Tibetan Plateau Lakes Research Articles

Limited Contribution of Glacier Mass Loss to the Recent Increase in Tibetan Plateau Lake Volume

The Tibetan Plateau (TP) plays an essential role in the water supply to Asia’s large river systems and, as the largest and highest mountain plateau in the world, it drives the Asian monsoon and influences global atmospheric circulation patterns. The increase in TP lake volume since the mid-1990s is well documented, however the drivers of lake growth remain largely unexplained. In this study we investigate changes in lake and glacier volumes, together with changes in precipitation and evapotranspiration at basin scale. We calculate the contribution of glacier mass loss to the lake volume increase for the period 1994-2015. We demonstrate that glacier mass loss does have a limited contribution to the lake volume increase (19 ± 21 % for the whole TP). Glacier mass loss is thus insufficient to explain all of the lake volume gain, and despite large spread in various products that estimate precipitation and evaporation, we suggest that an increase in precipitation excess (precipitation - evapotranspiration) may be sufficient to explain the lake volume gain.

Hydrochemistry Differences and Causes of Tectonic Lakes and Glacial Lakes in Tibetan Plateau

The Tibetan Plateau has the largest lake cluster in China and in the world. In order to clarify the differences of lake hydrochemistry of Tibetan Plateau, water samples were collected from 32 lakes, including 22 tectonic lakes and 11 glacial lakes, along the Tibetan Plateau road, from September to October 2016. We detected and analyzed the major ion concentrations and characteristics of samples, and discuss the hydrochemistry type, controlling factors, and major ion sources of lake water. The results showed that, firstly, tectonic lake samples on the Tibetan Plateau have much higher physicochemical parameters and ion contents than glacial lakes, and Total Dissolved Solids (TDS) contents fluctuate from high to low latitudes. The variations of ion concentrations in the northern part of the Qiagui Co were more fluctuating and have two obvious peaks, while the variations in the southern part were moderate. The TDS of glacial lakes were low and leveling off in the upper and middle reaches of the basin, while higher and more variable in the lower reaches. Secondly, the tectonic lakes were mainly chloride saline lakes, with Na+ as the major cation, and SO42−, Cl− as the major anions. Glacial lakes were mainly carbonate and sulfate type lakes, Ca2+ and Mg2+ were the major cations, HCO3− was the major anion, and SO42− was the second. Thirdly, the hydrochemistry processes of the tectonic lakes were mainly controlled by evaporation-crystallization, and the ions mainly came from the evaporites of basin. Glacial lake water samples were mainly influenced by the weathering of basin rocks, with ion sources strongly influenced by the weathering of basin carbonates than evaporites, with calcite and dolomite being important sources of Ca2+, Mg2+, and HCO3−.

Study of freeze-thaw cycle and key radiation transfer parameters in a Tibetan Plateau lake using LAKE2.0 model and field observations

AbstractThe Tibetan Plateau (TP) lakes are sensitive to climate change due to its seasonal ice cover, but few studies have paid attention to the freeze-thaw process of TP lakes and its key control parameters. By combining 216 simulation experiments using the LAKE2.0 model with the observations, we evaluated the effects of ice and snow albedo, ice (Kdi) and water (Kdw) extinction coefficients on the lake ice phenology, water temperature, sensible and latent heat fluxes. The reference experiment performs well in simulating the lake temperature, with a small positive bias increasing with depth, but it underestimates the ice thickness. The increase of ice albedo, snow albedo andKdiinduce a significant decrease in water temperature. Compared with the latent heat, the sensible heat flux is more sensitive to these three parameters. The ice thickness increases almost linearly with the increase of ice albedo but decreases with the increase ofKdi. The ice thickness and frozen days vary little withKdw, but increasingKdwcan decrease the water temperature. Compared with the ice albedo, theKdiand snow albedo have a large effect on the number of frozen days. This study brings to light the necessity to improve the parameterizations of the TP lakes freeze-thaw process.

