A substantial meltwater event on the northeastern Tibetan Plateau during the middle to late Holocene transition

Global warming has accelerated the degradation of permafrost and glaciers on the Tibetan Plateau, resulting in a substantial release of meltwater that is affecting the regional ecosystem. Despite the significant environmental effects of meltwater, there is a lack of comprehensive studies on the historical changes in meltwater. The key is to obtain reliable quantitative records of meltwater changes. Here, we present Holocene δDwax records from a loess and a peatland on the northeastern Tibetan Plateau, documenting the hydrogen isotopic composition of the regional summer precipitation and surface water affected by meltwater respectively. The two records together reveal substantially increased meltwater during the middle to late Holocene transition, lasting for approximately 1500 years. The meltwater event coincides with a series of exceptional warmth during 5-3 ka across the mid-latitude inland Asia, suggesting that the regional warming was the primary driver of the increased meltwater. This meltwater event had a considerable influence on regional ecology, leading to dramatic fluctuations in algal and bacterial populations and biomass. In addition, this meltwater event may have occurred over a larger area of glaciers and permafrost, where the water isotope records during 5 ka and 3 ka differ from low-latitude regions. This meltwater event, as a crucial aspect of the climatic changes during the middle to late Holocene transition in inland Asia, its driving mechanism and environmental impacts warrant further investigation.