Glacier melting phenology changes in the Tibetan Plateau from 1981 to 2020

Abstract

A comprehensive understanding of the spatiotemporal variability of glacier melt phenology across the Tibetan Plateau is crucial due to its significant impacts on hydrological processes, water supply, natural disasters, climate systems, and ecosystems. Key metrics, including glacier melting onset date (GMOD), end date (GMED), duration (GMDD), and accumulated temperature (GMAT), are essential for understanding these impacts. This study investigated these metrics using the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis of land surface data (ERA5-Land) for the period 1981–2020. Results indicated that GMOD advanced by 0.05 days⋅a⁻¹, GMED was delayed by 0.12 days⋅a⁻¹, GMDD increased by 0.22 days⋅a⁻¹, and GMAT rose by an average of 0.88 °C⋅a⁻¹. GMDD and GMAT exhibited significantly increasing trends (p < 0.05), indicating accelerating glacier retreat and intensified melt potentially reaching higher elevations. Between 1981 and 2020, notable increases in GMDD and GMAT occurred in the northwestern, northeastern, and southeastern regions of the Tibetan Plateau, especially in the Qilian, Hengduan, and Tanglha Mountains. A significant positive correlation existed between GMOD and elevation, while GMED, GMDD, and GMAT exhibited negative correlations. Smaller glaciers showed considerable increases in GMDD, medium-scale glaciers displayed significant delays in GMED, and larger glaciers demonstrated marked increases in GMAT. Additionally, debris-covered glaciers exhibited earlier melt onset and extended melt durations, with debris’ insulating effect influencing temporal and spatial changes in melt phenology. Net longwave radiation was a key meteorological factor influencing glacial melting phenology, with ENSO and AMO significantly affecting these changes.