Sedimentary grain-size record of Holocene runoff fluctuations in the Lake Lugu watershed, SE Tibetan Plateau

The Holocene ◽  
2020 ◽  
pp. 095968362097277
Author(s):  
Xiaonan Zhang ◽  
Hucai Zhang ◽  
Fengqin Chang ◽  
Umar Ashraf ◽  
Han Wu ◽  
...  
Keyword(s):  
Grain Size ◽  
Tibetan Plateau ◽  
Lake Level ◽  
Boreal Summer ◽  
Lake Basin ◽  
Lake Surface ◽  
The Holocene ◽  
Tropical Ssts ◽  
Moisture Conditions ◽  
Lake Lugu

Changes in moisture conditions or precipitation in the SE Tibetan Plateau during the Holocene have been studied using various environmental archives and proxies. However, due to different interpretations of the proxies and records, the pattern of Holocene precipitation/moisture variations in the region remains unclear. A lake-sediment-based reconstruction of runoff variations, which can directly and sensitively reflect changes in precipitation, provides the opportunity to reconstruct the evolution of moisture conditions in the SE Tibetan Plateau during the Holocene. In this study, we used a well-dated sediment core (LGH2) from Lake Lugu, a deep alpine lake charged mainly by precipitation on the lake surface and by runoff from the watershed, to reconstruct variations in runoff during the Holocene. In addition, 70 lake surface sediment samples were collected to examine the spatial variation of grain size. Endmember modeling analysis of the grain-size data was used to characterize the processes of sediment transport and runoff fluctuations. The carbonate content of core LGH2 shows that the lake level was generally high during 11,600–3100 cal years BP, and that the lake basin was closed after 3100 cal years BP and semi-closed since 90 cal years BP. Grain-size endmember EM 3, which represents the runoff input clastic materials, is used to reconstruct runoff fluctuations in the Lake Lugu watershed. The record indicates a gradual increase in runoff during 11,600–9000 cal years BP, stable and high runoff during 9000–2000 cal years BP, and weak runoff and a low lake level since 2000 cal years BP. Our reconstruction of runoff fluctuations tracks changes in regional temperature and tropical SSTs rather than in boreal summer insolation. This finding supports the hypothesis that increasing tropical SSTs strengthened ITCZ convection which enhanced the flux of water vapour from the ocean to the air, and hence the moisture supplies to SW China.

Recent seismic events preserved in lacustrine sediments from the SE Tibetan Plateau

2020 ◽  
Author(s):  
Yongbo Wang ◽  
Xuezhi Ma ◽  
Zhenyu Ni
Keyword(s):  
Grain Size ◽  
Tibetan Plateau ◽  
Sediment Cores ◽  
Lacustrine Sediments ◽  
Size Composition ◽  
Recurrence Time ◽  
Seismic Events ◽  
Lake Basin ◽  
The Tibetan Plateau ◽  
Fine Clay

<p>Large earthquakes are regarded as important contributors to long-term erosion rates and considerable hazard to infrastructure and society, which were difficult to track because of the long recurrence time exceeding the time span of historical records. Geological records, especially the continuously accumulated lacustrine sediments, hold the potential to capture signals of prehistoric seismic events, which has been barely reported from the Tibetan Plateau. Here we present lacustrine sediment records recovered from Basom Tso in Southeastern Tibetan Plateau, in which two seismic events were preserved. Sediment lithology, grain size composition, magnetic susceptibility and XRF scanning induced element compositions showed dramatic variations in two turbidite-like sediment segments. Particularly, the grain size showed an abrupt increase at the bottom of the Turbidites which was followed by a fining-up pattern and covered by a fine clay cap, expressing similar sedimentary processes caused by the seiche effect triggered by seismic events. Consistent patterns were recorded in the element contents as well, i.e. obvious bias in the counts of Fe, Zr, Ti, Ca. In addition, scuh pattern were preserved in sediment cores from different part of the lake basin, indicating a basin wide event layer. Finally, according to the dating results from <sup>137</sup>Cs and <sup>14</sup>C, the two Turbidites were formed around 1950 A.D. and during the late18<sup>th</sup>/early 19<sup>th</sup> century respectively. Such information was further confirmed by historical earthquake records that Chayu Earthquake (M=8.6, 1950 A.D.) and Nyingchi Earthquake (M=6.75, 1845 A.D.) have possibly responsible for the slump of underwater sediments and the formation of these two turbidites.</p>

