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Although glaciers in High Mountain Asia produce an enormous amount of water used by downstream populations, they remain poorly observed in the field. This study presents a geodetic mass balance of the glaciers in the Astore Basin (with differential GPS (dGPS) measurements on Harcho glacier) between 1999 and 2016. Changes near the terminus of Harcho glacier (below 3800 m a.s.l.) featured heterogeneous surface elevation changes, whereas the middle section shows the most negative changes. The surface elevation changes were positive above 4200 m a.s.l. The average annual mass balance was −0.08 ± 0.07 m w.e. a−1 derived from a dGPS and DEM comparison whereas Advanced Spaceborne Thermal Emission and Reflection Radiometer DEM-based results show a slightly positive, that is 0.03 ± 0.24 m w.e. a−1 in the same period. In contrast, the terminus indicates a substantial retreat of ~368 m (4.5 m a−1) between 1934 and 2016. The average mass balance of 19 glaciers (>2 km2) covering ~60% of the total glaciers in the Basin exhibit no net mass loss in the period of 2000−2016 and follow a pattern similar to adjacent Karakoram glaciers.
Despite their high value and importance for various glaciological applications, detailed ice thickness measurements of alpine glaciers are still very limited. Knowledge of bedrock topography is essential for paleoglaciological studies. The Guliya ice cap located on the Tibetan Plateau is one of the highest and largest ice caps in mid-low latitude regions. A detailed ground-penetrating radar (GPR) survey was conducted on the Guliya ice cap in 2015 using 20 and 40 MHz frequency antennas. An empirical Bayesian kriging method was used for ice thickness interpolation and uncertainty assessment. GPR measurements revealed complex basal topography of the Guliya glacier with a maximum thickness of 371.12 ± 13 m. The internal reflections caused by changes in the dielectric properties were registered on the 40 MHz radargrams at the summit and were attributed to density variations. As a result of this fieldwork, one of the largest ice thickness datasets in High Mountain Asia was obtained. Guliya glacier elevation changes were assessed by differencing digital elevation models. The glacier gained mass from 2000 to 2015 with an average rate of 0.270 ± 0.11 m w.e. a−1 at the summit and 0.279 ± 0.11 m w.e. a−1 at the lower elevations.
Using in-situ measured data from Qiyi Glacier, in combination with meteorological and run-off data from stations, a distributed degree-day model was developed for 631 investigated glaciers in the Beida River catchment to explore glacier mass change and its effect on streamflow. The results showed that the average mass balance was −272 ± 67 mm w.e. a−1, with an ice loss of 3.99 Gt during 1957–2013. Assuming a continuous linear trend, equilibrium line altitude rose by 242 m. Compared with morpho-topographic variables, climatic control is a more important factor affecting glacier change. Mass-balance sensitivity to air temperature was −239 mm w.e.°C−1 a−1, while to precipitation it was +1.1 mm w.e. mm−1 a−1. That is, a 210 mm increase in precipitation would be needed to compensate for the net mass loss induced by an air temperature increase of 1°C. Average annual glacier meltwater runoff was 1.51 × 108 m3 from 1957 to 2013, accounting for 15.2% of surface runoff. The time series of meltwater runoff changed abruptly in 2000, and its contribution to surface runoff increased from 13.9 to 20.4%.
