High-frequency post-LGM glacial fluctuations in central Tibet

The pattern of abrupt climate events post-dating the Last Glacial Maximum (LGM) remains a pressing problem, with implications for pinpointing the role of global and regional forcing in these events. Well-defined glacial evidence, such as those in the Tibetan Plateau (TP), could improve our understanding of the problem. However, the post-LGM glacial histories are still uncertain in central Tibet. This uncertainty is mostly due to the relative paucity of precisely-dated moraine sequences, which hinders efforts to unravel the mechanisms behind renewed glacial activities. Here, we report a well-established moraine chronology in the Xainza Range, eastern Gangdise Mountains, based on the new (n = 55) and previously published (n = 20) 10Be exposure-ages across the mountain range. The synthesized chronologic data indicate that the Xainza glaciers advanced at least fifteen times following the LGM, with eleven of which pre-dating the Little Ice Age (LIA). Among these pre-LIA moraine-building events, three repeated through the last deglaciation, two occurred during the Younger Dryas/Early Holocene (YD/EH) transition, and six were dated to the late- and mid-Holocene. We suggest that the Xainza glaciers reacted dynamically to regional and global climate changes after the end of LGM. The last deglacial re-advances likely registered changes in global summer temperature related to atmospheric CO2 levels, whereas the subsequent re-advances were dominated by regional climate variations. That is, monsoon precipitation likely accounted for glacial activities during the YD/EH transition, while regional cooling in summer was responsible for the late- and mid-Holocene glacial advances.