Abstract Details

ID: 362
Title: Complex interaction of subglacial hydrology and deforming bed processes and its implications for ice marginal stability: the example of the Middle Pleistocene British Ice Sheet from eastern England

Subglacial drainage is known to have a profound influence on glacier and ice sheet stability. Many scientists consider that such processes acted to cause abrupt climatic shifts in the North Atlantic region during Termination 1, and believe that meltwater-induced instabilities in the modern-day Greenland and Antarctic ice sheets could have similar climatic impacts in the future. Understanding the role played by porewater content and/or pressure, coupled with its temporal and spatial distribution within the subglacial bed, appear to be critical factors. These act to control the rheology and style of deformation within the subglacial deforming bed, and in-turn, the amount and distribution of ‘stick-slip’ at the ice-bed interface which facilitates ice motion. Within this paper, we present a model based upon sedimentological and structural evidence from Middle Pleistocene glacial deposits in Eastern England, which illustrate the symbiotic relationship between subglacial deforming bed processes, subglacial drainage within a pressurised channel system, and ice advance. The model shows the development of large-scale subglacial folds and thrusts within a subglacial mélange that relate to temporal changes in porewater content and/or pressure within the subglacial bed. These acted to control the development and stability of subglacial drainage beneath the margins of the British Ice Sheet, ultimately leading to an increase in the efficiency of subglacial drainage and the subsequent collapse of the subglacial shear zone. This potentially slowed or even stopped ice advance leading to the part-collapse of the ice margin.

Session: 70 The ice/bed interface in past and present ice sheets and glaciers: subglacial processes, sediments, landforms, and ecosystems
Authors: Jonathan Lee
Emrys Phillips
Presenter:Jonathan Lee
Type: poster