Numerical modelling of Langjökull Ice Cap, Iceland
This thesis describes the development and application of a mass balance model for Langjökull Ice Cap to enable an investigation into its state of balance. This model is then coupled to a numerical model of ice flow, also developed as part of this thesis, to allow an assessment of the sensitivity of the ice cap to future climate change. Using data collected at a field site on one of the ice cap’s outlet glaciers in the summer of 2000, an energy balance model was optimised in order to obtain the best fit between the predicted and observed ablation. Although the optimisation enabled a reasonable fit to the observed data, it was worse than could be obtained using a simpler degree-day model. This degree-day model was developed to calculated the mass balance of the whole ice cap; using 30 years of meteorological data, the results of this model suggested that the ice cap is currently in a state of expansion – the average net mass balance across the ice cap being 0.5 m w.e.yr-1. To aid the development of a numerical model of ice flow, the flow regime of Langjökull was investigated by looking at several different methods of calculating the velocities occurring there. The effects of sediment deformation were found to be important in accurately modelling the ice flow occurring at Langjökull Ice Cap, with a till viscosity of 6x109 Pa s found suitable for modelling this process. When the degree-day and the ice flow models were coupled together, the modelled ice cap was found to be strongly dependent on air temperature and, under climate change scenarios with warming rates of 0.02 and 0.04 yr-1, Langjökull is predicted to disappear within 200 year. The inclusion of sediment deformation was found to have little effect on the response of the ice cap to climate change.