Processes and dynamics during deglaciation of a polar continental shelf. Examples from the marine-based Barents Sea Ice Sheet

Abstract

The main objective of this PhD thesis was to reconstruct the pattern and main processes of the last deglaciation of the Barents Sea Ice Sheet. The thesis consists of an introductory part and five papers. The conclusions presented in the papers were based on data acquired with a suite of marine geophysical and geological methods, including multibeam-swath bathymetry data, chirp data, airgun and sparker seismic data and sediment (gravity) cores. Bathymetric data were used for identification and mapping of main geomorphic features on the seafloor. The distribution, geometry, reflection signature and seismic/acoustic stratigraphy of seabed sediments, were assessed based on chirp and seismic data. Sediment core analyses provided information about the depositional environment and age constraints for deglaciation. The primary focus was on two main study areas. The first area is Kveithola, a small submarine trough on the western margin of the continental shelf (NW of Bjørnøya). Results from Kveithola are presented in papers 1-2. In the first paper, the sedimentary environment in the trough from the time it was deglaciated before ~14.2 cal ka ago until the last sign of glacimarine sedimentation in the trough ~10.3 cal ka ago, is reconstructed. The second paper summarises both the complex retreat history of the Kveithola Ice Stream and the following glacimarine sedimentation in a conceptual model. The second study area was the central Barents Sea, which is addressed in papers 3-5. The third paper includes a map showing the distribution of large tunnel valleys on the seafloor, along with descriptions and discussions of their attributes, genesis and relevance for glacial history. The fourth paper focuses on the seafloor of upper Bjørnøyrenna, where a landform assemblage related to ice stream stagnation is presented and a new model of ice stream retreat in meltwater-dominated areas is introduced. In the final paper a new reconstruction of the deglaciation of the central Barents Sea is presented. The reconstruction includes main ice flow patterns, prolonged ice margin positions and glacial dynamics during the retreat of the ice sheet, based on both new and old data.