Coastal Communities Could Be in for Some Trouble

A strong El Niño and La Niña could cause flooding and erosion along the Pacific, according to new research.
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Flooding in Honolulu, Hawaii. (Photo: Theodore Trimmer/Shutterstock)

Flooding in Honolulu, Hawaii. (Photo: Theodore Trimmer/Shutterstock)

Coastal communities dotting the Pacific Ocean, already threatened by rising sea levels, will experience additional severe flooding and erosion from El Niño and La Niña, new research suggests.

According to a study published earlier this week in Nature Geoscience, coastal erosion and flooding could be much worse along the Pacific than previously thought, particularly when El Niño and La Niña are taken into consideration.

"We conclude that, if projections for an increasing frequency of extreme El Niño and La Niña events over the twenty-first century are confirmed, then populated regions on opposite sides of the Pacific Ocean basin could be alternately exposed to extreme coastal erosion and flooding, independent of sea-level rise," the authors write.

Climate change could double the frequency of extreme El Niño events and increase the frequency of extreme La Niña events throughout the next century by 73 percent.

Both El Niño and La Niña are complex weather patterns resulting from ocean temperature change in the Equatorial Pacific. El Niño—which occurs when ocean temperatures are unusually hot—can lead to warmer temperatures across Canada and the Western and northern United States; wetter conditions throughout the Gulf Coast; and drier conditions throughout the Pacific Northwest. The effects of El Niño worldwide have been linked to collapsed fisheries, enormous wildfires, and severe floods.

La Niña, on the other hand,  occurs when the ocean's surface temperatures are cooler than usual, and can lead to warmer temperatures throughout the Southeast, and cooler temperatures in the Northwest. According to the National Oceanic and Atmospheric Administration, 2011 was a record-breaking year for climate extremes and severe weather disasters—thanks in part to La Niña.

This study is the first of its kind, according to the United States Geological Survey, to examine the coastal impacts of El Niño and La Niña across the entire Pacific Ocean basin. Researchers from 13 organizations including the USGS, University of Sydney, and University of New South Wales analyzed coastal data from 48 beaches between 1979 and 2012. Each beach was located across the Pacific Ocean basin, throughout the mainland U.S., Canada, Japan, Australia, New Zealand, and Hawaii.

During the five largest El Niño events recorded throughout the data set, coastal areas along the Central Pacific, California, Pacific Northwest, and northern Japan eroded 69 percent more than during an average winter, according to their analysis. On the other hand, areas in the southern Pacific—like New Zealand, Australia, and southern Japan—eroded 68 percent less. During a La Niña event, erosion rates reversed. "For the top five winter La Niña events ... Australia and the Pacific Northwest experienced severe erosion, 110% above normal, but no strong or consistent signal for the other regions," the researchers write.

On average, El Niño and La Niña events occur every two to seven years. Yet emerging research suggests climate change could double the frequency of extreme El Niño events and increase the frequency of extreme La Niña events throughout the next century by 73 percent. This year, meteorologists are already predicting one of the strongest El Niño's on record.

Move over sea level rise—there’s a new climate threat in town.

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