Water clarity changes in 64 large alpine lakes on the Tibetan Plateau and the potential responses to lake expansion

Lakes are essential components of the water cycle and ecosystems. Therefore, the ecology and water security of lakes is of great concern. However, on the Tibetan Plateau (TP), which is known as the Asian water tower, knowledge of lake water quality is in its infancy. In this study, we developed a Moderate Resolution Imaging Spectroradiometer (MODIS)-based Secchi disk depth (Zsd) retrieval model and used the proposed model to study the temporal and spatial dynamics of water clarity in 64 lakes (>50 km2) located on the TP during the 2003–2018 period. The results show that the 64 lakes have an average long-term mean Zsd of 4.4 ± 3.0 m, where lakes in the northern TP generally exhibited lower Zsd levels than those located in the southern and northeastern parts of the TP. Among all selected lakes, the number of lakes showing (significantly) decreasing Zsd change trends was approximate to those showing (significantly) increasing change trends. Nevertheless, the two trends exhibited different spatial patterns. An analysis of the potential links between lake Zsd and environmental factors suggests that lake expansion is an essential factor affecting the increase in lake Zsd, while such an impact may be offset by the increase in phytoplankton induced by climate change in lakes showing a significant Zsd decreasing trend. In addition, land use types are partially responsible for the Zsd disparities between different lakes since lakes with high Zsd commonly occurred with high vegetation cover in their surrounding areas, while glacial melting and hydrological networks showed minor influences. This study is expected to enhance our understanding of lacustrine environments in TP and other global alpine lakes under the scenario of climate change.

Holocene hydroclimate in the source region of the Yellow River: A new sediment record from Lake Gyaring, NE Tibetan Plateau

Abstract The environmental history of the source region of the Yellow River (SRYR) is vital for understanding its hydrological response to climate processes in the alpine northeastern Tibetan Plateau (TP). In this study, we present the first sediment core record from Lake Gyaring, one of the largest fresh lakes in SRYR, using proxies of total organic carbon, total nitrogen, C/N ratio, δ13Corg, chlorophyll a, and grain size, to discuss the environmental variations over past 10 kyr. The results show that sedimentary organic matter mainly originated from the aquatic macrophytes and phytoplankton, the relative abundance of which can serve as a qualitative indicator of lake level changes of Lake Gyaring. From 10 to 6.2 cal kyr B.P., the notable expansion of macrophytes was favored by the warm conditions and an enlarged littoral zone due to lake-level decline. The abrupt cooling between 8.9 and 8 cal kyr B.P. led to temporal lake-level rises that significantly reduced macrophyte primary production. After 6.2 cal kyr B.P., the lake turned to be phytoplankton-dominated following the cooling trend and stepwise increase in lake level. The inferred climate pattern in the lake catchment with an overall dry early to mid Holocene and moister mid to late Holocene disagrees with the Asian monsoon variations. This phenomenon is well recognized by the lake-level records from most of the northeastern TP lakes, implying that strong evaporation in semi-arid lake catchments could have outweighed the increased regional precipitation during early to mid Holocene and vice versa for mid to late Holocene.

Modeling the Effects of Lakes in the Tibetan Plateau on Diurnal Variations of Regional Climate and Their Seasonality

AbstractIn this study, we investigated the effects of lakes in the Tibetan Plateau (TP) on diurnal variations of local climate and their seasonal changes by using the Weather Research and Forecasting (WRF) Model coupled with a one-dimensional physically based lake model. We conducted WRF simulations for the TP over 2000–10, and the model showed excellent performance in simulating near-surface air temperature, precipitation, lake surface temperature, and lake-region precipitation when compared to observations. We carried out additional WRF simulations where all the TP lakes were replaced with the nearest land-use types. The differences between these two sets of simulations were analyzed to quantify the effects of the TP lakes on the local climate. Our results indicate that the strongest lake-induced cooling occurred during the spring daytime, while the most significant warming occurred during the fall nighttime. The cooling and warming effects of the lakes further inhibited precipitation during summer afternoons and evenings and motivated it during fall early mornings, respectively. This study lays a solid foundation for further exploration of the role of TP lakes in climate systems at different time scales.

