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Study on formation mechanism and expansion mechanism of a moraine-dammed glacier lake

冰碛坝冰川湖形成机制及扩张机制研究

基本信息

批准号：
13573004
负责人：
YAMADA Tomomi
金额：
$ 7.23万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13573004/
关键词：
Nepal Bhutan Himalayas Imja Glacier Lake Lugge Glacier Lake Moraine-dammed glacier lake moraine debris-covered glacier calving glacier lake outburst flood 氷河湖の形成機構氷河湖の発達機構ネパールヒマラヤブータンヒマラヤ氷河湖台帳氷河期モレーン堰き止め湖 GLOF 氷河地下水

项目摘要

Supra-glacial lakes have been formed on the debris covered ablation area of shrinking large valley glaciers in the southern and northern slopes of Great Himalayas in this half century, maybe due to the recent global warming. Since the lake was dammed by unstable moraines, a glacier lake outburst flood (GLOF) is frequently happened and a serious disaster is generated along down stream. The GLOF newly appears as the new face of natural disaster in the Himalayan countries. Once the lake was formed, its expansion is quite high rate. The lake is not simultaneously formed on all the glaciers : it is born on one glacier but not on the neighbor glacier, though they are situated under the same climatic and morphological condition. For predicting lake formation and its rapid growth, formation and expansion mechanism were studied.Underground water basin is formed in the ablation area of a valley glacier and bounded by impermeable moraine. After lowering surface arrives at the water table, stable … More ponds appear on the glacier surface expanding ponds connect each other and finally grow up to a lake. Surface lowering rate of the ablation area depends on surface mass balance and surface level change derived from glacier dynamics. The negative mass balance / the emergence velocity in the compressive pressure field, which are common at the ablation area, make the surface lowering / uplifting, respectively. Such a glacier that the surface debris is thinner, the altitude of the ablation area is lower and more numbers of pond and exposed ice beside it, which usually develop on the ablation area, have advantage for the surface lowering because of more negative surface mass balance. More gentle inclination of the ablation area, the less emergence velocity, i.e., less surface uplift. Those conditions are deferent from each glacier. A glacial lake is first created on such a particular glacier as the surface lowering rate is higher than the other glaciers even though they are in the same climatic condition.It is found that large expansion rate of the lake is attributed to the active calving of the ice cliff, which is formed in the glacier terminus and directly contact with the up-lake end Surface lake water warmed up by sun radiation is transported into the ice cliff by stable valley wind and melts the ice cliff under the water, effectively the cliff scooped out is collapsed and fall into the lake. This mechanism makes the lake expansion and the glacier rapidly retreat, efficiently. On the other hand, bottom ice under the lake melts away by lake water of 2〜3℃ and lake deepens. Investigation of heat budget of the lake proves that heat energy to melt floating ice, produced by calving, and bottom ice is mainly supplied by sun radiation absorbed in lake-surface with low albedo.Results of the study was already published in 3 English reports and 3 Japanese repots. Less

半个世纪以来，在喜马拉雅山南坡和北方的大型河谷冰川消融区的碎屑覆盖下，形成了冰上湖泊，这可能与全球气候变暖有关。由于冰碛物的不稳定性，冰湖溃决洪水频繁发生，给下游沿着造成严重的灾害。冰川下的洪水是喜马拉雅地区国家自然灾害的新面孔。湖泊一旦形成，其扩张速度相当快。湖泊不是同时在所有冰川上形成的：它是在一个冰川上形成的，而不是在相邻的冰川上形成的，尽管它们位于相同的气候和形态条件下。为了预测湖泊的形成和快速增长，研究了湖泊的形成和扩展机制。下降面到达地下水位后，稳定 ...更多信息冰川表面出现池塘，不断扩大的池塘相互连接，最后形成湖泊。消融区的地表下降速率取决于冰川动力学引起的地表物质平衡和地表水位变化。在烧蚀区普遍存在的负质量平衡和压缩压力场中的出露速度分别使地表下降和抬升。冰川表面碎屑较薄、消融区海拔较低、消融区附近形成较多的冰池和露冰，有利于消融区表面物质负平衡的降低。烧蚀区域的倾斜度越小，出现速度越小，即，地表隆起较少。这些条件是不同的从每个冰川。在同一气候条件下，由于冰川的表面积下降速率大于其他冰川，因而形成了冰湖，冰湖的大幅度扩张是由于冰崖的主动崩解，它形成于冰川末端，直接与上游接触，湖端受太阳辐射加热的表层湖水被稳定的谷风输送到冰崖中，融化水下的冰崖，有效地将挖出的冰崖崩塌并坠入湖中。这种机制使湖泊扩张和冰川迅速退缩，有效。另一方面，湖底冰被2 ~ 3℃的湖水融化，湖水加深。通过对该湖热量收支的研究，证明了融化浮冰、冰解产生的浮冰和底冰所需的热能主要来自于湖面吸收的太阳辐射，而湖水的蒸发系数较低，这一研究结果已在3篇英文报道和3篇日文报道中发表。少