Strengthened Indian summer monsoon brought more rainfall to the western Tibetan Plateau during the early Holocene

Liu, Xiang-Jun; Zhang, Xiaojian; Wang, Danyang; Jin, Liya; Chen, Fahu

doi:10.1016/j.scib.2019.07.022

Cited by 16 publications

(11 citation statements)

References 11 publications

(36 reference statements)

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“…Melt water was also not a dominant factor that caused lakes in the TP expanded synchronously during the Holocene high lake level stage because glacier melting is more related to local climate conditions and lakes with and without glaciers in their catchments expanded in a similar pattern (Hudson and Quade, 2013). Hence, the ratio of paleo-Aw to modern Aw mainly represents the expansion of a lake in response to past increased precipitation (Liu et al, 2019). Here we use modern lake areas, largest Holocene lake areas and watershed areas reported by Hudson and Quade (2013) for lakes in the ITP.…”

Section: Spatial Lake Expansions In Inner Tibetan Plateau During the Holocene Highest Lake-level Stagementioning

confidence: 99%

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

2021

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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.

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Section: Spatial Lake Expansions In Inner Tibetan Plateau During the Holocene Highest Lake-level Stagementioning

confidence: 99%

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

2021

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“…The Tibetan Plateau (TP) is the largest and highest plateau on Earth, often regarded as the "Third Pole" due to both its high elevations and expansive c. 2.5 million km 2 coverage (Yao et al, 2012;Liu et al, 2019). Of the more than 1,400 lakes (larger than 1 km 2 ) distributed across the TP, c. 60% are within the endorheic TP (Zhang et al, 2020), and their lacustrine sediments preserve a wealth of information that helps researchers track past environmental and hydrological changes within the region (Hou et al, 2010;Long et al, 2014;Liu et al, 2018;Chongyi et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Radiocarbon and Luminescence Dating of Lacustrine Sediments in Zhari Namco, Southern Tibetan Plateau

Wang

Zhang³

et al. 2021

Front. Earth Sci.

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There are more than 1,000 lakes within the Tibetan Plateau (TP), all of which are sensitive to changes in regional climate and local hydrology. Lacustrine sediments within these lakes preserve a good record of these changes. However, determining their precise ages is difficult due to the complex nature of lake reservoir effects (LRE), which limit our understanding of paleoenvironmental changes. Focusing on an exposed 600 cm thick lacustrine sediment profile located in western Zhari Namco, we used a combination of both radiocarbon and optically stimulated luminescence (OSL) dating methods in order to evaluate the carbon reservoirs of bulk organic matter (BOM) and aquatic plant remnants (APR), and to explore the age differences between 14C and OSL and their respective reliability. We demonstrated that (i) OSL ages were changed in stratigraphic order, and the OSL age just below the beach gravel layer was consistent with previously reported paleoshoreline ages; (ii) 14C ages were divergent between BOM and grass leaves; (iii) 14C ages of BOM were older than 14C ages of APR; and (iv) all 14C ages were older than OSL ages. This could be attributed to changing LRE in the past, causing the 14C ages to appear unstable during the deposition period. Although the 14C ages of terrestrial plant remnants (TPR) were not affected by LRE, an analyzed twig nonetheless returned a 14C age older than its respective layer’s OSL age, suggesting it may have been preserved on land prior to transportation into the lake. Our study suggests that OSL ages are more reliable than 14C ages with respect to Zhari Namco lacustrine sediments. We recommend caution when interpreting paleoenvironmental changes based on lacustrine sediment 14C ages alone.

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“…Over the course of the past 30 years, extensive investigations of TP paleoenvironmental changes have been conducted by scientists within China and from abroad. However, most are focused on the last deglaciation and Holocene stages, with only a few records spanning the LGM (An et al, 2012;Liu et al, 2019;Chen et al, 2020 and references there in). Ice cores older than the Holocene are scarce on the TP, with only the Guliya ice cap records extending through the LGM (Thompson et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Climate Conditions on the Tibetan Plateau During the Last Glacial Maximum and Implications for the Survival of Paleolithic Foragers

Liu

et al. 2020

Front. Earth Sci.

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Environmental conditions on the Tibetan Plateau (TP) during the last glacial maximum (LGM) are poorly known. Existing studies of environmental proxies and climate model simulations are contradictory, with interpretations varying between cold-dry and cold-wet environmental conditions which differentially influenced lake volumes, loess deposition and vegetation communities across the TP. Genetic and archaeological studies suggest anatomically modern paleolithic foragers initially occupied the TP between 60 and 30 ka, and may have seasonally occupied the TP during the LGM. Hence, a better understanding for LGM environmental conditions is needed in order to estimate whether paleolithic foragers could have survived on the TP during the extreme LGM cold stage. Here we report the investigation of lacustrine sediments and beach deposits within two paleoshorelines around Dagze Co on the southern TP, ∼22 and ∼42 m higher than the present lake level. Optical age estimates suggest the sediments were deposited during the LGM and mid-Holocene, respectively. TraCE-21 climate model simulation results suggest that net annual LGM precipitation in the Dagze Co basin was lower than the mid-Holocene, but about the same as that of the past 1,000 years. Combining the optical age estimates with TraCE-21 and CAM4 climate model simulation results, we deduce that increased summer precipitation and glacier meltwater supply, combined with decreased lake surface evaporation, produced LGM lake levels ∼22 m higher than present. We also synthesized paleoenvironmental records reported across the TP spanning the LGM. This synthesis suggests that the LGM climate in the northern TP was cold and dry, but that some of the southern TP was cold and wet. These relatively wetter LGM conditions in the southern TP may have favored the growth of cold-resistant plants which, in turn, may have supported larger herbivore populations, and provided food for paleolithic foragers. We conclude that seasonal or short-term human occupation of the TP during the LGM was thus more likely in the southern TP than in the north.

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Strengthened Indian summer monsoon brought more rainfall to the western Tibetan Plateau during the early Holocene

Cited by 16 publications

References 11 publications

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

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

Radiocarbon and Luminescence Dating of Lacustrine Sediments in Zhari Namco, Southern Tibetan Plateau

Climate Conditions on the Tibetan Plateau During the Last Glacial Maximum and Implications for the Survival of Paleolithic Foragers

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