Search

Lakes and glaciers are widely distributed on the Tibetan Plateau and are linked via hydrological processes. They are experiencing rapid changes due to global warming, but their relationships during the Holocene are less well known due to limited coupled geological records. Here, we analyzed the δ13C-VPDB and δ18O-VPDB values and ion content of calcite and aragonite in a 407-cm-long sediment core from Guozha Co, a closed basin on the northwestern Tibetan Plateau supplied by glacial meltwater, in order to understand how the lake responded to glacier changes during the Holocene. Our results indicate that the glacial meltwater lowered the lake’s temperature and the δ18Olake water and δ18Oendogenic + authigenic carbonate values and diluted the ion concentrations in the lake water. Three stages of evolution, 8.7–4.0, 4.0–1.5, and 1.5 kyr BP to present, are distinguished based on the decrease in glacial meltwater recharge. Guozha Co has been a closed basin since at least 8.7 kyr BP, and it has changed from a fresh water lake during 8.7–1.5 kyr BP to a brackish lake from 1.5 kyr BP to present due to several climate events. The famous 4.2 kyr BP cold event was identified in the core at 4.0 kyr BP, while warm events occurred at 6.2, 3.9, 2.2, 0.9, and 0.4 kyr BP. Both glaciers and lakes in this area are controlled by climate, but they exhibit opposite changes, that is, glaciers retreat and lakes expand, and vice versa. Our results provide an accurate interpretation of the cold events based on carbonate minerals and carbon–oxygen isotopes in glacial meltwater–recharged lake sediments.

Water resources are rich on the Tibetan Plateau, with large amounts of glaciers, lakes, and permafrost. Terrestrial water storage (TWS) on the Tibetan Plateau has experienced a significant change in recent decades. However, there is a lack of research about the spatial difference between TWSC and lake water storage change (LWSC), which is helpful to understand the response of water storage to climate change. In this study, we estimate the change in TWS, lake water storage (LWS), soil moisture, and permafrost, respectively, according to satellite and model data during 2005−2013 in the inner Tibetan Plateau and glacial meltwater from previous literature. The results indicate a sizeable spatial difference between TWSC and LWSC. LWSC was mainly concentrated in the northeastern part (18.71 ± 1.35 Gt, 37.7% of the total) and southeastern part (22.68 ± 1.63 Gt, 45.6% of the total), but the increased TWS was mainly in the northeastern region (region B, 18.96 ± 1.26 Gt, 57%). Based on mass balance, LWSC was the primary cause of TWSC for the entire inner Tibetan Plateau. However, the TWS of the southeastern part increased by 3.97 ± 2.5 Gt, but LWS had increased by 22.68 ± 1.63 Gt, and groundwater had lost 16.91 ± 7.26 Gt. The increased TWS in the northeastern region was equivalent to the increased LWS, and groundwater had increased by 4.47 ± 4.87 Gt. Still, LWS only increased by 2.89 ± 0.21 Gt in the central part, and the increase in groundwater was the primary cause of TWSC. These results suggest that the primary cause of increased TWS shows a sizeable spatial difference. According to the water balance, an increase in precipitation was the primary cause of lake expansion for the entire inner Tibetan Plateau, which contributed 73% (36.28 Gt) to lake expansion (49.69 ± 3.58 Gt), and both glacial meltwater and permafrost degradation was 13.5%.

