Models and observational constraints for fast ice flow and marine ice sheet dynamics

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The ice sheets of Greenland and West Antarctica contain sufficient fresh water to raise global sea levels by about 13 metres. At present, there are no reliable predictions of how fast these ice sheets may shrink under projected climate change, and the future rate of sea level rise cannot be forecast accurately. Better predictions of ice sheet behaviour will require a number of physical processes to be represented more accurately in numerical models. Ice sheets do not flow evenly, but contain channels of fast flow known as ice streams. How these ice streams form, evolve and ultimately shut down again is only partially understood, and much of the physics involved is not represented in currebt ice sheet models. Similarly, the physics that controls the evolution of the edges of ice sheets (and hence their horizontal extent) is only partially understood. In particular, the edges of the Greenland and Antarctic ice sheets are defined in many places by the location where ice begins to float and forms an ice shelf. The rate at which ice flows through these junctions between ice sheets and ice shelves cannot be predicted accurately by present models, hampering efforts to estimate future sea level changes. The proposed research program will target these weaknesses in current ice sheet models by addressing the fundamental physics involved in ice stream flow and in the evolution of the margins of ice sheets. The research program will take a two-pronged approach, using sophisticated modern mathematical methods in conjunction with data from a new field program to derive improved representation of ice sheet physics for use in numerical simulations.