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Glaciers reflect integrated climate signals from inter-annual to centennial timescales. In using glacier extent as a climate-change detector, the challenge is to distinguish the roles of the inter-annual climate variability and long-term climatic change on the glacier change. Using cosmogenic nuclide 10Be dating method and glacier dynamical models, this study numerically reconstructed glacier extents at ~ 1850s AD (latest Little Ice Age period) in the Keqiong Qu I, Keqiong Qu II, Taqiong Qu I, and Taqiong Qu II valleys around the Kuoqionggangri peak, southern Tibetan Plateau, and quantified the effects of inter-annual summer temperature variability and long-term summer temperature change on the glacier retreats since then. Without change in mean annual precipitation, the summer temperature decrease of 0.40–0.53 °C from present was required to sustain the glacier lengths at their respective ~ 1850s AD moraines in the four valleys. The climate inferences from the glacier-climate modeling were similar to reconstructions at other glaciers on the Tibetan Plateau and the changes in long term climate reanalysis (HadCRUT5, BEST and NOAA 20CR v3). Forced by the inter-annual variabilities in summer temperature and annual precipitation, the glaciers had excursions of 150–200 m (5–8% of their lengths) from the ~ 1850s AD moraines. We therefore argued that the climate change was largely responsible for the glacier retreats from the ~ 1850s AD moraine positions in the region. [ABSTRACT FROM AUTHOR]

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]

• Emphasized outlet discrepancy among geothermal springs within one system. • Different ratio of mixed-in cold water causes thermal springs' outlet discrepancy. • Lithology controls geothermal water mixing behaviors during its discharge process. • Proposed a conceptual model of lithology governed geothermal springs formation. Geothermal springs within the same geothermal system are naturally considered with similar output manifestation, but usually distinct. A low temperature geothermal spring group (Bogexi) on eastern Tibetan Plateau was investigated and compared with the boiling geothermal spring group (Rekeng) in the same fault zone to get insights into the reasons behind. The Bogexi geothermal springs have quite lower output temperature (25.0–65.3℃) than the boiling Rekeng geothermal springs (84.5–90.0℃). Although all these two geothermal spring groups have the same hydrochemical facies of HCO 3 -Na, the Bogexi geothermal springs present lower concentration of Na+ and trace elements. The geothermal waters of Bogexi were originated from the precipitation and glacier/snow meltwater of the eastern Haizi mountains with the recharge elevation of 4,400–4,700 m. These recharged waters infiltrate into the geothermal system that with the reservoir temperature of 160-180℃ and are heated by tectonic deformation heat in the depth of 3,100–3,400 m. Lithology determines the fissures development in the shallow and furtherly controls the mixing behaviors and discharge characteristics of geothermal springs in the discharge area. As a result, the thermal groundwaters of Bogexi are mixed with great quantity of shallow cycling cold water with the mixing proportion averaging at 73–76 % during the ascending process, leading to their lower output temperatures and distinct hydrochemical and isotopic features from the boiling Rekeng geothermal springs. A conceptual model was proposed to portray the genesis of low temperature geothermal springs in high temperature geothermal system. The recharged water percolates downward and is heated in the deep thermal reservoir. Heated waters are enriched of chemical elements during this process and then flow upwards under the driving of hydraulic pressure. While the lithology determines the circulation of cold water in the discharge area. Karst lithology, usually with developed fissures and channels, can provide more favorable conditions for cold water cycling in the shallow part than other lithology. This leads to considerable cold water mixed into the upward-flowing geothermal groundwater, and differs these geothermal springs from other ones in the same fault zone in output temperature and hydrochemcial features. This research can improve the understanding of formation mechanism of output discrepancies of various springs within one geothermal system. [ABSTRACT FROM AUTHOR]

