Dynamics of ice flow and sediment transport at a polythermal glacier terminus: Storglaciaren, Sweden

Thumbnail Image
Date
2009-01-01
Authors
Major Professor
Advisor
Neal R. Iverson
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Altmetrics
Authors
Person
Moore, Peter
Adjunct Assistant Professor
Research Projects
Organizational Units
Organizational Unit
Geological and Atmospheric Sciences

The Department of Geological and Atmospheric Sciences offers majors in three areas: Geology (traditional, environmental, or hydrogeology, for work as a surveyor or in mineral exploration), Meteorology (studies in global atmosphere, weather technology, and modeling for work as a meteorologist), and Earth Sciences (interdisciplinary mixture of geology, meteorology, and other natural sciences, with option of teacher-licensure).

History
The Department of Geology and Mining was founded in 1898. In 1902 its name changed to the Department of Geology. In 1965 its name changed to the Department of Earth Science. In 1977 its name changed to the Department of Earth Sciences. In 1989 its name changed to the Department of Geological and Atmospheric Sciences.

Dates of Existence
1898-present

Historical Names

  • Department of Geology and Mining (1898-1902)
  • Department of Geology (1902-1965)
  • Department of Earth Science (1965-1977)
  • Department of Earth Sciences (1977-1989)

Related Units

Journal Issue
Is Version Of
Versions
Series
Abstract

Diverse field measurements and numerical modeling are used to address the problem of ice flow and sediment transport near the transition between cold-based and warm-based ice in a polythermal glacier terminus. With a two-dimensional finite element model, the impacts of different surface boundary conditions on ice flow trajectories are evaluated where ice flows over a slip/no-slip transition. Allowing ice to flow out of the top of the domain---explicitly forbidden in past theoretical treatments of the problem---significantly reduces stresses in the ice surrounding the transition. This modeling strategy was used with criteria for compressive ice fracture and frictional slip on existing fractures to determine conditions under which thrust faulting may occur in a glacier. The results indicate that compressive fracture of ice should be rare in glaciers, although slip is possible on existing fractures that are extensive, properly oriented, and weakened by elevated water pressure. Field measurements of englacial structure, surface and subsurface velocity, temperature, and stress were made at the terminus of Storglaciaren, a small polythermal glacier in northern Sweden. The formation of englacial debris bands in the northern part of the terminus has recently been ascribed to thrust faulting originating at an inferred slip/no-slip transition at the boundary between temperate and cold-based ice. Our field measurements indicate that the basal thermal transition (BTT) does not correspond to a slip/no-slip transition, although it may mark the start of a zone where water freezes to the glacier sole, thereby entraining sediment. Slip over a mostly weak bed beneath the accreted basal sediment limits longitudinal compressive stresses over most of the terminus. In the debris-laden northern part of the terminus, greater resistance to motion due to bed topography locally enhances longitudinal compression and causes upward transport of debris-laden basal ice. This upward transport is not, however, due to thrusting: strain rates are likely at least five orders of magnitude too small for fracture. Instead, structural and sedimentological observations along with stable isotope and tritium compositions in upglacier-dipping debris bands indicate that the debris-band sequence has been overturned by folding. The results highlight the role of studying ice mechanics and kinematics in a glacier terminus to constrain interpretations of glacial structural features and the landforms inherited from them.

Comments
Description
Keywords
Citation
Source
Subject Categories
Copyright
Thu Jan 01 00:00:00 UTC 2009