Investigating the potential contribution of the East Antarctic Ice Sheet to future sea level change.

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There is currently major uncertainty about the potential contribution of the Antarctic Ice Sheet (AIS) to global sea level change in the immediate and long term future. Part of the AIS rests on land that is below sea level and, hence, has a very different flow regime to other parts which rest on land above sea level. It is, therefore, susceptible to changes in ocean circulation as well as atmospheric change. A small change in ocean temperatures can have a large impact on ice flow, whereas a large change is required in atmospheric temperatures (which are in general tens of degrees below freezing over the AIS). A hypothesis exists that suggests marine based ice sheets (those that rest on bed below sea level) which also have a bed which deepens inland, are inherently unstable due to their configuration. A small thinning/retreat in the grounding line (the location where the ice sheet changes from being grounded on its bed to floating) makes the ice thinner inland where the bed is deeper, the ice is no longer able to ground and hence flows faster due to increased basal resistance. This leads to a feedback mechanism that could, in the worst case, lead to the breakup of large parts of the ice sheet. The smaller West AIS (WAIS) has so far been the region of greatest concern, with most of the ice sheet resting on bed below sea level and a strong thinning signal observed in one of the drainage sectors (Amundsen Sea sector). The larger East AIS (EAIS) has previously been considered to be stable, as the majority of the ice sheet rests on land above sea level. However, there are some large basins known to be below sea level (Wilkes and Aurora subglacial basins), though there is currently sparse data coverage from these basins. The ice in these regions is also currently exhibiting a surface thinning signal near the coastal regions that cannot be explained by changes in the snowfall pattern and hence must have a dynamic origin. Part of the uncertainty over ice sheet stability and future sea level change comes from the inadequacy of numerical models in reproducing the processes which occur at the grounding line, and hence in representing change in its location. Recent model developments are improving the representation of grounding line processes and a major data collection mission will in the near future provide detailed information about the nature of the bedrock in the two EAIS marine basins. These two advances will allow a better understanding of the nature of EAIS stability to be derived though numerical ice sheet modelling. This research, therefore, proposes to use an advanced numerical ice sheet model to investigate the changing dynamics of the marine sectors of the EAIS, in order to investigate the future stability of the ice sheet and its potential contribution to future global sea level change in both the immediate future, and on a decadal and millennial scale. The work will be carried out at the University of Durham, in association with other researchers at the forefront of Antarctic research at the Universities of Edinburgh and Bristol, and the British Antarctic Survey. Understanding and quantifying ice sheet stability and future change in global sea level is highly relevant to current concerns about global environmental change and its impact on millions of people living in low lying regions. The research is therefore timely and relevant to current research priorities.