Quasquicentennial shrinkage of glacier as a testimony of regional climate change: an example of Janapa Garang glacier (JPG), Baspa basin, Western Himalayas, India

The glaciers of the Indian Himalayas were much larger during the Little Ice Age (LIA) and started retreating post-LIA (16 to 19 century). The rate of recession accelerated dramatically in the twentieth century. If similar trends continue, power generation and the availability of water for irrigation and drinking purpose will be adversely affected. Hence, understanding the long term response of glaciers with respect to changing climatic conditions is essential. The present study evaluates and quantifies the comprehensive quasquicentennial (1888–2017) (129 years) response of the Janapa Garang glacier (JPG) regarding spatial changes in glacial geomorphic features, as well as area, volume, and ice-mass changes. The assessment of Janapa Garang is based on glacier boundaries derived from Survey of India (SOI) topographic maps (Survey years 1888 and 1962), Landsat 7 data of 1999 and Landsat 8 OLI/TIRS data of 2017. The remote sensing data have proved to be useful and economically viable for mapping the extent of JPG situated in remote, inaccessible and frosty environments. In addition, multi-temporal, multi-spectral characteristics and synoptic coverage of remote sensing data are potent for such studies. For quasquicentential scale, where the remote sensing data are not available, the historical SOI maps of 1888 and 1962 provide significant inputs. The quasquicentential response of JPG is preserved in the form of various glacial geomorphic features (accumulation zone, exposed ablation zone, moraine covered ablation zone, snout, lateral, medial and terminal moraines as well as deglaciated valley) and is reflected through reduction in glacier length, area, volume and ice-mass. The study reveals 3760 m total lengthwise retreat of JPG with variation in snout elevation by 362 m asl. The total percentage loss in the glacier area, volume, and ice mass from 1888–2017 is 38%, 51% and 50% respectively.