Change in lake water storage is an important factor influencing hydrological cycle, regional environment, and climate on the Tibetan Plateau (TP) because of the large number (>1000 lakes) and huge areas (>46,500 km2) of lakes. Due to the lack of in situ lake level monitoring for most lakes, and long-term continuous satellite altimetry data for some large lakes, estimates of water storage changes for all lakes throughout the TP over a long time is challenging. We have estimated the lake water storage changes of 315 lakes (each lake is >10 km2) during the period of 1976–2013 through an empirical equation based on Shuttle Radar Topography Mission (SRTM) DEM (Digital Elevation Model) data and Landsat images. These lakes are located within endorheic basins and occupied approximately 80% of the total lake surface areas of the TP in 2013 based on the results of this study and Zhang et al. (2014). The results showed that the lake water storage decreased by 23.69 Gt from 1976 to 1990 and increased by 140.8 Gt from 1990 to 2013. Increased water storage was mainly concentrated in the central TP (regions A) and northern TP (region B). The increase in total lake surface area during the period 2000–2013 in region B (1981.6 km2) was greater than that in region A (1869.1 km2), but the increase in the water storage in the former was half of that in the latter, indicating that lake surface area changes cannot represent the degree of lake water storage change due to differences in the topography and lake size. Although the total variation in the rate of the lake water storage change (7.19 Gt/y) was similar to the rate of increase in the mass (7 ± 7 Gt/y) estimated from Gravity Recovery and Climate Experiment (GRACE) data for the whole region, the spatial distribution of these variations was largely different. During the period 2000–2013, a trend analysis revealed that precipitation was perhaps the primary reason for lake change throughout the TP, while a decreasing evaporation rate only contributed approximately 1.5%, 2.5% and 1.7% to the expansions of the lakes in regions A, C and D respectively. However, based on modern glacier mass balance observation data, we estimated that glacial meltwater may have contributed 22.2%, 39.8%, 50.6% and 100% to the increasing water storage during the period 2000–2013 by rough estimates in regions A, B, C and D, respectively, indicating that glacial meltwater perhaps was a primary contributor to lake expansion in region D, which was located in an extremely cold and dry climate with a broad distribution of glaciers.

Lake water storage is essential information for lake research. Previous studies usually used bathymetric data to acquire underwater topography by interpolation method, and to therefore estimate water storage. However, due to the large area of Tibetan Plateau (TP) lakes, the method of bathymetry was challenging to cover the whole region of one lake, and the accuracy of the underwater topography, in which no bathymetric data covered, was low, which resulted in a comparatively large error of lake water storage estimation and its change. In this study, we used Shuttle Radar Topography Mission (SRTM) and in situ bathymetric data to establish the underwater topography of Hohxil Lake (HL) and Lexiewudan Lake (LL) in the Hohxil Region of North TP and estimate and analyzed the changes of lake level and water storage. The results showed HL and LL’s water storage was 5.12 km3 and 5.31 km3 in 2019, respectively, and their level increased by 0.5 m/y and 0.57 m/y during 2003−2018, respectively. They were consistent with those (0.5 m/y and 0.5 m/y) from altimetry data, and they were much more accurate than those results (0.077 m/y and 0.156 m/y) from bathymetric data. These findings indicated that this method could improve the accuracy of lake water storage and change estimation. We estimated water storage of two lakes by combining with multitemporal Landsat images, which had doubled since 1976. Our results suggested that the increasing precipitation may dominate the lake expansion by comparing with the change of temperature and precipitation and the increasing glacial meltwater contributed approximately 4.8% and 10.7% to lake expansion of HL and LL during 2000–2019 based on the glacier mass balance data, respectively.

Lake water storage changes in four lakes were analyzed based on in situ bathymetric survey data and Landsat images in the extremely dry and cold northwestern Tibetan Plateau region. The results indicated that Bangdag Co and Aksai Chin Lake, which are glacier-fed and closed lakes, showed decreasing trends from 1976 to 1996, then increasing trend from 1996 to 2015, during which period water storage increased by 1.24 km3 and 1.37 km3, respectively, and 65% of the water storage increase in Aksai Chin Lake during this period occurring in 2006 and 2013. Longmu Co, which is a non-glacier-fed lake, exhibited little variation from 1976 to 1996 and a slight increase of 0.1 km3 from 1996 to 2015. The precipitation, temperature and potential evaporation (Ep) trends indicated that lake shrinkage from 1976 to 1996 was attributed to less precipitation and less meltwater at lower surface air temperatures. Decreased Ep (15.5 mm/y) contributed approximately 2% and 4% to the lake expansion of Aksai Chin Lake and Bangdag Co from 2000 to 2009. Based on the assumption of equal precipitation-evaporation for the study area, glacial meltwater contributed 76.6% to the lake expansion of Bangdag Co from 2000 to 2015. Because change in lakes' water storage showed a large difference between glacier-fed lakes and non-glacier-fed lakes from 1996 to 2015 under relatively high precipitation conditions, it is suggested that glacial meltwater exerted more influence on increasing lake water storage associated with rising temperatures.