Long-Term Changes of Lake Level and Water Budget in the Nam Co Lake Basin, Central Tibetan Plateau

2014 ◽  
Vol 15 (3) ◽  
pp. 1312-1322 ◽  
Author(s):  
Yanhong Wu ◽  
Hongxing Zheng ◽  
Bing Zhang ◽  
Dongmei Chen ◽  
Liping Lei
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Water Budget ◽  
Lake Level ◽  
Lake Basin ◽  
The Tibetan Plateau ◽  
Nam Co ◽  
Long Term Changes ◽  
Nam Co Lake

Abstract Long-term changes in the water budget of lakes in the Tibetan Plateau due to climate change are of great interest not only for the importance of water management, but also for the critical challenge due to the lack of observations. In this paper, the water budget of Nam Co Lake during 1980–2010 is simulated using a dynamical monthly water balance model. The simulated lake level is in good agreement with field investigations and the remotely sensed lake level. The long-term hydrological simulation shows that from 1980 to 2010, lake level rose from 4718.34 to 4724.93 m, accompanied by an increase of lake water storage volume from 77.33 × 109 to 83.66 × 109 m3. For the net lake level rise (5.93 m) during the period 1980–2010, the proportional contributions of rainfall–runoff, glacier melt, precipitation on the lake, lake percolation, and evaporation are 104.7%, 56.6%, 41.7%, −22.2%, and −80.9%, respectively. A positive but diminishing annual water surplus is found in Nam Co Lake, implying a continuous but slowing rise in lake level as a hydrological consequence of climate change.

scholarly journals Tracking the impacts of the Aru glacier collapses on downstream lakes

2020 ◽  
Author(s):  
Yanbin Lei ◽  
Tandong Yao ◽  
Lide Tian ◽  
Yongwei Sheng ◽  
Jingjuan Liao ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Lake Level ◽  
In Situ Observation ◽  
Lake Surface ◽  
Level Increase ◽  
Lake Morphology ◽  
Western Tibetan Plateau ◽  
Ice Avalanche

Abstract. Two giant glaciers at the Aru range, western Tibetan Plateau, collapsed suddenly on 17 July and 21 September 2016, respectively, causing fatal damage to local people and their livestock. The ice avalanches, with a total volume of 150 × 106 m3, had almost melted by September 2019. Based on in-situ observation, bathymetry survey and satellite data, here we show the impacts of the two glacier collapses on the downstream lakes, the outflow Aru Co and the terminal Memar Co, in terms of lake morphology, water level and water temperature in the subsequent four years (2016–2019). After the first glacier collapse, the ice avalanche slid into Aru Co along with a large amount of debris, which significantly modified the lake’s shoreline and bathymetry. Lake surface temperature (LST) at Aru Co and Memar Co exhibited a significant decrease of 2–4 oC in the first 1–2 weeks after the first glacier collapse due to the intruding ice into Aru Co and its melting. Memar Co significantly deepened by 12.5 m between 2000 and 2018, with accelerated lake level increase after the glacier collapses. Memar Co expanded rapidly at a rate of 0.80 m/yr between 2016 and 2019, which is about 30 % higher than the average rising rate between 2003 and 2014. The meltwater from ice avalanches was found to contribute to about 26.4 % of the increase in lake storage between 2016 and 2019. This study implies that the Aru glacier collapses had long-term and dramatic impacts on the downstream lakes.

scholarly journals Orbital changes, variation in solar activity and increased anthropogenic activities: controls on the Holocene flood frequency in the Lake Ledro area, Northern Italy

2012 ◽  
Vol 8 (5) ◽  
pp. 4701-4744 ◽  
Author(s):  
B. Vannière ◽  
M. Magny ◽  
S. Joannin ◽  
A. Simonneau ◽  
S. B. Wirth ◽  
...  
Keyword(s):  
Lake Level ◽  
Large Scale ◽  
Northern Italy ◽  
Flood Frequency ◽  
Ice Age ◽  
Lake Basin ◽  
The Holocene ◽  
Short Intervals ◽  
Middle Holocene ◽  
Early And Middle Holocene

