Last Glacial climate reconstruction by exploring glacier sensitivity to climate on the southeastern slope of the western Nyaiqentanglha Shan, Tibetan Plateau

Improvements in understanding glacial extents and chronologies for the southeastern slope of the western Nyaiqentanglha Shan on the Tibetan Plateau are required to understand regional climate changes during the Last Glacial cycle. A two-dimensional numerical model of mass balance, based on snow-ice melting factors, and of ice flow for mountain glaciers is used to assess the glacier sensitivity to climatic change in a catchment of the region. The model can reproduce valley glaciers, wide-tongued glaciers and a coalescing glacier within step temperature lowering and precipitation increasing experiments. The model sensitivity experiments also indicate that the dependence of glacier growth on temperature and/or precipitation is nonlinear. The model results suggest that the valley glaciers respond more sensitively to an imposed climate change than wide-tongued and coalescing glaciers. Guided by field geological evidence of former glacier extent and other independent paleoclimate reconstructions, the model is also used to constrain the most realistic multi-year mean temperatures to be 2.9-4.6 degrees C and 1.8-2.5 degrees C lower than present in the glacial stages of the Last Glacial Maximum and middle marine oxygen isotope stage 3, respectively

The timing and cause of glacial activity during the last glacial in central Tibet based on Be-10 surface exposure dating east of Mount Jaggang, the Xainza range

Mountain glaciers are sensitive to climate change, and can provide valuable information for inferring former climates on the Tibetan Plateau (TP). The increasing glacial chronologies indicate that the timing of the local Last Glacial Maximum (LGM) recorded across the TP is asynchronous, implying different local influences of the mid-latitude westerlies and Asian Summer Monsoon in triggering glacier advances. However, the well-dated sites are still too few, especially in the transition zone between regions controlled by the two climate systems. Here we present detailed last glacial chronologies for the Mount Jaggang area, in the Xainza range, central Tibet, with forty-three apparent Be-10 exposure-ages ranging from 12.4 +/- 0.8 ka to 61.9 +/- 3.8 ka. These exposure-ages indicate that at least seven glacial episodes occurred during the last glacial cycle east of Mount Jaggang. These include: a local LGM that occurred at similar to 61.9 +/- 3.8 ka, possibly corresponding to Marine Isotope Stage 4 (MIS 4); subsequent glacial advances at similar to 43.2 +/- 2.6 ka and similar to 35.1 +/- 2.1 ka during MIS 3; one glacial re-advance/standstill at MIS3/2 transition (similar to 29.8 +/- 1.8 ka); and three glacial re-advances/standstills that occurred following MIS 3 at similar to 27.9 +/- 1.7 ka, similar to 21.8 +/- 13 ka, and similar to 15.1 +/- 0.9 ka. The timing of these glacial activities is roughly in agreement with North Atlantic millennial-scale climate oscillations (Heinrich events), suggesting the potential correlations between these abrupt climate changes and glacial fluctuations in the Mount Jaggang area. The successively reduced glacial extent might have resulted from an overall decrease in Asian Summer Monsoon intensity over this timeframe. (C) 2018 Elsevier Ltd. All rights reserved

Late Quaternary glacial history of the Altyn Tagh Range, northern Tibetan Plateau

Quantifying the timing and extent of late Quaternary glaciations across the Tibetan Plateau (TP) is critical to understanding regional and global climate changes. Despite significant advancements in our knowledge of glacial histories of the TP over the past several decades, chronological constraints are still lacking for the high glaciated mountain ranges on the northern TP, including the Altyn Tagh Range. In this study, we provide thirty-two new Be-10 exposure-ages to construct a late Quaternary glacial history of the Altyn Tagh Range at the Altyn "Pass" and Akato Tagh. The dating results from Altyn "Pass" indicate that glacier might have fully melted out of this area after Marine Isotope Stage 3 (MIS 3). The tentatively-defined minimum moraine ages north of Akato Tagh show that four glacial culminations possibly occurred during MIS 5, MIS 4, MIS 3 or 2, and the late Holocene. These dating results, together with the compiled exposure-ages from Sulamu Tagh, imply that the last glacial glacier fluctuations along the Altyn Tagh Range were likely driven by several factors: North Atlantic climate oscillations, northern hemispheric high-latitude summer solar insolation, atmospheric CO2 concentrations, and geometry of glacier catchment. The progressive reduction in glacier extent during the last glacial is likely associated with available precipitation, controlled by the mid-latitude westerlies

Quaternary glaciations in the Lopu Kangri area, central Gangdise Mountains, southern Tibetan Plateau