Grassland cover and its temporal changes are key parameters in the estimation and monitoring of ecosystems and their functions, especially via remote sensing. However, the most suitable model for estimating grassland cover and the differences between models has rarely been studied in alpine meadow grasslands. In this study, field measurements of grassland cover in Gannan Prefecture, from 2014 to 2016, were acquired using unmanned aerial vehicle (UAV) technology. Single-factor parametric and multi-factor parametric/non-parametric cover inversion models were then constructed based on 14 factors related to grassland cover, and the dynamic variation of the annual maximum cover was analyzed. The results show that (1) nine out of 14 factors (longitude, latitude, elevation, the concentrations of clay and sand in the surface and bottom soils, temperature, precipitation, enhanced vegetation index (EVI) and normalized difference vegetation index (NDVI)) exert a significant effect on grassland cover in the study area. The logarithmic model based on EVI presents the best performance, with an R² and RMSE of 0.52 and 16.96%, respectively. Single-factor grassland cover inversion models account for only 1-49% of the variation in cover during the growth season. (2) The optimum grassland cover inversion model is the artificial neural network (BP-ANN), with an R² and RMSE of 0.72 and 13.38%, and SDs of 0.062% and 1.615%, respectively. Both the accuracy and the stability of the BP-ANN model are higher than those of the single-factor parametric models and multi-factor parametric/non-parametric models. (3) The annual maximum cover in Gannan Prefecture presents an increasing trend over 60.60% of the entire study area, while 36.54% is presently stable and 2.86% exhibits a decreasing trend. [ABSTRACT FROM AUTHOR]

Glacial landforms on Mount Taibai, the main peak of the Qinling Mountains, China, are investigated to improve understanding of Quaternary palaeoclimate evolution in this key region of China's geographical north and south junction. Cosmogenic radionuclide 10Be exposure dating and glacier-climate modeling are used to reconstruct glacier evolution during the last glaciation in the Eryehai Valley, on the slopes of Mount Taibai. Chronological results indicate that the earliest initiation of the Mount Taibai glaciation was earlier than the global Last Glacial Maximum (gLGM). The glacier subsequently advanced further reaching its greatest extent during the gLGM between ∼23.50 ka and 21.76 ka. After this time, the glacier receded rapidly, before disappearing completely between ∼17.9 ka and 17.7 ka. We also analyzed a compilation of 229 recalculated 10Be exposure ages from the mountain ranges on the eastern Tibetan Plateau (TP), as well as in the Jaggang Mountains on the south-central TP, and found that a few mountain ranges on the eastern TP experienced two distinct millennial-scale moraine building events during the gLGM. Using glacier-climate modeling, temperature was calculated to have fallen from between ∼9.0 and 9.4 °C during the gLGM, with precipitation being 60–80% of the present-day value. If precipitation during the rapid retreat of the glacier between ∼21.76 ka and 18.10 ka were to be consistent with present trends, then the temperature would have needed to increase by a total of ∼1.3 °C during this period, with a mean rate of increase of 0.4 °C/ka. Combining our findings with other paleoclimate proxies, we infer that the main reason that there was no further glacial advance after the gLGM on Mount Taibai was the lower altitude of its peak relative to the Equilibrium-line Altitude (ELA). Our results provide the paleoclimatic conditions of the last glaciation in this critical area of China's geographical north and south junction, and deepen the understanding of how the East Asian Summer Monsoon (EASM) influences glaciers on the TP. • New CRN 10Be exposure age results elucidate the glacial evolutionary process since the last glaciation on Mount Taibai. • The earliest initiation of the Mount Taibai glaciation was earlier than the global Last Glacial Maximum. • The East Asian summer monsoonal was an important factor influencing the fluctuations in paleoglaciers of eastern China. • Some mountains on the eastern TP may have experienced two millennial-scale moraine building events during the gLGM. [ABSTRACT FROM AUTHOR]

Daily snow cover mapping is difficult when Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover products are cloud obscured. The daily cloud-free snow cover product provides an essential parameter for hydrological modeling, climate system studies, and snow-caused disaster monitoring on the Tibetan Plateau (TP). In this paper, we present an algorithm, Terra–Aqua–IMS (TAI), which combines MODIS Terra and Aqua (500 m) and the Interactive Multisensor Snow and Ice Mapping System (IMS; 4 km) to produce a daily cloud-free snow cover product (500 m). The overall accuracy of the new TAI over the TP is 94% as compared with ground stations in all-sky conditions; this value is significantly higher than the 64% of the blended MODIS Terra–Aqua product and the 55% and 50% of the original MODIS Terra and Aqua products, respectively. Without the IMS, the daily combination of MODIS Terra–Aqua can only remove limited cloud contamination: 37.3% of the annual mean cloud coverage compared with 46.6% (MODIS Terra) and 55.1% (MODIS Aqua). The resulting annual mean snow cover over the TP from the daily TAI data is 19.1%, which is much larger than the 4.7%–8.1% from the daily original MODIS Terra/Aqua and the blended Terra–Aqua snow product due to cloud blockage. [ABSTRACT FROM PUBLISHER]

