Domino effect of a natural cascade alpine lake system on the Third Pole (original) (raw)
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Remote Sensing
Lakes on the Tibetan Plateau (TP) have changed dramatically as a result of climate change during recent decades. Studying the changes in long-term lake water storage (LWS) is of great importance for regional water security and ecosystems. Nam Co Lake is the second largest lake in the central TP. To investigate the long-term changes in LWS, a distributed cryosphere-hydrology model (WEB-DHM) driven by multi-source data was evaluated and then applied to simulate hydrological processes across the whole Nam Co Lake basin from 1980 to 2016. Firstly, a comparison of runoff (lake inflow), land surface temperature, and snow depth between the model simulations and observations or remote sensing products showed that WEB-DHM could accurately simulate hydrological processes in the basin. Meanwhile, the simulated daily LWS was in good agreement with satellite-derived data during 2000–2016. Secondly, long-term simulations showed that LWS increased by 9.26 km3 during 1980–2016, reaching a maximum i...
Earth Surface Dynamics, 2019
The formation and development of glacial lakes in mountainous regions is one of the consequences of glacier recession. Such lakes may drain partially or completely when the stability of their dams is disturbed or as a consequence of impacts. We present a case study from the Central Asian mountain range of Tien Shan-a north-oriented tributary of the Adygine Valley, where the retreat of a polythermal glacier surrounded by per-mafrost has resulted in the formation of several generations of lakes. The aim of this study was to analyse the past development of different types of glacial lakes influenced by the same glacier, to project the site's future development , and to evaluate the outburst susceptibility of individual lakes with an outlook for expected future change. We addressed the problem using a combination of methods, namely bathymetric, geodetic and geophysical on-site surveys, satellite images and digital elevation model analysis, and modelling of glacier development. Based on this case of the glacial lakes being of varied age and type, we demonstrated the significance of glacier ice in lake development. Lake 3, which is in contact with the glacier terminus, has changed rapidly over the last decade, expanding both in area and depth and increasing its volume by more than 13 times (7800 to 106 000 m 3). The hydrological connections and routing of glacier meltwater have proved to be an important factor as well, since most lakes in the region are drained by subsurface channels. As the site is at the boundary between continuous and discontinuous permafrost, the subsurface water flow is strongly governed by the distribution of non-frozen zones above, within, or beneath the perennially frozen ground. In the evaluation of lake outburst susceptibility, we have highlighted the importance of field data, which can provide crucial information on lake stability. In our case, an understanding of the hydrological system at the site, and its regime, helped to categorise Lake 2 as having low outburst susceptibility, while Lake 1 and Lake 3 were labelled as lakes with medium outburst susceptibility. Further development of the site will be driven mainly by rising air temperatures and increasingly negative glacier mass balance. All three climate model scenarios predicted a significant glacier areal decrease by 2050, specifically leaving 73.2 % (A1B), 62.3 % (A2), and 55.6 % (B1) of the extent of the glacier in 2012. The glacier retreat will be accompanied by changes in glacier runoff, with the first peak expected around 2020, and the formation of additional lakes.
Asia's high plateaus are sensitive to climate change and have been experiencing rapid warming over the past few decades. We found 99 new lakes and extensive lake expansion on the Tibetan Plateau during the last four decades, 1970-2013, due to increased precipitation and cryospheric contributions to its water balance. This contrasts with disappearing lakes and drastic shrinkage of lake areas on the adjacent Mongolian Plateau: 208 lakes disappeared, and 75% of the remaining lakes have shrunk. We detected a statistically significant coincidental timing of lake area changes in both plateaus, associated with the climate regime shift that occurred during 1997/1998. This distinct change in 1997/1998 is thought to be driven by large-scale atmospheric circulation changes in response to climate warming. Our findings reveal that these two adjacent plateaus have been changing in opposite directions in response to climate change. These findings shed light on the complex role of the regional climate and water cycles and provide useful information for ecological and water resource planning in these fragile landscapes.
