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| 美国的极端海岸洪水事件预计会增加 |《科学报告》论文 |
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论文标题：Sea-level rise exponentially increases coastal flood frequency
期刊：Scientific Reports
作者：Mohsen Taherkhani, Sean Vitousek et.al
发表时间：2020/04/16
数字识别码：10.1038/s41598-020-62188-4
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《科学报告》发表的一项研究Sea-level rise exponentially increases coastal flood frequency发现，如果海平面继续按预期上升，美国沿海地区的极端洪水事件每五年就会增加一倍。目前“一生一遇”的极端水位每50年出现一次，但到21世纪结束前，美国大部分海岸线的水位可能每天都会超过这个水平。
来自美国地质调查局、伊利诺斯大学芝加哥分校、夏威夷大学的Mohsen Taherkhani、美国地质调查局的Sean Vitousek和同事调查了美国海岸线202个验潮站测得极端水位的频率，并将该数据与海平面上升的情景相结合，模拟了未来洪水事件的可能增加速度。
潮水研究中202个长期验潮站网络（A），和位于夏威夷火奴鲁鲁的单个站点的示例极端水位数据和GEV模型（B）
图片来源：Taherkhani 等
在研究使用的验潮站中，73%的验潮站发现，50年一遇的极端水位与日均最高水位之间的差距还不到一米，而大部分预测显示，到2100年的海平面上升幅度会超过一米。作者的模型预测，到2050年，当前的极端水位会从50年一遇的一生一次洪水事件变成在美国70%的沿海地区一年一遇的事件。在2100年结束前，此次测量中93%的地区预计每天都会超过现在一生一遇的极端水位。
这些数据表明，当前的极端水位在接下来的几十年里会很常见。低纬度地区将是最危险的地区，那里发生海岸洪水的频率预计每五年会翻一倍。对于夏威夷和加勒比海岸带最危险的地区而言，海平面每上升一厘米，那里出现极端水位的频率可能也会增加一倍。
作者认为，与此相关的海岸灾害，如海滩和悬崖侵蚀，可能会随洪水风险的增加而加速发生。
摘要：Sea-level rise will radically redefine the coastline of the 21st century. For many coastal regions, projections of global sea-level rise by the year 2100 (e.g., 0.5–2 meters) are comparable in magnitude to today’s extreme but short-lived increases in water level due to storms. Thus, the 21st century will see significant changes to coastal flooding regimes (where present-day, extreme-but-rare events become common), which poses a major risk to the safety and sustainability of coastal communities worldwide. So far, estimates of future coastal flooding frequency focus on endpoint scenarios, such as the increase in flooding by 2050 or 2100. Here, we investigate the continuous shift in coastal flooding regimes by quantifying continuous rates of increase in the occurrence of extreme water-level events due to sea-level rise. We find that the odds of exceeding critical water-level thresholds increases exponentially with sea-level rise, meaning that fixed amounts of sea-level rise of only ~1–10 cm in areas with a narrow range of present-day extreme water levels can double the odds of flooding. Combining these growth rates with established sea-level rise projections, we find that the odds of extreme flooding double approximately every 5 years into the future. Further, we find that the present-day 50-year extreme water level (i.e., 2% annual chance of exceedance, based on historical records) will be exceeded annually before 2050 for most (i.e., 70%) of the coastal regions in the United States. Looking even farther into the future, the present-day 50-year extreme water level will be exceeded almost every day during peak tide (i.e., daily mean higher high water) before the end of the 21st century for 90% of the U.S. coast. Our findings underscore the need for immediate planning and adaptation to mitigate the societal impacts of future flooding.
（来源：科学网）
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