Numerical Reconstruction of Three Holocene Glacial Events in Qiangyong Valley, Southern Tibetan Plateau and Their Implication for Holocene Climate Changes

The dating of well-preserved Holocene moraines in the Qiangyong Valley, southern Tibetan Plateau (TP), offers great potential for reconstructing Holocene glacier extents and examining climate changes in the region. Guided by Holocene moraine features, this study used Geographic Information System (GIS) model tools to reconstruct paleo-glacier surfaces and glacier equilibrium line altitude (ELA) depressions for three Holocene glacial stages in the valley. The GIS-based models showed that the Qiangyong Valley contained ice volumes of 8.1 x 10(8), 6.2 x 10(8), and 4.6 x 10(8) m(3) during the early Holocene, Neoglacial, and Little Ice Age (LIA) glacial stages, and that the ELA was decreased by similar to 230 +/- 25, similar to 210 +/- 25, and similar to 165 +/- 25 m, respectively, compared to modern conditions. Furthermore, the summer temperatures were estimated to be 1.56-1.79, 1.37-1.64, and 1.29-1.32 degrees C cooler than present to support the three Holocene glacier extents, based on the evidence that the respective precipitation increased by 20-98, 13-109, and 0.9-11 mm relative to the present, which were derived from the lacustrine pollen data for the southern TP. By comparison, this study found that the amplitudes of the ELA-based summer temperature depressions were much larger than the pollen-based counterparts for the three glacial stages, although the two proxies both showed increasing trends in the reconstructed summer temperatures.