could become the most severe ever recorded – has layered on top of that warming, and increased the likelihood that the higher sea levels will overlap with severe storms. The climate pattern characterized by high sea surface temperatures in the central and eastern tropical Pacific is already spurring extreme weather around the world, fueling destructive storms in Hawaii and unleashing Pacific hurricanes that have hammered beach towns. California will likely see the worst effects this winter when the state could get pummeled by moisture.
Storms do damage on their own, but the most destructive occur alongside high tides, according to a recent memo from the California Coastal Commission – and the “super” El Nino will increase the severity of both. The highest tides of the year in areas of California will occur in November and December, further increasing water levels during the months when the state tends to be hit by wet weather. He added that a wetter-than-average winter would also bring increased inland flooding risk.
Heavy storms caused massive coastal erosion, as enormous landslides ruptured and buried highways, and huge waves swept into harbors across Santa Cruz and the San Francisco Bay Area. Levees failed north of Sacramento and seawalls were overwhelmed, while relentless rains tore into thousands of homes and businesses. Twenty-one of California’s 58 counties were declared disaster areas.
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