Accurate prediction of coastal flooding requires a detailed understanding of all individual contributions to sea level variability and how they interact to trigger extreme sea level (ESL) events. In this study, we focus on the expansive (∼10,000 km) coastline of Western Australia, a region that experiences large latitudinal gradients in met‐ocean sources of sea level variability, as a case study to investigate the mechanisms responsible for ESLs and trends over the past 54 years (1966–2019). Using long‐term sea level records from tide gauges and satellite altimetry, we explore how different contributions to sea level variability at different time scales (from hourly to interannual) interact to generate ESLs. We observe that all individual, nontidal contributions to ESLs (i.e., atmospheric surge, seasonal and interannual variability) are of similar magnitude (of order 10 cm) along the entire coast and comparable to the tidal variations in the microtidal southwestern region. The results reveal the important role that seasonal and interannual sea level variability plays in generating ESLs, with these low‐frequency contributions being relatively large compared to typical global values. With mean sea level having risen by ∼10 cm over this 54‐year study period, sea level rise was also identified as making an increasingly significant contribution to observed increases in the frequency of ESLs. Overall, due to the comparatively large magnitude of low‐frequency sea level contributions (seasonal and longer), the Western Australia coast provides a useful case study to investigate how sustained periods of elevated sea level will impact coastlines worldwide more broadly in the future.

中文翻译：

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西澳大利亚州沿海极端海平面事件的气候驱动因素

准确预测沿海洪灾需要详细了解所有个人对海平面变化的贡献以及它们如何相互作用以触发极端海平面（ESL）事件。在本研究中，我们重点研究西澳大利亚州广阔的海岸线（约10,000公里），该地区在海平面变化的大洋来源中经历较大的纬度梯度，作为案例研究来调查造成ESL的机制和全球变暖趋势。过去54年（1966-2019年）。利用潮汐仪和卫星测高仪的长期海平面记录，我们探索了在不同时间尺度（从每小时到年际）对海平面变化的不同贡献如何相互作用以产生ESL。我们观察到，所有对ESL的非潮汐性贡献（例如，大气潮，季节性和年际变化）在整个海岸上具有相似的幅度（大约10厘米），可与西南部微潮的潮汐变化相提并论。结果揭示了季节性和年际海平面变化在产生ESL中所起的重要作用，与典型的全球值相比，这些低频贡献相对较大。在这54年的研究期内，由于平均海平面上升了约10厘米，海平面上升也被认为对观测到的ESL频率增加做出了越来越重要的贡献。总体而言，由于低频海平面贡献较大（季节性和更长的时间），