MODELLING FORMER ICE SHEETS - THE INTEGRATION OF GLACIOLOGY AND GLACIAL GEOLOGY

Reconstructions of past ice sheets have either been qualitative reconstructions of their extent, flow history and thermal regime based on glacial geological evidence or reconstructions based on the inversion or partial inversion of relative sea level data using simple numerical models of ice sheets as parts of coupled lithosphere models. The former fail to utilise the capacity of models to represent modern glaciological understanding and to create internally consistent ice sheets that are compatible with geological constraints. The latter fail to use glacial geological data that has the potential to provide strong constraints on models.

A high resolution, thermo-mechanical 3D numerical ice sheet model has been used to simulate the European ice sheet through the whole of the last glacial cycle. Its advantage is a high resolution that permits model results to be compared with glacial geological and geophysical data close to the scale at which they are observed. It is ultimately intended to use the model in inversions of geological and geophysical data to create a quantitative numerical glaciological reconstruction of ice sheet behaviour in space and time. As an intermediate step, a series of forward simulations have been undertaken through the last glacial cycle in which the ice sheet is driven by a climate function based on the Greenland ice core record and parameterisation of local climate, and steered so that its output is compatible with glacial geological evidence of ice margin fluctuation, flow patterns and thermal regimes.

The approach is a powerful means of integrating geological evidence to create palaeoglaciological reconstructions of ice sheets through a whole glacial cycle, to infer major changes in the nature of climate forcing on an ice sheet scale and to explain some of the key properties of former ice sheets.