Contrasting regional ice margin dynamics of the Scandinavian Ice Sheet revealed by the landform record

Abstract

Under current climate conditions the Greenland and Antarctic sheets are rapidly losing mass and these losses are projected to accelerate into the future. Consequently, potential changes in the ice marginal environment across these ice sheets are a future concern. Palaeo-ice sheets, such as the Scandinavian Ice Sheet, provide an opportunity to investigate ice-marginal changes over longer timescales that span a variety of physiographic and geological settings and climate conditions. Landform signatures across Fennoscandia reveal a range of palaeo-ice marginal settings, including lake-terminating, marine-terminating, and higher-altitude environments. This makes the landform record of the Scandinavian Ice Sheet a rich and diverse archive for studying ice margin behaviour. Furthermore, high-resolution digital elevation models (DEMs) that exist for the former bed of this ice sheet allow us to examine ice marginal settings and dynamics in unprecedented and consistent detail across Norway, Sweden and Finland. We present a geomorphological ice margin dataset of ~56,000 mapped features that categorises each ice margin by its dominant landform type of moraine, hummocky moraine, lateral meltwater channel or glaciofluvial sediment. We then use the morphology of the landforms and overprinting relationships to determine which landforms were likely formed prior to the last deglaciation. The distribution of landform-types in our dataset provides interesting insights into the behaviour of different sectors of the ice sheet. For example, we find ice margins characterised by lateral meltwater channels are almost exclusively found in locations of Quaternary sediment cover, which may indicate that surficial sediment thickness influences their formation, rather than the thermal regime of the ice. We also find ice margins defined by hummocky moraines are more prevalent at higher latitudes. We hypotheses this pattern may be controlled by lower ablation rates at higher latitudes. Additionally, we find contrasts in the density and size of the ice margins between the aquatic and land terminating environments, which results from differences in sedimentation processes within each environment.