Experimental determination of a double-valued drag relationship for glacier sliding
Experimental determination of a double-valued drag relationship for glacier sliding
复制标题
冰川滑动双值阻力关系的实验确定
作者：
L. Zoet;N. Iverson
冰川对海平面上升的贡献及其对景观演化的影响取决于鲜为人知的冰/床界面滑动速度和阻力之间的关系。用一种新的旋转实验装置进行的实验结果首次从经验上证明了一些滑动理论所提出的双值阻力关系：刚性正弦床上的稳定阻力随着床波背风侧空腔的增长而以越来越高的滑动速度增加、达到峰值和下降。如果空腔延伸到冰川上面向表面的拐点之外，则阻力随滑动速度的增加而减小，因此与冰接触的不利床坡随着空腔的进一步增长而减小。这些结果表明，由于天气或气候变化导致的滑动速度增加，冰川床上的剪切力可能会减少，从而需要更大的应变率来产生阻力应力，从而促进冰川更快的运动。虽然双值阻力关系还没有在真实冰川床的复杂几何形状中得到证明，但其潜在的主要含义和真实冰川床上凸起的特征凸应力面都为在冰盖模型中探索这种关系的影响提供了刺激。
Abstract The contribution of glaciers to sea-level rise and their effects on landscape evolution depend on the poorly known relationship between sliding speed and drag at the ice/bed interface. Results from experiments with a new rotary laboratory device demonstrate empirically for the first time a double-valued drag relationship like that suggested by some sliding theories: steady drag on a rigid, sinusoidal bed increases, peaks and declines at progressively higher sliding speeds due to growth of cavities in the lee sides of bed undulations. Drag decreases with increased sliding speed if cavities extend beyond the inflection points of up-glacier facing surfaces, so that adverse bed slopes in contact with ice diminish with further cavity growth. These results indicate that shear tractions on glacier beds can potentially decrease due to increases in sliding speed driven by weather or climate variability, promoting even more rapid glacier motion by requiring greater strain rates to produce resistive stresses. Although a double-valued drag relationship has not yet been demonstrated for the complicated geometries of real glacier beds, both its potential major implications and the characteristically convex stoss surfaces of bumps on real glacier beds provide stimulus for exploring the effects of this relationship in ice-sheet models.