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

Lead Research Organisation: National Oceanography Centre
Department Name: Science and Technology

Abstract

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.

Planned Impact

Our project will provide the scientific basis for decisions by three major types of stakeholder.

UK Flood-Risk Management (Environment Agency; Department for Environment Food and Rural Affairs; Scottish Government): Project results will be disseminated to DEFRA and the Environment Agency (EA) who manage the risk of flooding in England and Wales, and Scottish Government that has responsibility for policy on flood management in Scotland. Our results will be used within a multi-risk framework for UK flooding that includes storm surge and rainfall sources. The EA will be involved in Work Block 6, which will utilise their 'National Flood and Coastal Defence Database' of both government and third party assets. Our analysis of potential magnitude of landslide-tsunami generated flood inundation, frequency and societal cost would be incorporated with their previous initiatives such as 'Risk Assessment for Flood and Coastal Defence Strategic Planning (RASP)'. RASP provides a flexible hierarchical method for assessing flood risk from multiple sources, and strategic prioritisation of flood defences and targeting of flood warning and emergency preparedness. We will inform the Department of Business, Innovations and Skills (as they have interest in foresight and analysis of future risks to the UK), Department of Energy and Climate Change (for offshore energy structures), and Department of Transport of project results.
The Intergovernmental Oceanographic Commission of UNESCO (IOC) has a mandate from the international community to co-ordinate tsunami early warning and mitigation in the North Atlantic. They have established a tsunami information centre and have a series working groups, including those for 'hazard assessment, risk and modelling', and 'regional tsunami warning system architecture'. They provide the correct route for project results to inform future warning and mitigation strategies for landslide-tsunami. They also provide a forum for exchange of technical information with European partners (such as those involved with the EU Transfers FP6 project in 2006-2009). We will report to the two IOC working groups on our tsunami modelling and estimates of UK risk and vulnerability. Key project results and final report will be disseminated through the IOC.

Re-Insurance Sector: Willis and their Research Network will be strongly involved as formal project partners, especially in building of geospatial data bases and estimates of societal cost. Willis is the world's 3rd largest insurance and re-insurance broker and the Willis Research Network (WRN) that they created is the world's largest collaboration between academic partners worldwide and the insurance industry. They facilitate access to other WRN members working on related risks, and access to the global insurance sector through WRN meetings. Willis will provide their staff time for project meetings, workshops, and ad-hoc discussions with project members. The consortium project will have access to the global insurance sector through additional meetings hosted and organised by Willis. Willis will host two of the PDRA positions in their offices in London, and during these visits the PDRAs will learn how geospatial tools are used by industry.

Wider Users: The subject of infrequent but potentially high impact landslide needs to be conveyed carefully to a wider (non-scientific) audience, as shown by previous press coverage of landslide-tsunamis in the Canary Islands. Project results will be disseminated by press releases (from both NOC and NERC Arctic Research Programme Office) and by a dedicated website. The cruise will form part of the NOC Classroom-at-Sea project to involve school children. We seek to involve the NERC Arctic Research Programme's Knowledge Exchange co-ordinator with this wider dissemination of the project and its results.

Publications

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Description Submarine landslides can generate potentially very damaging and widespread tsunami. For example, the Storegga Slide that occurred 8,200 years ago offshore Norway is larger than Scotland. It produce a major tsunami that ran up to heights of up to 20m around surrounding coasts. A repeat of this scale of landslide-tsunami is one of the most damaging natural events that could impact the UK.

A first important result of our study is that an even larger landslide has been found below the Storegga Slide. This older event occurred at 55-60,000 years ago. Therefore, megalsides in this area have recurrence intervals of less than 100,000 years. This is important because events with recurrence intervals of less than100,000 years should be considered on the UK National Risk Register, and in the design of nuclear power stations.

A second key result originates from dating the Traenadjupet and Nyk Slides located further along the Norwegian Margin, to the north of the Storegga Slide. It was previously thought that we would need another glacial advance to the shelf edge, to dump more sediment, and thereby cause a new landslide. However, our work on the Traenadjupet and Nyk Slides shows that they occurred within 15,000 years, without another ice stream advance. This shows that we do not need another ice stream advance to cause another large submarine slide from the same source area.

Finally, we show that the Traenadjupet Slide did not create a major tsunami along the nearest coastlines. This suggests that not all very large submarine slides are strongly tsunamigenic.
Exploitation Route These findings will directly inform a decision on whether landslide tsunamis are included in the next iteration of the UK National Risk Register.
Sectors Environment,Security and Diplomacy

URL http://projects.noc.ac.uk/landslide-tsunami/
 
Description Submarine landslides can generate potentially very damaging and far travelling tsunami. For example, the Storegga Slide that occurred 8,200 years ago offshore Norway is larger than Scotland. It produce a major tsunami that ran up to heights of up to 20m around surrounding coasts. A repeat of this scale of landslide-tsunami is one of the most damaging natural events that could impact the UK. An important result of our study is that an even larger landslide has been found below the Storegga Slide. This older event occurred at 52-60,000 years ago. This shows that two mega-landslides can occur within one glacial cycle, and that they have recurrence intervals of less than 100,000 years. This is important because events with recurrence intervals of ~100,000 years should be considered on the UK National Risk Register, and in the design of nuclear power stations. We presented this project's results to the UK Natural Hazards Partnership, and this resulted in an invitation from the Cabinet Office to brief the UK Government's Chief Scientist. We then provided that briefing. This work is now underpinning an assessment of whether landslide-tsunami should now be added to the UK National Risk Register in 2018.
First Year Of Impact 2016
Sector Environment,Security and Diplomacy
Impact Types Societal

 
Description Briefing Document on Landslide-tsunami hazards to UK Chief Scientist
Geographic Reach National 
Policy Influence Type Gave evidence to a government review
Impact This work underpins whether landslide-tsunamis need to be included in the next iteration of the UK national Risk Register, which is due in July 2017.
URL https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/419549/20150331_2015-NRR-W...
 
Description Comment in response to the Office of Nuclear Regulation (ONR) interim report on the Japanese earthquake and tsunami: implications for the UK nuclear industry
Geographic Reach Multiple continents/international 
Policy Influence Type Gave evidence to a government review
Impact Comment on tsunami hazards to UK power stations Target audience(s): Government Department
URL http://projects.noc.ac.uk/landslide-tsunami/
 
Description Evidence to Government Review of Threats to Seafloor Cables
Geographic Reach Multiple continents/international 
Policy Influence Type Gave evidence to a government review
Impact I gave written evidence to the Department for Digital, Culture, Media and Sport a review by their Telecoms Security Team on seafloor cables that carry > 95% of global data traffic. This aimed to understand what a significant loss of transAtlantic cables would have on the UK, and the implications for the national security risk assessment