Response of Tibetan Plateau lakes to climate change: Trends, patterns, and mechanisms
Earth-Science Reviews, 2020
The wide distribution of natural lakes over the Tibetan Plateau, the highest and largest plateau on Earth, have received extensive attention due to global warming. In this Review, we examine lake evolution, spatial patterns and driving mechanisms over the Tibetan Plateau. The changes in lake area, level and volume show a slight decrease from 1976 to the mid-1990s, followed by a continuous rapid increase. The spatial patterns show an overall lake growth in the north of the inner plateau against a reduction in the south, which are accompanied by most of the lakes cooling in the north against warming in the south, and longer ice cover duration in the north compared with the south. The changes in lake temperature are negatively correlated with water level variations and lake ice duration. Enhanced precipitation is the dominant contributor to increased lake water storage, followed by glacier mass loss and permafrost thawing. The decadal or longer lake expansion since the mid-1990s could have been driven by the positive phase of Atlantic Multidecadal Oscillation, and clear inflection points of lake area/level identified in 1997/1998 and 2015/2016 are attributed to strong El Niño events. In the near-term, the lakes will continue to expand. Future interdisciplinary lake studies are urgently required to improve understanding of climate-cryosphere-hydrosphere interactions and water resources management.
The Cryosphere, 2024
Simulating the ice phenology of deep alpine lakes is important and challenging in coupled atmosphere–lake models. In this study, the Weather Research and Forecasting (WRF) model, coupled with two lake models, the freshwater lake (WRF–FLake) model and the default lake (WRF–CLake) model, was applied to Nam Co, a typical deep alpine lake located in the centre of the Tibetan Plateau, to simulate its lake ice phenology. Due to the large errors in simulating lake ice phenology, related key parameters and parameterizations were improved in the coupled model based on observations and physics-based schemes. By improving the momentum, hydraulic, and thermal roughness length parameterizations, both the WRF–FLake model and the WRF–CLake model reasonably simulated the lake freeze-up date. By improving the key parameters associated with shortwave radiation transfer processes when lake ice exists, both models generally simulated the lake break-up date well. Compared with WRF–CLake without improvements, the coupled model with both revised lake models significantly improved the simulation of lake ice phenology. However, there were still considerable errors in simulating the spatial patterns of freeze-up and break-up dates, implying that significant challenges in simulating the lake ice phenology still exist in representing some important model physics, including lake physics such as grid-scale water circulation and atmospheric processes such as snowfall and surface snow dynamics. Therefore, this work can provide valuable new implications for advancing lake ice phenology simulations in coupled models, and the improved model also has practical application prospects in weather and climate forecasts.
Linkages of the dynamics of glaciers and lakes with the climate elements over the Tibetan Plateau
Research paper , 2018
Future climate warming is expected to have a significant effect on the operation of Earth and Ecological systems. A key concern in the future is water resource availability. In regions such as the Tibet Plateau (TP) lakes and glaciers appear to be highly sensitive to climate forcing and variations in the size and extent of these systems will have profound socioeconomic and environmental consequences in South and Central Asia. Although the variety of glaciers and lake son the TP is a heavily researched and discussed topic the interaction between glaciers/lakes and climate change has not be thoroughly investigated. Here we present, through a review of existing studies and original remote sensing analysis, a reconstruction of changes in the spatial coverage of glaciers and lakes on the TP from 1990 to 2015 along with an analysis of climate data for the same period. The results revealed that these systems responded to changes in both temperature and precipitation but the nature