Remote sensing data, including those from Landsat Thematic Mapper/Enhanced Thematic Mapper Plus (TM/ETM +), the Shuttle Radar Topography Mission Digital Elevation Model (SRTM4.1 DEM), and the Geoscience Laser Altimeter System Ice, Cloud, and Land Elevation Satellite (Glas/ICESat), show that from 1991 to 2013 the glacier area in the Depuchangdake region of northwestern Tibet decreased from 409 to 393 km2, an overall loss of 16 km2, or 3.9% of the entire 1991 glacial area. The mean glacier-thinning rate was − 0.40 ± 0.16 m equivalent height of water per year (w.e./yr), equating to a glacier mass balance of − 0.16 ± 0.07 km3 w.e./yr. Total mass loss from 2003 to 2009 was − 1.13 ± 0.46 km3. Glacier retreat likely reflects increases in annual total radiation, annual positive degree days, and maximum temperature, with concurrent increases in precipitation insufficient to replenish glacial mass loss. The rate of glacier retreat in Depuchangdake is less than that for Himalayan glaciers in Indian monsoon-dominated areas, but greater than that for Karakoram glaciers in mid-latitude westerly-dominated areas. Glacier type, climate zone, and climate change all impact on the differing degrees of long-term regional glacial change rate; however, special glacier distribution forms can sometimes lead to exceptional circumstances.
Glacier area changes on the Tibetan Plateau were studied in different drainage basins based on Landsat satellite images from three epochs: 263 in the mid-1970s, 150 in 1999–2002 and 148 in 2013/14. Three mosaics (M1976, M2001 and M2013) with minimal cloud and snow cover were constructed, and the uncertainty due to each epoch having a finite span was accounted for. Glacier outlines (TPG1976, TPG2001 and TPG2013) were digitized manually with guidance from the SRTM DEM v4.1 and Google Earth imagery. To achieve complete multi-temporal coverage in a reasonable time, only debris-free ice was delineated. Area mapping uncertainty was evaluated at three study sites, Mount Qomolangma (Everest), Mount Naimona'Nyi, Mount Geladandong, where the largest differences between present and earlier measurements were within ~±4%. Area differences with previous inventories ranged from −19.6% (TPG1976 minus the first Chinese Glacier Inventory) to −3.6% and −1.1% (TPG2013 and TPG2001, respectively minus the second Chinese Glacier Inventory), while the difference TPG2001 minus the GAMDAM Glacier Inventory was +10.4%. Glacier area on the plateau decreased from 44 366 ± 2827 km2 (1.7% of the study area) in the 1970s to 42 210 ± 1621 km2 in 2001 and 41 137 ± 1616 km2 in 2013. Shrinkage was faster in external drainage basins of the southeast than in the interior basins of the northwest, from a maximum of −0.43% a−1 (−1.60% a−1 during 1994–2013) in the Mekong catchment down to a minimum of −0.12% a−1 in the Tarim interior drainage.
We investigate the impact of climate change on Gurenhekou glacier, southern Tibetan Plateau, which is representative of the tens of thousands of mountain glaciers in the region. We apply a three-dimensional, thermomechanically coupled full-Stokes model to simulate the evolution of the glacier. The steep and rugged bedrock geometry requires use of such a flow model. We parameterize the temperature and surface mass-balance (SMB) uncertainties using nearby automatic weather and meteorological stations, 6 year measured SMB data and an energy-balance model for a nearby glacier. Summer air temperature increased at 0.02 Ka−1 over the past 50 years, and the glacier has retreated at an average rate of 8.3 m a−1. Prognostic simulations suggest an accelerated annual average retreat rate of ~9.1 ma−1 along the central flowline for the next 25 years under continued steady warming. However, regional climate models suggest a marked increase in warming rate over Tibet during the 21st century, and this rate causes about a 0.9 ± 0.3% a−1 loss of glaciated area and 1.1 ± 0.6% a−1 shrinkage of glacier volume. These results, the rather high warming rates predicted and the small sizes of most Tibetan glaciers, suggest that significant numbers of glaciers will be lost in the region during the 21st century.