Interdecadal summer warming of the Tibetan Plateau potentially regulated by a sea surface temperature anomaly in the Labrador Sea

AbstractDownward clear‐sky longwave radiation, which is related to atmospheric water vapour content, has been suggested as an important factor causing an interdecadal increase in boreal summer surface temperature over the Tibetan Plateau (TP). We reveal the relationship between the 2 m air temperature (t2m) and water vapour over the TP in boreal summer, as well as the mechanism modulating the change in atmospheric water vapour. In recent decades, spatiotemporal variations between water vapour and t2m in boreal summer over the TP have shown synchronicity at the decadal scale. Moreover, Rossby wave trains which originate over the Northwest Atlantic and trigger an anomalous anticyclone between the northeastern TP and Baikal Lake are suggested to play a crucial role in decadal warming over the TP. First, the anomalous anticyclone, with an equivalent barotropic structure, can directly heat near‐surface air across the northeastern TP. Second, it promotes net water vapour input into the northeastern TP, leading to an increase of the total water vapour content over the entire TP, ultimately contributing to warming. Finally, a linear baroclinic model experiment further indicates that the Rossby wave trains are mainly associated with interdecadal increases in sea surface temperature (SST) in the Labrador Sea, with the SST in Baffin Bay playing a secondary role.

Historical trends of PCBs and PBDEs as reconstructed in a lake sediment from southern Tibetan Plateau

High-altitude lake sediment can be used as a natural archive to reconstruct the history of pollutants. In this work, the temporal distribution of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were determined using a high-resolution gas chromatography coupled with high-resolution mass spectrometer (HRGC/HRMS) in an alpine lake sediment core collected from the southern Tibetan Plateau (TP) to examine whether the expected decreasing trends due to the implementation of the international Conventions could be observed. The concentrations of PCBs and PBDEs in the sediment core were in the range of 11.8–142 pg/g dw and ND-457 pg/g dw, and their fluxes were in the range of 2.51–31.7 ng/(m2·yr) and ND-43.2 ng/(m2·yr), respectively. The prevalence of low-chlorinated (tri-CB) PCBs and low-brominated (tri- to tetra-) PBDEs in most sections of the sediment profiles was observed, suggesting that the light molecular weight PCBs and PBDEs have most likely reached lake sediments by long-range atmospheric transport from distant sources. Despite the restrictions on their applications, the sediment records for the concentrations and fluxes showed no corresponding decreasing trend with restrictions for PCBs, which suggested that these POPs (e.g., PCBs) were still emitted to the environment owing to the influence of primary or secondary emissions. To our knowledge, this is the first report on input history of atmospheric PCBs and PBDEs recorded in TP Lake sediment.

Comparison to Changes of Lake Ice Phenology and Air Temperature over Northern Europe, Tibetan Plateau and Mongolian Plateau

Lake ice is a sensitive factor for the Earth’s environment and climate change research. In the comparative study on climate change to the Earth three-pole (Antarctic, Arctic, and Tibetan Plateau), the lake ice phenology can be used to represent seasonal climate changes. In this paper, the lake ice phenology and the corresponding daily temperature for 48 lakes in Northern Europe, Tibetan Plateau and Mongolia Plateau were used as the typical case for comparative research. Based on passive microwave remote sensing data. The results showed that the average lake ice cover duration experienced a consistent decreasing for the three regions from 1978-2018. However, in the northern Tibetan Plateau, though the lake ice cover duration showed a shortening trend from 1978 to 2000, it displayed a prolonged trend from 2000 to 2018. Moreover, the air temperature changes of the lake area had a significant correlation with the changes of ice cover duration in each region, and the change of 0 °C isotherm in the Northern Europe lakes are more sensitive than the Mongolian Plateau and the Tibetan Plateau. The air temperature played a major role in the change of lake ice phenology, but there were still other factors that affected the lake ice phenology changes, especially in northern Tibetan Plateau. By comparing the analysis of the ice cover duration in the three regions and the effect of air temperature on the lake ice cover duration change, it provides more evidences for the study on climate change research in different regions.

Subpixel Mapping of Surface Water in the Tibetan Plateau with MODIS Data

This article presents a comprehensive subpixel water mapping algorithm to automatically produce routinely open water fraction maps in the Tibetan Plateau (TP) with the Moderate Resolution Imaging Spectroradiometer (MODIS). A multi-index threshold endmember extraction method was applied to select the endmembers from MODIS images. To incorporate endmember variability, an endmember selection strategy, called the combined use of typical and neighboring endmembers, was adopted in multiple endmember spectral mixture analysis (MESMA), which can assure a robust subpixel water fractions estimation. The accuracy of the algorithm was assessed at both the local scale and regional scale. At the local scale, a comparison using the eight pairs of MODIS/Landsat 8 Operational Land Imager (OLI) water maps demonstrated that subpixels water fractions were well retrieved with a root mean square error (RMSE) of 7.86% and determination coefficient (R2) of 0.98. At the regional scale, the MODIS water fraction map in October 2014 matches well with the TP lake data set and the Global Lake and Wetland Database (GLWD) in both latitudinal and longitudinal distribution. The lake area estimation is more consistent with the reference TP lake data set (difference of −3.15%) than the MODIS Land Water Mask (MOD44W) (difference of −6.39%).

