Coastal vulnerability across the Pacific dominated by El Niño/Southern Oscillation

Abstract

To predict future coastal hazards, it is important to quantify any links between climate drivers and spatial patterns of coastal change. However, most studies of future coastal vulnerability do not account for the dynamic components of coastal water levels during storms, notably wave-driven processes, storm surges and seasonal water level anomalies, although these components can add metres to water levels during extreme events. Here we synthesize multi-decadal, co-located data assimilated between 1979 and 2012 that describe wave climate, local water levels and coastal change for 48 beaches throughout the Pacific Ocean basin. We find that observed coastal erosion across the Pacific varies most closely with El Niño/Southern Oscillation, with a smaller influence from the Southern Annular Mode and the Pacific North American pattern. In the northern and southern Pacific Ocean, regional wave and water level anomalies are significantly correlated to a suite of climate indices, particularly during boreal winter; conditions in the northeast Pacific Ocean are often opposite to those in the western and southern Pacific. We conclude that, if projections for an increasing frequency of extreme El Niño and La Niña events over the twenty-first century are confirmed, then populated regions on opposite sides of the Pacific Ocean basin could be alternately exposed to extreme coastal erosion and flooding, independent of sea-level rise

Global changes of extreme coastal wave energy fluxes triggered by intensified teleconnection patterns

“…El Niño conditions are also generally associated with a strengthening of the Aleutian low and of high pressures west of the Rocky Mountains [Philander, 1983;Barnard et al, 2015]. This enforces the winds over north-western Canada and Alaska, explaining why the long-term increase of ENSO is correlated with the growth of extreme WEF along the north-eastern Pacific coasts (Figures 4t and 4u).…”

“…In the north-western Pacific, a progressive shift southward of the jet stream and of the storm-tracks under El Niño conditions results in a colder and more stable climate [Wang et al, 2000;Barnard et al, 2015], exemplified by strong negative correlation between the trends in extreme WEF and the ENSO index (ρ ¼ À0:95). A rather strong negative correlation is also observed for the northern tropical Atlantic (ρ ¼ À0:91; Figures 4v and 4w).…”

“…Regional impacts of climate change in coastal areas could be dominated by increased flooding and erosion from storm wave extremes, independent of relative sea level rise (RSLR) [Ruggiero, 2013;Barnard et al, 2015]. Yet the focus in literature when addressing future coastal impacts has been prevalently on the effects of RSLR [Hinkel et al, 2014].…”

Developments in large-scale coastal flood hazard mapping

“…During extreme events, the energetic atmospheric conditions result in transfer of mass and energy in the water element, which through the interaction with the bathymetry are manifested as increased water levels. When the latter coincide with spring tides, they can lead to extreme events, affecting landward areas which are normally protected by water (Barnard et al, 2015;Bertin et al, 2014).…”

Two Centuries of Climate Change and Climate Variability, East Coast Australia

“…The IPO also appears to modulate the frequency of El Niño events, whereby the occurrence of El Niño events is shown to be significantly elevated during the positive phase, with the last 350 years showing that the frequency of La Niña is significantly higher during negative IPO phases [6]. Reference [11] reported that for recent decades , coastal vulnerability across the Pacific correlates with ENSO. The combination of IPO and ENSO provides the broad framework for understanding Australian climate episodic behaviour.…”