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Mountain glaciers are one of the most sensitive indicators of climate change. Reconstructing past glacier extents provides valuable insights into the climate change for specific regions where instrumental records are not enough and even absent. In the paper we mapped the outlines for 691 Little Ice Age (LIA) glaciers in terms of prominent moraines beyond contemporary glaciers in the Tanggula Mountains, central Tibetan Plateau (TP). Based on these glacier outlines, we reconstructed the ice thicknesses and surfaces for the LIA glaciers in the region. Accordingly, we calculated the equilibrium-line altitudes (ELAs) for contemporary and LIA glaciers. By comparing the ELAs between the contemporary and LIA glaciers, we estimated the LIA summer temperature decreases in different subregions of the Tanggula Mountains. Since the LIA, the ELA have risen by 35.6 ± 18.8 m, 26.1 ± 17.6 m, and 63.1 ± 38.6 m in the respective western, central, and eastern subregions of the Tanggula Mountains. Assuming no change in precipitation, the LIA summer temperature would decrease by 0.22 ± 0.12 °C, 0.14 ± 0.09 °C, and 0.34 ± 0.21 °C in the three subregions, respectively. Moreover, glaciers in the western, central, and eastern subregions have lost 13.3%, 23.9%, and 42.8% of their area, 15.4%, 25.3%, and 39.6% of their length, and 20.8%, 39.0%, and 61.0% of their volume, respectively. By compiling the LIA ELA data from previous studies, we also estimated the LIA summer temperature changes for other regions of the TP. The LIA ELA and summer temperature changes relative to the present showed a decreasing trend from the edges towards the interior on the TP. • LIA glaciers and summer climate were reconstructed at the Tanggula Mountains. • LIA summers were 0.22 ± 0.12 °C, 0.14 ± 0.09 °C, and 0.34 ± 0.21 °C cooler than present in three subregions. • Summer temperature change had a decreasing trend from the edges towards the interior on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Abstract: Fully understanding the timing and climate of Last Glacial Maximum (LGM) is still lack in the head of the Tashkurgan Valley, northwest Tibetan Plateau (TP). The recent improvements in cosmogenic 10Be exposure dating and glacier modeling present an opportunity to estimate the LGM climatic conditions. In the paper, we investigated the moraines and used the 10Be exposure dating on the moraine boulders to constrain the timing of the LGM, the Kuzigun glacial stage in the head of the Tashkurgan Valley. Then, we used a coupled mass-balance and ice-flow model to quantify the paleoclimate from past glacier extents constrained by mapped and dated Kuzigun glacial moraines in the area. We showed that the glaciers terminated at an elevation of 4100–4200 m asl during the Kuzigun glacial stage and the glacial stage occurred during or slightly before 15–23 ka, corresponding to the timing of the global LGM. The modeled mass balances indicated that present-day equilibrium line altitude (ELA) ranges from 5150 to 5250 m asl, and LGM ELA is between 4550 and 4600 m asl in the area, suggesting an ELA lowering of ∼600 m during the LGM. Model results suggested that the temperature during the LGM in the head of the Tashkurgan Valley is 5–8 °C colder than today, considering a 30–70% reduction in precipitation compared to today. The paleoclimate estimates are generally consistence with previous studies that showed the LGM climate was colder and drier than today on the TP. [Copyright &y& Elsevier]

Abstract: There is a great deal of controversy regarding the fate of glaciers and ice fields on the Tibetan Plateau in the face of continued anthropogenic global warming. Paleoclimate reconstructions and spatial analyses aimed at mapping past climate changes are the key to understanding the climatic response of the Tibetan Plateau to changing conditions. Specifically, the numerous lakes distributed across the Tibetan Plateau can provide high-resolution (spatial and temporal) climate reconstructions to investigate past changes in the climate system. In this paper, we review the primary limitation to exploiting these valuable paleoclimate archives: errors in radiocarbon-based age models. We review the techniques that have been used to estimate 14C reservoir ages on the Tibetan Plateau and compile the published 14C reservoir ages to examine their spatial and temporal patterns and to assess the imposed chronological uncertainties. Using site-specific evaluations of Bangong Co and Lake Qinghai, we demonstrate that 14C age model uncertainties permit equally probable and contrasting interpretations of existing paleoclimate records. We also examine 14C-induced uncertainties in the spatial climatic response on the Tibetan Plateau to (1) the termination of the Last Glacial Maximum and (2) the Holocene Thermal Maximum. We conclude with recommendations for reducing uncertainties in future lake-based paleoclimate studies on the Tibetan Plateau. [Copyright &y& Elsevier]