Proglacial Lakes in High Mountain Environments

Lakes are a characteristic feature of glacial landscapes. They are found in the vicinity of current or past glaciers and ice sheets, in high alpine cirques, inner-alpine valleys as well as lowlands. In recent years, new lakes have emerged in glacier forefields and surface areas and volumes of many proglacial lakes are reported to be growing in many mountain areas due to climate-induced glacier melt. Some proglacial lakes have attracted public and scientific attention due to disastrous events such as lake outburst floods or increasing hazard potential and risk downstream. Proglacial lake formation is the result of glacier retreat exposing a topographic bedrock depression or space behind a sediment dam that inhibits runoff and provokes storage of water and sediment. Proglacial lakes thus are first-order sediment sinks and interrupt the sediment cascade and sediment transfer dynamics from uplands to lowlands. They often are of societal relevance in mountain areas ranging from water supply to energy production, hazard and risk, as well as tourism issues. This review summarises the role of proglacial lakes for geomorphic systems in high mountain environments. We start with a look at the basic terminology and formation principles, followed by an overview of global lake distribution patterns. The geomorphologic significance of proglacial lakes is discussed with respect to the current state of knowledge. Recent developments that allow a modelling of potential future lakes in mountain areas, once the glacier melt, are presented and discussed in the light of natural hazards and risks, as well as socio-economic dimensions of proglacial lake formation.