Recent changes in the snout position and surface velocity of Gangotri glacier observed from space

Abstract

Glacier mass variations have a direct impact on some of the key components of the global water cycle, including sea level rise and freshwater availability. Apart from being one of the largest Himalayan glaciers, Gangotri is one of the sources of water for the Ganges river, which has a considerable influence on the socioeconomic structure of a largely over-populated catchment area accounting for ∼26% of India's landmass. In this study, we present the most recent assessment of the Gangotri glacier dynamics, combining the use of interferometric techniques on synthetic aperture radar data and sub-pixel offset tracking on Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery. Results show that on average, the Gangotri glacier snout has receded at a rate of 21.3 ± 3 m year −1 over a period of 6 years (2004-2010). While glacier surface velocity near the snout is estimated to be between 24.8 ± 2.3 and 28.9 ± 2.3 m year −1 , interior portions of the glacier recorded velocities in the range of 13.9 ± 2.3 to 70.2 ± 2.3 m year −1 . Further, the average glacier surface velocity in the northern (lower) portions (28.1 ± 2.3 m year −1 ) is observed to be significantly lower than in the southern (higher) portions (48.1 ± 2.3 m year −1 ) of the Gangotri glacier. These values are calculated with an uncertainty of less than 5 m year −1 . Results also highlight a consistent retreat and non-uniform dynamics of the Gangotri glacier.

Overall recession and mass budget of Gangotri Glacier, Garhwal Himalayas, from 1965 to 2015 using remote sensing data

“…The processing errors were also examined for the locations of stable ground near the snout of the Gangotri Glacier where the slope conditions were nearly the same as the glacier (Saraswat and others, 2013). The location of the stable ground and the errors associated with the processing for all pairs of data are shown in the Supplementary A relationship similar to Pellicciotti and others (2015) and Holzer and others (2015) between recent surface velocity (2008/09) and down-wasting during the entire observation period was also estimated through a profile along the central glacial flow line for all investigated glaciers (Fig.…”

Glacier retreat monitoring from SAR coherence images: application to Gangotri glacier

“…11 The depletion of glaciers can have adverse effects, starting from the change in flow regime of rivers to occurrence of catastrophic events such as glacial outbursts and flooding of areas in the downstream side of the glaciers. 8,23 Hence a long-term monitoring of glacier change is crucial not only in assessing the future consequences, but also in understanding the effects of local, regional, and global environment 10 . However, due to the remote location and the large size of glaciers, field measurements are difficult to perform and the number of sites available for observation is sparse compared to the number of glaciers 20 .…”

Area and mass changes of Siachen Glacier (East Karakoram)

“…Saraswat and others (2013) estimated that there is a bias of ∼20% in the coherence estimates especially in glacierized regions, which have low coherence values. Since the members of the interferometric pairs used in this study were acquired one year apart (Table 2), the glacierized region is affected by motion-related decorrelation whereas the ice-free area is free from this effect.…”

“…High-resolution orthorectified Cartosat-I (along with the gap-filled Landsat image) and Hexagon imagery was used to manually delineate debris-covered ice boundaries for the years 2007 and 1980, respectively. In order to support the identification of the debris-covered tongue and to study changes in snout position, we have used coherence mapping, which relies on high-precision interferometric techniques utilizing SAR data. This method has been effectively used to delineate glaciers automatically (Atwood and others, 2010), study changes in snout position (Saraswat and others, 2013) and identify debris-covered portions of glaciers (Frey and others, 2012).…”