Accelerating glacier retreat on Yulong mountain, Tibetan Plateau, since the late 1990s
Accelerating glacier retreat on Yulong mountain, Tibetan Plateau, since the late 1990s
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DOI：
10.3189/172756507782202900
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发表时间：
2007
影响因子：
3.4
通讯作者：
H. Pang;Yuanqing He;Ningning Zhang
中科院分区：
文献类型：
--
作者：
H. Pang;Yuanqing He;Ningning Zhang
青藏高原是中低纬度地区冰川最集中的地区。近百年来的气候波动和20世纪80年代以来青藏高原的气候变暖对这些冰川产生了重大影响。冰川退缩对青藏高原及周边地区产生了重大的社会和环境影响。供水变化、冰川湖溃决洪水频发、冰川泥石流灾害、河流水流不稳定等，都对当地人口造成影响。玉龙山位于中国云南丽江以北的横断山脉（青藏高原东南缘），是欧亚大陆最南端的冰川区（图1）。与青藏高原大部分地区的极地/副极地冰川相比，玉龙山上的冰川是典型的温带（海洋）冰川。自1999年以来，人们对该地区的冰川变化进行了调查。玉龙山上最大的冰川是白水一号冰川（BG1），它为白水河流域提供水源，面积1.52平方公里，长2.7公里（蒲，1994）。 1999年起对BG1终点站进行高程监测，结果见表1。根据Li和Su(1996)的资料，1982年BG1终点站海拔为4100m；根据我们的调查，2006 年为 4300m。平均而言，1982年至2006年上升了8.3ma，1999年至2006年上升了14.3ma，即近几年终点站后退率有所增加。该结果与 Dyurgerov (2003) 一致，后者指出全球范围内冰川面积和体积的显着损失，特别是自 20 世纪 80 年代末以来加速。近年来，BG1冷盆地发育大面积裂缝。它们形成于堆积带，但在 1982 年的调查中并未发现。图 2 显示了 2005 年 8 月至 2006 年 4 月期间在 4900ma.s.l. 的 firn 盆地中形成的新裂缝的照片，以及 2006 年 6 月形成的胚胎裂缝。最近形成的裂缝和破裂可能与陡峭且多变的基岩上更快的冰川运动（由于较高的温度）有关。的 20 世纪 90 年代。我们建议在夏季高温时，融雪进入裂缝。然后，重新冻结会导致冰盆地破裂和不稳定，并加速流动。因此，冰川稳定性受到冰雪盆地中发育的裂缝的严重影响。杨公河5号冰川（YG5）注入杨公河（图1）。 YG5面积0.72平方公里，长1.8公里，平衡线高度为4620ma.s.l。 （濮，1994）。 2004 年 3 月 12 日，YG5 发生冰川崩塌事件并伴有小型落石。图3显示了冰川崩塌的位置。 2006年4月21日至5月3日，我们到达塌方现场并对事件进行了调查。残余（即已经部分融化）塌陷冰体呈扇形（图3），根据全球定位系统（GPS）测量，外（弧）长约为870 m，高度为15 m。根据我们的调查并结合地形图，冰川初始断开位置的海拔高度约为4480m。崩塌冰体海拔3700m。因此冰体下降约780m。 4480ma.s.l以下冰川面积冰川面积0.44平方公里，占冰川总面积的61%。 20世纪80年代之前，青藏高原东南部季风温带冰川地区曾报道过一些冰川末期塌陷事件（Li等，1986）。这些事件被认为是冰川涌动现象。然而，2004年玉龙山YG5冰川崩塌事件被认为不是激增，因为崩塌的冰体很大（超过一半的冰川）。根据玉龙山以南25公里丽江气象站1951年至2005年的气温数据，引发崩塌事件的因素之一可能如下。冰川学杂志，卷。 53、181号，2007年
The Tibetan Plateau is the most glacier-concentrated area of the midand low latitudes. Climate fluctuations over the past century and climatic warming since the 1980s on the Tibetan Plateau have had a significant influence on these glaciers. Glacier retreat has significant social and environmental impacts in the Tibetan Plateau and surrounding regions. Water-supply variability, frequent glacial lake outburst flooding, glacial debris-flow hazards, unstable river and stream-flow, etc., all impact on the local population. Yulong mountain, located in the Hengduan range (southeastern edge of the Tibetan Plateau), north of Lijiang, Yunnan province, China, is the southernmost glacierized area of mainland Eurasia (Fig. 1). Glaciers on Yulong mountain are typically temperate (maritime) compared with the polar/ subpolar glaciers of most of the Tibetan Plateau. Glacier variations in this region have been investigated since 1999. The largest glacier on Yulong mountain, Baishui glacier No. 1 (BG1), which feeds the Baishui river basin, has an area of 1.52 km and is 2.7 km long (Pu, 1994). The elevation of the terminus of BG1 has been monitored since 1999. Results are listed in Table 1. According to Li and Su (1996), the elevation of the BG1 terminus was 4100m in 1982; it was 4300m in 2006 based on our investigations. On average, it rose by 8.3ma between 1982 and 2006, and 14.3ma from 1999 to 2006, i.e. the terminus retreat rate has increased in recent years. The result is in agreement with Dyurgerov (2003), who indicated significant loss in glacier area and volume on the global scale, accelerating especially since the end of the 1980s. In recent years, large crevasses have developed in the firn basin of BG1. These formed in the accumulation zone and were not found during investigations in 1982. Figure 2 shows photographs of a new crevasse, formed between August 2005 and April 2006, in the firn basin at 4900ma.s.l., and an embryonic crevasse developed in June 2006. The recently developed crevasses and ruptures may be linked to more rapid glacier movement over steep and variable bedrock (as a result of higher temperatures) since the 1990s. We suggest that during high-temperature summers, snowmelt enters the crevasses. Refreezing then leads to rupturing and instability of the firn basin and a speed-up of the flow. Thus, glacier stability is seriously impacted by crevasses developing in the firn basin. Yanggong glacier No. 5 (YG5) feeds the Yanggong river (Fig. 1). YG5 has an area of 0.72 km, is 1.8 km long and has an equilibrium-line altitude of 4620ma.s.l. (Pu, 1994). On 12 March 2004, a glacier-fall event at YG5 was accompanied by a small rockfall. Figure 3 shows the locality of the glacier collapse. On 21 April and 3 May 2006 we reached the collapse spot and investigated the event. The residual (i.e. it had suffered some melt) collapsed ice body was fanshaped (Fig. 3), with an outside (arc) length of about 870m, based on global positioning system (GPS) measurement, and a height of 15m. The altitude of the initial glacier disconnection location is about 4480m, based on our investigation combined with the topography map. The elevation of the collapsed ice body is 3700m. Therefore the ice body fell about 780m. The area of the glacier below 4480ma.s.l. is 0.44 km, accounting for 61% of the total glacier area. Some glacier terminal fall events prior to the 1980s have been reported from the monsoonal temperate-glacier region of the southeastern Tibetan Plateau (Li and others, 1986). These events were thought to be glacier surge phenomena. However, the 2004 YG5 glacier-fall event on Yulong mountain is thought not to be a surge since the collapsed ice body is large (more than half of the glacier). Based on temperature data from 1951 to 2005 at Lijiang weather station, 25 km south of Yulong mountain, one factor that triggered the collapse event may be as follows. The Journal of Glaciology, Vol. 53, No. 181, 2007