The Scandinavian ice sheet: from MIS 4 to the end of the Last Glacial Maximum

Glacial rebound modelling, to establish constraints on past ice sheets from the observational evidence of palaeo shoreline elevations, is well established for the post-LGM period where the observational evidence is relatively abundant and well distributed spatially and in time. This is particularly the case for Scandinavia. For the earlier part of the glacial cycle this evidence becomes increasingly sparse and uncertain such that, with the exception of the Eemian period, there are very few, if any, direct sea level indicators that constrain any part of the Scandinavian ice sheet evolution before the Last Glacial Maximum (LGM). Instead we assume that ice-sheet basal conditions during Marine Isotope Stage 3 (MIS 3) are the same as those for the LGM, focus on establishing these conditions from the rebound analysis for the LGM and Lateglacial period, and then extrapolate to the earlier period using observationally constrained locations of the ice margins. The glacial rebound modelling and inversion follows previously established formulation with the exception that the effects of water loading from proglacial lakes that form within the Baltic Basin and elsewhere have been included. The data set for the inversion of the sea- and lake-level data has been extended to include marine limit data to extend the observational record further back in time. The result is a sequence of time slices for the Scandinavian ice sheet from the time of MIS 4 to the Lateglacial that are characterised by frozen basal conditions until late in the LGM interval when rapid thinning occurred in the eastern and southern sectors of the ice sheet. The primary function of these models is as an interpolator between the fragmentary observational constraints and to produce quantitative models for the glaciation history with predictive capabilities, such as the evolution of the Baltic Basin.