Researchers at the US Geological Survey (USGS) has concluded that last year's seasonal El Nino was responsible for severe erosion along the West Coast during the winter and could be an indicator of things to come.

The 2009-10 winter seasons along the U.S. West Coast was characterized by high wave energy and ocean water levels. This led to more beach erosion in coastal areas.

The stormy conditions of the 2009-10 El Niño winter eroded the beaches to often unprecedented levels at sites throughout California and vulnerable sites in the Pacific Northwest, said Patrick Barnard, USGS coastal geologist.

In California, the researchers found that winter wave energy was 20 percent above average for the years dating back to 1997, resulting in shoreline erosion that exceeded the average by 36 percent.

The most severe erosion took place at Ocean Beach in San Francisco where the winter shoreline retreated 75 percent more than in a typical winter. The erosion resulted in the collapse of one lane of a major roadway and led to a $5 million emergency remediation project. Sites in San Diego, Santa Barbara and Ventura also saw significant erosion.

The beach erosion observed throughout the U.S. west coast during the 2009-10 El Niño is linked to the El Niño Modoki ('pseudo' El Niño) phenomenon, where the warmer sea surface temperature is focused in the central equatorial Pacific (as opposed to the eastern Pacific during a classic El Niño).

USGS scientists said that warmer waters in the central Pacific are expected in the coming decades under many climate change scenarios, El Niño Modoki is projected to become a more dominant climate signal. Combined with high sea levels brought on by global climate change, stronger winter storms are likely to contribute to higher rates of beach erosion along the U.S. West Coast.

The researchers took advantage of up to 13 years of seasonal beach survey data along 148 miles of coastline and tracked shoreline changes through a range of wave conditions.

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