Repeated glacial fluctuations during the Last Glacial Maximum in the southeastern Tibetan Plateau: ¹⁰Be surface exposure dating of moraines in the Lahaku Valley, Haizishan Plateau, China

Climate fluctuations during the late stages of the Last Glacial Maximum (LGM) resulted in the complex evolution of mid-latitude alpine glaciers in both hemispheres. Yet, the finding of repeated LGM glacial fluctuations has yet to be reported across the vast Tibetan Plateau (TP). Here, we present a record of glacial behavior during the LGM from the southeastern TP, based on 10Be surface exposure dating and detailed geomorphological mapping in the northwestern Haizishan Plateau. Sixty-three 10Be exposure-ages from nine recessional moraines constrain their age to 16.4 +/- 1.9-20.5 +/- 1.4 ka, providing clear evidence of repeated LGM glacial fluctuations for the first time in the TP. We propose that inter-annual to multi-decadal climatic variabilities were likely responsible for these high-frequency glacial oscillations. A synthesis of the new and published 10Be data across the Shaluli Mountains suggests that the LGM termination was synchronous and three apparent phases of glacial fluctuations may have occurred across the region during the LGM. These glacial fluctuations are likely linked to changes in regional summer temperatures that reflect the Indo-Pacific Warm Pool sea surface temperatures. Monsoon precipitation may contribute to the amplitude of these fluctuations.