of this response, and the controlling factor, was spatially diverse. During this interval the total number of lakes increased from 868 to 1207, thus a large number of new lakes (n = 339) formed. The total water surface area of the lakes increase from 38,823.3 km 2 in 1990 to 48,793.0 km 2 in 2015, at a rate of 383.5 km 2 yr-1. Over this period intensive glacial shrinkage occurred, primarily driven by increasing average temperature, except in the Karakoram Mountains where a slight increase in glacier extent was explained by low and stable temperatures along with increasing precipitation. The expansion of lakes in the central and northeastern TP can, therefore, be explained by a trend of increasing precipitation and the accelerated melting of glaciers associated with rising temperatures, both of which contributed to the enhanced total basin runoff. The shrinkage of lake areas along the Himalayan Mountains is accounted for by low precipitation coupled with high evaporation and limited basin space. The lakes within the Qaidam Basin express a complex pattern of response in association with fluctuating precipitation and strong evaporation. The pattern of shrinking glaciers and expanding lakes indicate that water-cycle processes on the TP have been accelerating during the past 25 years. Under current climates and future climate change, the shrinkage of glaciers and the enlargement of lakes may be expected to continue to accelerate until a "tipping point" is reached when the meltwater of declining glaciers can no longer sustain the enhanced
2019
Formation and development of glacial lakes in mountain regions is one of the consequences of glacier recession. Such lakes may drain partially or completely when the stability of their dam is disturbed or as a consequence of impacts. We presented a case study from Central-Asian mountain range of Tien Shan, a north-oriented tributary Adygine valley, where a the retreat of a polythermal glacier surrounded by permafrostglacier retreat resulted in the formation of several generations of lakes. The aim of this study iwas to analyse the past development of different types of glacial lakes influenced by the same glacier, to project site’s future development, and to evaluate the hazard outburst susceptibility of individual lakes with an outlook for expected future change. We addressed the problem with a combination of methods, namely bathymetric, geodetic, and geophysical on-site survey, satellite image and digital elevation model (DEM) analysis, and modelling of glacier development. Based ...
Response of downstream lakes to Aru glacier collapses on the western Tibetan Plateau
The Cryosphere, 2021
The lower parts of two glaciers in the Aru range on the western Tibetan Plateau (TP) collapsed on 17 July and 21 September 2016, respectively, causing fatal damage to local people and their livestock. The giant ice avalanches, with a total volume of 150 × 106 m3, had almost melted by September 2019 (about 30 % of the second ice avalanche remained). The impact of these extreme disasters on downstream lakes has not been investigated yet. Based on in situ observation, bathymetry survey and satellite data, we explore the impact of the ice avalanches on the two downstream lakes (i.e., Aru Co and Memar Co) in terms of lake morphology, water level and water temperature in the subsequent 4 years (2016–2019). After the first glacier collapse, the ice avalanche slid into Aru Co along with a large amount of debris, which generated great impact waves in Aru Co and significantly modified the lake's shoreline and underwater topography. An ice volume of at least 7.1 × 106 m3 was discharged into Aru Co, spread over the lake surface and considerably lowered its surface temperature by 2–4 ∘C in the first 2 weeks after the first glacier collapse. Due to the large amount of meltwater input, Memar Co exhibited more rapid expansion after the glacier collapses (2016–2019) than before (2003–2014), in particular during the warm season. The melting of ice avalanches was found to contribute to about 23 % of the increase in lake storage between 2016 and 2019. Our results indicate that the Aru glacier collapses had both short-term and long-term impacts on the downstream lakes and provide a baseline in understanding the future lake response to glacier melting on the TP under a warming climate.
