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Retreat pattern and dynamics of glaciers and ice sheets: reconstructions based on meltwater features
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. (Paleoglaciology)
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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 and glaciers, 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 regional ice retreat reconstructions in high-relief 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 as the primary data for mapping glacial meltwater landforms. Following a methods study, reconstructions of the deglacial dynamics are carried out for 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 central Transbaikalia 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.

Deglacial dynamics of the CIS reveals that the ice divide shifted to the Coast Mountains in north-central British Columbia and the eastern ice margin retreated towards the ice divide in late glacial time.

This thesis demonstrates the potential to reconstruct ice retreat patterns and deglacial dynamics at regional scales by interpretation of the meltwater landform record.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University , 2012. , 17 p.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 30
Keyword [en]
Palaeoglaciology, Cordilleran Ice Sheet, deglaciation, glacial meltwater features, glacial lake
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-68958ISBN: 978-91-7447-429-9 (print)OAI: oai:DiVA.org:su-68958DiVA: diva2:474287
Public defence
2012-02-10, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Submitted. Paper 6: Manuscript. Available from: 2012-01-19 Created: 2012-01-09 Last updated: 2012-01-09Bibliographically approved
List of papers
1. Evaluation of data sources for mapping glacial meltwater features
Open this publication in new window or tab >>Evaluation of data sources for mapping glacial meltwater features
2012 (English)In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 33, no 8, 2355-2377 p.Article in journal (Refereed) Published
Abstract [en]

The meltwater system of disintegrating ice sheets provides an important source of information for the reconstruction of ice-retreat patterns during deglaciation. Recent method development in glacial geomorphology, using satellite imagery and digital elevation models (DEMs) for glacial landform mapping, has predominantly been focused on the identification of lineation and other large-scale accumulation features. Landforms created by meltwater have often been neglected in these efforts. Meltwater features such as channels, deltas and fossil shorelines were traditionally mapped using stereo interpretation of aerial photographs. However, during the transition into the digital era, driven by a wish to cover large areas more economically, meltwater features were lost in most mapping surveys. We have evaluated different sets of satellite images and DEMs for their suitability to map glacial meltwater features (lateral meltwater channels, eskers, deltas, ice-dammed lake drainage channels and fossil shorelines) in comparison with the traditional mapping from aerial photographs. Several sets of satellite images and DEMs were employed to map the landform record of three reference areas, located in northwestern Scotland, northeastern Finland and western Sweden. The employed satellite imagery consisted of Landsat 7 Enhanced Thematic Mapper Plus (ETM+), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Satellite Pour l’Observation de la Terre (SPOT) 5 and Indian Remote Sensing (IRS)1C, and the DEMs used were from NEXTMap Britain, Panorama, National elevation data set of Sweden and National Land Survey of Finland. ASTER images yielded better results than the panchromatic band of Landsat 7 ETM+ in all three regions, despite the same spatial resolution of the data. In agreement with previous studies, this study shows that DEMs display accumulation features such as eskers suitably well. Satellite images are shown to be insufficiently detailed for the interpretation of smaller features such as meltwater channels. Hence, satellite imagery and DEMs of intermediate resolution contain meltwater system information only at a general level that allows for the identification of landforms of medium to large sizes. It is therefore pertinent that data with an appropriate spatial and spectral resolution are accessed to fulfil the need of a particular mapping effort. Stereointerpretation of aerial photographs continues to be an advisable method for local meltwater system reconstructions; alternatively, it can be replaced by mapping fromhigh-resolution DEMs such as NEXTMap Britain. For regional to sub-continental reconstructions, the use of ASTER satellite imagery is recommended, because it provides both spectral and spatial resolutions suitable for the identification of meltwater features on a medium to large scale.