Using new, daily cloud-free snow-cover products, this study examines snow cover dynamics and their response to climate change. The results demonstrate that the daily cloud-free snow-cover products not only posses the advantages of the AMSR-E (unaffected by weather conditions) and MODIS (relatively higher resolution) products, but are also characterized by high snow and overall classification accuracies (∼85% and ∼98%, respectively), substantially greater than those of the existing daily snow-cover products for all sky conditions and very similar to, or even slightly greater than, those of the daily MODIS products for clear-sky conditions. Using the snow-cover products, we analyzed the snow cover dynamics over the Tibetan Plateau and determined that the maximum number of snow-covered days (SCD) in a year followed a decreasing tendency from 2003 to 2010, with a decrease in snow-covered area (SCA) equivalent to 55.3% of the total Tibetan Plateau area. There is also a slightly increasing tendency in the maximum snow cover area (SCA), and a slightly decreasing tendency in the persistent snow cover area (i.e., pixels of SCD > 350 days) was observed for the 8-year period, which was characterized by increases in temperature (0.09 °C/year) and in precipitation (0.26 mm/year). This suggests that, on the Tibetan Plateau, changes in temperature and precipitation exert a considerable influence on the regional SCD and SCA, as well as the distribution of persistent snow cover. [ABSTRACT FROM AUTHOR]

Understanding the changes in number and areal extent of lakes, as well as their abundance and size distribution is important for assessments of regional and global water resources, biogeochemical cycles, and changes in climate. In this study, changes in lake area greater than 1 km are mapped using Landsat datasets, spanning the 1970s, 1990, 2000, and 2010. In addition, high-resolution images (GeoCover Landsat mosaic 2000, with a pixel size of 14.25 m) are used for the first time to map lakes as small as 0.001 km across the entire Tibetan Plateau (TP). Results show that the numbers and areal extent of individual lakes >1 km in size show a slight decrease between the 1970s and 1990, followed by a clear increase from 1990 to 2010. Ninety-nine new lakes are identified between the 1970s and 2010, 71 of which are found between 1990 and 2010. This indicates the accelerated glacier melt and/or increased difference of precipitation minus evaporation since the 1990s. More than 80 % of the lakes show an increase in their area between the 1970s and 2010. The lake census, using 2000 imagery, shows that there are 32,843 lakes with a total area of 43,151.08 ± 411.49 km, which makes up 1.4 % of the total area of the TP. Around 96 % of all lakes are small, with an area <1 km, while the 1,204 large lakes (>1 km) account for 96 % of the total lake area. The TP is subdivided into 12 greater drainage basins, and of these the inner TP dominates in terms of the number of lakes (55.03 %), the total area of lakes (66 %), and lake density (0.026/km compared to the mean, 0.011/km). A plot of lake abundance against size shows that the size distribution of lakes departs from a typical power-law distribution, but displays such a distribution at the mean elevation (4,715 m), with an r value of 0.97 and a slope of −0.66. The slopes of the abundance-size equations from each of the 12 greater basins, and from all basins together, are larger than −1, supporting the inference that larger lakes, rather than the small lakes, contribute more to the total lake surface area across the TP. The lake inventory provided in this study, along with the assessment of lake size distribution, have important implications for estimates of water balance, for water resource management, and for lake area estimations in the TP. [ABSTRACT FROM AUTHOR]

Lake level and area variations are sensitive to regional climate changes and can be used to indirectly estimate water balances of lakes. In this study, 10 of the largest lakes in China, ∼1000 km or larger, are examined to determine changes in lake level and area derived respectively from ICESat and Landsat data recorded between 2003 and 2009. The time series of lake level and area of Selin Co, Nam Co, and Qinghai Lake in the Tibetan Plateau (TP) and Xingkai Lake in northeastern China exhibit an increasing trend, with Selin Co showing the fastest rise in lake level (0.69 m/a), area (32.59 km/a), and volume (1.25 km/a) among the 10 examined lakes. Bosten and Hulun lakes in the arid and semiarid region of northern China show a decline in both lake level and area, with Bosten Lake showing the largest decrease in lake level (−0.43 m/a) and Hulun Lake showing the largest area shrinkage (−35.56 km/a). However, Dongting, Poyang, Taihu, and Hongze lakes in the mid-lower reaches of the Yangtze River basin present seasonal variability without any apparent tendencies. The lake level and area show strong correlations for Selin Co, Nam Co, Qinghai, Poyang, Hulun, and Bosten lakes ( R >0.80) and for Taihu, Hongze, and Xingkai lakes (∼0.70) and weak correlation for East Dongting Lake (0.37). The lake level changes and water volume changes are in very good agreement for all lakes ( R > 0.98). Water balances of the 10 lakes are derived on the basis of both lake level and area changes, with Selin Co, Nam Co, Qinghai, and Xingkai lakes showing positive water budgets of 9.08, 4.07, 2.88, and 1.09 km, respectively. Bosten and Hulun lakes show negative budgets of −3.01 and −4.73 km, respectively, and the four lakes along the Yangtze River show no obvious variations. Possible explanations for the lake level and area changes in these four lakes are also discussed. This study suggests that satellite remote sensing could serve as a fast and effective tool for estimating lake water balance. [ABSTRACT FROM AUTHOR]

