Timing And Climate Drivers Of Quaternary Glaciations In The Gongga Shan,Eastern Tibetan Plateau

The Gongga Mountain is the largest area of modern glaciation in the Hengduan Mountains and,with a summit elevation of 7556 m,is the highest mountain on the eastern margin of the Tibetan Plateau.The typical monsoonal temperate glaciers,which are very sensitive to climate change,have developed in this region.The mountain is climatically dominated by the East Asian and South Asian monsoons.These glaciers experienced large advances and retreats during the glacial-interglacial cycles of the Quaternary,and the glacial landforms are well-preserved in the valley,in the basin,and on the piedmont.The accurate dating of paleo-glaciations and the palaeoclimatic simulations for multiple glaciations would not only establish the chronological framework and extent of the paleo-glaciers in the Tibetan Plateau,but also provide insights into the climate-driven mechanism of paleoglacial evolution.Paleoclimatic reconstructions are critical to advancing understanding such spatial and temporal patterns of paleoglaciation.Moreover,these studies would also provide more similar climate scenario or early signal for predicting future climate changes.Based on the detailed geomorphology and stratigraphy of glacial sedimentology,we present the first ¹⁰Be exposure ages from the western slope of the Gongga Shan,and then combined with the published ages of glacial deposits in the area to establish chronological framework of Quaternary glaciations in the whole region.In addition,we used the 2-D ice-flow model to reconstruct the past glacier extents and paleoclimate of the Little Ice Age,Neoglacial,early Holocene,Heinrich 1?H1?,LGM_G?global last glacial maximum?and mid-MIS3.There are three conclusions as follows:1.The exposure ages of ¹⁰Be for the Zimei stage and Weishida stage of on the western slope of the Gongga Shan are 16.55±1.61¹8.62±1.80 ka?n=8?and 10.00±0.99¹0.52±1.03ka?n=6?,corresponding to the timing of the H1 and early Holocene,respectively.Based on the published glacial chronology data of the Gongga Shan,we have identified that this region have experienced at least seven glacial advance events during the Quaternary,which are equivalent in age to the MIS6,mid-MIS3,LGM_G,H1,Early Holocene,Neoglacial,and Little Ice Ages.The result shows that the paleo-glaciers in this area could not only recorded climate change on the glacial-interglacial scale,but also were sensitive to the climate changes in sub-orbital-scale.2.Based on the 2-D glacier flow model,the paleo-glacier area of the H1 and early Holocene in the Gongga Valley were 65.8 km² and 66.47 km²,respectively.The corresponding ice volumes were 9.98¹1.44 km³ and 9.8¹1.15 km³,alternatively.The paleo-glacier area of Mid-MIS3,LGM_G,Neoglacial and the Little Ice Age for Hailuogou area were 111.1 km²,85.1 km²,66.85 km²and 54.5 km²,respectively.The ice volume were 15.07¹6.19 km³,8.87¹0.71 km³,7.36⁷.49km³ and 5.7⁵.96 km³,correspondingly.Assuming that the precipitation is equivalent to that of modern??P=100%?,the temperatures during the mid-MIS3,LGM_G,H1,early Holocene,Neoglacial and the Little Ice Age were 8.4°C,6.0°C,3.0°C,2.4°C,3.0°C and 1.7°C lower than present.3.Based on the published paleoprecipitation data,we set the annual precipitation ratio?compared to present?of the Gongga Shan during mid-MIS3,LGM_G,H1,early Holocene,Neoglacial period and Little Ice Age periods were set to be 140%²00%,40%⁸0%,50%¹00%,100%¹30%,100¹20%,and 80¹00%respectively,the correspongding annunal temperatures should to be reduced by 5.0⁶.8°C?6.9⁹.2°C?3.0⁴.8°C?1.6².4°C?2.2³.0°C and1.7².5°C,respectively.During the period of LGM_G,H1,Neoglacial period and the Little Ice Age periods,the glacial advance were mainly driven by the decrease in temperature.While during Mid-MIS3 and early Holocene,the glacial advance is the consequences of richer precipitation and lower temperature.