Glacier icefield and icesheet dynamics

Glaciers, icefields and ice sheets respond to climate change on a time-scale determined by (i) the size of the ice mass, (ii) the dynamic and thermodynamic regime of the ice mass, (iii) the topographic environment (i.e. slope and hypsometry of the glacier bed) and (iv) the general climatic environment (e.g. maritime versus continental). All ice masses experience instantaneous areally averaged thinning or thickening in response to negative or positive mass balance. The four factors noted above govern the longer term ice-volume response that is witnessed at the ice-sheet margin: changes in glacier length and area.

Rigorous quantification of this response requires consideration of ice dynamics and glacier-specific topographic and climatic conditions. However, very instructive simple models have been developed to estimate glacier response times to step changes in climate (Nye, 1960; Johannesson et al., 1989; Harrison et al., 2001). These studies do not explicitly simulate ice dynamics, but apply a scaling relationship for the area and volume responses of an ice mass to climate (or mass balance) changes. For a characteristic thickness scale H representing the region in the ice mass most affected by the climate change, the simplest assumption is that rates of volume and area change are constant and proportional dV _ H dA dt dt

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