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AGU: Geophysical Research Letters

 

Keywords

  • glaciology
  • cryoshere
  • seismology

Index Terms

  • Cryosphere: Glaciology
  • Cryosphere: Dynamics
  • Cryosphere: Ice streams
  • Cryosphere: Tundra
  • Exploration Geophysics: Seismic methods

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L10501, 6 PP., 2008
doi:10.1029/2008GL033712

Complex fabric development revealed by englacial seismic reflectivity: Jakobshavn Isbræ, Greenland

H. J. Horgan

Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania, USA

S. Anandakrishnan

Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania, USA

R. B. Alley

Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania, USA

L. E. Peters

Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania, USA

G. P. Tsoflias

Department of Geology, University of Kansas, Lawrence, Kansas, USA

D. E. Voigt

Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania, USA

J. P. Winberry

Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania, USA

High-resolution reflection seismic data from Jakobshavn Isbræ, Greenland, reveal complex fabric development. Abundant englacial reflectivity occurs for approximately half the thickness of the ice (the lower half), and disruption of the englacial reflectors occurs in the lower 10–15% of the ice-thickness. These depths correspond to the higher impurity-content, and more easily deformed, ice from the Younger Dryas and Last Glacial Maximum to Stage-3. We conclude that the reflectivity results from contrasting seismic velocities due to changes in the crystal orientation fabric of the ice, and suggest that these fabric changes are caused by variations in impurity loading and subsequent deformation history. These findings emphasize the difference between ice-divide and ice-stream crystal orientation fabrics and have implications for predictive ice sheet modeling.

Received 19 February 2008; accepted 17 April 2008; published 21 May 2008.

Citation: Horgan, H. J., S. Anandakrishnan, R. B. Alley, L. E. Peters, G. P. Tsoflias, D. E. Voigt, and J. P. Winberry (2008), Complex fabric development revealed by englacial seismic reflectivity: Jakobshavn Isbræ, Greenland, Geophys. Res. Lett., 35, L10501, doi:10.1029/2008GL033712.

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