Most powerful El Niño yet caused severe coastal erosion on US West Coast

Extreme El Niño events​ are expected to occur more frequently in the future.

In a new Nature Communications study, the 2015/16 El Niño event was found to have caused unprecedented levels of erosion along the west coast of the United States. Patrick L. Barnard and colleagues analyzed the wave conditions, water levels, and coastal response of 29 beaches in California, Oregon, and Washington. Climate change contributed to the extreme event which resulted in coastal erosion 76 percent above normal winter shoreline retreat.

We spoke to Barnard about the work.

ResearchGate: What motivated this study?

Patrick Barnard: We wanted a greater understanding of the coastal impacts of extreme El Niño events​, especially as events of this magnitude are expected to occur more frequently in the future.

RG: Was the 2015/16 El Niño event special?

​​Barnard: Yes, the 2015-16 event produced numerous records, including the highest sea surface temperatures in the ​eastern tropical Pacific, highest number of hurricanes in the eastern tropical Pacific, the most powerful hurricane ever in the region with sustained winds up to 345 km/hour (Hurricane Patricia), and largest extreme wave conditions across the US West Coast.

The winter erosion along the US was by far the highest ever observed, 76 percent more than the typical winter. Collectively, all these observations indicate that this was one of the most powerful El Niño events in the historical record, dating back to 1871.

RG: Has climate change played a role in this?

Barnard: Yes, ​in addition to the record sea surface temperatures which lead to highest number of hurricanes ever recorded, climate change influenced this extreme El Niño event,​ which are expected to become more frequent due to climate change. ​

​This event coincided with a major drought in California, conditions predicted for the 21st century by most climate models. Higher sea levels also​ accompanied this El Niño event​, including a recent acceleration along the US West coast, which exacerbated impacts.

RG: What long-term affect will this have on US west coast beaches?

Barnard: Beaches may not recover for years. Most shorelines were still 10-20 meters more eroded in the fall of 2016 than in fall 2015, prior to the winter storm season. This leaves coastal communities more vulnerable to future storms, including a greater risk of flooding and infrastructure damages due to narrower beaches. Sand was transported far offshore, in some cases lost from the littoral system, but also observed abandoned in surf zone bars that haven't yet migrated back to shore.

For California, the multi-year drought, which limited sand production from coastal watersheds, leading up to an exceptionally dry El Niño with extreme wave​ conditions, is the worst-case scenario for coastal erosion. But this is a scenario that is likely to become more common in the future due to projected climate trends, which will be exacerbated by accelerating sea level rise.

RG: What’s next for your research?

Barnard: We would like to understand the impacts of this event across the entire Pacific basin, and use our models to assess the impacts of such an event when coupled with projected sea level rise during the course of the 21st century. ​

Featured image courtesy of Sharon Mollerus.