BRITICE-CHRONO: Constraining rates and style of marine influenced ice sheet decay

Recent satellite measurements of the Earth's polar ice sheets highlight that changes in ice extent and thickness are occurring at rates far higher than expected. The challenge for researchers is to place these observations into a longer-term context and produce computer models ('ice sheet forecasts') that reliably predict the fate of ice sheets over this century and beyond. Although remote from habitation, the polar ice sheets influence global sea level. Retreat by increased melting and iceberg calving produces higher sea levels and concerns exist that sea level may rise by metres displacing many millions of people, and their livelihoods, from their coastal homes. At this point in time, it is not possible to study the full life cycle of the present Antarctic or Greenland ice sheets as they are still evolving and undergoing large-scale changes. Instead, we will use an ice sheet that has now fully retreated; the ice sheet that covered most of Britain, Ireland and the North Sea during the last ice age.

The last British-Irish ice sheet covered up to 1,000,000 km2 at its maximum size, around 25,000 yrs ago, and was relatively small by global standards. However, its character, setting and behaviour have striking parallels with both the modern West Antarctic and Greenland Ice Sheets. Large parts of the British-Irish Ice Sheet were marine-influenced just like in west Antarctica today; and numerous fast-flowing ice streams carried much of its mass, just like in the Greenland Ice Sheet today. All three are or were highly dynamic, in climatically sensitive regions, with marine sectors, ocean-terminating margins and land-based glaciers. All these common factors make the British-Irish Ice Sheet a powerful analogue for understanding ice sheet dynamics on a range of timescales, operating now and in the future.

Recent work by members of this consortium has revealed the pattern of ice sheet retreat that once covered the British Isles, as recorded by end moraines and other glacial landforms. Other work by members of this consortium has used sophisticated computer models to simulate the ice sheet's response to climate change at the end of the last Ice Age. However, these models can only be as good as the geological data on which they are based, and the pattern is poorly constrained in time. We need to know more about the style, rate and timing of ice sheet decay in response to past climate change. Such knowledge allows us to further refine computer modelling so that better predictions can be made. The main focus of the project therefore, is to collect sediments and rocks deposited by the last ice sheet that covered the British Isles, and use these, along with organic remains, to date (e.g. by radiocarbon analyses) the retreat of the ice sheet margins. The project will use over 200 carefully chosen sites, dating some 800 samples in order to achieve this. Offshore, samples will be extracted using coring devices lowered from a research ship to the seabed, and onshore by manual sampling and by use of small drilling rigs. Once the samples are dated and added to the pattern information provided by the landforms, maps of the shrinking ice sheet will be produced. These will provide crucial information on the timing and rates of change across the whole ice sheet. The British-Irish Ice Sheet will become the best constrained anywhere in the world and be the benchmark against which ice sheet models are improved and tested in the future.

Knowledge on the character and age of the seafloor sediments surrounding the British Isles is also useful for many industrial, archaeological and heritage applications. Accordingly, the project is closely linked to partners interested, for example, in locating offshore windfarms, electricity cables between Britain and Ireland, and heritage bodies aiming to preserve offshore archaeological remains.

The key tenet of Britice-CHRONO is addressing the concerns of the Intergovernmental Panel on Climate Change (IPCC) about the ability to predict rates of change and the dynamics of collapsing ice sheets. Numerical ice sheet models are capable of prediction, but they need further developing and crucially, validating against the pattern and timings of shrinking ice sheets. We lack the observations and relevant duration of evidence from contemporary ice sheets and an analogue from the past is a more achievable target. We aim to provide the World's best reconstruction of ice sheet (IS) demise across the transition from marine-terminating to entirely land-based using the now-disappeared British-Irish Ice Sheet (BIIS). Thus our key contribution, during years 4-5, is providing modellers with the reconstructions necessary to develop and test the purportedly-leading IS models to assess the impacts of iceberg calving, tidal regime, grounding line dynamics and ice stream mechanics in governing rapid ice sheet retreat. The end game is to improve predictions for the possible rapid collapse of sites of global significance (e.g. West Antarctica and Greenland). This research will improve the evidence base from which IPCC advises the 194 member countries about future environmental and socio-economic impacts arising from IS collapse and the associated threats from atmosphere-ocean-ice interactions. The increased credibility of such a coupled predictive model, via Britice-CHRONO and other ongoing research, will hopefully kick-start mitigation procedures in areas vulnerable to sea level change and support-mechanisms for areas with limited resources to react instantaneously to climate change-related natural disasters.

Britice-CHRONO will collate and collect geological and geomorphological data both on- and offshore around Britain and Ireland, with the associated interpretation of the area's deglacial and postglacial history. Britice-CHRONO will thus generate information of considerable benefit to marine and terrestrial industries, conservation agencies responsible for Bio- and Geodiversity, and the heritage environment (HE). Britice-CHRONO's outcomes will also allow for a more cost-effective design for the various phases of development projects (e.g. Aggregates, Power Infrastructure, Renewable Energy), as explained in the Pathways to Impact.

Britice-CHRONO research will also benefit both terrestrial and marine bio- and geo-diversity, and enable Natural England (NE), Countryside Council for Wales (CCW), Scottish Natural Heritage (SNH) to meet some of their marine obligations. The research would help in identifying new conservation sites and improving understanding of existing protected sites both on- and offshore. The proposal also aligns with significant marine Historic Environment (HE) elements of English Heritage and Historic Scotland's plans for heritage protection. The interplay of deglaciation and a marine ice margin will inform archaeologists and the HE community about the position of the coast and extent of terrestrial environments during a period with rapidly changing sea levels. The research will aid understanding of the environments available to early human communities and thereby inform management of HE assets across the present land-sea boundary.

Reading stories preserved in the landscape has contributed significantly to popular culture of late, with landmark television series such as Coast, and the British Isles: a natural history and the Making of Scotland's Landscape. The research proposed would reveal the seldom seen glacial heritage preserved on Britain and Ireland's seascape, and shows the scale and dynamic magnitude of changes that affected these islands during the last deglaciation. This understanding of the pattern and controls on ice sheet decline has considerable potential for raising literacy and enthusiasm about science, the natural environment and global change issues, especially for children and the public.