Topographic controls on the surging behaviour of Sabche Glacier, Nepal (1967 to 2017)
Topographic controls on the surging behaviour of Sabche Glacier, Nepal (1967 to 2017)
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DOI：
10.1016/j.rse.2018.03.036
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发表时间：
2018-06
影响因子：
13.5
通讯作者：
A. Lovell;J. Carr;C. Stokes
中科院分区：
文献类型：
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作者：
A. Lovell;J. Carr;C. Stokes
利用1967年至2017年的Landsat，Pléiades和CORONA卫星图像，我们绘制了Sabche冰川终点位置，冰面速度和表面高程的变化，并报告了尼泊尔中部涌动行为的首次观测结果。我们的观测表明，在过去的50年里，萨布切冰川激增了四倍。最近的三次激增发生在10至11年的周期，这是有记录以来最短的激增周期之一。对最近一次激增（2012年以后）的详细分析表明，冰川前进了2.2公里，最大速度为1.6 ± 0.10米/天。在这一过程中，冰川末端的地表高度增加了90 ± 6.19 m a−1，相应的地表高度下降了10 ± 6.19 m a−1至60 ± 6.19 m a− 1.3 km。这种质量转移的体积约为2.7 × 107± 0.1 × 107 m3 a −1。Sabche冰川是在喜马拉雅山脉中部观察到的第一个浪涌型冰川，但这与先前的全球分析一致，该分析表明该地区应该存在浪涌型冰川。我们假设，激增至少部分地控制了冰下地形，从而一个主要的冰下overdeepening和收缩3公里的终点冰川提供了阻力，冰川流动的积累区消融区。这种过度加深似乎在储存物质，直到越过一个门槛，之后冰川流出冰下洼地，迅速越过基岩唇，沿着山谷向下涌动。因此，虽然激增可能是促进冰下过程（如冰下水文和/或基础热制度的变化），冰川的地形设置似乎调制的时间和持续时间的每一个浪涌。
Using a combination of Landsat, Pléiades and CORONA satellite imagery from 1967 to 2017, we map changes in the terminus position, ice surface velocity and surface elevation of Sabche Glacier, and report the first observations of surging behaviour in central Nepal. Our observations show that Sabche Glacier surged four times over the last 50 years. The three most recent surges occurred at 10 to 11-year cycles, which is one of the shortest surge cycles ever recorded. Detailed analysis of the most recent surge (2012 onwards), indicates that the glacier advanced 2.2 km and experienced maximum velocities of 1.6 ± 0.10 m day−1. During this surge, there was a surface elevation gain at the terminus of up to 90 ± 6.19 m a−1, with a corresponding surface lowering of between 10 ± 6.19 and 60 ± 6.19 m a−1, 3 km up-glacier of the terminus. This transfer of mass amounted to a volume of ~2.7 × 107± 0.1 × 107m3a−1. Sabche Glacier is the first surge-type glacier to be observed in the central Himalayas, but this is consistent with a previous global analysis which indicates that surge-type glaciers should exist in the region. We hypothesise that the surge is at least partially controlled by subglacial topography, whereby a major subglacial overdeepening and constriction 3 km up-glacier of the terminus provides resistance to glacier flow from the accumulation area to the ablation area. This overdeepening appears to store mass until a threshold is crossed, after which the glacier flows out of the subglacial depression and rapidly surges over a bedrock lip and down the valley. Thus, whilst the surges are likely to be facilitated by subglacial processes (e.g. changes in subglacial hydrology and/or basal thermal regime), the topographic setting of the glacier appears to be modulating both the timing and duration of each surge.