Geographica Helvetica, 2012
Die Hochgebirgs-Kryosphäre, insbesondere Schnee, Permafrost und Gletscher, spielt in Bezug auf die Auswirkungen eines sich ändernden Klimas auf die Gebirgsökosysteme eine Schlüsselrolle aufgrund (i) ihrer starken Sensitivität infolge von Temperaturen nahe dem Schmelzpunkt, (ii) ihrer Funktion als (Haupt-) Steuerungsgrösse des hydrologischen Abflusses und (iii) des Einflusses von Veränderungen bezüglich der saisonalen Schneedecke, da diese Boden-Atmosphäre Wechselwirkungen auf verschiedene Weise stark beeinflusst. Um den Einfluss des Klimawandels auf die Kryosphäre und die damit verbundenen Auswirkungen für die Gesellschaft verlässlich bestimmen zu können, ist ein besseres Verständnis der für die Wechselwirkungen zwischen alpiner Kryosphäre und Atmosphäre relevanten Prozesse auf verschiedenen räumlichen und zeitlichen Skalen vonnöten. Da Veränderungen der Kryosphäre im Hochgebirge mit geomorphologischen Prozessen gekoppelt sind, können diese zu Naturgefahren aufgrund aktueller und zukünftiger Klimaänderungen führen. Temperaturabhängige Prozesse (z.B. Phasenübergänge von Wasser, Deformation von Eis sowie Eis/ Fels-Gemischen, Vorrat an Schnee/Eis, Permafrostdegradation) beeinflussen die physikalischen Faktoren, die den Sedimenttransport steuern (z.B. Gletscher, Blockgletscher, Murgänge), das hydrologische System sowie die Stabilität steiler Hänge. Aktuelle Forschungen an der Universität Freiburg im Bereich der alpinen Kryosphäre und Geomorphologie beschäftigen sich insbesondere mit der Entwicklung neuer Mess-und Modelliermethoden, um periglaziale und glaziale Systeme in Gebirgsregionen zu untersuchen und langfristig zu beobachten. Dies beinhaltet prozess-basierte Modellstudien, Monitoringstrategien sowie Impact-Studien in Bezug auf Hydrologie und Naturgefahren. In diesem Beitrag wird das Potential dieser neuen Modellier-, Mess-und Auswertungsmethoden für die Grundlagenforschung und ihrer Anwendung in den Gebirgsregionen der Schweiz vorgestellt. The highmountain cryosphere, in particular snow, permafrost and glaciers, plays a key role regarding climate change impacts on mountain ecosystems because of (i) its high climate sensitivity due to the proximity to the melting point, (ii) its major controlling function on hydrological runoff, and (iii) particularly because of the influence of seasonal snow on ground-atmosphere processes. In order to reliably assess the influence of climatic changes on the cryosphere and consequently their impacts on society, more detailed knowledge of the relevant processes that determine the interactions between the alpine cryosphere and the atmosphere on different spatial and temporal scales is required. As cryospheric changes in high mountains are strongly coupled to geomorphic processes these may result in dramatic changes in response to ongoing and future climatic evolution. Temperature dependent mechanisms (e.g. phase change of water, deformation of ice and ice/rock mixture, storage of snow/ice, permafrost degradation) will affect the physical factors controlling the transfer of sediment (e.g. glaciers, rock glaciers, debris flows), the hydrological system and the stability of steep slopes. Research in alpine cryosphere and geomorphology at the University of Fribourg particularly focuses on the development of new measurement and modelling techniques to investigate and monitor mountain periglacial and glacial systems, including process-based modelling studies, monitoring strategies, and analyses of the impact on hydrology and natural hazards. In this contribution, the potential of these new modelling, measurement and analysis techniques for fundamental and applied research on mountain regions in Switzerland is presented.
Glacier lake outburst floods (GLOFs) have been intensely investigated in High Mountain Asia (HMA) in recent years and are often the first hazard related to the cryosphere mentioned in the region. As glaciers recede and surrounding slopes become increasingly unstable, such events are expected to increase, although this trend has yet to manifest. Many studies have investigated individual events and while several regional inventories exist, they either do not cover all types of GLOF or are geographically constrained. Further, downstream impacts are rarely discussed. Previous inventories have relied on academic sources and have not been combined with existing inventories of glaciers and lakes. In this study, we present the first comprehensive inventory of GLOFs in HMA, including details on the time of their occurrence, processes of lake formation and drainage involved as well as downstream impacts. We document 682 individual GLOFs that occurred between 1833 and 2022. Of these, 20% were recurring events from just three ephemeral ice-dammed lakes. In combination, the documented events resulted in 6907 fatalities, with 6000 of these linked to a single GLOF, three times higher than a previous assessment for the region. The integration of previous inventories of glaciers and lakes within this database will inform future assessments of potential drivers of GLOFs, allowing more robust projections to be developed. The presented database and future updated versions are traceable, version controlled and can be directly incorporated into further analysis.