Abstract. Two lacustrine sediment cores from Lake Ledro in Northern Italy were studied to produce chronologies of flood events for the past 10 000 yr. For this purpose, we have developed an automatic method that objectively identifies the sedimentary imprint of river floods in the downstream lake basin. The automatic counting of flood deposits was based on colour data extracted from processed core photographs, and the count data were processed to capture the flood signal. Automatic quantification was compared with naked-eye counting. Counts were performed twice on the proximal and distal cores to provide an objective and reproducible record of flood frequency. Geophysical and geochemical analyses made it possible to distinguish event deposits from background sedimentation. Flood frequency and reconstructed sedimentary dynamics were compared with lake-level changes and pollen dynamics inferred from vegetation data. The data suggest a record marked by low flood frequency during the early and middle Holocene (10 000–4500 cal BP). Only modest increases during short intervals are recorded at ca. 8000, 7500, and 7100 cal BP. The last third of the Holocene is characterised by a shift toward increased flood frequency at ca. 4500–4000 cal BP. With the exception of two short intervals around 2900–2500 and 1800–1400 cal BP, which show a slightly reduced number of floods, the trend of increasing flood frequency prevailed until the 20th century, reaching a maximum between the 16th and the 19th centuries. Brief-flood frequency increases recorded during the early and middle Holocene can be attributed to cold climatic oscillations. On a centennial time scale, major changes in flood frequency, such as those observed at ca. 4500 and 500 cal BP, can be attributed to large-scale climatic changes such as the Neo-glacial and Little Ice Age, which are under orbital and possibly solar control. The role of climate as the main forcing factor in flood activity is supported by the lake-level records: the major lake-level rises are synchronous with flood frequency increases. However, in the Bronze Age and during the Middle Ages and modern times, forest clearing and land use are indicated by pollen and archaeological data. These human activities have clearly affected the sediment record of flood activity, and they can partially explain the amplitude of the increases in flood activity.

scholarly journals The Driving Forces Underlying Spatiotemporal Lake Extent Changes in the Inner Tibetan Plateau During the Holocene

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiangjun Liu ◽  
David Madsen ◽  
Xiaojian Zhang
Keyword(s):  
Tibetan Plateau ◽  
Lake Level ◽  
Climate Model ◽  
Driving Forces ◽  
Early Holocene ◽  
Water Vapor Transport ◽  
The Tibetan Plateau ◽  
Lake Levels ◽  
The Holocene ◽  
Spatial Differences

The Inner Tibetan Plateau (ITP), the central and western part of the Tibetan Plateau (TP), covers about one-fourth of the entire TP and contains more than 800 endorheic lakes larger than 1 km2. These lakes are important water reservoirs and sensitive to TP climate changes. They regulate regional water circulations, and further influence local ecosystems. Many lakes in ITP are surrounded by conspicuous paleoshorelines indicating much higher past lake levels. Previous studies found that lakes in the western ITP (west of ∼86°E) apparently expanded to higher levels than those to the east during the Holocene high lake level stage, however, there is no in-depth study on the reasons for the spatial differences of high lake levels within the ITP. In this study, we first identify Holocene lake level (or lake extent) changes over the ITP by combining published lake level variation data with our reconstruction of Dagze Co lake level variations. We then investigate spatial differences in the magnitude of lake expansions and explore the underlying forces driving these differences using the transient climate evolution of the last 21 ka (TraCE-21ka) and Kiel Climate Model (KCM) simulation results. We find that lakes in the ITP expanded to their highest levels during the early Holocene when the Indian summer monsoon (ISM) greatly intensified. After the mid-Holocene, lake levels fell as a result of the weakening of the ISM. The early Holocene northward shift of the westerly jet and a positive phase of the Atlantic multidecadal oscillation (AMO) resulted in the intensification of southwesterly winds on the southwest TP flank. Concurrently, westerly winds over the TP weakened, causing a differential increase in water vapor transport to the ITP with higher precipitation levels in the southwestern ITP and lower levels to the northeast. These wind-driven differential precipitation levels caused lakes in the southwestern ITP to expand to higher levels than those in the central, northern and northeastern ITP. During the early Holocene, expansion of lakes in the northwestern ITP was enhanced by an increase in glacier melt water besides the increased summer rainfall associated with the intensified ISM.

