Snout monitoring of the Gangotri glacier (Uttarakhand, India) during the ablation season (May to September) in years 2005 and 2015 by using rapid static and kinematic GPS survey reveals that the retreating rate has been comparatively more declined than shown by the earlier studies. Our study is based on the individual measurement by the remote sensing, added by the ground observations by using Differential global positioning system (DGPS) to determine the precise recession rate of the glacier at sub-centimeter level of accuracy. The GPS dataset show that the total average retreat along the snout has been 102.57 ± 0.05 m from 2005 to 2015 with an average rate as 10.26 ± 0.05 m/yr. Additionally, the shift in snout position was also measured through multi-temporal satellite data from 1989 to 2016. The results indicate that the Gangotri glacier snout has retreated by 585.62 ± 38.30 m during this period with an average retreat of 26.75 ± 4.36 m/yr from 1989 to 1999, 21.58 ± 3.77 m/yr from 1999 to 2009 and 14.60 ± 4.81 m/yr from 2009 to 2016. Such a decline in retreat is further confirmed by the satellite data set. A close examination of meltwater discharge and retreating rate (r² = 0.95) show that both parameters are strongly correlated. Therefore, we suggest that a consistent decrease in meltwater discharge from 1999 to 2015 is in agreement with decreasing trend of retreating rate during the recent years. To determine the possible causes of decreased retreating rate, a relationship between debris thickness and melt rate was also established by ablation stakes. Further, we infer that the declining trend in the glacier retreat is not only controlled by prevailing weather conditions (rainfall and air temperature) but is also governed by increased debris cover on the glacier surface which prevents the ice to melt.

中文翻译：

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通过运动学GPS调查和卫星数据估算印度Garhwal喜马拉雅山Gangotri冰川的衰退率

在2005年和2015年的消融季节（5月至9月），对Gangotri冰川（印度北阿坎德邦）的口鼻监测使用快速静态和运动学GPS调查显示，退缩速度的下降幅度要比早期研究的下降幅度更大。我们的研究基于遥感的个体测量结果，再通过使用差分全球定位系统（DGPS）来确定地面的观测值，从而确定亚厘米级精度的冰川的精确衰退率。GPS数据集显示，从2005年到2015年，沿口鼻部的平均平均撤退量为102.57±0.05 m，平均速率为10.26±0.05 m / yr。此外，还通过1989年至2016年的多时相卫星数据测量了口鼻部位置的变化。结果表明，在这段时期内，Gangotri冰川的鼻子减少了585.62±38.30 m，从1989年到1999年平均每年退缩26.75±4.36 m / yr，从1999年到2009年平均每年退缩21.58±3.77 m / yr和14.60±4.81 m /从2009年到2016年。卫星数据集进一步证实了这种退缩。仔细检查融水的排放和回水率（r ²  = 0.95）表明这两个参数是高度相关的。因此，我们认为从1999年到2015年，融水排放量的持续下降与近年来退缩率的下降趋势是一致的。为了确定退刀率降低的可能原因，还通过消融桩建立了碎屑厚度与熔化率之间的关系。此外，我们推断，冰川退缩的下降趋势不仅受到主要天气条件（降雨和气温）的控制，而且还受到冰川表面上增加的碎屑覆盖率（防止冰融化）的控制。