The role of Tibetan Plateau lakes in surface water cycle under global changes

The role of Tibetan Plateau lakes in surface water cycle under global changes

Salinity reduces bacterial diversity, but increases network complexity in Tibetan Plateau lakes

Salinity is one of the most important environmental factors influencing bacterial plankton communities in lake waters, while its influence on bacterial interactions has been less explored. Here, we investigated the influence of salinity on the bacterial diversity, interactions and community structure in Tibetan Plateau lakes. Our results revealed that saline lakes (salinity between 0.5 and 50g/L) harboured similar or even higher bacterial diversity compared with freshwater lakes (< 0.5g/L), while hyper-saline lakes (> 50g/L) exhibited the lowest diversity. Network analysis demonstrated that hyper-saline lakes exhibited the highest network complexity, with higher total correlation numbers (particularly the negative correlations), but lower network module numbers than freshwater and saline lakes. Furthermore, salinity dominantly explained the bacterial community structure variations in saline lakes, while those in freshwater and hyper-saline lakes were predominately explained by water temperature and geospatial distance, respectively. The core operational taxonomic units (OTUs), which were ubiquitously present in all lakes, were less sensitive to enhancing salinity than the indicative OTUs whose presence was dependent on lake type. Our findings offer a new understanding of how salinity influences bacterial community in plateau lakes.

TEX86 as a potential proxy of lake water pH in the Tibetan Plateau

Water pH represents one of the most important indicators of chemical and biological changes in lacustrine systems. However, although water pH is also a major influence on inland water bodies and related ecosystems, it is not well studied in the lakes of the Tibetan Plateau (TP). The applicability of diatom assemblages, an effective proxy of variations in water pH in freshwater lakes, is greatly limited in the TP because the alkaline environment in most of the lakes is unfavorable for the preservation of diatom frustules. Isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs) are a series of specific membrane lipids biosynthesized by archaea, which appear to be a promising method for reflecting lake water pH variations. In this study, we analyzed the distribution of iGDGTs in the surface sediments of 34 alpine TP lakes and combined the data with published iGDGTs results from across the TP, in order to examine the effect of various environmental factors on iGDGT cyclization. The results show that water pH appears to be the most important factor affecting the degree of cyclization of iGDGTs in high-elevation alkaline lakes. This also suggests that the novel temperature proxy, TEX86, is also a promising water pH proxy for alpine lakes in the region. Despite a moderate correlation is observed between TEX86 and water pH, caution is needed in the interpretation of the TEX86 records, since other factors, such as temperature and the dissolved oxygen level, may also have an influence. Nevertheless, TEX86 appears to be a promising indicator of water pH for the alkaline lakes of the TP, and it could be a potentially useful tool for reconstructing pH in alkaline lakes in other areas, after regional calibrations.

Hydrogen isotope fractionation variations of n-alkanes and fatty acids in algae and submerged plants from Tibetan Plateau lakes: Implications for palaeoclimatic reconstruction

