Inter-annual and multi-decadal climate variability in hazard forecasting can exacerbate coastal impacts

<p>It has been demonstrated that modes of climate variability influence ocean wave and wind climate variability at inter-annual and multi-decadal scales (Od&#233;riz et al., 2021), trigger local impacts modifying coastal erosion patterns (Barnard et al., 2015) and disturbing seasonal coastal risk (Wahl & Plant, 2015). Besides, extreme events and modes of variability that have occurred simultaneously have above-normal struck coastlines around the world (Barnard et al., 2017) and have evidenced that omitting them in hazard forecasting can lead to underestimating coastal impacts. Moreover, in long-term analysis, the internal natural variability that modes of variability cause on wave climate can mask global warming trends in areas with vast natural fluctuations, such as the Southern Ocean (Od&#233;riz et al., 2021).<br />The complexity of spatiotemporal scales, in addition to a misconception of teleconnections, have led modes of variability to not integrate into coastal management and underestimate their impact on physical and biological hazards. This study identifies energetic and calm teleconnections induced by the leading polar (Arctic Oscillation-AO and Antarctic Oscillation-AAO) and tropical (El Ni&#241;o Southern Oscillation-ENSO) modes of variability on the world&#8217;s coasts. Teleconnections are comprehensively characterized by (1) sign, (2) duration, (3) amplitude, and (4) spatial patterns. Global spatial-temporal fluctuations are analysed by season, parameter (near-surface wind velocity, total-wave power, swell-wave power, and wind sea-wave power), and planetary systems (winds and wave climates).<br />As an example of the results, we found that wind velocity increases up to ~+1m/s around Tuvalu Island, induced by La Ni&#241;a (the negative phase of ENSO); in Chile induced by the positive phase of AO; while in Guinea, Indonesia, and Papua New Guinea this increase is triggered by El Ni&#241;o (the positive phase of ENSO). In addition, the wave power of westerly swells increases up to ~+10 kW/m over an average season, induced by the positive phase of AO in Ireland, Norway, and the UK; in the USA induced by El Ni&#241;o; and in Australia, New Zealand, and Chile influenced by the positive phase of AAO. This framework can serve as a source of predictability and provide a basis for a proactive response to coastal impacts in anomalous seasons and be transferred to financial risk and insurance instruments.</p>