Dilatant till facilitates ice-stream flow in northeast Greenland

We present radio-echo sounding (RES), global positioning system (GPS), and active-source seismic data across the central portion of the Northeast Greenland Ice Stream (NEGIS). NEGIS widens downglacier from a small region of high geothermal flux near the ice divide. Our data reveal high-porosity (40+...

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Bibliographic Details
Published in:Earth and Planetary Science Letters
Main Authors: Christianson, K, Peters, LE, Alley, RB, Anandakrishnan, S, Jacobel, RW, Riverman, KL, Muto, A, Keisling, BA
Format: Article in Journal/Newspaper
Language:English
Published: Elsevier Science Bv 2014
Subjects:
Earth Sciences
Physical Geography and Environmental Geoscience
Glaciology
Greenland
Online Access:https://doi.org/10.1016/j.epsl.2014.05.060
http://ecite.utas.edu.au/103750
Description
Summary:We present radio-echo sounding (RES), global positioning system (GPS), and active-source seismic data across the central portion of the Northeast Greenland Ice Stream (NEGIS). NEGIS widens downglacier from a small region of high geothermal flux near the ice divide. Our data reveal high-porosity (40+%) water-saturated till lubricating the ice stream. Ice accelerates and thins as it flows into NEGIS, producing marginal troughs in surface topography. These troughs create steep gradients in the subglacial hydropotential that generate parallel sticky and slippery bands beneath the shear margins. The low-porosity sticky sediment bands limit ice entrainment across the margins and thus restrict further widening, producing the long, narrow, and relatively stable ice stream. However, the observed relations among surface elevation, basal water routing, broad sedimentary drape, and till dilatancy suggest that rapid shifts in ice dynamics are possible, including rapid transmission of ocean forcing inland. The source and routing of the subglacial till are unclear, but our data help constrain hypotheses.

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