Intellectual Merit: The contribution from the Greenland and Antarctic ice sheets to 21st century sea level rise is highly uncertain. Most estimates in the recent Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) were obtained using relatively crude ice sheet models forced with Global Climate Model (GCM) output, without including climate feedbacks associated with changing ice sheets. The PI will explore the response of the Greenland ice sheet to anthropogenic greenhouse forcing by using a dynamic ice sheet model bi-directionally coupled to the new version of the Community Climate System Model (CCSM4). With this coupling, ice sheets will be able to modify local and global climate via changes in surface albedo, topography, and freshwater fluxes to the ocean. Modifications of local climate could change the ice-sheet mass balance and need to be taken into account. This study will be the first with a U.S. Atmosphere-Ocean GCM coupled bi-directionally to an ice sheet model, and its outcomes will constitute a primary contribution of CCSM to AR5 estimates of sea level change. The PI and his colleagues will address the following research questions: the magnitude of changes in surface melting of the Greenland ice sheet and associated feedbacks, under a variety of forcing scenarios; the evolution of fast-flowing features, such as outlet glaciers, in similar forcing scenarios; and the potential impacts of ice sheet changes on local and global climate. Climate-change projections will be complemented by simulations of the previous interglacial, when sea level was 3-6 m higher than at present.
This research is both urgent and high risk. Urgent, because if not completed and accepted for publication by late 2010 the research will not be considered for inclusion in the IPCC AR5 of global climate change. It is high risk because ice sheet processes are both highly complex and operate at different timescales than climate processes; this will be the first attempt to simulate and predict ice sheet and climate evolution to anthropogenic forcings using a fully coupled approach between a sophisticated ice sheet model and a state-of-the-art earth system model.
Broader Impacts: The research will provide valuable insights about the impacts and trajectory of anthropogenic global climate change, including quantitative probabilities of sea level changes. It will provide funding for an outstanding female post-doctoral scientist.
