Extreme glacier melt on the Central Tibetan Plateau during the summer of 2022: detection and mechanisms

Extreme glacier melt events accelerate mass loss, increase glacier instability, and temporarily increase downstream runoff, potentially alleviating drought conditions. Yet the glacier energy–mass balance in the Geladandong region – a headwater region of the Yangtze River (China's longest river) and one of the source regions feeding Siling Co (Tibet's largest lake) – and its connection to the unprecedented 2022 summer melt remain insufficiently quantified. To address this gap, we integrated in-situ mass balance observations and glacio-meteorological data from a 5700 m monitoring site with an energy-mass balance model and applied a novel dual-threshold framework (based on mean and standard deviation) to identify extreme mass loss/melt events in short-term glacier mass balance records. Our novel methodology identified 2021/22 as a period of extreme mass loss and melt intensity, with melt during the 2022 summer heatwave reaching unprecedented extremes. These heatwaves caused an increase in melt amount of 317.8 mm w.e., amounting to 1.66 and 1.69 times the values recorded for the same period in 2019/20 and 2020/21, respectively. This extreme melt was driven by energy balance anomalies over the glacier surface. In terms of net contributions to the +28.2 W m −2 melt energy anomaly during the three identified heatwave windows, enhanced sensible heat flux was the largest term (+17.0 W m −2 ; 60.3 %), followed by increased net longwave radiation (+14.0 W m −2 ; 49.7 %) and increased net shortwave radiation (+5.1 W m −2 ; 18.1 %) associated with reduced albedo, with negative contributions from latent heat flux and subsurface heat flux. Such anomalies were driven by large-scale atmospheric circulation patterns, specifically the eastward extension and northward displacement of the South Asian High (SAH), together with near-neutral mid-latitude westerlies. This study advances the understanding of glacier mass balance responses to extreme weather and climate events on the central Tibetan Plateau.