Gangotri glacier dynamics from multi-sensor SAR and optical data

The present study has analyzed dynamics of Gangotri glacier using multiple remote sensing (RS) datasets and ground based observations. Interferometric Synthetic Aperture Radar (InSAR) data pairs from European Remote Sensing satellite (ERS 1/2) tandem pair for spring of 1996, Sentinel-1 SAR pairs and Japanese's Advance Land Observation System (ALOS) PALSAR-2 SAR data for Spring of 2015 were used to derive glacier-surface velocity at seasonal time scale using Differential InSAR (DInSAR) techniques. Bi-static TanDEM-X (Experimental) data was used for the 1st time to estimate glacier surface elevation changes for a period of 22, 44, 88 days during summer of 2012 using InSAR techniques in this study. Annual glacier velocity was also estimated using temporal panchromatic data of LANDSAT-5 (30 m), LANDSAT-7/8 (15 m), Sentinel-2 (10 m) and Indian Remote Sensing Satellite IRS-1C/1D panchromatic (5 m) data during 1998–2019 with feature tracking approach. This study has estimated glacier surface velocity and surface elevation changes for the major parts of Gangotri glacier and its tributary glaciers using medium to high resolution optical and SAR datasets, at annual and seasonal time scale, which is an improvement over earlier studies, wherein snout based glacier recession or only main glacier velocities were reported. The velocity and slope were used to assess glacier-ice thickness distribution using Glabtop-2, slope dependent and laminar flow based methods over the Gangotri group of glaciers. The estimated ice thickness was estimated in the range of 58–550 m for the complete glacier while few small areas in middle &amp; upper regions carry higher thickness of about 607 m. The estimated glacier-ice thickness was found in the range of 58–67 m at the snout region. The estimation was validated using 2014 field measurements from Terrestrial Laser Scanner (TLS) for the first time and correlation was found to be 0.799 at snout of the glacier.</p

Glacier environment and climate change in Bhutan—an overview

Bhutan, a part of the Eastern Himalayas, is a tiny land-locked country hosting rich biodiversity apart from glaciers and snow capped mountains. With similar to 70% of Bhutan under forest cover, this water-rich country promises to maintain at least 60% of the landmass under forest in perpetuity at any given point of time. Yet, climate change hasn't pardoned this carbon-neutral nation. This article conveys a brief idea about the dent that climate change is leaving on the glacier environment in Bhutan. Bhutan is undergoing warming at an unprecedented rate with evidences suggesting higher warming trends during winter months and also at higher altitudes (&gt;4000 m.a.s.l.) (Sharma et al., 2009). With large diversity of glaciers in the region, comprehensive field-based studies have been difficult due to rugged terrain, political issues and limited manpower and financial aid. Yet several remote sensing based have suggested glaciers in Bhutan are melting. Evidences suggest oldest stage of glaciers in Bhutan extended down to 2600 m.a.s.l. (Mool et al., 2001); whereas in the present day, they are found only above 4000 m.a.s.l. Glacial retreat in Bhutan has been extensive (Karma et al., 2003; Rupper et al., 2012; Naito et al., 2012; Bajracharya and Shrestha, 2011; Bajracharya et al., 2014; Veettil et al., 2015) leading to formation of supra-glacial, pro-glacial and moraine dammed lakes. Particularly in Bhutan and Eastern Himalayas, threat from glacial lake outburst floods is high. With 22 potentially dangerous glacial lakes, there is high risk and hazard potential to the regions lying downstream from outburst. In spite of being an environmentally sustainable country with a conservative approach, Bhutan is at the frontline of climate change-related threats. Future water security is not warranted under this scenario. This can have serious implications on water-dependent-economy of Bhutan that thrives on hydropower, agriculture and tourism. Extensive research is called for in Bhutan, apart from efforts to adapt and mitigate climate change

Glacier environment and climate change in Bhutan—an overview

Bhutan, a part of the Eastern Himalayas, is a tiny land-locked country hosting rich biodiversity apart from glaciers and snow capped mountains. With similar to 70% of Bhutan under forest cover, this water-rich country promises to maintain at least 60% of the landmass under forest in perpetuity at any given point of time. Yet, climate change hasn't pardoned this carbon-neutral nation. This article conveys a brief idea about the dent that climate change is leaving on the glacier environment in Bhutan. Bhutan is undergoing warming at an unprecedented rate with evidences suggesting higher warming trends during winter months and also at higher altitudes (&gt;4000 m.a.s.l.) (Sharma et al., 2009). With large diversity of glaciers in the region, comprehensive field-based studies have been difficult due to rugged terrain, political issues and limited manpower and financial aid. Yet several remote sensing based have suggested glaciers in Bhutan are melting. Evidences suggest oldest stage of glaciers in Bhutan extended down to 2600 m.a.s.l. (Mool et al., 2001); whereas in the present day, they are found only above 4000 m.a.s.l. Glacial retreat in Bhutan has been extensive (Karma et al., 2003; Rupper et al., 2012; Naito et al., 2012; Bajracharya and Shrestha, 2011; Bajracharya et al., 2014; Veettil et al., 2015) leading to formation of supra-glacial, pro-glacial and moraine dammed lakes. Particularly in Bhutan and Eastern Himalayas, threat from glacial lake outburst floods is high. With 22 potentially dangerous glacial lakes, there is high risk and hazard potential to the regions lying downstream from outburst. In spite of being an environmentally sustainable country with a conservative approach, Bhutan is at the frontline of climate change-related threats. Future water security is not warranted under this scenario. This can have serious implications on water-dependent-economy of Bhutan that thrives on hydropower, agriculture and tourism. Extensive research is called for in Bhutan, apart from efforts to adapt and mitigate climate change

Facies detection of surge-type glaciers, Karakoram Himalaya using Sentinel-1 images

Glacier facies or radar glacier zones (RGZs) of the surge-type glaciers of the Karakoram Himalaya were classified based on the differences in the backscatter values utilizing multi-temporal SAR data from Sentinel-1 satellite of the years 2018 and 2019. Distinct zones of glaciers such as dry snow zones, percolation zones, wet snow zone, bare ice zone and debris-covered area can be discernible on the false-color composite image made from the early summer-late summer-winter (R-G-B) of SAR images obtained from Sentinel-1. The result suggests an interesting blended pattern of facies distribution on surge-type glaciers showing the impression of accumulation zones at the lower most parts of the glaciers contrary to typical non surge-type glaciers. We found that the facies of the surge-type glaciers of the Karakoram Himalaya did not follow the relationship with the elevation in terms of their distribution on the surface of glaciers. We also compared our results with the surface temperature of the glaciers derived from the thermal band of Landsat ETM+