The Gangdise Mountains are located in a transition zone between the Indian Summer Monsoon-dominated Himalaya Mountains and the Westerlies-dominated Qiangtang Plateau. The timing and extent of the paleoglaciations in the central Gangdise Mountains remain unclear. We investigated the glacial history of the southeastern slopes of Lopu Kangri using Be-10 exposure dating and summarized the dating results for the western and eastern sectors of the Gangdise Mountains. Glacial events were constrained to >= 243.88 +/- 25.88 ka, >= 43.09 +/- 4.18 ka, 24.19 +/- 2.29 ka, 19.78 +/- 1.9 ka, 10.62 +/- 1 ka, 2.75 +/- 0.37 ka, 1.8 +/- 0.18 ka, 0.32 +/- 0.04 ka and 0.22 +/- 0.04 ka, representing paleoglaciations which occurred during marine isotope stage (MIS) 8/7 or earlier, MIS 3 or earlier, early MIS 2, the global Last Glacial Maximum (LGM), the early Holocene, the Neoglacial and the Little Ice Age (LIA). Evidence of MIS 5 or earlier glaciations, and the glaciations during MIS 3, early and late MIS 2, the global LGM and the LIA, can be found in the western or eastern sectors of the Gangdise Mountains. The spatial trend in Delta ELA values in the Gangdise and surrounding mountain ranges would appear to have been controlled by particular precipitation distribution patterns. The glacial events identified in the Gangdise Mountains during MIS 2, the Neoglacial and the LIA appear consistent with previously-identified cold periods. Precipitation was most likely a contributory cause of the glaciations during the MIS 3, early Holocene, the Neoglacial and the LIA. (C) 2018 Elsevier Ltd. All rights reserved

Simulated Impact of the Tibetan Glacier Expansion on the Eurasian Climate and Glacial Surface Mass Balance during the Last Glacial Maximum

Glaciers over the Tibetan Plateau and surrounding regions during the Last Glacial Maximum (LGM) were much more extensive than during the preindustrial period (PI). The climate impact of such glacial expansion is studied here using the Community Atmosphere Model, version 4 (CAM4). To cover the range of uncertainty in glacier area during the LGM, the following three values are tested: 0.35 x 10(6), 0.53 x 10(6), and 0.70 x 10(6) km(2). The added glacier is distributed approximately equally over the Pamir region and the Himalayas. If 0.70 x 10(6) km(2) is used, the annual mean surface temperature of the glaciated regions would be cooled by similar to 3.5 degrees C. The annual mean precipitation would be reduced by 0.2 mm day(-1) (10%) and 2.5 mm day(-1) (24%) over the Pamir region and Himalayas, respectively. The surface mass balance (SMB) of the glaciers changes by 0.55 m yr(-1) (280%) and 20.32 m yr(-1) (220%) over the two regions, respectively. The changes in SMB remain large (0.29 and 20.13 m yr(-1)), even if the area of the Tibetan glacier were 0.35x10(6) km(2). Therefore, based on the results of this particular model, the expansion of glaciers can either enhance or slow the glacial growth. Moreover, the expansion of glaciers over the Himalayas reduces summer precipitation in central and northern China by similar to 0.5 mm day(-1) and increases summer precipitation in southern Asia by similar to 0.6 mm day(-1). The expansion of glaciers over the Pamir region has a negligible influence on the precipitation in these monsoonal regions, which is likely due to its large distance from the main monsoonal regions

Evaporite minerals and geochemistry of the upper 400 m sediments in a core from the Western Qaidam Basin, Tibet

Qaidam Basin is a tectonically controlled depression on the northern margin of the Tibetan Plateau. In 2008, a long core was drilled in the Qahansilatu sub-basin in the western Qaidam basin. The sediment layers in the upper 400 m alternate between evaporite mineral layers and carbonaceous clay layers. The detailed mineralogical investigation focused on evaporite minerals including halite, gypsum, mirabilite, thenardite, glauberite, eugsterite, and bloedite. Gypsum and halite make up the majority of the evaporate minerals. Environmentally induced variations in the mineralogy and crystal habit of the sulfates have been extensively investigated. Gypsum has prismatic and pyramid habits, such as disc pyramid, stubby prismatic, slender prismatic. Visible isolated gypsum and aggregates (rosette/radial and twins) are mostly scattered in carbonaceous clay layers, suggesting that secondary gypsum is well developed. Gypsum may be a precursor mineral of glauberite, and thenardite is the precursor of bloedite. As a metastable and rare mineral, eugsterite does not appear in other Tibetan areas. It forms at the expense of pre-existing gypsum or thenardite in the core at an experimental temperature of higher than room temperature. The presence of eugsterite indicates a warm and/or hot climate at its deposition time. Mineralogical variations have been explained by the brine evolution of Na-Cl, Na-Ca-SO4, Na-SO4, Na-SO4-Cl, Na-Ca-SO4-Cl, Ca-SO4, and Na-Mg-SO4. For instance, Na-Mg-SO4 corresponds to bloedite, while Na-Ca-SO4-Cl to the assemblage of halite, gypsum and glauberite. The evaporite minerals and carbonaceous clay layers' alternation indicates the shift between dry and wet climate. According to the thickness, 18 evaporite stages and/or dry climate stages were identified from 0.97 Ma to about 0.03 Ma. The two early dry climate stages are identified at 0.96-0.97 Ma and 0.87 Ma. The other 16 evaporite stages occurred from 0.78 Ma to about 0.03 Ma. The evaporate-rich stages suggested that evaporation was high and groundwater inflow was sufficient at the sub-basin