On the mechanics of ice-stream shear margins

被引:58
作者
Schoof, C [1 ]
机构
[1] Univ British Columbia, Dept Earth & Ocean Sci, Vancouver, BC V6T 1Z4, Canada
关键词
D O I
10.3189/172756504781830024
中图分类号
P9 [自然地理学];
学科分类号
0705 ; 070501 ;
摘要
We investigate the mechanics of ice-stream shear margins based oil the assumption that the underlying bed behaves plastically Sliding is assumed to occur if a prescribed, locally defined yield stress is attained, while no sliding is assumed possible if basal shear stress is lower than the yield stress. Mathematically, the ice-flow problem takes the form of a contact problem, in which the zones of sliding are part of the solution and cannot be prescribed arbitrarily Simplistic assumptions about the location of till failure, or about mechanical conditions at the bed, predict stress singularities at the margins which lead to corresponding singularities in the basal melt rate. The ice-flow problem is solved using a complex variable method, and an associated quasi-static thermal problem is also solved using a Green's function. High stress concentrations, which coincide with high rates of strain heating, are found on the ice-stream side of the margins, where basal melting is also greatest. Our results further indicate that a temperate zone may form over time above the bed in the margins. These findings differ from earlier studies based on different sliding laws, suggesting a high sensitivity of margin behaviour to basal conditions.
引用
收藏
页码:208 / 218
页数:11
相关论文
共 33 条
[11]  
Gillow K., 1998, Ph.D. thesis
[12]   Measurement of temperature in a margin of Ice Stream B, Antarctica: implications for margin migration and lateral drag [J].
Harrison, WD ;
Echelmeyer, KA ;
Larsen, CF .
JOURNAL OF GLACIOLOGY, 1998, 44 (148) :615-624
[13]   Rheology of till beneath Storglaciaren, Sweden [J].
Hooke, RL ;
Hanson, B ;
Iverson, NR ;
Jansson, P ;
Fischer, UH .
JOURNAL OF GLACIOLOGY, 1997, 43 (143) :172-179
[14]   ON THE DISTRIBUTION OF STRESS AND VELOCITY IN AN ICE STRIP, WHICH IS PARTLY SLIDING OVER AND PARTLY ADHERING TO ITS BED, BY USING A NEWTONIAN VISCOUS APPROXIMATION [J].
HUTTER, K ;
OLUNLOYO, VOS .
PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, 1980, 373 (1754) :385-403
[15]  
ISAACSON E, 1966, ANAL NUMERICAL METHO
[16]   Coupling between a glacier and a soft bed: I. A relation between effective pressure and local sheer stress determined from till elasticity [J].
Iverson, NR ;
Baker, RW ;
Hooke, RL ;
Hanson, B ;
Jansson, P .
JOURNAL OF GLACIOLOGY, 1999, 45 (149) :31-40
[17]   Ring-shear studies of till deformation: Coulomb-plastic behavior and distributed strain in glacier beds [J].
Iverson, NR ;
Hooyer, TS ;
Baker, RW .
JOURNAL OF GLACIOLOGY, 1998, 44 (148) :634-642
[18]  
Jackson R, 1997, CARDIOVASC RISK FACT, V7, P43
[19]   Thermal effects on the location of ice stream margins [J].
Jacobson, HP ;
Raymond, CE .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1998, 103 (B6) :12111-12122