Comprehensive estimation of lake volume changes on the Tibetan Plateau during 1976–2019 and basin-wide glacier contribution

This study was supported by grants from the Natural Science Foundation of China (41831177 , 41871056), the European Space Agency within the Dragon 4 program ( 4000121469/17/I-NB), the Swiss National Science Foundation (No. 200021E_177652/1) within the framework of the DFG Research Unit GlobalCDA (FOR2630), and the French Space Agency (CNES ). G. Zhang wants to thank the China Scholarship Council for supporting his visit to University of Zurich (the former affiliation of T. Bolch) from December 2017 to December 2018.Volume changes and water balances of the lakes on the Tibetan Plateau (TP) are spatially heterogeneous and the lake-basin scale drivers remain unclear. In this study, we comprehensively estimated water volume changes for 1132 lakes larger than 1 km2 and determined the glacier contribution to lake volume change at basin-wide scale using satellite stereo and multispectral images. Overall, the water mass stored in the lakes increased by 169.7 ± 15.1 Gt (3.9 ± 0.4 Gt yr−1) between 1976 and 2019, mainly in the Inner-TP (157.6 ± 11.6 or 3.7 ± 0.3 Gt yr−1). A substantial increase in mass occurred between 1995 and 2019 (214.9 ± 12.7 Gt or 9.0 ± 0.5 Gt yr−1), following a period of decrease (−45.2 ± 8.2 Gt or −2.4 ± 0.4 Gt yr−1) prior to 1995. A slowdown in the rate of water mass increase occurred between 2010 and 2015 (23.1 ± 6.5 Gt or 4.6 ± 1.3 Gt yr−1), followed again by a high value between 2015 and 2019 (65.7 ± 6.7 Gt or 16.4 ± 1.7 Gt yr−1). The increased lake-water mass occurred predominately in glacier-fed lakes (127.1 ± 14.3 Gt) in contrast to non-glacier-fed lakes (42.6 ± 4.9 Gt), and in endorheic lakes (161.9 ± 14.0 Gt) against exorheic lakes (7.8 ± 5.8 Gt) over 1976–2019. Endorheic and glacier-fed lakes showed strongly contrasting patterns with a remarkable storage increase in the northern TP and slight decrease in the southern TP. The ratio of excess glacier meltwater runoff to lake volume increase between 2000 and ~2019 was less than 30% for the entire Inner-TP based on several independent data sets. Among individual lake-basins, 14 showed a glacier contribution to lake volume increase of 0.3% to 29.1%. The other eight basins exhibited a greater glacier contribution of 116% to 436%, which could be explained by decreased net precipitation. The lake volume change and basin scale glacier contribution reveal that the enhanced precipitation predominantly drives lake volume increase but it is spatially heterogeneous.PostprintPeer reviewe

Lake storage variation on the endorheic Tibetan Plateau and its attribution to climate change since the new millennium

Citation: Yao, F., Wang, J., Yang, K., Wang, C., Walter, B. A., & Crétaux, J.-F. (2018). Lake storage variation on the endorheic Tibetan Plateau and its attribution to climate change since the new millennium. Environmental Research Letters, 13(6), 064011. https://doi.org/10.1088/1748-9326/aab5d3Alpine lakes in the interior of Tibet, the endorheic Changtang Plateau (CP), serve as ‘sentinels’ of regional climate change. Recent studies indicated that accelerated climate change has driven a widespread area expansion in lakes across the CP, but comprehensive and accurate quantifications of their storage changes are hitherto rare. This study integrated optical imagery and digital elevation models to uncover the fine spatial details of lake water storage (LWS) changes across the CP at an annual timescale after the new millennium (from 2002–2015). Validated by hypsometric information based on long-term altimetry measurements, our estimated LWS variations outperform some existing studies with reduced estimation biases and improved spatiotemporal coverages. The net LWS increased at an average rate of 7.34 ± 0.62 Gt yr−1 (cumulatively 95.42 ± 8.06 Gt), manifested as a dramatic monotonic increase of 9.05 ± 0.65 Gt yr−1 before 2012, a deceleration and pause in 2013–2014, and then an intriguing decline after 2014. Observations from the Gravity Recovery and Climate Experiment satellites reveal that the LWS pattern is in remarkable agreement with that of regional mass changes: a net effect of precipitation minus evapotranspiration (P-ET) in endorheic basins. Despite some regional variations, P-ET explains ∼70% of the net LWS gain from 2002–2012 and the entire LWS loss after 2013. These findings clearly suggest that the water budget from net precipitation (i.e. P-ET) dominates those of glacier melt and permafrost degradation, and thus acts as the primary contributor to recent lake area/volume variations in endorheic Tibet. The produced lake areas and volume change dataset is freely available through PANAGEA (https://doi.pangaea.de/ 10.1594/PANGAEA.888706)

Satellites reveal widespread decline in global lake water storage

Climate change and human activities increasingly threaten lakes that store 87% of Earth's liquid surface fresh water. Yet, recent trends and drivers of lake volume change remain largely unknown globally. Here, we analyze the 1972 largest global lakes using three decades of satellite observations, climate data, and hydrologic models, finding statistically significant storage declines for 53% of these water bodies over the period 1992-2020. The net volume loss in natural lakes is largely attributable to climate warming, increasing evaporative demand, and human water consumption, whereas sedimentation dominates storage losses in reservoirs. We estimate that roughly one-quarter of the world's population resides in a basin of a drying lake, underscoring the necessity of incorporating climate change and sedimentation impacts into sustainable water resources management

