Journal
JOURNAL OF GLACIOLOGY
Volume 57, Issue 201, Pages 39-52Publisher
INT GLACIOL SOC
DOI: 10.3189/002214311795306619
Keywords
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Funding
- US National Science Foundation (NSF) [OPP9615417, OPP0083132, OPP0636996, OPP9615502, OPP9615454, OPP 0636795]
- NSF
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We used observations and modeling of Sip le Dome, West Antarctica, a ridge ice divide, to infer the importance of linear deformation mechanisms in ice-sheet flow. We determined the crossover stress (a threshold value of the effective deviatoric stress below which linear flow mechanisms dominate over nonlinear flow mechanisms) by combining measurements of ice properties with in situ deformation rate measurements and a finite-element ice flow model that accounts for the effects of viscous anisotropy induced by preferred crystal-orientation fabric. We found that a crossover stress of 0.18 bar produces the best match between predicted and observed deformation rates. For Sip le Dome, this means that including a linear term in the flow law is necessary, but generally the flow is still dominated by the nonlinear (Glen; n = 3) term. The pattern of flow near the divide at Sip le Dome is also strongly affected by crystal fabric. Measurements of sonic velocity, which is a proxy for vertically oriented crystal fabric, suggest that a bed-parallel shear band exists several hundred meters above the bed within the Ice Age ice.
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