FAST TIDEWATER GLACIERS
FAST TIDEWATER GLACIERS
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DOI：
10.1029/jb092ib09p09051
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发表时间：
1987-08-10
期刊：
影响因子：
--
通讯作者：
POST, A
中科院分区：
文献类型：
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作者：
MEIER, MF;POST, A
一些冰山崩解的出口冰川以通常与汹涌的冰川相关的速度持续流动，并表现出与海洋冰盖建议的情况有关的极不稳定的情况。已知没有温带潮水冰川有漂浮的末端，但许多极地和亚极地潮水冰川有。温带崩解冰川的快速流动几乎完全是由于底部滑动，似乎是床上的有效压力(可能接近于零)和末端的纵向背应力的函数。冰川的末端边界条件(崩解关系)尚不完全清楚，但对这些冰川的动态来说是至关重要的。搁浅的潮水冰川的崩解关系已经在经验基础上提出，但没有经过严格的检验；漂浮终端的崩解关系几乎是未知的。这一点，再加上对底部滑动的不完善理解，抑制了我们对这些冰川稳定性的理解的信心。哥伦比亚冰川(阿拉斯加)是一个具有启发性的例子，因为在不到10年的时间里，人们已经观察到了它的几何形状、崩解速度和动态发生的重大变化。崩解通量的增加比冰川通量的增加更快，导致冰川变薄和退缩，导致冰川速度显著增加。短期的流速变化与背压的变化(冰退、潮汐变化)和注入到床上的水的流量有关。这些结果与冰川底部滑动、冰川涌动和海洋冰川稳定性的机制有关。
Some iceberg‐calving outlet glaciers flow continuously at speeds normally associated with surging glaciers arid exhibit dramatic instability scenarios related to those suggested for marine ice sheets. No temperate tidewater glaciers are known to have floating termini, but many polar and subpolar tidewater glaciers do. The fast flow of temperate calving glaciers is almost entirely due to basal sliding and appears to be a function of the effective pressure on the bed, which may approach zero, and the longitudinal back stress on the terminus. The terminus boundary condition (the calving relation) is imperfectly known yet is vital to the dynamics of these glaciers. Calving relations for grounded tidewater glaciers have been suggested on empirical grounds but have not been rigorously tested; the calving relations for floating termini are virtually unknown. This, together with the imperfect understanding of basal sliding, inhibits confidence in our understanding of the stability of these glaciers. Columbia Glacier (Alaska) is an instructive example because observations have been made on the major changes in its geometry, calving rate, and dynamics that have occurred in less than 10 years. The calving flux has increased more rapidly than the glacier flux, causing thinning and retreat; as a result, the ice velocity has increased markedly. The short‐term velocity changes relate to changes in back pressure (ice recession, tidal changes) and the flux of water injected to the bed. These results have relevance to the mechanisms of basal sliding, glacier surges, and the stability of marine ice streams.