National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-67391 (URN)10.1080/01431161.2011.608738 (DOI)000302162700002 ()
Available from: 2011-12-28 Created: 2011-12-28 Last updated: 2017-12-08Bibliographically approved
2. Glacial geomorphology and glacial lakes of central Transbaikalia, Siberia, Russia
Open this publication in new window or tab >>Glacial geomorphology and glacial lakes of central Transbaikalia, Siberia, Russia
2011 (English)In: Journal of Maps, ISSN 1744-5647, 18-30 p.Article in journal (Refereed) Published
Abstract [en]

A glacial geomorphological map is presented covering the poorly investigated mountainous region ofcentral Transbaikalia, Russia. Interpretation of geomorphology is achieved using remotely sensed data (SRTM digital elevation model, Landsat 7 ETM+ satellite imagery and Google Maps). Glacially modified terrain is mapped together with moraines, glacial lineations and meltwater channels, in order to provide an estimate of the area affected by glaciation. The glacial landform record varies across the mapped region implying that the character of glaciation was not uniform in the area. Several moraine generations occur in the main valleys and at some places glaciers blocked the drainage routes, which resulted in the formation of glacial lakes. The largest, Glacial Lake Vitim, was dammed by a glacier lobe blocking the Vitim valley in the Kodar Range. A distinct fossil shoreline of Glacial Lake Vitim occurs along a substantial part of the former shore at a level of 840 m a.s.l. A col through which the lake drained to the River Nercha occurs at an elevation consistent with the shoreline level of 840 m a.s.l. The existence of another glacial lake in the Chara basin is inferred from mapped delta surfaces and a probable blockage of the Chara River by advancing valley glaciers. The rich and diverse geomorphology and the sedimentary record of glacial lakes represent a potential for more detailed studies of the glacial and climate history of this remote region.

National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-67383 (URN)10.4113/jom.2011.1132 (DOI)000290233500003 ()
Note
authorCount :2Available from: 2011-12-28 Created: 2011-12-28 Last updated: 2012-01-09Bibliographically approved
3. Glacial meltwater landforms of central British Columbia
Open this publication in new window or tab >>Glacial meltwater landforms of central British Columbia
2011 (English)In: Journal of Maps, ISSN 1744-5647, 486-506 p.Article in journal (Refereed) Published
Abstract [en]

The Cordilleran Ice Sheet (CIS), which grew and melted repeatedly across the mountain ranges of westernmost Canada during the late Cenozoic, has imprinted its legacy in the form of glacial landforms, such as meltwater landforms. However, despite their abundance, a coherent effort to map meltwater landforms has been lacking. Here, we present a first regional geomorphological map of glacial meltwater landforms of central British Columbia. Series of well-developed meltwater channels occur at higher elevations on the Interior Plateau, in marginal ranges east of the Coast Mountains, in the Skeena and Omineca mountains, and, in much lower abundances, in the Rocky Mountains. Single-ridged eskers, that in direction are consistent with the regional ice flow direction from glacial lineations, occur in elevated areas of the Interior Plateau. Multiple-ridged larger eskers and esker complexes are, on the other hand, confined to the main topographic lows. The geographical distribution of meltwater landforms is a new reliable dataset for use in palaeoglaciological reconstructions and inference of late glacial ice sheet dynamics in central British Columbia.

National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-67387 (URN)10.4113/jom.2011.1205 (DOI)
Available from: 2011-12-28 Created: 2011-12-28 Last updated: 2012-01-09Bibliographically approved
4. Glacial Lake Vitim, a 3000 km³ outburst flood from Siberia to the Arctic Ocean
Open this publication in new window or tab >>Glacial Lake Vitim, a 3000 km³ outburst flood from Siberia to the Arctic Ocean
2011 (English)In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 76, no 3, 393-396 p.Article in journal (Refereed) Published
Abstract [en]

A prominent lake formed when glaciers descending from the Kodar Range blocked the River Vitim in central Transbaikalia, Siberia. Glacial Lake Vitim, evidenced by palaeoshorelines and deltas, covered 23,500 km2 and held a volume of ~3000 km3. We infer that a large canyon in the area of the postulated ice dam served as a spillway during an outburst flood that drained through the rivers Vitim and Lena into the Arctic Ocean. The inferred outburst flood, of a magnitude comparable to the largest known floods on Earth, possibly explains a freshwater spike at ~13 cal ka BP inferred from Arctic Ocean sediments.

