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Shear heating and weakening of the margins of West Antarctic ice streams
Author(s) -
Perol Thibaut,
Rice James R.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl063638
Subject(s) - geology , ice wedge , ice stream , shear stress , shear (geology) , geomorphology , streams , ice sheet , geotechnical engineering , petrology , climatology , sea ice , permafrost , materials science , cryosphere , oceanography , composite material , computer network , computer science
Ice streams are fast flowing bands of ice separated from stagnant ridges by shear margins. The mechanisms controlling the location of the margins remain unclear. We use published ice deformation data and a simple one‐dimensional thermal model to show that West Antarctic ice stream margins have temperate ice over a substantial fraction of their thickness, a condition that may control their width. The model predicts a triple‐valued relation between the thickness‐averaged lateral shear stress and the lateral shear strain rate. Observed strain rates at the margins imply that they support slightly less lateral shear stress than adjacent ice within the stream. This requires enhanced basal resistance near the margin. We suggest, in agreement with the limited observations, the presence of a channelized drainage system at the margin that reduces the pore fluid pressure at the ice‐till interface, thus increasing the shear stress acting on the yielding Coulomb plastic bed.