California’s iconic beaches are eroding at a record rate, new research shows, after an extreme El Niño weather pattern hit the coast with extraordinary force during the northern hemisphere winter of 2015-16.
The El Niño–Southern Oscillation climate cycle sees water temperatures rise over the tropical western Pacific Ocean, which in turn affects global weather and can contribute to extreme events.
One of these impacts is the slow erosion of coastlines during winter months as sea waters rise and storms increase, often threatening coastal communities.
According to a team led by Patrick Barnard at the Pacific Coastal and Marine Science Centre in California, last year’s El Niño was one of the three strongest events on record and may have been the most powerful event of its kind in 145 years.
“With seasonally elevated water levels, higher wave energy and southerly wave directional shifts common during El Niño, the North American west coast has historically experienced severe coastal erosion during El Niño winters,” the researchers explain in Nature Communications.
To gauge the full impact, the team studied wave conditions and water levels during the 2015-16 winter and tracked their effects on 29 beaches in California, Oregon and Washington.
During a typical El Niño cycle, storms and cyclones can lead to larger and more forceful waves, and Barnard and colleagues found a 50% increase in wave energy across all studied regions.
This finding was coupled with an 11-centimetre increase in water levels, and record low levels of sand across the beaches. On 10 December 2015, the California and Oregon coasts also copped one of the most energetic single wave events on record, with maximum heights reaching 19 metres.
These drivers all contributed to the biggest shoreline retreat on record, with erosion up 76% on previous averages.
The damage to California’s beaches provides an uncomfortable glimpse into a future affected by climate change, the researchers note.
“Water levels anomalies of seven to 17 centimetres above normal were measured across the US West Coast during the El Niño winter of 2015-16, similar to anticipated global mean sea-level increases expected within the next few decades,” they wrote.