Basal ice temperatures during late Weichselian deglaciation: comparison of landform assemblages in west-central Sweden

Abstract

AbstractThe mountainous area of west-central Sweden has a varied glacial morphology and three unique landform assemblages appear to mark areas of different basal thermal conditions during the decay of late Weichselian ice. A glacial geomorphological map was constructed through interpretation of aerial photographs at a scale 1:60 000. The relative abundance of landforms interpreted to indicate a frozen bed, a thawed bed, and late-frozen to thawed-bed conditions were used for a first-order reconstruction of the basal temperature pattern of the decaying ice sheet. The features used to outline areas with different temperature regimes during deglaciation are glacial scouring, flutings, eskers, meltwater channels, boulder blankets, Rogen moraines, relict surfaces and thermoerosion features.In the northern part of the area, as well as along most of the water divide to the Atlantic Ocean, the ice was warm-based during deglaciation. Glacially scoured bedrock, fluting/ drumlinization, subglacial eskers and extensive glacial lake sediments characterize the area. In the high mountain area, lateral meltwater channels are short and curve downslope to form chutes or eskers. The basal ice conditions changed from frozen- to thawedbed in a late stage of the late Weichselian cycle in most of the southern part of the area, shown by the Rogen moraines on both sides of the ice divide. However, substantial areas in the eastern and southern low mountains had frozen-bed conditions during the complete late Weichselian. In the high mountains in the north, only the summits were frozen.