Variation of the winter mid-latitude Westerlies in the Northern Hemisphere during the Holocene revealed by aeolian deposits in the southern Tibetan Plateau

2021 ◽  
pp. 1-9
Author(s):  
Fuyuan Gao ◽  
Junhuai Yang ◽  
Shuyuan Wang ◽  
Youjun Wang ◽  
Kaiming Li ◽  
...  
Keyword(s):  
Grain Size ◽  
Tibetan Plateau ◽  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
The Holocene ◽  
Aeolian Deposits ◽  
Grain Size Distributions ◽  
Southern Tibetan Plateau ◽  
Vegetation Water ◽  
End Members

Abstract The mid-latitude Westerlies (MLW) are one of the most important atmospheric circulation systems in the Northern Hemisphere, exerting a huge influence on the climate of the region downwind, and thus on vegetation, water resources, and human wellbeing. However, the seasonal variation of the MLW during the Holocene is not yet been fully understood, especially when its contribution is the most important. Here, we used end-member (EM) modeling analysis of the grain-size distributions of a high-altitude aeolian sedimentary sequence (4452 m a.s.l.) from the Yarlung Zangbo River valley in the southern Tibetan Plateau to reveal variations in the winter MLW during the Holocene. Analysis of seasonal differences in modern atmospheric circulation suggests that the southern Tibetan Plateau was heavily influenced by the mid-latitude Westerlies at the 400, 500, and 600 hPa levels in winter, while it was seldom influenced at these levels in summer. Four grain-size end-members are identified, representing distinct aerodynamic environments, of which EM1 (modal grain size 8.1 μm) can be used as a proxy of the winter MLW. A reconstruction of the variation of the winter MLW during the Holocene based on EM1 revealed that a weaker winter MLW occurred during the Early to Middle Holocene, and a stronger winter MLW during the Middle to Late Holocene. Overall, we suggest that this change in the winter MLW was closely related to the insolation/temperature/pressure gradient between low and high latitudes in the Northern Hemisphere.

Constraints on Paleoclimate from 11.5 to 5.0 ka from Shoreline dating and Hydrologic Budget Modeling of Baqan Tso, Southwestern Tibetan Plateau

2015 ◽  
Vol 83 (1) ◽  
pp. 80-93 ◽  
Author(s):  
Tyler Huth ◽  
Adam M. Hudson ◽  
Jay Quade ◽  
Lei Guoliang ◽  
Zhang Hucai
Keyword(s):  
Tibetan Plateau ◽  
Lake Level ◽  
Regional Climate ◽  
Surface Heat ◽  
Early Holocene ◽  
Lake Area ◽  
Lake Surface ◽  
Western Tibetan Plateau ◽  
End Members ◽  
Land Runoff

Abstract14C dating of shoreline deposits of closed-basin lake Baqan Tso in the western Tibetan Plateau shows that lake level regressed from the undated highstand (46 m above modern, 4.3 × modern surface area) of likely earliest Holocene age by 11.5 ka, and remained larger than modern until at least ≈ 5.0 ka. The shoreline record broadly matches other regional climate records, with lake level closely following Northern Hemisphere summer insolation overprinted by sub-millennial lake-level oscillations. A model coupling modern land runoff and lake surface heat closely reproduces estimated modern precipitation of ≈ 240 mm/yr. We estimate that the Baqan Tso basin required ≈ 380 mm/yr precipitation to sustain the maximum early Holocene lake area, a 55% increase over modern. Precipitation increases, not glacial meltwater, drove lake-level changes, as Baqan Tso basin was not glaciated during the Holocene. Our estimate assumes early Holocene insolation (≈ 1.3% overall increase), and mean annual increases of 2°C in temperature, and 37% in relative humidity. We additionally developed a Holocene precipitation history for Baqan Tso using dated paleolake areas. Using the modern and early Holocene model results as end-members, we estimate precipitation in the western Tibetan Plateau which was 300–380 mm/yr between 5.0 and 11.5 ka, with error of ± 29–57 mm/yr (± 12–15%).

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