Numerous studies have confirmed the rapid retreat of Tibetan Plateau glaciers in recent decades, and resulting reductions in glacier volume. However, high-resolution determinations of the changes in glacier thickness remain sparse. This paper presents results based on differential GPS measurements to accurately measure glacier thickness change over the past few years. Measurements from the lower part of Gurenhekou glacier show an average thickness change of –3.82 m over a 4 year period. On the lower part of Kangwure glacier we measured an average thickness change of –2.70 m over 3 years. On the upper part of Naimona’Nyi glacier (northern branch), western Himalaya, thickness changed by –1.34 m on average between 2008 and 2010, and –0.87 m between 2010 and 2013. Large temporal changes in thinning rates were found on Naimona’Nyi glacier, due to variations in local precipitation. Our measurements also show variable changes in glacier thickness over different parts of each glacier, with little dependence on elevation. The limited data also show glacier thinning in the accumulation zone.
Stable isotopes are a primary tool for inferring past temperature changes and atmospheric moisture variability from ice cores. A 33 m ice core representing the period 1850–2004 was retrieved from the Tanggula Mountains, central Tibetan Plateau (5743 m a.s.l.), in August 2005. Annual average stable isotope (δ18O, δD) values generally increase during the period, while the second-order parameter of deuterium excess (d-excess) generally decreases. High annual average d-excess values (18.2‰) throughout the ice core suggest a significant contribution of continental recycled moisture. d-excess values shift from relatively higher values during 1850–1940 to lower values since the 1940s. Annual isotope values and reconstructed accumulation are compared with climate indices, local station temperature records and northern India monsoon precipitation. Significant correlation is observed between δ18O and the Southern Oscillation, NINO3.4 and Dipole Mode indices. Annual average d-excess values revealed a significant negative correlation with the Dipole Mode index. Results suggest a relatively greater contribution of westerly-dominated continental moisture prior to the 1940s and an increase in the contribution of moisture evaporated under more humid conditions since the 1940s.
The volume distribution of atmospheric dust particles (microparticles) of 1–30 μm diameter in Muztagata, Dunde, Dasuopu and Everest ice cores from the Tibetan Plateau was measured and fitted as a log-normal function in order to characterize their basic size properties. Our results reveal that whether the volume distribution fits the log-normal function or not largely depends on the dust concentration and the specific dust-storm event but is independent of physiographical location and season. Our results show only high-concentration samples obey the log-normal distribution in volume, with mode sizes ranging from 3 to 161 μm. The log-normal distribution was largely attributed to the mid-sized particles between 3 and 15 μm, which contribute most (>70%) of the total volume. The volume size distribution characteristics for mineral dust particles from ice cores reveal that the coarse particles might be common in the upper-level troposphere over the Tibetan Plateau. These dust size features are useful to advance our understanding of dust effects on climate, and provide clues to better characterize atmospheric dynamics over the Tibetan Plateau that will help to improve the current models.
Temperature variation on the Tibetan Plateau over the last 1000 years has been inferred using a composite δ18O record from four ice cores. Data from a new ice core recovered from the Puruogangri ice field in the central Tibetan Plateau are combined with those from three other cores (Dunde, Guliya and Dasuopu) recovered previously. The ice-core δ18O composite record indicates that the temperature change on the whole Tibetan Plateau is similar to that in the Northern Hemisphere on multi-decadal timescales except that there is no decreasing trend from AD 1000 to the late 19th century. The δ18O composite record from the northern Tibetan Plateau, however, indicates a cooling trend from AD 1000 to the late 19th century, which is more consistent with the Northern Hemisphere temperature reconstruction. The δ18O composite record reveals the existence of the Medieval Warm Period and the Little Ice Age (LIA) on the Tibetan Plateau. However, on the Tibetan Plateau the LIA is not the coldest period during the last millennium as in other regions in the Northern Hemisphere. The present study indicates that the 20th-century warming on the Tibetan Plateau is abrupt, and is warmer than at any time during the past 1000 years.
