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Caterpillar‐like ice motion in the ablation zone of the Greenland ice sheet
Author(s) -
Ryser C.,
Lüthi M. P.,
Andrews L. C.,
Catania G. A.,
Funk M.,
Hawley R.,
Hoffman M.,
Neumann T. A.
Publication year - 2014
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
eISSN - 2169-9011
pISSN - 2169-9003
DOI - 10.1002/2013jf003067
Subject(s) - geology , ice stream , ice sheet , meltwater , ice divide , arctic ice pack , fast ice , geomorphology , pancake ice , greenland ice sheet , pressure ridge , deformation (meteorology) , sea ice , snow , climatology , cryosphere , oceanography
Current understanding of ice dynamics predicts that increasing availability and variability of meltwater will have an impact on basal motion and therefore on the evolution and future behavior of the Greenland ice sheet. We present measurements of ice deformation, subglacial water pressure, and surface velocity that show periodic and episodic variations on several time scales (seasonal, multiday, and diurnal). These variations, observed with GPS and sensors at different depths throughout the ice column, are not synchronous but show delayed responses of ice deformation with increasing depth and basal water pressure in antiphase with surface velocity. With the help of a Full‐Stokes ice flow model, these observations are explained as ice motion in a caterpillar‐like fashion. Caused by patches of different basal slipperiness, horizontal stress transfer through the stiff central part of the ice body leads to spatially varying surface velocities and ice deformation patterns. Variation of this basal slipperiness induces characteristic patterns of ice deformation variability that explain the observed behavior. Ice flow in the ablation zone of the Greenland ice sheet is therefore controlled by activation of basal patches by varying slipperiness in the course of a melt season, leading to caterpillar‐like ice motion superposed on the classical shear deformation.