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Quantifying glacial erosion contributes to our understanding of landscape evolution and topographic relief production in high altitude and high latitude areas. Combining in situ10Be and 26Al analysis of bedrock, boulder, and river sand samples, geomorphological mapping, and field investigations, we examine glacial erosion patterns of former ice caps in the Shaluli Shan of the southeastern Tibetan Plateau. The general landform pattern shows a zonal pattern of landscape modification produced by ice caps of up to 4000 km2 during pre‐LGM (Last Glacial Maximum) glaciations, while the dating results and landforms on the plateau surface imply that the LGM ice cap further modified the scoured terrain into different zones. Modeled glacial erosion depth of 0–0.38 m per 100 ka bedrock sample located close to the western margin of the LGM ice cap, indicates limited erosion prior to LGM and Late Glacial moraine deposition. A strong erosion zone exists proximal to the LGM ice cap marginal zone, indicated by modeled glacial erosion depth >2.23 m per 100 ka from bedrock samples. Modeled glacial erosion depths of 0–1.77 m per 100 ka from samples collected along the edge of a central upland, confirm the presence of a zone of intermediate erosion in‐between the central upland and the strong erosion zone. Significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate restricted glacial erosion during the last glaciation. Our study, for the first time, shows clear evidence for preservation of glacial landforms formed during previous glaciations under non‐erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the Haizishan ice cap during the LGM. © 2018 John Wiley & Sons, Ltd. We apply 10Be and 26Al exposure dating from bedrock, erratics and river sediments to tell the erosional efficiency of ice caps that covered the Haizishan Plateau. These ice caps in southeastern Tibetan Plateau had a concentric basal thermal regime, including areas of deposition, strong‐ and intermediate erosion, and of preservation under non‐erosive ice. [ABSTRACT FROM AUTHOR]

We present a glacial geomorphological map at a scale of 1:200,000 of the Maidika region in the southeastern part of the central Tibetan Plateau covering 13,600 km2. Based on the 90 m resolution SRTM elevation model, the 30 m resolution ASTER GDEM elevation model, and the Landsat ETM+ satellite imagery of 30/15 m resolution, we have mapped glacial valleys, marginal moraines, glacial lineations, and hummocky terrain. Glacial landforms occur frequently and indicate extensive past glaciation with alpine style valley glaciers as well as more extensive ice fields. Of particular interest is the presence of glacial lineation swarms, which is unusual for the Tibetan Plateau glacial landform record. Based on the distribution of glacial landforms, we present a generalized maximum glacial extent reconstruction covering 6045 km2or 44% of the map. [ABSTRACT FROM PUBLISHER]

The Tibetan Plateau holds an ample record of past glaciations, and there is an extensive set of glacial deposits dated by exposure dating. Here a compilation is presented of 10Be exposure ages from 485 glacial deposits with 1855 individual samples on the Tibetan Plateau, and ELA depression estimates for the glacial deposits based on a simple toe to headwall ratio approach. To recalculate the Tibetan Plateau exposure ages, 10Be production rates from 24 calibration sites across the world are compiled and recalibrated yielding an updated global reference 10Be production rate. The recalculated exposure ages from the Tibetan Plateau glacial deposits are then divided into three groups based on exposure age clustering, to discriminate good (well-clustered) from poor (scattered) deglaciation ages. A major part of the glacial deposits have exposure ages affected by prior or incomplete exposure, complicating exposure age interpretations. The well-clustered deglaciation ages are primarily from mountain ranges along the margins of the Tibetan Plateau with a main peak between 10 and 30 ka, indicating glacial advances during the global LGM. A large number of deglaciation ages older than 30 ka indicates maximum glaciation predating the LGM, but the exposure age scatter generally prohibits accurate definition of the glacial chronology. The ELA depression estimates scatter significantly, but the main part is remarkably low. Average ELA depressions of 337 ± 197 m for the LGM and 494 ± 280 m for the pre-LGM indicate restricted glacier expansion. [ABSTRACT FROM AUTHOR]

We present a glacial geomorphological map covering 1.04 × 105 km2 of the Shaluli Shan (Shan = Mountain), southeastern Tibetan Plateau. Using a 90 m digital elevation model from the Shuttle Radar Topography Mission and 15/30 m Landsat Enhanced Thematic Mapper Plus satellite imagery, we have mapped glacial valleys, marginal moraines, hummocky terrain, glacial lineations and ice-scoured terrain. Lineations and scoured areas largely overlap on the low relief granite plateau of the Shaluli Shan and relate to former ice cap glaciation. These landscape features indicate that past ice cap glaciation included basal sliding conditions, and thus warm-based ice. Glacial valleys and marginal moraines are dominant landforms in the high mountain ranges of Shaluli Shan and occur on and fringing the plateau. This glacial geomorphological map forms the basis for paleoglaciological reconstructions of this southeastern Tibetan Plateau region and indicates the former presence of multiple glaciations involving valley glaciers and ice caps. The map is presented at a scale of 1:630,000. [ABSTRACT FROM AUTHOR]

