California coast braces for another battering as new El Niño-related wave emerges in Pacific

Key Points:

• California beach communities face rising sea levels and increased sand erosion in the coming weeks due to a strengthening El Niño and an approaching coastally trapped Kelvin wave, which could raise sea levels off the coast by about 6 inches for months.
• Coastally trapped Kelvin waves, linked to El Niño, travel along the Pacific coast and elevate sea levels, increase ocean temperatures, and push nutrient-rich waters deeper, thereby heightening flood risks and beach erosion, especially when combined with storms.
• The current Kelvin wave is expected to reach Southern California by early October, following a path from the west coast of Mexico through the Gulf of California and up the Baja California peninsula, potentially exacerbating damage already caused by climate change and a long-lasting marine heat wave.
• NOAA forecasts a 75% chance that this El Niño will be the strongest since 1950, with ocean temperatures at record highs, increasing the likelihood of late-season tropical storms and hurricanes in the eastern Pacific that could further impact California’s coast.
• Previous strong El Niño events, such as in 2015-16, saw multiple coastally trapped Kelvin waves causing significant coastal erosion, suggesting the strongest waves and associated impacts may still be forthcoming this season.