On the response of valley glaciers to climatic change

Abstract

In many cases the response of a glacier to changing climatic conditions is complicated due to the large number of feedback loops that play a role. Examples are: ice thickness - mass balance feedback, nonlinearities arising from complicated geometry, dependence of ablation on glacier geometry, coupling between debris cover, ice flow and ablation etc. In this paper an attempt is made to quantify such processes by carrying out numerical experiments with an ice-flow model. Some conclusions and suggestions are: (i) The longitudinal bed profile is very important. Apart from the well-known fact that glaciers are more sensitive when the bed slope is small, a reversed slope (slight overdeepening) creates branching of the equilibrium states, i.e., for the same climatic conditions two glaciers of different geometry can both be in a stable steady state. (ii) Due to the height-mass balance feedback, glaciers on a smaller slope react slower to climatic change. (iii) The mass balance gradient as observed on long valley glaciers is to a substantial part determined by systematic changes (along-valley) in glacier width and surface albedo. The balance gradient is thus coupled to the dynamics, and this should be studied further.