2000—2018年西昆仑山冰川表面运动特征研究——基于ITS_LIVE数据

The characteristics of glacier surface velocity in the West Kunlun Mountains derived from ITS_LIVE data from 2000 to 2018

近年来,西昆仑山冰川物质平衡异常现象受到广泛关注,然而该地区冰川末端却同时存在前进(常态)、后退、稳定及跃动多种状态。冰川末端进退不仅与气候变化引起的物质平衡变化有关,还与冰川的运动速度变化密切相关。以往研究多集中在前者,而对后者研究较少。因此,本文基于ITS_LIVE v01速度产品,结合西昆仑山冰川表面高程变化及冰川厚度资料,分析西昆仑山地区具有不同变化状态的冰川在2000—2018年的表面运动速度变化特征。结果表明,西昆仑山冰川在研究时段内的多年平均运动速度为6.35 m·a^(-1),年均速度波动上升,这主要是由该区域冰川表面高程整体上呈增加趋势[(0.15±0.02)m·a^(-1)]即冰川物质增加所造成;末端前进冰川的多年平均运动速度为4.07 m·a^(-1),年平均运动速度在研究时段内呈增加趋势,这主要与该类冰川在研究时段内物质略微增加有关;末端后退冰川多年平均速度约为4.86 m·a^(-1),年平均运动速度在研究时段内呈减小趋势,这主要与该类冰川物质亏损、减薄有关;末端稳定冰川多年平均速度约为3.04 m·a^(-1),年平均运动速度在研究时段内保持稳定,该类冰川在研究时段物质平衡也基本处于零平衡状态。研究区内末端前进冰川的多年平均运动速度较末端后退冰川的偏小,主要是因为末端前进冰川的平均厚度较末端后退冰川的偏小。2000—2018年西昆仑山有7条冰川发生跃动,多年平均运动速度为13.21 m·a^(-1),物质积累[(0.35±0.02)m·a^(-1)]引起速度增加。长度规模较大的后退冰川在2000年之前发生过跃动,由于目前处于平静期,冰川上部积累的物质未能及时输送到下部导致冰舌厚度减薄并后退。

In recent years,the retreat of global glaciers has accelerated in the context of climate warming.However,there is a positive glacier mass balance anomaly in the West Kunlun Mountains of the northwestern Qinghai-Xizang Plateau.Previous studies found that the mass gain in this region started as early as 1970s,and several glaciers have recently surged.Many large-scale glaciers are concentrated in the main peak area of West Kunlun Mountains,and the mass balance anomaly of glaciers in the West Kunlun Mountains has attracted extensive attention.However,there many states of the glacier tongue simultaneously,such as advance(normal),shrinkage,stable and surge.The advance and retreat of glaciers are not only related to the mass balance influenced by climate change,but also closely related to the glacier velocity.Previous studies mostly focused on the former,but less on the latter.Therefore,this study uses the ITS_LIVE v01 velocity product,combined with the glacier surface elevation changes and thickness to analyze the characteristics and possible causes of glacier surface velocity change with different states of terminus dynamic in the West Kunlun Mountains from 2000 to 2018,to further understand the glacier motion and velocity changes under the same climate change scenario.The results showed that during the study period,the mean velocity of glaciers in the West Kunlun Mountains was 6.35 m·a^(-1),and showed a fluctuating upward trend,which was caused by the mass gain caused by the thickening of glacier[(0.15±0.02)m·a^(-1)].The mean velocity of advanced glacier was about 4.07 m·a^(-1),and showed an increasing trend during the study period,which was resulted by the slight mass gain,the average velocity of retreat glacier was about 4.86 m·a^(-1),and showed an decreasing trend,this was caused by the mass loss during the period,the mean velocity of stable glacier was 3.04 m·a^(-1),and the mass balance of this type glacier was basically stable from 2000 to 2018.In the study area,the mean velocity of advanced glacier is smaller than the retreat glacier,because the value of retreat glacier is larger than the advanced glacier.From 2000 to 2018,seven glaciers surged,and the surge period was concentrated in 2010—2015.During the study period,the thickness of the surge-type glaciers increased significantly[(0.35±0.02)m·a^(-1)],resulting in an acceleration in velocity.The retreat glacier with a large length in the West Kunlun Mountains experienced a surge before 2000 and in a quiet period now,mass cannot be transported from the upstream to the downstream,leading to the thinning and retreat of the glacier tongue.