"Grey swan" storm surges pose a greater coastal flood hazard than climate change
"Grey swan" storm surges pose a greater coastal flood hazard than climate change
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DOI：
10.1007/s10236-021-01453-0
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发表时间：
2021-05-07
期刊：
影响因子：
2.3
通讯作者：
Byrne, David
中科院分区：
文献类型：
--
作者：
Horsburgh, Kevin;Haigh, Ivan D.;Byrne, David
在本文中，我们表明，在接下来的几十年中，中纬度风暴系统的自然变化可能是沿海极端海平面比平均海平面上升或气候引起的风暴变化更重要的驱动因素。由于风暴潮的偶发性、当地海平面响应的可变性以及我们短暂的观测记录，了解风暴潮的自然变化至少与了解全球变暖导致的预计长期平均海平面变化一样重要。我们以 2013 年 12 月的北大西洋风暴 Xaver 作为基线，使用气象预报修改工具来创建“灰天鹅”事件，同时保持风暴系统的关键物理特性。在这里，我们将“灰天鹅”定义为基于自然变化而预期但不在观测记录范围内的事件。对于每个合成风暴事件，我们使用业务预报系统中常规使用的水动力模型模拟了北海的风暴潮和波浪。灰天鹅风暴产生的风暴潮持续高于 2013 年 12 月事件期间在英国东海岸所有分析潮汐站位置所经历的风暴潮。我们的模拟中获得的额外风暴潮高度与欧洲海岸线 2100 年平均海平面上升的高端预测相当。我们的结果强烈表明，中纬度风暴能够产生比以往观测到的更极端的风暴潮和波浪，很可能是由于自然变化造成的。我们证实了之前的观察结果，即半封闭盆地中更极端的风暴潮可能是由于减慢风暴移动速度而引起的，并且我们就减慢风暴传播使动态响应接近平衡提供了一种新颖的解释。我们没有发现海岸最大波高有任何显着变化，变化主要局限于更深的水域。世界上许多其他地区都经历过由中纬度天气系统驱动的风暴潮。因此，我们的方法可以被更广泛地采用，以识别物理上合理的、低概率的、潜在灾难性的沿海洪水事件，并协助重大事件规划。
In this paper, we show that over the next few decades, the natural variability of mid-latitude storm systems is likely to be a more important driver of coastal extreme sea levels than either mean sea level rise or climatically induced changes to storminess. Due to their episodic nature, the variability of local sea level response, and our short observational record, understanding the natural variability of storm surges is at least as important as understanding projected long-term mean sea level changes due to global warming. Using the December 2013 North Atlantic Storm Xaver as a baseline, we used a meteorological forecast modification tool to create "grey swan" events, whilst maintaining key physical properties of the storm system. Here we define "grey swan" to mean an event which is expected on the grounds of natural variability but is not within the observational record. For each of these synthesised storm events, we simulated storm tides and waves in the North Sea using hydrodynamic models that are routinely used in operational forecasting systems. The grey swan storms produced storm surges that were consistently higher than those experienced during the December 2013 event at all analysed tide gauge locations along the UK east coast. The additional storm surge elevations obtained in our simulations are comparable to high-end projected mean sea level rises for the year 2100 for the European coastline. Our results indicate strongly that mid-latitude storms, capable of generating more extreme storm surges and waves than ever observed, are likely due to natural variability. We confirmed previous observations that more extreme storm surges in semi-enclosed basins can be caused by slowing down the speed of movement of the storm, and we provide a novel explanation in terms of slower storm propagation allowing the dynamical response to approach equilibrium. We did not find any significant changes to maximum wave heights at the coast, with changes largely confined to deeper water. Many other regions of the world experience storm surges driven by mid-latitude weather systems. Our approach could therefore be adopted more widely to identify physically plausible, low probability, potentially catastrophic coastal flood events and to assist with major incident planning.