Mass balance of lake terminating Gepang Gath glacier (western Himalaya, India) and the role of glacier–lake interactions

Abstract

The mass balance of lake-terminating glaciers responds to annual atmospheric variations, while calving-induced ice loss at the front is driven by local ice–water interactions. The current glaciological studies underestimate glacier response by neglecting the significant annual ice loss at the terminus through calving processes. This study integrates field measurements with remote sensing data to investigate the glaciological characteristics and proglacial lake evolution of the Gepang Gath glacier in the Chandra basin, Western Himalaya, India. Long-term observations reveal a continuous expansion of the proglacial lake from 0.21 ± 0.06 km² (1962) to 1.21 ± 0.05 km² (2023), along with terminus retreat of ∼2.76 km, attributed to calving at the ice–water interface. The glacier’s surface exhibits complex debris cover, with thicknesses up to 35 cm, creating significant spatial variations in surface mass balance. In-situ, glaciological measurements reveal a highly negative glacier-wide mass balance of −0.90 ± 0.30 m w.e. a−¹ between the years 2014 and 2023. The geodetic estimates also reveal a negative mass balance of −0.61 ± 0.1 m w.e. a−¹ over the past decade (2013–2023). The frontal area change (0.42 km²) and geodetic mass balance show a total volumetric ice loss of −21.77 × 10⁶ m³ w.e. during the same period. Overall, the yearly frontal ice loss exacerbates the mass loss by 17–22%. These findings suggest that the presence of proglacial lakes plays a significant role in intensifying ice mass loss from Himalayan glaciers, strongly regulating their overall evolution.