Extreme Glacier Melt in the Central Tibetan Plateau during the Summer of 2022: Detection and Mechanisms

Abstract. Extreme glacier melt events accelerate mass loss, increase glacier instability, and temporarily mitigate downstream drought. However, the glacier energy-mass balance in the Geladandong region—the headwater of both the Yangtze River (China’s longest river) and 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 (October 2019–July 2022) and glacio- meteorological data from a 5,700 m monitoring site (October 2020–July 2022) with a surface 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 2021–2022 as a period of extreme mass loss and melt intensity, with melt during the 2022 summer heatwave reaching unprecedented extremes. Over 52 days, the heatwave generated 1,135 mm w.e. of melt—accounting for 65.2 % of the total 2021–2022 melt, equivalent to 1.8 and 2.3 times the melt recorded in 2019–2020 and 2020–2021, respectively. This extreme melt was driven by energy balance anomalies over glacier surface, including reduced albedo, increased incoming longwave radiation, and enhanced sensible heat fluxes, with these processes strongly linked to persistent high temperatures and diminished precipitation. Such anomalies in the energy balance were driven by large-scale atmospheric circulation anomalies—specifically, the concurrent intensification and westward expansion of the Western Pacific Subtropical High (WPSH) and the eastward extension of the South Asian High (SAH). This study establishes a novel framework for identifying extreme mass loss events and substantially advances understanding of glacier mass balance responses to extreme weather and climate events.