Abstract: The Bayan Har Shan, a prominent upland area in the northeastern sector of the Tibetan Plateau, hosts an extensive glacial geological record. To reconstruct its palaeoglaciology we have determined 10Be exposure ages based on 67 samples from boulders, surface pebbles, and sediment sections in conjunction with studies of the glacial geology (remote sensing and field studies) and numerical glacier modelling. Exposure ages from moraines and glacial sediments in Bayan Har Shan range from 3 ka to 129 ka, with a large disparity in exposure ages for individual sites and within the recognised four morphostratigraphical groups. The exposure age disparity cannot be explained by differences in inheritance without using unrealistic assumptions but it can be explained by differences in post-depositional shielding which produces exposure ages younger than the deglaciation age. We present a palaeoglaciological time-slice reconstruction in which the most restricted glaciation, with glaciers less than 10 km long, occurred before 40–65 ka. More extensive glaciations occurred before 60–100 ka and 95–165 ka. Maximum glaciation is poorly constrained but probably even older. The Bayan Har Shan exposure age dataset indicates that glaciers on the northeastern Tibetan Plateau have remained surprisingly restricted for at least 40 ka, including the global last glacial maximum (LGM). This case of a missing LGM is further supported by high-resolution glacier modelling experiments. [Copyright &y& Elsevier]

Please clickhereto download the map associated with this article. The glacial geomorphology of the central Tibetan Plateau was mapped over 285,000 km2.Here we present a map covering 135,000 km at a scale of 1:660,000. The glacial geomorphology was mapped using 15 and 30 m resolution Landsat 7 ETM+ satellite imagery, a 90 m resolution SRTM digital elevation model, and satellite and aerial images displayed in Google Earth. Four landform categories were discernible and mapped; glacial valleys, marginal moraines, glacial lineations, and hummocky terrain. The mapped landforms indicate multiple glacial advances of valley and piedmont glaciers. The mapped landform record lends no support to individual ice centres having coalesced to form a plateau-wide ice sheet. [ABSTRACT FROM PUBLISHER]

Abstract: Cosmogenic exposure dating has greatly enhanced our ability to define glacial chronologies spanning several global cold periods, and glacial boulder exposure ages are now routinely used to constrain deglaciation ages. However, exposure dating involves assumptions about the geological history of the sample that are difficult to test and yet may have a profound effect on the inferred age. Two principal geological factors yield erroneous inferred ages: exposure prior to glaciation (yielding exposure ages that are too old) and incomplete exposure due to post-depositional shielding (yielding exposure ages that are too young). Here we show that incomplete exposure is more important than prior exposure, using datasets of glacial boulder 10Be exposure ages from the Tibetan Plateau (1420 boulders), Northern Hemisphere palaeo-ice sheets (631 boulders), and present-day glaciers (208 boulders). No boulders from present-day glaciers and few boulders from the palaeo-ice sheets have exposure ages significantly older than independently known deglaciation ages, indicating that prior exposure is of limited significance. Further, while a simple post-depositional landform degradation model can predict the exposure age distribution of boulders from the Tibetan Plateau, a prior exposure model fails, indicating that incomplete exposure is important. The large global dataset demonstrates that, in the absence of other evidence, glacial boulder exposure ages should be viewed as minimum limiting deglaciation ages. [ABSTRACT FROM AUTHOR]

The glacial geomorphology of the central Tibetan Plateau was mapped over 285,000 km². Here we present a map covering 135,000 km² at a scale of 1:660,000. The glacial geomorphology was mapped using 15 and 30 m resolution Landsat 7 ETM+ satellite imagery, a 90 m resolution SRTM digital elevation model, and satellite and aerial images displayed in Google Earth. Four landform categories were discernible and mapped; glacial valleys, marginal moraines, glacial lineations, and hummocky terrain. The mapped landforms indicate multiple glacial advances of valley and piedmont glaciers. The mapped landform record lends no support to individual ice centres having coalesced to form a plateau-wide ice sheet. [ABSTRACT FROM AUTHOR]

