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Derivation of deformation characteristics in fast-moving glaciers

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Title: Derivation of deformation characteristics in fast-moving glaciers
Authors: Herzfeld, Ute C. Browse this author
Clarke, Garry K. C. Browse this author
Mayer, Helmut Browse this author
Greve, Ralf Browse this author →KAKEN DB
Issue Date: Apr-2004
Publisher: Elsevier
Journal Title: Computers & Geosciences
Volume: 30
Issue: 3
Start Page: 291
End Page: 302
Publisher DOI: 10.1016/j.cageo.2003.10.012
Abstract: Crevasse patterns are the writings in a glacier’s history book – the movement, strain and deformation frozen in ice. Therefore by analysis of crevasse patterns we can learn about the ice-dynamic processes which the glacier has experienced. Direct measurement of ice movement and deformation is time-consuming and costly, in particular for large glaciers; typically, observations are lacking when sudden changes occur. Analysis of crevasse patterns provides a means to reconstruct past and ongoing deformation processes mathematically. This is especially important for fast-moving ice. Ice movement and deformation are commonly described and analyzed using continuum mechanics and measurements of ice velocities or strain rates. Here, we present a different approach to the study of ice deformation based on principles of structural geology. Fast ice movement manifests itself in the occurrence of crevasses. Because crevasses remain after the deformation event and may be transported, overprinted or closed, their analysis based on aerial videography and photography or satellite data gives information on past deformation events and resulting strain states. In our treatment, we distinguish (A) continuously fastmoving glaciers and ice streams, and (B) surge-type glaciers, based on observations of two prototypes, Jakobshavns Isbræ, Greenland, for (A), and Bering Glacier, Alaska, during the 1993-1995 surge, for (B). Classes of ice-deformation types are derived from aerial images of ice surfaces using structural geology, i.e. structural glaciology. For each type, the deformation gradient matrix is formed. Relationships between invariants used in structural geology and continuum mechanics and the singular value decomposition are established and applied to ice-surface classification. Deformation during a surge is mostly one of the extensional deformation types. Continuously, or infinitesimally repeated, deformation acting in continuously fast-moving ice causes different typical crevasse patterns. The structural-geology approach also includes a way to treat the problem of shear, as observed in the margins of fast-moving ice streams within slow-moving surrounding ice. In this paper we provide the first link between a physical analysis of ice-surface deformation and a connectionist-geostatistical analysis of the same problem.
Type: article (author version)
Appears in Collections:低温科学研究所 (Institute of Low Temperature Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: Greve Ralf

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