INQUA Abstract

Extent of the Scandinavian Ice Sheet during the last glacial-interglacial cycle

Cornelia Winguth, David M. Mickelson, Eiliv Larsen, Jessica Darter

Several aspects of the Scandinavian Ice Sheet's extent during the last glacial-interglacial cycle are still unknown or controversial. The ice sheet's maximum lateral extent was probably time-transgressive and was reached earlier on the western margin (ca. 28-23 cal ka BP) than on the eastern side (after 17 cal ka BP). For the time of 21 ka BP, a key time in paleoclimate modeling, the position of the eastern ice margin is not known. The ice sheet's vertical extent in the mountainous areas of western Norway at the last glacial maximum has long been disputed due to divergent geologic evidence.

We use a two-dimensional, time-dependent, thermomechanically coupled ice flow model along two E-W transects running at ca. 62EN and at ca. 67-59EN, respectively, in order to address these questions. The model is mainly driven by temperature and precipitation. Estimates of LGM and later climate conditions in the area are taken from various GCM and regional climate model studies as well as paleoclimate reconstructions from proxy data. The GISP δ¹⁸O record has been adapted to the local data in order to provide us with a continuous temperature record used as input for time-transient model runs. Known ice extents through time, especially on the western margin, are used for model validation. In addition, consolidation samples have been sampled along the northern flowline and these will provide minimum thickness estimates.

Our model results seem to support the "nunatak theory" for western Norway, suggesting that the ice sheet did not completely cover all mountain peaks. This is in good agreement with ice thickness values derived from cosmogenic dating in an area close to the southern transect and with a trimline that has been interpreted as the vertical Younger Dryas ice extent. According to first model results for the northern transect, the eastern margin was probably located ca. 300 km west from its maximum extent at 21 cal. ka BP.