Glacier Energy and Mass Balance in the Inland Tibetan Plateau: Seasonal and Interannual Variability in Relation to Atmospheric Changes

The Tibetan glaciers are greatly affected by the circulations of the westerlies and the Indian summer monsoon (ISM), but the mechanisms remain to be elucidated. In this project, we investigated the surface energy and mass balance of the Qiangtang No.1 Glacier in the inland Tibetan Plateau. Combining 4-year mass balance and meteorological records near the equilibrium line altitude with an energy-based mass balance model, we found that the meteorological conditions, which determined the glacier surface ablation and mass accumulation, are critically linked to changes in the intensity of the westerlies and the ISM. The 4-year mass balance comparisons demonstrated that the enhancement of the ISM in June and July, especially June, greatly increases the mass accumulation but inhibits the glacial ablation in the melt season, shifting the mass balance in a positive direction. Moreover, the occurrence of the westerlies enhancement interrupts the dominance of the ISM in the melt season. The intensified westerlies in the early melt season (June) could not only reduce the mass accumulation but also enhance the mass loss in the following months. In addition, the enhancement of the westerlies in the main melt season (July) could also greatly influence the local meteorological conditions, with lower temperatures and humidity but higher wind speeds. Such meteorological changes significantly reduce glacial ablation because more energy is consumed by sublimation and/or evaporation, rather than surface melting. These findings will enhance our understanding of the mechanisms underlying glacier changes and their relationships with the westerlies and the ISM in the inland Tibetan Plateau.