Modelling Geomorphic Systems: Glacial

The cryosphere contains a rich archive of the climate record, and is an important part of the global hydrological cycle. The investigation of the glacial behaviour informs our understanding of the forces that have shaped landscapes in glaciated terrains, and is key to developing understanding of past and future climate change and global climate teleconnections. Numerical modelling of glacial systems allows us to understand quantitatively the processes that drive glaciers. Three major model types exist: those that use ice extents to understand climate changes; those that investigate the forces that control ice dynamics; and those that investigate the erosional consequences of glaciation. Glacier models can be applied with a range of spatial extents, from individual cirque glaciers (e.g. Murray and Locke, 1989; Ballantyne, 2002; Coleman et al., 2009; Hughes, 2009) to continental ice sheets (e.g. Marshall and Clarke, 1999; Hubbard et al., 2005). The basis of any glacier model is a calculation of mass balance; the relationship between ice accumulation and ablation at a given point in time, under the current climate conditions. Mass balance controls glacier dynamics, which respond to processes operating on timescales of different orders of magnitude (e.g. climate change, tectonic uplift). Increasingly complex models require more variables to be specified as inputs, and so are more difficult to apply accurately; the model builder must decide which variables to exclude. However, if the input parameters are well constrained, results from complex models should be more robust. Numerical models can be mathematically 1or 2-D, equivalent to what is more commonly described as spatially 2-D (e.g. along a line of section) or 3-D (e.g. a map view extent), which must include ice thickness. In this section, types of glacier model that can be applied to a range of different aspects of the cryosphere are discussed, alongside methodological concerns in applying different models, and important considerations in a modelling project. However, modelling studies of smaller glaciers that are confined by topography (i.e. valley glaciers) are the focus. For a starting point for models describing ice sheets, ice shelves and marine ice margin processes, glacier hydrology and isostatic adjustment, the reader is directed towards Petrenko and Whitworth (2002), Jamieson et al. (2008), Cuffey and Patterson (2010), Benn and Evans (2010) and references therein.