ABSTRACT. Surface digital elevation models (DEMs) and slope-related estimates of glacier thickness enable modelling of glacier-bed topographies over large ice-covered areas. Due to the erosive power of glaciers, such bed topographies can contain numerous overdeepenings, which when exposed following glacier retreat may fill with water and form new lakes. In this study, the bed overdeepenings for �28 000 glaciers (40 775

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Some observations which pertain to the interaction of ice and lake water in a high alpine environment and which were made in recent years in connection with hydroelectric projects and flood protection work are presented. In 1966, when the thin flat snout of Griesgletscher (Walliser Alpen) became submerged during the first filling of a newly constructed reservoir, waves of only very small amplitude were generated by the calving of a bout 150000 m3 of ice because most of the energy was dissipated by local turbulence. Far more spectacular waves have been experienced near steep ice cliffs in connection with work for flood control. For the design of an air bubbler system, air and water temperatures were measured in winter 1974–75 at Grimselsee, one of the largest reservoirs in the Bernese Alps. These measurements showed that the warmest water at the bottom of the lake was drained away during winter for the production of electricity. A strong temperature invenion forms in the air a bove the water behind the dam, as the lake level is lowered by several tens of metres.

Abstract. The potential contribution of glaciers and ice caps to sea level rise is usually calculated by comparing the estimated total ice volume with the surface area of the ocean. Part of this total ice volume, however, does not contribute to sea-level rise, because it is below the surface of the ocean or below the levels of future lakes on land. The present communication points to this so far overlooked phenomenon and provides a first order-of-magnitude estimate. It is shown that the effect is small (most likely 1 to 5 cm sea-level equivalent) but systematic, could primarily affect earlier stages of global glacier vanishing and should therefore be adequately considered. Now-available techniques of slope-related high-resolution glacier-bed modelling have the potential to provide more detailed assessments in the future.