A comprehensive multidecadal glacier inventory dataset for the Chandra-Bhaga Basin, Western Himalaya, India

Delineation of Glaciers is a challenging task in the Himalaya due to its complex topography, cloud cover, seasonal snow cover, hillshade, debris cover. Glacio-hydrological studies including mass balance, run-off, and dynamic 15 modelling rely on the availability of consistent and reliable glacier inventory datasets. This article on data set presents a homogenous, multidecadal inventory of glaciers in the Chandra-Bhaga Basin (CB Basin), western Himalaya, for 1993, 2000, 2010, and 2019. Landsat Thematic Mapper (TM), Enhanced Thematic mapper (ETM+), and Operational Land Imager (OLI) imageries, with minimum snow and cloud cover have been used for enhanced accuracy and consistency. Uncertainty assessment for the generated glacier inventory was performed, 20 following various approaches such as buffer method, standard error estimation, and manual digitisation error and the maximum uncertainty has been quantified. We have identified and manually mapped a total of 251 glaciers with an area > 0.5 km 2 , and in order to minimise the uncertainty, field surveys were carried out on 6 glaciers in the basin. Out of these 251 glaciers, 217 are clean ice and 35 were debris-covered glaciers. The estimated total glacier area was 996 ± 62 km 2 in 1993 that decreased to 973 ± 70 km 2 in 2019. Apart from quantifying temporal 25 changes in glacier area, this inventory further allows the estimation of supraglacial debris cover and glacier volume. The supraglacial debris cover area has increased by 14.1 ± 2.54 km 2 (15.2 %) during 1993-2019. Accuracy of the debris cover dataset estimated using ground surveys is 82 % with a kappa coefficient of 0.87. Moreover, a glacier ice volume dataset was also generated by incorporating the inventory into Glacier Bed Topography Version 2 (GlabTop2) model and shows a total of 112.5 ± 41 km 3 of ice volume stored in the CB Basin glaciers. 30 For accuracy assessment of the DEMs generated using ASTER Stereopairs images, DGPS surveys were carried out on (28 GCPs) and off (6 GCPs) the glaciers. Glacier volume uncertainty with respect to the generated DEMs and model bias is 5.3 km 3 and 35.5 km 3 respectively. Overestimation of glacier volume due to over deepening is estimated to be 1.2 km 3 . The impact of climate change on the Himalayan glaciers is a matter of serious concern and such holistic multitemporal inventory datasets can help quantify that impact with improved certainty. of the interpolation for ice thickness calculation using a different set of random points, and finally average of n ice thickness is distributed for entire glacier. In this study n is taken as 3. A more detailed description of the model can be found in Frey et al. (2014). The ice thickness estimation from GlabTop2 model was validated against observations from Chhota Shigri, Patsio, and Hamtah glaciers (Table 1). The study summarizes the status of glaciers in the CB Basin by quantifying the glacier area and debris cover changes in the recent decades as well as the ice thickness and volume in the basin. The three sets of spatio-temporal data generated in this study will aid in future research endeavors focusing on glacio-hydrological and policy-based studies as well as contribute towards improving existing inventory information’s at both local and regional scales. Also, constant monitoring of and further studies into the associated feedback processes necessary of the on these and the increasing demand for freshwater resources.