Late Quaternary modeling and paleoclimate evolution of the Mount Taibai glacier (Qinling Mountains, China) constrained by cosmogenic radionuclide exposure dating

Abstract

Glacial landforms on Mount Taibai, the main peak of the Qinling Mountains, China, are investigated to improve understanding of Quaternary palaeoclimate evolution in this key region of China's geographical north and south junction. Cosmogenic radionuclide 10Be exposure dating and glacier-climate modeling are used to reconstruct glacier evolution during the last glaciation in the Eryehai Valley, on the slopes of Mount Taibai. Chronological results indicate that the earliest initiation of the Mount Taibai glaciation was earlier than the global Last Glacial Maximum (gLGM). The glacier subsequently advanced further reaching its greatest extent during the gLGM between ∼23.50 ka and 21.76 ka. After this time, the glacier receded rapidly, before disappearing completely between ∼17.9 ka and 17.7 ka. We also analyzed a compilation of 229 recalculated 10Be exposure ages from the mountain ranges on the eastern Tibetan Plateau (TP), as well as in the Jaggang Mountains on the south-central TP, and found that a few mountain ranges on the eastern TP experienced two distinct millennial-scale moraine building events during the gLGM. Using glacier-climate modeling, temperature was calculated to have fallen from between ∼9.0 and 9.4 °C during the gLGM, with precipitation being 60–80% of the present-day value. If precipitation during the rapid retreat of the glacier between ∼21.76 ka and 18.10 ka were to be consistent with present trends, then the temperature would have needed to increase by a total of ∼1.3 °C during this period, with a mean rate of increase of 0.4 °C/ka. Combining our findings with other paleoclimate proxies, we infer that the main reason that there was no further glacial advance after the gLGM on Mount Taibai was the lower altitude of its peak relative to the Equilibrium-line Altitude (ELA). Our results provide the paleoclimatic conditions of the last glaciation in this critical area of China's geographical north and south junction, and deepen the understanding of how the East Asian Summer Monsoon (EASM) influences glaciers on the TP.