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El Niño/Southern Oscillation (ENSO) Dominates Coastal Vulnerability Across the Pacific

Barnard et al. say it is important to quantify any links there are between drivers of climate and coastal change patterns to predict coastal hazards in the future. The dynamic components of coastal water levels during storms, especially wave-driven processes, storm surges and seasonal water level anomalies are not accounted for by most studies of coastal vulnerability in the future, though during extreme events these components can add metres to water levels. In this study Barnard et al. synthesised multi-decadal, co-located data that had been assimilated between 1979 and 2012 describing wave climate, local levels of water and coastal change for 48 beaches throughout the Pacific Ocean basin. They found that across the Pacific observed coastal erosion most closely varies with the ENSO, though there is a smaller influence from the Southern Annular Mode and the Pacific North American pattern. Regional wave and water level anomalies in the northern and southern Pacific Ocean correlate significantly with a suite of climate indices, in particular during the boreal winter; in the northeast Pacific Ocean conditions are often opposite to those in the western and southern Pacific. If projections for an increasing frequency of extreme El Niño and La Niña events over the 21^st century are confirmed, Barnard et al. conclude that on opposite sides of the Pacific Ocean basin populated regions could alternately be exposed to extreme coastal erosion and flooding, independent of rising sea level.

Sources & Further reading

1. Barnard, P. L., A. D. Short, M. D. Harley, K. D. Splinter, S. Vitousek, I. L. Turner, J. Allan, M. Banno, K. R. Bryan, A. Doria, J. E. Hansen, S. Kato, Y. Kuriyama, E. Randall-Goodwin, P. Ruggiero, I. J. Walker and D. K. Heathfield (2015). "Coastal vulnerability across the Pacific dominated by El Nino/Southern Oscillation." Nature Geosci 8(10): 801-807.