Snow over the Tibetan Plateau (TP) is an important water source of major Asian rivers and greatly influences water availability in the downstream areas. In this study, snow cover dynamics of the four characteristic lake basins, Cedo Caka, Selin Co, Nam Co, and Yamzhog Yumco during hydrological years 2001-2010 (September through August) are examined at the basin scale using the flexible multiday combined MODIS snow cover products. The time series of multiday, seasonal, and annual snow covered area (SCA), onset/disappearance dates of snow, snow covered days (SCD), peaks of maximum SCA, and snow cover index (SCI) for each hydrological year (HY) are examined. Results show there is no obvious trend of snow cover change in the examined period, although Nam Co basin has the greatest SCA in all four basins and in all years, and Cedo Caka and Selin Co basins show the smallest SCA in most of the years. Overall, the HY2007 shows a greater snow extent and HY2010 a smaller for the region, with exceptions for the Nam Co basin where the HY2003 is the greatest and for Cedo Caka basin where the HY2004 is the smallest. Statistical analysis between lake level changes and lake basin's SCA, precipitation and pan evaporation (ETpan) changes shows that (1) Cedo Caka's water level rise was highly correlated with the basin's SCA changes (r = 0.94, p = 0.063); (2) Selin Co's water level rise was significantly correlated with the basin's SCA, precipitation and ETpan changes (r = 0.99, p = 0.029); and (3) lake level changes of Nam Co and Yamzhog Yumco were correlated with their corresponding lake basin's SCA, precipitation and ETpa„ changes (r = 0.87 and r = 0.86, respectively), although insignificant at the 95% level. This could have been due to precipitation and ETpan data of a distant meteorological station for Nam Co lake basin and the complex hydrological processes in the Yamzhog Yumco basin. This study suggests that the examination of time series snow cover dynamics is important to evaluate the water budget of lake basins with snow as a major component of water balance. [ABSTRACT FROM AUTHOR]

The Geoscience Laser Altimeter System (GLAS) instrument onboard the Ice, Cloud and land Elevation Satellite (ICESat) provides elevation data with very high accuracy which can be used as ground data to evaluate the vertical accuracy of an existing Digital Elevation Model (DEM). In this article, we examine the differences between ICESat elevation data (from the 1064 nm channel) and Shuttle Radar Topography Mission (SRTM) DEM of 3 arcsec resolution (90 m) and map-based DEMs in the Qinghai-Tibet (or Tibetan) Plateau, China. Both DEMs are linearly correlated with ICESat elevation for different land covers and the SRTM DEM shows a stronger correlation with ICESat elevations than the map-based DEM on all land-cover types. The statistics indicate that land cover, surface slope and roughness influence the vertical accuracy of the two DEMs. The standard deviation of the elevation differences between the two DEMs and the ICESat elevation gradually increases as the vegetation stands, terrain slope or surface roughness increase. The SRTM DEM consistently shows a smaller vertical error than the map-based DEM. The overall means and standard deviations of the elevation differences between ICESat and SRTM DEM and between ICESat and the map-based DEM over the study area are 1.03 ± 15.20 and 4.58 ± 26.01 m, respectively. Our results suggest that the SRTM DEM has a higher accuracy than the map-based DEM of the region. It is found that ICESat elevation increases when snow is falling and decreases during snow or glacier melting, while the SRTM DEM gives a relative stable elevation of the snow/land interface or a glacier elevation where the C-band can penetrate through or reach it. Therefore, this makes the SRTM DEM a promising dataset (baseline) for monitoring glacier volume change since 2000. [ABSTRACT FROM AUTHOR]

