Will climate change in the Arctic increase the landslide-tsunami risk to the UK?

海底滑坡可能比陆地滑坡大得多，许多还会引发破坏性的海啸。挪威近海的斯托尔加滑坡覆盖的面积比苏格兰还大，其中的沉积物足以覆盖整个苏格兰，深度达80米。这个巨大的滑坡发生在8200年前，向下延伸了800公里。它产生了海啸，在挪威海周围上升了20米，在苏格兰大陆上升了3-8米。英国面临的其他自然灾害很少有可能造成像斯托尔加滑坡海啸那样规模的破坏。斯托尔加滑梯并不是挪威海唯一的巨型海底滑梯。公开的数据表明，在过去的2万年里，至少发生了6次这样的滑坡。例如，发生在4000年前的特拉阿佐佩特滑坡涉及了约900立方千米的沉积物。根据4000年的重复周期（过去8000年发生2次，或2万年发生6次），在未来200年里，有5%的概率发生一次主要的海底滑坡，并可能发生海啸。设得兰群岛1500年和5500年的沉积物，以及8200年的Storegga沉积物，被认为表明了海啸的影响，并提供了证据，表明北极海啸的危害仍然知之甚少。考虑到北极滑坡引发的海啸的潜在影响，我们需要严格评估它们在未来100-200年对英国构成的危害，它们对社会的潜在成本，现有海防措施对英国的保护程度，以及如何将海啸危害纳入多灾害洪水风险管理。这个项目是及时的，因为北极地区快速的气候变化可能会增加山体滑坡海啸带来的风险。与未来冰融化相关的地壳反弹可能会产生更大、更频繁的地震，比如可能引发8200年前的斯托尔加滑坡。据预测，北极在未来几十年将经历特别迅速的变暖，这可能导致海洋沉积物中的天然气水合物（甲烷和水的冰状化合物）分离，削弱沉积物，并可能增加山体滑坡的风险。我们的目标将通过一系列综合的工作块来实现，这些工作块将检查保存在近期地质记录中的挪威海山体滑坡的频率，设得兰群岛的相关海啸沉积物，由于冰融化导致的地震频率和规模的未来趋势，滑坡稳定性和山体滑坡引发的海啸，英国的海啸淹没以及潜在的社会成本。这形成了一个工作流程，从对过去山体滑坡的观察开始，通过对其后果的建模发展到预测未来潜在的山体滑坡和相关海啸的后果并对其进行成本计算。将特别注意社会影响和缓解战略，包括审查目前海防的有效性。这将通过项目一开始就与利益相关者的参与来实现，包括管理英国洪水风险的政府机构、负责海啸预警系统的国际机构以及再保险部门。主要成果将是：(1)更好地了解过去北极滑坡的频率及其对英国造成的海啸影响；(2)改进潜艇滑坡和相关海啸的模型，帮助理解为什么某些滑坡会引发海啸，而其他滑坡不会。（iii）单一建模策略，从一个耦合的滑坡-海啸源开始，跟踪海啸在挪威海的传播，并以英国海岸的淹没结束。将对各种规模和来源的海啸源进行测试（iv）详细评估海啸洪水对英国的后果和社会成本，包括现有防洪措施的有效性(v)评估气候变化如何改变滑坡频率，从而改变英国的海啸风险。

Submarine landslides can be far larger than terrestrial landslides, and many generate destructive tsunamis. The Storegga Slide offshore Norway covers an area larger than Scotland and contains enough sediment to cover all of Scotland to a depth of 80 m. This huge slide occurred 8,200 years ago and extends for 800 km down slope. It produced a tsunami with a run up >20 m around the Norwegian Sea and 3-8 m on the Scottish mainland. The UK faces few other natural hazards that could cause damage on the scale of a repeat of the Storegga Slide tsunami. The Storegga Slide is not the only huge submarine slide in the Norwegian Sea. Published data suggest that there have been at least six such slides in the last 20,000 years. For instance, the Traenadjupet Slide occurred 4,000 years ago and involved ~900 km3 of sediment. Based on a recurrence interval of 4,000 years (2 events in the last 8,000 years, or 6 events in 20,000 years), there is a 5% probability of a major submarine slide, and possible tsunami, occurring in the next 200 years. Sedimentary deposits in Shetland dated at 1500 and 5500 years, in addition to the 8200 year Storegga deposit, are thought to indicate tsunami impacts and provide evidence that the Arctic tsunami hazard is still poorly understood.Given the potential impact of tsunamis generated by Arctic landslides, we need a rigorous assessment of the hazard they pose to the UK over the next 100-200 years, their potential cost to society, degree to which existing sea defences protect the UK, and how tsunami hazards could be incorporated into multi-hazard flood risk management. This project is timely because rapid climatic change in the Arctic could increase the risk posed by landslide-tsunamis. Crustal rebound associated with future ice melting may produce larger and more frequent earthquakes, such as probably triggered the Storegga Slide 8200 years ago. The Arctic is also predicted to undergo particularly rapid warming in the next few decades that could lead to dissociation of gas hydrates (ice-like compounds of methane and water) in marine sediments, weakening the sediment and potentially increasing the landsliding risk. Our objectives will be achieved through an integrated series of work blocks that examine the frequency of landslides in the Norwegian Sea preserved in the recent geological record, associated tsunami deposits in Shetland, future trends in frequency and size of earthquakes due to ice melting, slope stability and tsunami generation by landslides, tsunami inundation of the UK and potential societal costs. This forms a work flow that starts with observations of past landslides and evolves through modelling of their consequences to predicting and costing the consequences of potential future landslides and associated tsunamis. Particular attention will be paid to societal impacts and mitigation strategies, including examination of the effectiveness of current sea defences. This will be achieved through engagement of stakeholders from the start of the project, including government agencies that manage UK flood risk, international bodies responsible for tsunami warning systems, and the re-insurance sector. The main deliverables will be:(i) better understanding of frequency of past Arctic landslides and resulting tsunami impact on the UK(ii) improved models for submarine landslides and associated tsunamis that help to understand why certain landslides cause tsunamis, and others don't.(iii) a single modelling strategy that starts with a coupled landslide-tsunami source, tracks propagation of the tsunami across the Norwegian Sea, and ends with inundation of the UK coast. Tsunami sources of various sizes and origins will be tested (iv) a detailed evaluation of the consequences and societal cost to the UK of tsunami flooding , including the effectiveness of existing flood defences(v) an assessment of how climate change may alter landslide frequency and thus tsunami risk to the UK.