Dynamics of Glaciers and Large Ice Masses

Abstract

In this article I discuss the fluid-mechanical aspects of that part of the world's ice which manifests itself as glaciers and ice sheets. Although different in their extent, glaciers and ice sheets have in common that they move under the influence of their own weight. Ice sheets spread in two spatial directions; glaciers are basically unidirectional and confined to a valley or a system of valleys (see Figures I and 2). On appropriate scales (intermediate, i.e. a few tens or hundreds of km, for ice sheets, global for glaciers) and for qualitative studies ice-sheet and glacier flow is planar. Plain strain is thus the restriction I concentrate on in this review. Although glaciers are situated in the remoter parts of thinly populated areas their study is important, first, because their advance and retreat is an indicator of the variation of the climate; second, because they occa­ sionally endanger valley inhabitants by ice avalanches and outbursts of ice-dammed lakes, and third, because they may someday be economically exploited as subglacial water catchments. The Arctic and Antarctic regions nowadays grow in significance mainly because they are exploited for their natural resources. Figures I and 2 provide typical overviews of two Alpine glaciers, the Grosser Aletschgletscher and the Fieschergletscher. Both photographs il­ lustrate the channelized nature of the flow. These glaciers are fed from the higher mountain regions by several tributaries and are in their lower portions confined to a single valley. The position of the snout varies ac­ cording to the climate. The snout of the Fieschergletscher in Figure 2 is wedge-type, a form that is typical for a retreating glacier. By contrast, advancing glaciers have claw-like snouts (see Figure 10). It is one purpose of glaciology to understand and describe how glaciers and ice sheets flow and in what sense their behavior can be related to that of the geophysical environment, the atmosphere, and the substratum the