As greenhouse warming is predicted to intensify the El Niño–Southern Oscillation (ENSO), it is key to understand relationships between the magnitudes and spatial distribution of ENSO events and associated extreme sea levels (ESLs). Current understanding is lacking for river deltas, where human societies and ecosystems are particularly vulnerable to coastal hazards. Using long-term tide gauge records, we report on ESLs during historical ENSO events of different magnitudes, spatial distribution and temporal evolution in the Guayas delta–Gulf of Guayaquil (Ecuador), the largest estuarine system on the Pacific coast of South America and a relevant hotspot for coastal hazards. Here, we found a landward amplification of sea level anomalies during Eastern Pacific El Niño events, with monthly mean values peaking from +43 cm at the open coast to +75 cm in the inner delta, producing among the highest ENSO driven ESLs ever documented. This landward amplification is shown to coincide with a sea-to-land gradient from a predominantly oceanic (thermosteric) to meteorological (fluvial) El Niño contribution to these ESLs, demonstrating the strong coupling between these two forcings of El Niño. Our findings highlight the strong exposure of coastal societies and ecosystems to ENSO driven ESLs and the pressing need for adaptation measures in face of continued global warming.

由于预计温室变暖会加剧厄尔尼诺-南方涛动 (ENSO)，因此了解 ENSO 事件的幅度和空间分布与相关极端海平面 (ESL) 之间的关系至关重要。目前对河流三角洲缺乏了解，那里的人类社会和生态系统特别容易受到沿海灾害的影响。使用长期的潮汐测量记录，我们报告了瓜亚斯三角洲瓜亚基尔湾（厄瓜多尔）的不同震级、空间分布和时间演变的历史 ENSO 事件期间的 ESL，这是南美洲太平洋沿岸最大的河口系统和一个沿海灾害的相关热点。在这里，我们发现东太平洋厄尔尼诺事件期间海平面异常向陆地放大，月平均值从开阔海岸的 +43 厘米到内三角洲的 +75 厘米达到峰值，是有史以来最高的 ENSO 驱动的 ESL。这种向陆地的放大显示与从占主导地位的海洋（热温）到气象（河流）厄尔尼诺对这些 ESL 的贡献的海陆梯度相吻合，这表明厄尔尼诺现象的这两种强迫之间存在强耦合。我们的研究结果强调了沿海社会和生态系统对 ENSO 驱动的 ESL 的强烈暴露，以及面对持续的全球变暖，迫切需要采取适应措施。证明了这两种厄尔尼诺现象之间的强耦合。我们的研究结果强调了沿海社会和生态系统对 ENSO 驱动的 ESL 的强烈暴露，以及面对持续的全球变暖，迫切需要采取适应措施。证明了这两种厄尔尼诺现象之间的强耦合。我们的研究结果强调了沿海社会和生态系统对 ENSO 驱动的 ESL 的强烈暴露，以及面对持续的全球变暖，迫切需要采取适应措施。