Assessing Climate Variability and Cryosphere Response in Baltistan through ERA5-Land Data

Abstract

he Karakoram mountain range harbors the greatest concentration of glaciers and permanent snowfields outside the polar regions, making seasonal snowmelt the cornerstone of freshwater availability for the Indus River system. Despite this critical hydrological role, the spatiotemporal dynamics of snow and glacier melt in Baltistan Division remain poorly constrained, largely due to the scarcity of ground-based observations and the complexity of the terrain. This study addresses that gap by examining near-surface air temperature and snowmelt variability across the four districts of Baltistan Division Skardu, Shigar, Khaplu (Ghanche), and Kharmang during the primary melt season (March–June) from 2020 to 2025. ERA5-Land reanalysis data at approximately 9 km resolution, accessed through Google Earth Engine (GEE), were processed into daily day-of-year (DOY) time series to enable systematic interannual comparison. All study years exhibited a coherent seasonal warming trajectory from approximately ?20°C in early March to near 0°C or above by late June. Snowmelt onset was observed between DOY 97 and 125, with peak melt intensities occurring between DOY 155 and 180. The year 2022 stood out as the warmest early-season year, associated with anomalously early snowmelt initiation but suppressed peak melt consistent with early depletion of the winter snowpack. In contrast, 2023 exhibited a pronounced cold anomaly between DOY 130 and 150, yet ultimately recorded the highest snowmelt peak of the study period (~0.015 m day?¹), reflecting enhanced snow accumulation during the delayed spring. These findings demonstrate significant interannual variability in cryospheric response and carry direct implications for flood risk assessment, water resource planning, and hydropower management in the Upper Indus Basin.