Abstract: In this study, ICESat altimetry data are used to provide precise lake elevations of the Tibetan Plateau (TP) during the period of 2003–2009. Among the 261 lakes examined ICESat data are available on 111 lakes: 74 lakes with ICESat footprints for 4–7years and 37 lakes with footprints for 1–3years. This is the first time that precise lake elevation data are provided for the 111 lakes. Those ICESat elevation data can be used as baselines for future changes in lake levels as well as for changes during the 2003–2009 period. It is found that in the 74 lakes (56 salt lakes) examined, 62 (i.e. 84%) of all lakes and 50 (i.e. 89%) of the salt lakes show tendency of lake level increase. The mean lake water level increase rate is 0.23m/year for the 56 salt lakes and 0.27m/year for the 50 salt lakes of water level increase. The largest lake level increase rate (0.80m/year) found in this study is the lake Cedo Caka. The 74 lakes are grouped into four subareas based on geographical locations and change tendencies in lake levels. Three of the four subareas show increased lake levels. The mean lake level change rates for subareas I, II, III, IV, and the entire TP are 0.12, 0.26, 0.19, −0.11, and 0.2m/year, respectively. These recent increases in lake level, particularly for a high percentage of salt lakes, supports accelerated glacier melting due to global warming as the most likely cause. [Copyright &y& Elsevier]

Lake surface water temperature (LSWT) is of vital importance for hydrological and meteorological studies. The LSWT ground measurements in the Tibetan Plateau (TP) were quite scarce because of its harsh environment. Thermal infrared remote sensing is a reliable way to calculate historical LSWT. In this study, we present the first and longest 35-year (1981–2015) daytime lake-averaged LSWT data of 97 large lakes (>80 km2 each) in the TP using the 4-km Advanced Very High Resolution Radiometer (AVHRR) Global Area Coverage (GAC) data. The LSWT dataset, taking advantage of observations from NOAA's afternoon satellites, includes three time scales, i.e., daily, 8-day-averaged, and monthly-averaged. The AVHRR-derived LSWT has a similar accuracy (RMSE = 1.7 °C) to that from other data products such as MODIS (RMSE = 1.7 °C) and ARC-Lake (RMSE = 2.0 °C). An inter-comparison of different sensors indicates that for studies such as those considering long-term climate change, the relative bias of different AVHRR sensors cannot be ignored. The proposed dataset should be, to some extent, a valuable asset for better understanding the hydrologic/climatic property and its changes over the TP. Design Type(s) data collection and processing objective • statistical analysis and modeling objective • time series design Measurement Type(s) temperature of water Technology Type(s) satellite imaging Factor Type(s) geographic location • size • temporal_interval Sample Characteristic(s) Tibetan Plateau • lake Machine-accessible metadata file describing the reported data (ISA-Tab format) [ABSTRACT FROM AUTHOR]

Inter-annual climate variability has the potential to induce hundred-to-thousand meters of glacier length change, comparable to the glacier retreats from their Little Ice Age (LIA) positions (Roe and O'Neal, 2009). Distinguishing the roles of inter-annual climate variability and climate change in glacier changes can help us read the true climate signal from the history of glacial activity and provide a basis for detailed attribution of currently observed glacier retreats. Here, we used ArcGIS tools to reconstruct the LIA glacier in the Hailuogou catchment on the southeastern Tibetan Plateau (TP) and calculated the corresponding glacier equilibrium-line altitude (ELA). Based on the LIA ELA, we inferred the climate change supporting the LIA glaciers in the region. Further, we quantified the impact of inter-annual climate variability on the Hailuogou Glacier change using a three-stage linear model. During the LIA, the area of the Hailuogou Glacier was 42.64 km2 and its volume was 3.73 × 109 m3. The LIA ELA was 5068 m above sea level (a.s.l.), lowering by 213 m relatively to the present. The LIA summer temperature was estimated to be ∼1.31–2.21 °C colder than the present with the LIA precipitation constraint being 90–100% of the modern precipitation. Forced by the inter-annual variabilities in summer temperature and annual precipitation, the Hailuogou Glacier has a possible maximum negative excursion of 459 m, which can only explain 19.3% of the actual retreat since the LIA. According to the probability density function (PDF) of the modeled length anomalies, the likelihood is <1% for the actual glacier retreat completely due to the inter-annual climate variability. We therefore argued that the inter-annual climate variability alone cannot explain the glacier retreat since the LIA in the Hailuogou catchment. Further, glacier geometry and topography might be the main factors determining the strength of the response of the Hailuogou Glacier to inter-annual climate variability. • The LIA summer temperature was estimated to be ∼1.31–2.21 °C colder than the present. • The LIA Hailuogou Glacier had an area of 42.64 km2 and a volume of 3.73 × 109 m3. • The LIA ELA was 5068 m above sea level (a.s.l.), lowering by 213 m relatively to the present. • The inter-annual climate variability alone cannot explain the retreat of Hailuogou Glacier since the Little Ice Age (LIA). [ABSTRACT FROM AUTHOR]

