Retreat pattern and dynamics of glaciers and ice sheets: reconstructions based on meltwater features

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Retreat pattern and dynamics of glaciers and ice sheets: reconstructions based on meltwater features
Martin Margold

Department of Physical Geography and Quaternary Geology Stockholm University

© 2012 Martin Margold ISSN: 1653-7211 ISBN: 978-91-7447-429-9 Paper I © 2012 Taylor & Francis Paper II © 2011 Journal of Maps Paper III © 2011 Journal of Maps Paper IV © 2011 Elsevier Printed byUniversitetsservice US-AB, Stockholm, Sweden

Doctoral dissertation 2012 Department of Physical Geography and Quaternary Geology Stockholm University

ABSTRACT Glaciers and ice sheets covered extensive areas in the Northern Hemisphere during the last glacial period. Subsequently to the Last Glacial Maximum (LGM), they retreated rapidly and, except for Greenland and some other ice caps andglaciers, they vanished after the last glacial termination. This thesis examines the dynamics of deglacial environments by analysing the glacial geomorphological record with focus on the landforms created by glacial meltwater. The aims are (i) to evaluate the data available for mapping glacial meltwater features at the regional scale, and (ii) to demonstrate the potential of such features for regionalice retreat reconstructions in highrelief landscapes. Meltwater landforms such as ice-marginal meltwater channels, eskers, deltas and fossil glacial lake shorelines are used to infer former ice surface slope directions and successive positions of retreating ice margins. Evaluated high-resolution satellite imagery and digital elevation models reveal their potential to replace aerial photographs asthe primary data for regional mapping surveys including the glacial meltwater system. Following a methods study, reconstructions of the deglacial dynamics are carried out for the area of central Transbaikalia, Siberia, Russia, and for the Cordilleran Ice Sheet (CIS) in central British Columbia, Canada, using regional geomorphological mapping surveys. Mapped glacial landforms in centralTransbaikalia show evidence of a significant glaciation that possibly extended beyond the high mountain areas. Large glacial lakes were formed as advancing glaciers blocked rivers, and of these, Glacial Lake Vitim was the most prominent. Traces of intensive fluvial erosion in the postulated area of glacial damming possibly indicate a high-magnitude outburst flood from this glacial lake. Deglacial dynamics ofthe CIS reconstructed from the meltwater landform record reveals that the configuration of its southern sector changed after the local LGM. The ice divide shifted to the Coast Mountains in north-central British Columbia and the eastern margin retreated from the Rocky Mountains. Similarly to the situation in central British Columbia, the Liard Lobe in the northeastern sector of the CIS alsoretreated in a western direction towards the ice divide. The role of eastern accumulation areas appears to have diminished after the LGM and little evidence is available for their survival during the later stages of deglaciation. The results presented in this thesis demonstrate the potential to reconstruct ice retreat patterns and deglacial dynamics at regional scales by interpretation of the meltwaterlandform record from shrinking glaciers and ice sheets.

Retreat pattern and dynamics of glaciers and ice sheets: reconstructions based on meltwater features
Martin Margold

This thesis consists of a summary and six papers: Paper I Margold, M., Jansson, K.N. (2012): Evaluation of data sources for mapping glacial meltwater features. International Journal of Remote Sensing 33, 2355–2377. PaperII Margold, M., Jansson, K.N. (2011): Glacial geomorphology and glacial lakes of central Transbaikalia, Siberia, Russia. Journal of Maps 2011, 18–30. [Map in pdf format on enclosed CD] Paper III Margold, M., Jansson, K.N., Kleman, J., Stroeven, A.P. (2011): Glacial meltwater features of central British Columbia, Canada. Journal of Maps 2011, 486–506. [Map in pdf format on enclosed CD] Paper IV...
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