Manifestations of a glacier surge in central Himalaya using multi-temporal satellite data

Our understanding of identifying and monitoring surge-type glacier distribution patterns, fluctuations, periodicities, and occurrence mechanism under the changing climate is challenging and scarce due to small numbers, limitations on the spatiotemporal coverage of remote sensing observations, and insufficient field-based glaciological data from the High Mountain Asia. The surging glaciers have caused major hazards, and their movement can destroy peripheral and downstream areas like roads, connecting bridges, villages, and hydropower stations and trigger a glacial lake outburst flood or form a dammed (moraine or ice) lake in High Mountain Asia (HMA) in the recent past. Many glaciers have experienced a mass loss and retreat due to ongoing climate change in HMA in recent decades, whereas studies conducted in the Karakorum, Pamir, Tien Shan, and Kunlun Shan regions have reported the surging of the glaciers. Whereas, in the central Himalayan region, very limited studies have been able to identify and explain in detail the surging glaciers and their surge mechanism. In this study, we identified an unnamed glacier surge in the central Himalaya, triggered between 12 September and 14 October 2019 (on a monthly scale) using multi-source high-resolution remote sensing data (CARTOSAT-1 [2011 and 2012], LISS-IV-2A [2011, 2017, and 2020], Landsat-5 [TM], 7 [ETM +], 8 [OLI/TIRS], and Sentinel [2A and 2B]) in conjunction with shuttle radar topography mission [SRTM], Advanced Spaceborne Thermal Emission and Reflection Radiometer [ASTER], and High Mountain Asia digital elevation model (DEM) database. We used a series of algorithms package named MicMac ASTER (MMASTER) tool for generating DEMs from data of two telescopes for the estimation of the surface elevation change, and to calculate the surface velocity, we employed the "Co-registration of Optically Sensed Images and Correlation" (COSI-Corr), a Fourier-based, highly advanced matching program. Based on the observations of the glacier terminus fluctuation, surface velocity, and surface elevation change from 1993 to 2022, this study revealed that the unnamed glacier underwent a surge for the first time in the past three decades. The glacier's surface velocity increased from 7 ± 3 m year^-1 during quiescence (2001-2002) to 163 ± 1 m year^-1 during the surge (2019-2020) and then decreased to 17 ± 2 m year^-1 between 2021 and 2022. Between 12 September and 14 October 2019, there was a sudden and significant increase in surface velocity of 863 m within a month (i.e., 27 m/day compared to the month prior), indicating the initiation of the surge. Overall, the present study results suggest that the glacier's velocity varied considerably during the observed period, with periods of gradual increase, sudden increase, and subsequent decrease. Further, the changes in glacier surface suggest a total mean elevation change of 0.26 ± 0.2 m year^-1 between 2000 and 2020. In this study, we present novel observations of a glacier surge in the central Himalaya, compare its characteristics to surge-type glaciers reported elsewhere, and discuss the possible mechanisms controlling its behavior.