Ice-marginal terrestrial landsystems: Svalbard polythermal glaciers

Temperate glacier margins are mainly wet-based for at least part of the year and are located in terrain that contains discontinuous or no permafrost. Such glaciers are considered as active when they are capable of forward momentum even during overall recession. This is manifest in the small winter readvances that characterize receding outlet glaciers in places like Iceland (e.g. Sharp, 1984; Boulton, 1986; Krüger, 1995). Cold winter conditions result in the penetration of a seasonal cold wave from the atmosphere through the thin ice. This produces a narrow marginal frozen zone thought to be significant in the production of some frontal moraines. In some settings the marginal frozen zone may persist for several years and is therefore technically discontinuous permafrost. The processes and major landform-sediment associations of active temperate glacier margins have been studied in great detail (e.g. Sharp, 1982, 1984; Harris and Bothamley, 1984; Krüger and Thomsen, 1984; Krüger, 1985, 1993, 1994a, 1997; Boulton, 1986; Boulton and Hindmarsh, 1987; Benn, 1995; Evans and Twigg, 2002), thereby informing models of landform production (e.g. Boulton and Eyles, 1979; Gustavson and Boothroyd, 1987; Krüger, 1987; Benn and Evans, 1998).