Patterns of coastal response and recovery from the 2015-16 El Niño

Interannual climate variability across the Pacific Ocean basin associated with the El Niño-Southern Oscillation is a dominant driver of coastal hazards risk across the basin, with the Eastern North Pacific region typically subjected to elevated waves and water levels during El Niño conditions. Based on the sea surface temperature anomaly, tropical cyclone activity, and deep-water wave conditions, the 2015-16 El Niño was one of the strongest El Niño events ever recorded, similar to the 1982-83 and 1997-98 events, although the detailed patterns of physical forcing were unique (e.g., storm tracks, wave direction, timing of water level anomaly). Winter beach erosion across the study area was 76% greater than normal and most beaches in California eroded beyond historical extremes. However, the patterns of physical forcing in the two subsequent years facilitated significant beach recovery in many locations, driven by low wave energy and in some areas by elevated fluvial discharge rates. Here we summarize the behavior of over 30 beaches scattered across the North American West Coast, from Baja Mexico to Washington, during the winter of 2015-16, and highlight the pattern of post-El Niño recovery in select locations. A greater understanding of the coastal response and recovery to El Niño events is critical to better assessing coastal hazards risk over the course of the next century, as recent research suggests a likely increase in the frequency of extreme El Niño events similar to the winters of 1982-83, 1997-98, and 2015-16.