Glacial changes during the Little Ice Age (LIA) in the Himalayan Mountains are important for understanding changes in the monsoonal and westerly climate of the so-called ‘the Third Pole’. However, knowledge of these changes and their dynamics remains limited because of the region's geographical inaccessibility, in addition to geopolitical reasons. In this study, we used high resolution three-dimensional images from Google Earth to identify lateral and terminal moraines as delineators of paleoglacier boundaries, and mapped the boundaries of both modern and LIA glaciers. ArcGIS 9.3 software was applied to map data and to calculate glacier lengths and areas; modern glacier surface elevation data were derived from SRTM (Shuttle Radar Topography Mission) records. Three methods, the toe-to-headwall altitude ratio (THAR), the toe-to-summit altitude method (TSAM), and the toe-to-ridge altitude method (TRAM) were used to estimate equilibrium line altitude (ELA). The transient snowlines (TSL) of ninety-one modern glaciers were acquired using Landsat 8 OLI images in late summer to evaluate the reliability of the calculated ELAs. Our results showed that the total length and total area of two hundred and twenty glaciers in the central and western Himalaya (CWH) had decreased respectively by 35% and 31% since the LIA. The TRAM method was the preferred method for the reconstruction of ELAs. The mean depression of ELAs from the LIA to the first decade of the 21st Century, as reconstructed using the TRAM method, was 123 m. The ELA depression and rate of change of glacier length and glacier area displayed generally increasing trends from west to east along the central and western Himalaya, suggesting that the moisture was most likely transported from an easterly direction. These changes were more intensive on southern than northern slopes, suggesting that southerly and westerly precipitation likely increased over the same period. We speculated that the CWH had been influenced by both the Indian Summer Monsoon (ISM) and Westerlies since the LIA. ISM moisture, as in modern times, was the main factor controlling the distribution of glaciers during the LIA. Further, precipitation carried by the Westerlies likely intensified along southerly pathways along the CWH during the LIA.

Most lakes of the Tibetan Plateau (TP) were experiencing quick expansion in recent decades; a detailed study on the changes in lakes of different supply types will help to understand the cause of the changes by analysing area change of thirty-four lakes and water level change of eight lakes in the northwestern TP. All lakes are classified into three types: non-glacier-fed lakes, upstream lakes and glacier-fed lakes. The glacier-fed lakes are separated into glacier-fed_P1 (quick expansion region) and glacier-fed_P2 (slow expansion region). Combining the changes in precipitation, temperature and evaporation, less precipitation may be the main reason for lake shrinkage from 1976 to 1996, and quickly increasing precipitation led to the lakes’ expansion from 1996 to 2000. However, after 2000, upstream lakes remained in a stable state with slight variation, non-glacier-fed lakes and glacier-fed_P2 lakes exhibited a slightly increasing rate with high precipitation and high evaporation, and glacier-fed_P1 lakes still expanded quickly. Based on the assumption of same precipitation and evaporation, glacial meltwater may make an important contribution (>52%) to the increase in water storage of Bangdag Co and Meima Co. The results suggest that glacial meltwater augments the increased rate of glacier-fed_P2 lakes and plays a much more important role in the expansion of glacier-fed_P1 lakes compared to other lakes.