We here present a detailed glacial geomorphological map covering 136,500 km² of the Bayan Har sector of the northeastern Tibetan Plateau - an area previously suggested to have nourished the most extensive Quaternary glaciers of the Tibetan Plateau. The map, presented at a scale of 1:650,000, is based on remote sensing of a 90 m SRTM digital elevation model and 15/30 m Landsat ETM+ satellite imagery. Seven landform types have been mapped; glacial valleys, glacial troughs, glacial lineations, marginal moraines, marginal moraine remnants, meltwater channels and hummocky terrain. A large number of glacial landforms exist, concentrated around mountain blocks protruding above the surrounding plateau area, testifying to former glacial activity. In contrast, large plateau areas of lower altitude lack glacial landforms. The mapped glacial geomorphology indicates multiple former glacial advances primarily by valley and piedmont glaciers, but lends no support to the hypothesis of ice sheet scale glaciation in the area. The presented glacial geomorphological map demonstrates the usefulness of remote sensing techniques for mapping the glacial geomorphology of the Tibetan Plateau, and it will be used for reconstructing the paleoglaciology of the Bayan Har sector of the northeastern Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Abstract: Reconstructing the paleoglaciation of the Tibetan Plateau is critical to understanding linkages between regional climate changes and global climate changes, and here we focus on the glacial history of the Shaluli Shan, an area of the southeastern Tibetan Plateau that receives much of its precipitation from monsoon flow. Based on field investigation, geomorphological mapping, and 10Be exposure dating of moraines, we identify glacial deposits from the Late Glacial, with minimum ages at 13.0 ± 1.2 –17.1 ± 1.6 ka, global Last Glacial Maximum (gLGM) at 21.6 ± 2.0 ka, and pre-gLGM at 102.3 ± 10.0–183.6 ± 17.0 ka. These ages are consistent with and significantly extend the known range from most prior chronological work using terrestrial cosmogenic nuclides in this area, and include a set of dates for the Kuzhaori moraine that raise questions about prior chronologies based on the electron spin resonance technique. Ice caps about 4000 km2 in size covered the Haizishan Plateau and the Xinlong Plateau during the global LGM, with large glaciers extending far down outlet valleys. The presence of ice cap glaciation, here, contrasts strongly to glaciation elsewhere in the Shaluli Shan and more central regions of the Tibetan Plateau where ice expansion remained constricted to valleys. This work provides important insights into the paleoclimate pattern and monsoon evolution of the Tibetan Plateau over past glacial cycles and indicates that the Shaluli Shan has a glacial chronology more consistent with the Northern Hemisphere paleo-ice sheets than other areas of the Tibetan Plateau. [Copyright &y& Elsevier]

Abstract: Glacial geomorphological mapping from satellite imagery and field investigations provide the basis for a reconstruction of the extent and style of glaciation of the Shaluli Shan, a mountainous area on the southeastern Tibetan Plateau. Our studies provide evidence for multiple glaciations, including the formation of regional ice caps and valley glaciers. The low-relief topography within the Shaluli Shan, the Haizishan Plateau, and Xinlong Plateau display zonal distributions of glacial landforms that is similar to those imprinted by Northern Hemisphere ice sheets during the last glacial cycle, indicating the presence of regional, polythermal ice caps. Abundant alpine glacial landforms occur on high mountain ranges. The pattern of glaciated valleys centered on high mountain ranges and ice-scoured low relief granite plateaus with distinctive patterns of glacial lineations indicate a strong topographic control on erosional and depositional patterns by glaciers and ice caps. In contrast to the Shaluli Shan, areas farther north and west on the Tibetan Plateau have not yielded similar landform evidence for regional ice caps with complex thermal basal conditions. Such spatial differences across the Tibetan Plateau are the result of variations in climate and topography that control the extent and style of glaciations and that reinforce the importance of detailed geomorphological mapping for understanding paleoclimate variations and characteristics of former glaciations. [Copyright &y& Elsevier]

Abstract: The Tibetan Plateau is a topographic feature of extraordinary dimension and has an important impact on regional and global climate. However, the glacial history of the Tibetan Plateau is more poorly constrained than that of most other formerly glaciated regions such as in North America and Eurasia. On the basis of some field evidence it has been hypothesized that the Tibetan Plateau was covered by an ice sheet during the Last Glacial Maximum (LGM). Abundant field- and chronological evidence for a predominance of local valley glaciation during the past 300,000 calendar years (that is, 300 ka), coupled to an absence of glacial landforms and sediments in extensive areas of the plateau, now refute this concept. This, furthermore, calls into question previous ice sheet modeling attempts which generally arrive at ice volumes considerably larger than allowed for by field evidence. Surprisingly, the robustness of such numerical ice sheet model results has not been widely queried, despite potentially important climate ramifications. We simulated the growth and decay of ice on the Tibetan Plateau during the last 125 ka in response to a large ensemble of climate forcings (90 members) derived from Global Circulation Models (GCMs), using a similar 3D thermomechanical ice sheet model as employed in previous studies. The numerical results include as extreme end members as an ice-free Tibetan Plateau and a plateau-scale ice sheet comparable, in volume, to the contemporary Greenland ice sheet. We further demonstrate that numerical simulations that acceptably conform to published reconstructions of Quaternary ice extent on the Tibetan Plateau cannot be achieved with the employed stand-alone ice sheet model when merely forced by paleoclimates derived from currently available GCMs. Progress is, however, expected if future investigations employ ice sheet models with higher resolution, bidirectional ice sheet-atmosphere feedbacks, improved treatment of the surface mass balance, and regional climate data and climate reconstructions. [Copyright &y& Elsevier]