Ola Fredin

Glacial inception and Quaternary mountain glaciations in Fennoscandia

Abstract The aim of this review is twofold. First, the role of the Fennoscandian mountains as a nucleation center for glacial inception is investigated. The second objective is to review glacial erosion by mountain glaciers throughout the Quaternary. All available field data and several modelling experiments show that the Fennoscandian mountains seeded the last glaciation. Since the mountains seem to be of key importance for ice-sheet inception, it is reasonable to assume a similar inception pattern throughout most of the major Pleistocene glaciations. This pattern also implies prolonged periods of glacial ice in the Fennoscandian mountains during late Cenozoic time. Mountain-based glaciers thus have had a long time to act on their substratum resulting in a profound geomorphological impact.

Relict lateral moraines in northern Sweden—evidence for an early mountain centred ice sheet

Glacial geomorphology along the eastern rim of the Scandinavian mountain range includes glacial landforms from the last deglaciation as well as from earlier glacial stages. One of the most prominent landform groups from earlier glacial stages, and the most diagnostic for ice sheet reconstruction, is a set of lateral moraines. In this paper, we describe these lateral moraines within a key area around Kvikkjokk, northern Sweden. Position of these lateral moraines in relation to the last deglaciation patterns indicates that they were formed before the last glacial maximum (LGM). The location and morphology of moraines show that they were deposited by a mountain centred ice sheet with outlet glaciers along major valleys, emanating from the highlands west of the Kvikkjokk area. This ice sheet was likely less than 170-km wide and no more than 600-m thick. Climatologically and glaciologically, we expect the relict lateral moraines to have been deposited before 75 ka BP (marine oxygen isotope stage 4). Their preservation is a consequence of subsequent overriding of nonerosive cold-based ice. Ice-marginal landforms and deposits from mountain centred ice sheet configurations in Fennoscandia are scarce. Therefore, the relict lateral moraines are important tools for reconstructing these elusive early glacial stages, possibly correlated to the ice sheet inception.

Ice sheet growth under dirty conditions: implications of debris cover for early glaciation advances

Abstract Debris-covered glaciers respond differently to any given set of climatic conditions than clean glaciers. This difference stems from change in ablation rate caused by a debris cover, approaching zero ablation with sufficiently thick protective cover, a mechanism not yet considered in the context of ice sheet growth. Critical to applying the mechanism to ice sheets is supply of debris. We postulate that periods after major interglacials offer the best conditions for dirty advances. This is because the volume of debris, previously deposited and weathered in interglacial time, the latter a function of exposure length, should be at a maximum. Advances of dirty ice sheets generate landforms and in positions deviating from clean-ice advances under similar climatic conditions. Hence, inferences of both ice sheet properties inferred from such dirty ice advances and the climate conditions related to such advances must be cautious. Furthermore, modeling of past ice sheets must consider the effect of debris cover whenever indications exist for such a cover.