Lake water storage is an important factor in analyses of lake water balance. However, it is difficult to calculate the water storage of lakes on the Tibetan Plateau due to the lack of bathymetric data. Lake water storage and changes in Chibuzhang Co (CC) and Duoersuodong Co (DC), which are located in an endorheic system and have been connected since 2006, were estimated based on in situ bathymetric data, satellite altimetry data and Landsat images of the central Tibetan Plateau. In 2016, the maximum depth and water storage of DC were 68.7 m and 12.2 ± 1.72 km3, respectively, with an area of 490.2 km2, and those of CC were 116.3 m and 16.2 ± 2.27 km3, respectively, with an area of 575.4 km2. The total lake water storage in DC and CC increased by 24.5% (2.4 km3) and 14.1% (2 km3) from 2003 to 2014, respectively, based on satellite altimetry data and Landsat images using an empirical equation. The relationship between lake changes and meteorological factors indicated that both increased glacial meltwater and increased precipitation were important drivers of each lake’s expansion and that a small increase in evaporation (2.5 mm/y) had little negative impact on lake expansion (0.41 m/y). Heterogeneous changes in the two lakes from 1993 to 2005 were mainly due to water from CC supplying DC through a channel, and the lake level of DC was always lower than that of CC until 2006, indicating that the geological conditions around both lakes were also an important factor in the lake changes. The assumption was that all glacial meltwater from the Puruogangri and Geladandong glaciers was supplied to the two lakes through runoff with minimal evaporation, and glacial meltwater made an approximately 19.3 ± 4.5% contribution to the lake expansions (0.4 km3/y) of DC and CC from 2003 to 2014 based on the results of the glacier mass balance.

Lakes on the Tibetan Plateau are very sensitive to climate change and have expanded rapidly in recent decades. In this study, lake water storage change (LWSC) of 150 lakes since 1976 was estimated based on multi-temporal Landsat images and Shuttle Radar Topography Mission data. The lakes were then separated into glacier-fed and non-glacier-fed lakes based on the second Chinese glacier inventory and basin boundaries. The results indicate that most lakes had a shrinking trend and total water storage decreased by 5.53 ± 0.4 km3 from 1976 to 1990; however, most lakes expanded and increased in total water storage by 110.15 ± 7.93 km3 from 1990 to 2013. The water storage increase in glacier-fed lakes was 84% of the total increase in water storage from 1990 to 2013. An analysis of the relationship between the lakes and climate indicators suggests that both precipitation and glacial meltwater were the most important factors in lake change, in contrast, changes in evaporation had a limited influence on lake level and volume changes. Based on an assumption of similar precipitation and evaporation across neighbouring closed basins, we compared differences in LWSC between glacier-fed and non-glacier-fed lakes to analyze the cause of lake change. Our results suggest that less precipitation was the primary cause for lake contractions from 1976 to 1990. Glacial meltwater contributed at least 43.5%, 46.4% and 58.7% to the total increased water storage for the periods 1990–2000, 2000–2005 and 2005–2013, respectively. The results further suggest that increasing glacial meltwater had a contribution to lake expansion equivalent to that of precipitation-evaporation during 1990–2013.

This study focuses on the characteristics, seasonal variations, and controlling mechanisms of the ionic composition of the Tangra Yumco basin for lake water, river water, and rainfall, which is located in the central Tibetan Plateau. The results showed that Na+ is the major cation in the lake water, Ca2+ is the major cation in the river water and rainfall, and $${\text{HCO}}_{3}^{ - }$$ is the major anion in all the water samples. A comparison of the concentrations of calcium in the river water, lake water, and lake sediments reveal significant carbonate precipitation within the lake. The chemical composition of the lake water is mainly controlled by evaporation and crystallization, whereas the compositions of river water and rainfall are mainly controlled by carbonate weathering. Because the TDS content of the river water is lower than the lake water, the TDS content of the lake water is diluted, forming a decreasing trend during the beginning of the Indian summer monsoon. The lake water TDS content then increases rapidly from August to early September due to enhanced evaporation of the lake surface water and the introduction of a large amount of material carried by surface runoff. It then decreases slightly until December due to precipitation in the lake water and less input from the surroundings of the lake.