The hydrogen isotope compositions (δD) of n-alkanes and fatty acids (FAs) are widely applied in palaeoclimatic reconstructions, and the determinations of their hydrogen isotope fractionation factor values (ε) are vital for quantitatively reconstructing past precipitation variations. Currently, studies on n-alkane and FA ε values focus on terrestrial plants, which, however, show large uncertainties because of the influence of evapotranspiration. Therefore, in this study, we analysed the ε values of algae and submerged plants immersed in lakes, which are not affected by evapotranspiration, to understand the hydrogen isotope fractionation of plant lipid synthesis. By investigating the δD values of lipids (n-alkanes and FAs) in algae and submerged plants and the δD values of co-existing water (including lake bottom water, surface sediment water, and leaf water of algae and submerged plants) from five Tibetan Plateau lakes, we find that the n-alkane ε values of algae and submerged plants show narrow changes, ranging from −176 to −159‰ and −167 to −142‰, respectively. The FA ε values of algae and submerged plants also show small variations, ranging from −160 to −121‰ (except Chara) and −161 to −138‰, respectively. Therefore, the average biosynthetic hydrogen isotope fractionation of these plants is −162‰ for n-alkanes and −145‰ for FAs, and the small ε differences between FAs and n-alkanes can be related to the different magnitudes of FA utilization in n-alkane synthesis. Finally, we find that the biosynthetic hydrogen isotope fractionation factors of aquatic plants are close to those of terrestrial grasses but slightly more negative than those of terrestrial woody plants. Thus, our results are helpful for understanding the hydrogen isotope fractionation variations in terrestrial plant lipids, which is beneficial for palaeohydrological reconstructions.

Investigating Water Variation of Lakes in Tibetan Plateau Using Remote Sensed Data Over the Past 20 Years

Water storage change of the lakes in the Tibetan Plateau is regarded as one of the most critical regional hydrological consequences owing to climate change. In this study, we investigate the water storage changes in 22 lakes in the Tibetan Plateau based on sequential remote sensed lake area and water level, which are derived from moderate resolution imaging spectroradiometer (MODIS) surface reflectance and Laboratoire D’Etudes en Géophysique et Océanographie Spatiales (LEGOS) altimetry data, respectively. Water storage of the lake is estimated on the basis of the relationship between lake area and water level. The method can be seen as an alternative to the conventional hydrological approaches. The results show that, during 2001–2017, most of the studied lakes in the Tibetan Plateau have shown significant increasing trends in water storage accompanied with larger lake area and higher water level. The changes in lake water storage are found in close relation to variations of climate factors such as precipitation, potential evaporation, and temperature in most lakes. The climate change impacts, however, can be amplified or attenuated by other environmental factors in some lake catchments.

Numerical study on the climatic effect of the lake clusters over Tibetan Plateau in summer

The weather research and forecasting model including a one-dimensional thermal diffusion lake model is adopted to investigate the summer climatic effect of the lake clusters over Tibetan Plateau (TP) during 2008–2014 based on two experiments with and without the lakes. Overall, the model can reasonably reproduce the daily variations of lake surface temperature and the spatial patterns of 2 m air temperature (T2m) and precipitation over TP during summer. Sensitivity results show that the effects of TP lakes on the over-lake T2m and precipitation exhibit distinctive seasonal and diurnal features and strong space dependence. Generally, the TP lakes tend to cool the local T2m and enhance the precipitation over the lake and surrounding areas. With the summer advances, the cooling effect of TP lakes weakens while the lake-induced enhancement of precipitation becomes more evident. During daytime, the TP lakes decrease the T2m and suppress the short-duration (≤ 6 h) rainfall in afternoon. However, the TP lakes increase the T2m and strengthen the convective rainfall over the lake and surrounding areas by simultaneously enhancing both short and long-duration (> 6 h) precipitation during nighttime. The lakes over the southeastern central TP (CTP) lead to slight warming and pronounced precipitation increases, while the other lakes in CTP mainly cause significant cooling and suppressed precipitation. Such opposite effects are mainly because the lakes over the western and northeastern CTP hardly produce nighttime warming and the associated circulation changes favorable for the convective precipitation as found over the southeastern CTP, suggesting that the climate effects of TP lakes may be modulated by the lake intrinsic features, local terrain distributions, and background atmospheric circulations.

Assessment of Water Storage Change in China’s Lakes and Reservoirs over the Last Three Decades

Lakes and reservoirs are essential elements of the hydrological and biochemical cycles, considered sentinels of global climate change. However, comprehensive quantifications of their water storage changes (∆V) at a large spatiotemporal scale are still rare. Here, we integrated a global surface water dataset and SRTM digital elevation models, both available from Google Earth Engine platform at a spatial resolution of 30 m, to evaluate ∆V for a total of 760 lakes and reservoirs across China at an annual timescale since 1984. The results indicated that (1) the aggregated water storage went through a slight increase of 41.5 Gt (1.7 Gt/yr) during 1985–2005, a significant decrease of 100 Gt (-20.6 Gt/yr) during 2005–2009, and then increased by 136.3 Gt (21.3 Gt/yr) during 2009–2015. (2) The increasing trend was largely attributed to lakes and reservoirs in the Tibetan Plateau Lake Zone, and the decreasing trend was mainly due to the North and Northwest Lake Zone, with little variations observed for the Northeast and Southwest Lake Zones. (3) Qinghai lake was associated with the largest increase (18.3 Gt) and Poyang lake presented the largest decline (-9.2 Gt). The results can help advance our understanding of the impact of climate change and improve future projection.

