Calving Laws for Ice Sheet Models CALISMO

Sea levels will rise significantly in the coming decades as a result of greenhouse gas emissions, but there are large uncertainties about how fast they will rise in different emission futures. In a warming climate, the main causes of sea level rise are thermal expansion of sea water, melting of glaciers and ice sheets, and ice-flow directly into the oceans (dynamic ice loss). Dynamic ice loss from the Greenland and Antarctic Ice Sheets is, by a large margin, the greatest source of uncertainty in predictions of sea level rise, and ranges from 10 cm to over 1 m by 2100 in a high emissions scenario. The upper and lower limits of this range have very different implications for coastal communities and economies, hampering efforts to plan for the future. Identifying safe limits on carbon emissions and adopting appropriate mitigation strategies require reliable predictions of dynamic ice loss from the ice sheets.

Dynamic ice loss is complex because it is controlled by the fracture and detachment of icebergs (calving) and the submarine melt of ice in contact with the ocean. Calving and melting can reduce resistance to ice flow, leading to faster transfer of mass from land to the oceans and potentially to irreversible ice-sheet collapse. Despite their importance, calving and submarine melting are very poorly represented in the models used to predict ice-sheet response to climate change, resulting in high uncertainties in future dynamic ice loss and hence sea-level rise. There is an urgent need to develop reliable calving laws for ice sheet-models, based on a thorough understanding of calving processes and their interactions with ice flow and submarine melt.

We aim to solve this problem using a new high-resolution model of fracturing, ice-dynamics and ocean processes (FIDO), to build a solid foundation for the development of the calving laws required for predictive ice-sheet models. FIDO combines state-of-the-art methods of modelling ice-flow and ocean circulation with a revolutionary ice-fracture model. Unlike conventional approaches, the fracture model represents ice as assemblages of particles linked by breakable bonds - much like real ice - allowing calving to be simulated with impressive realism. We will use FIDO to simulate calving, submarine melt and ice flow in a wide range of environmental conditions, and rigorously test the validity of the results using satellite observations of ice margin behaviour in Greenland and Antarctica.

From the FIDO model results, we will distil the essential rules of calving and define new, comprehensive calving laws incorporating interactions with submarine melt and ice dynamics. In collaboration with UK and international partners, we will implement our new calving laws in models of the Greenland and Antarctic Ice Sheets, to predict their 21st Century sea-level contributions for a range of greenhouse gas emission scenarios. We anticipate radically improved sea-level rise predictions by 2020, in readiness for the 6th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR6).

Our impact strategy has two strands. First, we will publish our scientific results in good time to provide input for the Sixth Assessment Report of the IPCC (AR6), scheduled for 2020/21. This will have far-reaching impacts both within and beyond the scientific community. IPCC reports provide the scientific foundation for decisions by a wide range of international and national organisations, including governments, local authorities, businesses and insurance companies. Second, we will communicate our findings directly to the general public and engage with debate on the significance of climate change and its impacts. Through live events and mainstream and social media, we will reach out to school students, families, television audiences and consumers of online news media. Our planned public engagement activities are as follows.

1) GeoBus Workshop and Educational Materials
Climate and glacier science are very relevant topics for schools, providing highly topical examples of the interplay between human activities and the natural world. We will develop and run a workshop on "Glaciers and Climate Change" for the St Andrews GeoBus project, a unique and highly successful educational outreach project that runs workshops and brings resources to secondary schools across Scotland and the north of England on a weekly basis. The Glaciers and Climate Change workshop will help pupils understand and discuss the impact of carbon emissions on glaciers, ice sheets and sea levels, and discuss how these issues affect them. We will also produce a classroom education pack to allow students to explore the principles of the greenhouse effect and its impacts.

2) Science Festivals
The GeoBus school materials will be used as the basis for interactive exhibits at the Edinburgh and Cheltenham Science Festivals in 2020. The exhibit will aim to engage and inspire people of all ages, focusing on the theme: 'today's decisions, tomorrow's world', and will include activities, demonstrations, competitions and looped videos of iceberg calving events and sea-level simulations.

3) News Stories on Mainstream and Online Media.
The publicity surrounding publication of an IPCC report creates an appetite for climate-change related news stories and information, offering excellent opportunities to communicate science findings to a wide range of audiences. We will build on personal previous experience of working with TV news organisations (e.g. ITN, Associated Press) to produce short features on ice sheets and sea-level rise. In addition, we will produce features for The Conversation and glacier and climate science blogs (e.g. AntarcticGlaciers.org, RealClimate).