Hydro-geothermal systems are usually governed by faults on their genesis, distribution, behaviors. A faults-controlled hydro-geothermal field on Tibetan Plateau is investigated to get insights into the regulation of faults on the output features and discharge regimes of thermal groundwater with the aid of hydrochemistry, environmental isotopes (2H, 18O, 3H, 14C) and topographical, hydrological and hydrogeological analysis. Thermal groundwater in Xihai geothermal field has lower pH (5.97–7.38) than the local nonthermal water (6.47–8.13). It originates from the meteoric water of northeastern mountainous area with the elevation of 3988–5110 m, and percolates downwards along the NE-trending primary fault F5 with the circulation depth of 3270–4855 m. The deep cycling groundwater is heated by the terrestrial heat flow with reservoir temperature of 134.95–201.09°C. Thermal groundwater has the residence time up to more than 20 ka beneath, leading to sufficient water-rock interactions and higher TDS (818.00–886.60 mg/L) and much saltier hydrochemical facies (HCO 3 –Mg·Ca) than the local nonthermal water. Faults and fissures developed in the discharge area of geothermal field provide favorable conditions for nonthermal water infiltrating downwards and mixing with the upwelling thermal groundwater. The ratio of nonthermal water mixed-in reaches to 59.5–85.6% for thermal groundwater in the discharge area of Xihai geothermal field and presents a gradual increase along the upward flow path of thermal groundwater or with the increase of distance to the primary faults. These large ratio of nonthermal water mixed-in would cool the thermal groundwater and change its output physicochemical and isotopic features, and lead to underestimation of geothermal potential and hydro-geothermal behaviors based on the apparent data of sampled thermal groundwaters from the discharge area. Thus, the 'cover' effects of nonthermal water mixed-in should be concerned for geothermal fields that with well-developed faults and fissures in the discharge area. [Display omitted] • Cold water mixing would greatly mask the feature of hydro-geothermal system. • Mixing effect presents much intenser along the thermal groundwater discharge flow path. • Tectonic faults control the mixing and discharging regime of geothermal water. • Nonthermal water mixed-in should be concerned in the geothermal resource assessment. [ABSTRACT FROM AUTHOR]

No glacial lake census exists for the Third Pole region, which includes the Pamir-Hindu Kush-Karakoram-Himalayas and the Tibetan Plateau. Therefore, comprehensive information is lacking about the distribution of and changes in glacial lakes caused by current global warming conditions. In this study, the first glacial lake inventories for the Third Pole were conducted for ~ 1990, 2000, and 2010 using Landsat TM/ETM + data. Glacial lake spatial distributions, corresponding areas and temporal changes were examined. The significant results are as follows. (1) There were 4602, 4981, and 5701 glacial lakes (> 0.003 km 2 ) covering areas of 553.9 ± 90, 581.2 ± 97, and 682.4 ± 110 km 2 in ~ 1990, 2000, and 2010, respectively; these lakes are primarily located in the Brahmaputra (39%), Indus (28%), and Amu Darya (10%) basins. (2) Small lakes (< 0.2 km 2 ) are more sensitive to climate changes. (3) Lakes closer to glaciers and at higher altitudes, particularly those connected to glacier termini, have undergone larger area changes. (4) Glacier-fed lakes are dominant in both quantity and area (> 70%) and exhibit faster expansion trends overall compared to non-glacier-fed lakes. We conclude that glacier meltwater may play a dominant role in the areal expansion of most glacial lakes in the Third Pole. In addition, the patterns of the glacier-fed lakes correspond well with warming temperature trends and negative glacier mass balance patterns. This paper presents an important database of glacial lakes and provides a basis for long-term monitoring and evaluation of outburst flood disasters primarily caused by glacial lakes in the Third Pole. [ABSTRACT FROM AUTHOR]