Assessment of Cryosat-2 and SARAL/AltiKa altimetry for measuring inland water and coastal sea level variations: A case study on Tibetan Plateau lake and Taiwan Coast

Satellite altimetry has been proven as an effective technology to accurately measure water level, ice elevation, and flat land surface changes since the 1990s. To overcome limitations of pulse-limited altimetry, new altimetric missions such as Cryosat-2 and Satellite with ARgos and AltiKa (SARAL/AltiKa), have been designed to have higher along-track spatial resolution to measure more accurately inland water levels for small water bodies, and coastal sea level changes. In this study, we evaluate the performance of Cryosat-2 low-resolution (LRM) and SARin modes and SARAL/AltiKa Ka-band data on two connected lakes in central Tibetan Plateau, and in the coastal region of Taiwan. Results are compared with in situ tide gauge data in Taiwan and altimetric lake level time series from the CNES Hydroweb database. Our results show that water level change trends observed by Cryosat-2 20-Hz retracked observations, the SARAL/AltiKa 40-Hz Ice-1 retracked data, and the Hydroweb measurements are consistent with the estimated water level trend of ∼0.30 m/y, during 2011–2017, and 2013–2015, for the Tibetan Migriggyangzham Co and Dorsoidong Co, respectively. For the coastal region, the performance of SARAL/AltiKa is better than that of Cryosat-2 LRM data in Taiwan. This finding demonstrates the superiority of the Ka-band over Ku-band radar altimetry.

Arsenic in permafrost-affected rivers and lakes of Tibetan Plateau, China

ABSTRACTWith the climate warming leading to thawing permafrost, the trace metal releasing from the permafrost is of increasing importance. The source area of the Yellow river (SAYR) in Tibet Plateau, underlain by permafrost which provides important source water, was investigated. One hundred and eleven water samples across SAYR were collected in April 2014, when permafrost thawing began and the precipitation season had not arrived yet. It was found that the arsenic concentration level was relatively higher than other pristine surface water in the world, but similar to other source regions on the Tibetan Plateau, showing SAYR is pristine and can serve as a reference region for determining the human influence on permafrost-affected landscapes. The positive correlation of arsenic with sulfate suggested that the arsenic was predominantly derived from the weathering process of arsenic-rich sulfides. Climate warming enhanced thawing depth of permafrost may accelerate the release and mobilization of arsenic to the surface water.

Boron circulation and recharge pattern in Zabuye drainage basin, Tibetan plateau

Zabuye salt lake is famous for abundance of B and Li resource, especially for natural product of lithium carbonate mineral. Based on systematic measurement of chemical compositions and boron isotope, the fractionation mechanisms of boron were discussed to constrain possible boron cycle among different reservoirs. The excellent consistency of borax isotopic composition on the basis of fractionation between hydroboracite and borax and basicboron structure indicates that boron isotopic fractionation occurred during lake water evolution, such as crystallization, adsorption, and alteration processes. The increase of δ11B values in brine with corresponding pH varying from 9.86 to 9.01 suggests that pH has predominent control over the separation because 11B will preferentially concentrated in trigonal (B(OH)3) species. Very low δ11B values of brine in Zabuye salt lake imply a negative origin as almost all natural geochemical processes will result in positive values without any other extra boron input. Similar fractionation factor between carbonate-rich clay and brine to that between sediment and brine in other salt lakes in Tibetan Plateau also strongly support the accumulation of boron from the input of carbonate-rich clay. Unlike the consecutive evaporation in Bange salt lake with relatively positive δ11B values, Zabuye salt lake has experienced crystallization from initial brine and subsequent redissolution of carbonate-rich clay processes and the extracted boron is carried into the lake by river water and rising springs.