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Modelling the influence of glacier hydrology on the dynamics of large ice sheets

Modelling the influence of glacier hydrology on the dynamics of large ice sheets

Glacier hydrology, that is the systems which carry water within and at the bed of ice sheets and glaciers, are one of the fundamental controls on the velocity of ice masses, and hence their possible responses to climate change. The flow rates of valley glaciers are known to be influenced by the changes in the amount of water in their hydrological systems which occur over the course of a year due to the changing seasons, and there is increasing evidence that the Greenland Ice Sheet in particular may experience annual velocity variations in response to increased summer melting. Geomorphological evidence from areas occupied by ice sheets during the last glacial period also suggests that the great Quaternary ice sheets carried substantial amounts of water at their beds, and that this basal water affected their flow rates. Fast glacier flow, which occurs in modern-day ice streams and some of the large outlet glaciers which drain both the Greenland and Antarctic Ice Sheets seems in particular to depend on the presence of basal water at high pressure.

This project aims to incorporate a physically-based numerical model of subglacial hydrology into a state-of-the-art thermomechanical ice sheet model, the GLIMMER model being developed by Dr Anthony Payne and his co-workers as part of the CPOM project. This builds on earlier work in which such a model was included in a 2-dimensional ice sheet flow model. This earlier model has been successfully applied to the flow and time-dependent behaviour of the Scandinavian Ice Sheet during the last glacial period. These results showed that the inclusion of basal hydrology led to the development of a thinner, more dynamic ice sheet, with distinct areas of fast ice flow, than in a model without basal hydrology. Patterns of fast flow with this model ice sheet, and their complex temporal and spatial evolution matched qualitatively with geomorphological evidence for areas of fast ice flow in central Scandinavia from the latter part of the last glaciation.

Digital Elevation Model of Scandinavia
Figure 1. 25km resolution Digital Elevation Model of Scandinavia used as input data for the model.

Modelled ice sheet extend
Figure 2. Modelled ice sheet extend at 20,000 years before present. Arrows are modelled ice sheet velocity, showing direction and velocity. The areas affected by fast flow due to high basal water pressure are clearly visible.

This project will incorporate the hydrological model from this earlier ice flow model into the GLIMMER ice sheet model. This should allow, for the first time, a better understanding of the interactions between ice flow, temperature within an ice sheet and basal hydrology. This should then allow us to better understand both the dynamics of the large palaeo-ice sheets of Europe and North America, and also the responses of Greenland and Antarctica to past climate changes, and possible future anthropogenic climate changes.


  • Arnold, N.S., Van Andel, Tj. H. And Valen, V. 2002. Extent, and dynamics of the Scandinavian Ice Sheet during Oxygen Isotope Stage 3 (65000 - 25000 yrs BP). Quaternary Research 57 38-48.
  • Arnold, N.S. and Sharp, M.J. 2002. Flow variability in the Scandinavian Ice Sheet: modelling the coupling between ice sheet flow and hydrology. Quaternary Science Reviews 21 485-502.