| dc.description.abstract | Ice streams play a fundamental role in the stability and dynamics of ice sheets. They are
defined by their rapid flow and this is enabled by conditions and processes at the icebed
interface. A significant limitation to our understanding of this environment is that
most studies, of both contemporary and palaeo-ice streams, have focussed on only one
or two, discrete spatial scales of analysis and so integration between scales is restricted.
This thesis investigates palaeo-ice streams at multiple scales in order to examine their
subglacial processes and characteristics, and to assess the links between and the
application of different spatial scales of analysis. Seven palaeo-ice streams from the
British and Laurentide ice sheets were investigated at the macroscale, which involved
geomorphological mapping, spatial analysis of subglacial lineations and examination of
bed characteristics. Two ice streams were also investigated at smaller scales, which
included sedimentological analysis (mesoscale) and micromorphological analysis
(microscale).
Macroscale results showed that subglacial lineations display certain spatial
characteristics, including: clustering according to elongation ratio; distribution of low
elongation ratios throughout the ice streams; and a decrease in maximum elongation
ratio towards the ice stream lateral margins. The latter of which is considered to reflect
the transverse distribution of ice velocity. In some cases, a decline in subglacial
lineation concentration and elongation ratio coincided with topographic obstacles at the
ice stream bed. The most common bed characteristics identified were: widespread till,
fine grained sedimentary bedrock with a moderate permeability, low relief and a flat
topographic curvature.
Key subglacial processes identified included deformation, which was observed at all
three scales, and high pore water pressures, for which multiple lines of evidence were
found at the meso and micro scales. Spatial variability in both strain and pore water
pressure was also common. The multiscale approach allowed robust interpretations of
fast flow mechanisms, which furthers knowledge of the sediment and landform
characteristics that may result from these flow mechanisms. A summary of the
processes that can be identified at each of the spatial scales is given | en_US |
