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In California, 13-Foot Waves Are a 'Harbinger'

Study says giant swells have become more common, with signs pointing to climate change
By Newser Editors and Wire Services
Posted Aug 4, 2023 1:15 PM CDT
California's Waves Are Getting Bigger
Powerful waves batter the Capitola Wharf after a storm destroyed a section of the structure on Jan. 5 in Capitola, California.   (Shmuel Thaler/Santa Cruz Sentinel via AP, File)

Waves are getting bigger, and surf at least 13 feet tall is becoming more common off California's coast as the planet warms, according to innovative new research that tracked the increasing height from historical data gathered over the past 90 years. Oceanographer Peter Bromirski at the Scripps Institution of Oceanography used the unusual method of analyzing seismic records dating back to 1931 to measure the change in wave height, per the AP. When waves ricochet off the shore, they collide with incoming waves and cause a ripple of energy through the seafloor that can be picked up by seismographs designed to detect earthquakes. The greater the impact, the taller the wave is.

Until now, scientists relied on a network of buoys by the National Oceanic and Atmospheric Administration that collect data on wave height along US coasts, but that data along the California coast only went back to 1980. To go back further, the scientist gathered a team of undergraduate students to analyze daily seismic readings covering decades of winters. It was a slow, painstaking process that took years and involved digitizing drums of paper records. The team found that average winter wave heights have grown by as much as a foot since 1970, when global warming is believed to have begun accelerating.

Swells at least 13 feet tall are also happening a lot more often, occurring at least twice as often between 1996 to 2016 than from 1949 to 1969. Bromirski was also surprised to find extended periods of exceptionally low wave heights prior to about 1970 and none of those periods since. "Erosion, coastal flooding, damage to coastal infrastructure is ... something that we're seeing more frequently than in the past," he said. "Combined with sea level rise, bigger waves mean that is going to happen more often." The study, published Tuesday in the Journal of Geophysical Research: Oceans, adds to the evidence that climate change is causing massive shifts in the world's oceans. Other studies have shown waves are not only getting taller but also more powerful.

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Damage from intense storms and massive surf is already playing out. This winter, California's severe storms and giant waves collapsed bluffs, damaged piers, and flooded parts of the state's Highway 1. Oceanographer Gary Griggs at UC Santa Cruz, not involved in the research, said it adds to growing scientific data showing how fast the world is warming and seas are rising. "We know hurricanes are more intense and last longer, and now we've got ... waves increasing in power. So those are all consistent," he said. "The challenge ... [is] how to really respond to that."

(More waves stories.)

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