Glacial geology and glaciology of the Younger Dryas ice cap in Scotland

• Main Author: Golledge, Nicholas Robert
• Other Authors: Hubbard, Alun, Sugden, David, Thomas, Chris
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Edinburgh 2009
• Subjects: Younger Dryas stadial; global climate change; glaciers; ice sheet hysteresis; Ice cap; Ice Sheet
• Online Access: http://hdl.handle.net/1842/3789

This thesis uses geological field data and numerical ice sheet modelling to study the Younger Dryas ice cap in Scotland. The Younger Dryas stadial is important because it represents the most recent period of high-magnitude global climate change, and was marked by the expansion of ice sheets in North America and Scandinavia, and the regrowth of glaciers in the British Isles. An integrated methodology linking field results and modelling is developed and applied here, specifically focussing on the deposits, landforms, and palaeoglaciology of Younger Dryas glaciers in western Scotland. This combined approach enables data of different scales to be compared, and connected, from local sedimentological investigations and empirically derived reconstructions, to regional ice-sheet simulations from a high-resolution numerical model. Previous geological mapping in western Scotland resulted in contradictory views of the thickness and extent of ice during the Younger Dryas, consequently leading to uncertainty about the dynamics of the former ice cap. By using a ‘landsystem’ method to characterise the terrain, it is argued here that geological evidence in the study area implies a relatively thick central ice cap that fed steep outlet glaciers around its margins. These glaciers oscillated throughout the stadial, and during deglaciation produced suites of moraines that marked successive positions of glacier retreat. Widespread preservation of superimposed landforms, and of sediment sequences pre-dating the Younger Dryas, suggest that, despite being active, the Younger Dryas ice cap was not particularly erosive in its central area and only subtly modified its bed. These geological interpretations are supported by high-resolution numerical modelling of the ice cap, which reveals clear spatial variability in the velocity structure, thermal regime, and flow mechanism of the ice cap; patterns that led to local contrasts in basal processes and diversity in the geological imprint. These model experiments also highlight the non-linear ...