This study examines precipitation samples collected at the Yushu meteorological station on the eastern Tibetan Plateau from November 2000 to November 2002. Results show that air-temperature effects control δ18O in precipitation in this area. Values of δ18O in precipitation positively correlate with air temperature, especially for monthly averages. Our data also show δ18O values in precipitation positively correlate with dew point and surface pressure in the Yushu region. Similar to other stations (Tuotuohe, Nagqu, Gaize and Shiquanhe) lying in the transition zone between the regions in the south dominated by the monsoon and those in the north dominated by the westerlies, because of the effect of monsoon precipitation, precipitation rates are high, and heavy isotopes are more depleted in summer at the Yushu station. Accordingly, values of δ18O in precipitation correlate more strongly with air temperature and dew point before the monsoon onset and after the monsoon retreat than during the monsoon period. That is, intense monsoon activities weaken the correlations between δ18O and air temperature and dew point. Clearly, dew point, surface pressure and the monsoon intensity contribute to controlling the δ18O values in precipitation at the Yushu station.
The bacterial DNA structures at different depths in the Puruogangri (Tibetan Plateau) ice core (83.45m) were investigated by the denaturing gradient gel electrophoresis (DGGE) DNA fingerprinting technique. DGGE profiles indicated that the bacterial species diversity in glacial ice is high, and indigenous species represented by common bands in all samples may grow on the glacial surface. Bacterial diversity, as estimated by Shannon indices (mean 2.91; SD 0.25; n = 13), was comparable to that of soil habitats and had a positive correlation with Ca2+ concentration (R = 0.71; P< 0.01), a good proxy of dust. This suggested that the soil ecosystem was the main source of bacteria in this glacier. The low similarity indices (0–43%) were found between the ice-core samples, which corresponded to the episodic deposition under defined climatic conditions and low activity of microorganisms in glacial ice. The profiles of bacterial species composition in glacial ice may be a bio-indicator of climatic changes or dating.
Observations of the δ18O in precipitation from four ice cores (Puruogangri, Dasuopu, Guliya and Dunde) from the Tibetan Plateau (TP) provide additional important perspectives on climatic warming during the 20th century in a region where there is a lack of instrumental and observational climate data. The average δ18O and surface air temperature over the TP show very similar fluctuations since 1955, which provides new evidence that the δ18O in the ice cores is at least in part a temperature signal. Nevertheless differences and similarities exist among the four records. Some climatic events, particularly the major cooling episodes, are synchronously recorded in Puruogangri and Dasuopu and in the Bange meteorological air-temperature record. The major features of the ice cores allow them to be classified into two groups, the northern TP group (Dunde and Guliya) and southern TP group (Puruogangri and Dasuopu). This classification is determined by the different processes driving climate change between the northern and southern regions of the TP. Moreover, the δ18O variability between the ice cores within each region further documents the smaller-scale regional variability.
Al, Mn, Rb, Sr, Ba, Cs, Bi and Sb were measured at various depth intervals of a 41.6 m firn/ ice core drilled at an elevation of 7010 m near the top of Muztagh Ata glacier, east Pamirs (38˚17’ N, 75˚06’ E), central Asia. These data, spanning the mid-1950s to 2000, were obtained by analyzing 101 sections using a sector-field double-focusing inductively coupled plasma mass spectrometer (ICP-MS) instrument. This study provides the first time series for these metals from central Asia. Concentrations are 11.7–329 ng mL−1 for Al, 0.33–42.7 ng mL−1 for Mn, 0.42–17.8 ng mL−1 for Sr, 0.04–1.4 ng mL−1 for Rb, 0.18–10.4 ng mL−1 for Ba, 2–167 pg mL−1 for Cs, 2–51 pg mL−1 for Sb and 1–31 pg mL−1 for Bi. Large variations in metal concentrations were found during the study period. Pronounced increases in concentrations were observed for Sb and Bi from the mid-1960s to the beginning of the 1990s, suggesting increased anthropogenic sources of Sb and Bi in central Asia during the same period. However, the decrease of Sb and Bi concentrations during the mid- to late 1990s reflects a reduction in anthropogenic activities in central Asia.
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