Keyword
Glacial lake outburst flood (GLOF), Freshwater influx, Transbaikalia, Ice-dammed lake
National Category
Physical Geography Geosciences, Multidisciplinary Climate Research Geology
Research subject
Quarternary Geology; Physical Geography
Identifiers
urn:nbn:se:su:diva-67379 (URN)10.1016/j.yqres.2011.06.009 (DOI)000296672100011 ()
Available from: 2012-11-19 Created: 2011-12-28 Last updated: 2017-12-08Bibliographically approved
5. Late-glacial retreat pattern of the Cordilleran Ice Sheet in central British Columbia reconstructed from glacial meltwater landforms
Open this publication in new window or tab >>Late-glacial retreat pattern of the Cordilleran Ice Sheet in central British Columbia reconstructed from glacial meltwater landforms
Show others...
(English)Article in journal (Refereed) Submitted
Abstract [en]

The Cordilleran Ice Sheet (CIS) covered much of the mountainous northwestern part of North America during Pleistocene glaciations. In contrast to other ephemeral Pleistocene ice sheets, the pattern and timing of growth and decay of the CIS are poorly understood. Here, we present a reconstruction of the pattern of late-glacial ice sheet retreat in central British Columbia based on a palaeoglaciological interpretation of ice-marginal meltwater channels, eskers, and deltas mapped from satellite imagery and digital elevation models. A consistent spatial pattern of high-elevation ice-marginal meltwater channels (1600-2400 m a.s.l.) occurs across central British Columbia. They indicate the presence of ice domes over the Skeena Mountains and the central Coast Mountains early during deglaciation. Ice sourced in the Coast Mountains remained dominant over the southern and east-central parts of the Interior Plateau during late-glacial time. Our reconstruction shows a successive westward retreat of the ice margin away from the western foot of the Rocky Mountains, accompanied by the formation and rapid evolution of a glacial lake in the upper Fraser River basin. Final stages of deglaciation were characterized by the frontal retreat of ice lobes through the valleys of the Skeena and Omineca mountains and by the formation of large esker systems in the most prominent topographic lows of the Interior Plateau. We conclude that the CIS underwent a large-scale reconfiguration early during deglaciation and subsequently diminished by thinning and complex frontal retreat towards the Coast Mountains.

Keyword
Cordilleran Ice Sheet, ice retreat pattern, deglaciation, glacial meltwater landforms
National Category
Physical Geography Geology Climate Research Geosciences, Multidisciplinary
Research subject
Quarternary Geology; Physical Geography
Identifiers
urn:nbn:se:su:diva-68954 (URN)
Available from: 2012-01-09 Created: 2012-01-09 Last updated: 2012-01-09Bibliographically approved
6. Late-glacial ice dynamics of the Cordilleran Ice Sheet in northern British Columbia and southern Yukon Territory: retreat pattern of the Liard Lobe reconstructed from the glacial landform record
Open this publication in new window or tab >>Late-glacial ice dynamics of the Cordilleran Ice Sheet in northern British Columbia and southern Yukon Territory: retreat pattern of the Liard Lobe reconstructed from the glacial landform record
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The Liard Lobe formed a part of the northeastern sector of the Cordilleran Ice Sheet and drained ice from accumulation areas in the Selwyn, Pelly, Cassiar and Skeena mountains. This study reconstructs the ice retreat pattern of the Liard Lobe during the last deglaciation from the glacial landform record that is comprised of glacial lineations and landforms of the meltwater system such as eskers, meltwater channels, perched deltas and outwash fans. The spatial distribution of these landforms defines the successive configurations of the ice sheet during the deglaciation. The Liard Lobe retreated to the west and southwest across the Hyland Highland from its local Last Glacial Maximum position in the southeastern Mackenzie Mountains where it coalesced with the Laurentide Ice Sheet. The retreat across the Liard Lowland and a subsequent splitting of the thus far uniform ice surface into several ice lobes is evidenced by large esker complexes that stretch across the Liard Lowland cutting across the contemporary drainage network. Ice margin positions from the late stage of deglaciation are reconstructed locally at the foot of the Cassiar Mountains and farther up-valley in an eastern facing valley of the Cassiar Mountains. The presented landform record indicates that the deglaciation of the Liard Lobe was accomplished mainly by active ice retreat and that ice stagnation did not play a significant role in the deglaciation of this region.

National Category
Physical Geography Geology Climate Research Geosciences, Multidisciplinary
Research subject
Physical Geography; Quarternary Geology
Identifiers
urn:nbn:se:su:diva-68957 (URN)
Available from: 2012-01-09 Created: 2012-01-09 Last updated: 2012-01-09Bibliographically approved

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