Glacial erosion: status and outlook
Glacial erosion: status and outlook
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DOI：
10.1017/aog.2019.38
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发表时间：
2019-12-01
影响因子：
2.9
通讯作者：
Zoet, L. K.
中科院分区：
文献类型：
--
作者：
Alley, R. B.;Cuffey, K. M.;Zoet, L. K.
冰川侵蚀速率在多个数量级之间变化，这种变化的大部分不能归因于基础滑动速率。冰下土起着润滑“断层泥”或“锯末”的作用，必须清除冰下基岩的快速侵蚀。这种侵蚀发生的地方和时候尤其如此，特别是当来自于模盆的水流进入河床，并且不受过冷或其他过程的限制时。溪流也可能直接侵蚀基岩，很可能具有强烈的时间演化。侵蚀主要是由采石造成的，由变化不定的地表融化和冰下地震引起的水系剧烈波动也起到了辅助作用。碎屑床摩擦对磨蚀、采石和一般冰川流动有显著影响。当冬季冷空气进入bergschrunds时，冻胀会导致环形顶壁的侵蚀，产生温度梯度，推动水流沿着预融化的薄膜流向生长的冰透镜，从而破裂岩石，冰川将产生的冰块移走。在许多情况下，最近的冰下基岩侵蚀和沉积物通量远高于长期平均值。在冰期旋回中，冰谷形式的演变对侵蚀和沉积有强烈的反馈作用。其中大部分都没有得到很好的量化，部分还有待商榷。冰川侵蚀和相互作用对构造和火山过程以及气候和生物地球化学通量都很重要，这激发了积极的研究。
Glacier-erosion rates range across orders of magnitude, and much of this variation cannot be attributed to basal sliding rates. Subglacial till acts as lubricating 'fault gouge' or 'sawdust', and must be removed for rapid subglacial bedrock erosion. Such erosion occurs especially where and when moulin-fed streams access the bed and are unconstrained by supercooling or other processes. Streams also may directly erode bedrock, likely with strong time-evolution. Erosion is primarily by quarrying, aided by strong fluctuations in the water system driven by variable surface melt and by subglacial earthquakes. Debris-bed friction significantly affects abrasion, quarrying and general glacier flow. Frost heave drives cirque headwall erosion as winter cold air enters bergschrunds, creating temperature gradients to drive water flow along premelted films to growing ice lenses that fracture rock, and the glacier removes the resulting blocks. Recent subglacial bedrock erosion and sediment flux are in many cases much higher than long-term averages. Over glacial cycles, evolution of glacial-valley form feeds back strongly on erosion and deposition. Most of this is poorly quantified, with parts open to argument. Glacial erosion and interactions are important to tectonic and volcanic processes as well as climate and biogeochemical fluxes, motivating vigorous research.