Assessing the utility of geospatial technologies to investigate environmental change within lake systems

Over 50% of the world's population live within 3. km of rivers and lakes highlighting the on-going importance of freshwater resources to human health and societal well-being. Whilst covering c. 3.5% of the Earth's non-glaciated land mass, trends in the environmental quality of the world's standing waters (natural lakes and reservoirs) are poorly understood, at least in comparison with rivers, and so evaluation of their current condition and sensitivity to change are global priorities. Here it is argued that a geospatial approach harnessing existing global datasets, along with new generation remote sensing products, offers the basis to characterise trajectories of change in lake properties e.g., water quality, physical structure, hydrological regime and ecological behaviour. This approach furthermore provides the evidence base to understand the relative importance of climatic forcing and/or changing catchment processes, e.g. land cover and soil moisture data, which coupled with climate data provide the basis to model regional water balance and runoff estimates over time. Using examples derived primarily from the Danube Basin but also other parts of the World, we demonstrate the power of the approach and its utility to assess the sensitivity of lake systems to environmental change, and hence better manage these key resources in the future

Correction to: Water Resources in Africa under Global Change: Monitoring Surface Waters from Space

International audienc

Monitoring variations in lake water storage with satellite imagery and citizen science

Despite lakes being a key part of the global water cycle and a crucial water resource, there is limited understanding of whether regional or lake‐specific factors control water storage variations in small lakes. Here, we study groups of small, unregulated lakes in North Carolina, Washington, Illinois, and Wisconsin, USA using lake level measurements gathered by citizen scientists and lake surface area measurements from optical satellite imagery. We show the lake level measurements to be highly accurate when compared to automated gauges (mean absolute error = 1.6 cm). We compare variations in lake water storage between pairs of lakes within these four states. On average, water storage variations in lake pairs across all study regions are moderately positively correlated (ρ = 0.49) with substantial spread in the degree of correlation. The distance between lake pairs and the extent to which their changes in volume are correlated show a weak but statistically significant negative relationship. Our results indicate that, on regional scales, distance is not a primary factor governing lake water storage patterns, which suggests that other, perhaps lakes‐specific, factors must also play important roles

Continental mass change from GRACE over 2002-2011 and its impact on sea level

Present-day continental mass variation as observed by space gravimetry reveals secular mass decline and accumulation. Whereas the former contributes to sea-level rise, the latter results in sea-level fall. As such, consideration of mass accumulation (rather than focussing solely on mass loss) is important for reliable overall estimates of sea-level change. Using data from the Gravity Recovery And Climate Experiment satellite mission, we quantify mass-change trends in 19 continental areas that exhibit a dominant signal. The integrated mass change within these regions is representative of the variation over the whole land areas. During the integer 9-year period of May 2002 to April 2011, GIA-adjusted mass gain and mass loss in these areas contributed, on average, to −(0.7 ± 0.4) mm/year of sea-level fall and + (1.8 ± 0.2) mm/year of sea-level rise; the net effect was + (1.1 ± 0.6) mm/year. Ice melting over Greenland, Iceland, Svalbard, the Canadian Arctic archipelago, Antarctica, Alaska and Patagonia was responsible for + (1.4±0.2) mm/year of the total balance. Hence, land-water mass accumulation compensated about 20 % of the impact of ice-melt water influx to the oceans. In order to assess the impact of geocentre motion, we converted geocentre coordinates derived from satellite laser ranging (SLR) to degree-one geopotential coefficients. We found geocentre motion to introduce small biases to mass-change and sea-level change estimates; its overall effect is + (0.1 ± 0.1) mm/year. This value, however, should be taken with care owing to questionable reliability of secular trends in SLR-derived geocentre coordinates

Back arc extension and collision : an experimental approach of the tectonics of Asia

International audienceThe deformation of the eastern Asian lithosphere during the first part of the India-Asia collision was dominated by subduction-related extension interacting with far effects of the collision. In order to investigate the role of large-scale extension in collision tectonics, we performed analogue experiments of indentation with a model of lithosphere subjected to extension. We used a three-layer rheological model of continental lithosphere resting upon an asthenosphere of low viscosity and strained along its southern boundary by a rigid indenter progressing northward. The lithosphere model was scaled to be gravitationally unstable and to spread under its ownweight, so that extension occurred in thewhole model. The eastern boundarywas free or weakly confined and always allowed eastward spreading of the model. We studied the pattern of deformation for different boundary conditions. The experimental pattern of deformation includes a thickened zone in front of the indenter, a major northeast-trending left-lateral shear zone starting from the northwest corner of the indenter, antithetic north-south right-lateral shear zones more or less developed to the east of the indenter, and a purely extensional domain in the southeastern part of the model. In this domain, graben opening is driven by gravitational spreading, whereas it is driven by gravitational spreading and indentation in the northeastern part where grabens opened along strike-slip faults. The results are compared with the Oligo- Miocene deformation pattern of Asia consecutive to the collision of India. Our experiments bring a physical basis to models which favour distributed deformation within a slowly extruded wide region extending from the Baikal Rift to the Okhotsk Sea and to southeast Asia and Indonesia. In this large domain, the opening of backarc basins (Japan Sea, Okinawa Trough, South China Sea) and continental grabens (North China grabens) have been associated with approximately north-south-trending right-lateral strike-slip faults, which accommodated the northward penetration of India into Eurasia