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Glacier detachments and rock-ice avalanches in the Petra Pervogo range, Tajikistan (1973–2019)
Natural Hazards and Earth System Sciences ( IF 4.6 ) Pub Date : 2021-05-05 , DOI: 10.5194/nhess-21-1409-2021
Silvan Leinss , Enrico Bernardini , Mylène Jacquemart , Mikhail Dokukin

Glacier detachments are a rare, but hazardous, phenomenon of glacier instability, whereof only a handful have been documented to date. Common to all known cases is that many million cubic meters of ice detached from the bed of relatively low-angle valley glaciers and turned into long-runout mass flows. Recently, two such detachments were observed in the Petra Pervogo range in Tajikistan. Using a variety of satellite imagery, including Landsat 1–8, Sentinel-2, ASTER, TanDEM-X, WorldView, and Keyhole, we characterized these events and identified in total 17 mass flows involving glacier ice (detachments, ice, and rock-ice avalanches; rock avalanches falling on glaciers) that clustered in four different catchments between 1973 and 2019. The runout distances range from 2 to 19 km, and the largest detached glacier volume was 8.8×106 m3. A total of 11 out of 13 detachments, ice, or rock-ice avalanches occurred between July and September in years with mean annual air temperatures above the trend of the past 46 years. The relatively large number of locally clustered events indicates that the Petra Pervogo range has particularly favorable conditions for glacier instabilities. The images and geology of the region suggest that easily erodible lithologies are widespread. These soft lithologies may be also one reason for the high density of surging glaciers in the Petra Pervogo range and the wider Pamir region. We conclude that high temperatures, combined with soft, fine-grained sediments, may increase the likelihood of mass wasting events and appear to be critical factors facilitating the detachment of entire valley glaciers, whereas such events appear to be relatively robust against earthquakes for our study area. The observed recurrence of mass wasting events make the Petra Pervogo range a potential candidate to witness glacier detachments by field studies.

中文翻译:

塔吉克斯坦佩特拉Pervogo山脉的冰川支流和冰雪崩(1973–2019)

冰川脱离是一种罕见的但危险的冰川不稳定现象,迄今为止,仅有极少数的文献记载。所有已知情况的共同点是,数百万立方米的冰从相对低角度的山谷冰川河床中分离出来,变成了长期存在的质量流。最近,在塔吉克斯坦的佩特拉Pervogo山脉中观察到两个这样的支队。利用包括Landsat 1-8,Sentinel-2,ASTER,TanDEM-X,WorldView和Keyhole在内的各种卫星图像,我们对这些事件进行了特征描述,并确定了涉及冰川冰块(分离,冰块和岩石-冰雪崩;落在冰川上的岩石雪崩)在1973年至2019年之间聚集在四个不同的流域中。径流距离从2到19 km不等,最大的独立冰川体积为8.8×10 6 平方米3。在每年的7月至9月之间,总共发生了13个支队,冰或岩冰雪崩中的11个,平均年气温高于过去46年的趋势。相对大量的局部聚集事件表明,佩特拉Pervogo范围具有冰川不稳定的特别有利条件。该地区的图像和地质表明,容易侵蚀的岩性很普遍。这些软岩性可能也是佩特拉佩尔沃戈山脉和更广泛的帕米尔地区激流冰川高密度的原因之一。我们得出的结论是,高温加上柔软的细颗粒沉积物可能会增加发生质量浪费事件的可能性,并且似乎是促进整个山谷冰川分离的关键因素,而在我们的研究范围内,此类事件似乎相对抗震性强。观测到的大规模消减事件的再次发生使佩特拉Pervogo系列成为通过野外研究见证冰川脱离的潜在候选者。
更新日期:2021-05-06
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