TY - JOUR
T1 - Dilatant till facilitates ice-stream flow in northeast Greenland
AU - Christianson, Knut
AU - Peters, Leo E.
AU - Alley, Richard B.
AU - Anandakrishnan, Sridhar
AU - Jacobel, Robert W.
AU - Riverman, Kiya L.
AU - Muto, Atsuhiro
AU - Keisling, Benjamin A.
N1 - Funding Information:
The U.S. National Science Foundation (grant OPP-0424589 ) funded this work. UNAVCO provided GPS base station data. CH2MHILL Polar Services, the New York Air National Guard, Kenn Borek Air, the Alfred Wegener Institute for Polar and Marine Research, and the North Greenland Eemain Ice Drilling project provided logistical support. We thank Bernd Kulessa and an anonymous reviewer for comments that improved this manuscript. GMT, QGIS, and the NWRC and Columbia colormaps were used to create figures (licensed under creative commons attribution share-alike 3.0 ( http://creativecommons.org/licenses/by-sa/3.0/deed.en ) from sources http://commons.wikipedia.org/wiki/File:North_Rhine-Westphalia_Topography_01.svg and http://fr.wikipedia.org/wiki/Fichier:Columbia_Mapa_Relieve.svg , respectively).
PY - 2014/9/1
Y1 - 2014/9/1
N2 - 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.
AB - 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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U2 - 10.1016/j.epsl.2014.05.060
DO - 10.1016/j.epsl.2014.05.060
M3 - Article
AN - SCOPUS:84902455514
SN - 0012-821X
VL - 401
SP - 57
EP - 69
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -