Permafrost in the Upper Indus Basin: An active layer dynamics

Abstract

Permafrost in the Upper Indus Basin (UIB) in Ladakh, India, is a critical water source and is less studied. Identifying permafrost and its characteristics is a crucial knowledge gap in the UIB. Thus, understanding the permafrost active layer dynamics is critical and essential due to its implications on regional hydrology, infrastructure stability, and disaster occurrence. For this purpose, an experimental site is prepared with 11 plots having two near-surface ground temperature loggers each, i.e., 22 in total, in the upper Ganglass catchment, a sub-region of the UIB, Ladakh. The permafrost active layer thickness characteristics and its thaw progression are simulated using the 1-D GEOtop model with forcing from these 22 loggers from 2016 to 2020. The snow days are calculated using the near-surface ground temperature. The simulation results show no permafrost at 4727 m a.s.l. consistently, whereas all the plots above 4900 m a.s.l. show permafrost active layer thickness, in particular, up to 4 m at 4942 m a.s.l. Permafrost characteristics significantly differ between a warmer (colder) year with low (high) snow. The mean surface offset of the catchment ranges between −0.01° and 5.5°C. These findings on permafrost and associated periglacial processes will provide a critical knowledge base for the stability of high-elevation infrastructure, glacial lakes, regional hydrology and climate, particularly for water.