Holocene environmental changes in Bangong Co basin (Western Tibet). Part 4: Discussion and conclusions

Gasse, Françoise; Fontes, Jean-Charles; Campo, Elise Van; Wei, Kai

doi:10.1016/0031-0182(95)00035-6

Cited by 328 publications

(167 citation statements)

References 17 publications

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“…6h; Gasse et al, 1996). Increasing δ 18 O after 3.3 586 ka is interrupted at 2.4 ka by a period of steady to lower δ 18 O that lasted until 1.3 ka.…”

Section: Plateau 573mentioning

confidence: 99%

Late-Holocene Indian summer monsoon variability revealed from a 3300-year-long lake sediment record from Nir’pa Co, southeastern Tibet

et al. 2016

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Late Holocene Indian summer monsoon variability revealed from a 3,300-year-long 1 lake sediment record from Nir'pa Co, southeastern years. Constrained by modern calibration elevated silt and lithics and low sand and clay 24 between 3.3-2.4 ka and 1.3 ka to the present indicate two pluvial phases with lake levels 25 near their current overflow elevation. Between 2.4-1.3 ka, a sharp increase in sand and 26 corresponding decrease in lithics and silt suggest drier conditions and lower lake levels at 27Nir'pa Co. Hydroclimate expressions in the sedimentological proxies during the 28Medieval Climate Anomaly (MCA) and Little Ice Age (LIA) are not statistically 29 significant, suggesting that these events were minor compared to the millennial scale 30 variability on which they were superimposed. However, decreasing sand and increasing 31 lithics and silt during the MCA between 950-800 cal yr B.P. may suggest briefly wetter 32 conditions while increasing sand and reduced lithics and silt from 500-200 cal yr B.P. an area referred to as the Third Pole Environment (Qiu, 2008), show that the Indian 47 summer monsoon (ISM) reached a maximum during the early and middle Holocene 48 between 10 and approximately 6 ka when boreal summer insolation peaked and strong 49 tropical Pacific sea surface temperature (SST) gradients resembled a La Niña-like mean 50 state (Koutavas et al., 2006;He et al., 2004;Bird et al., 2014;Cai et al., 2012; Yanhong 51 et al., 2006;Marchitto et al., 2010;Morrill et al., 2003). The late Holocene, in contrast, 52 has been characterized by increasing aridity as summer insolation waned and an 53 increasingly El Niño-like mean state developed in the tropical Pacific. Despite an 54 improved understanding of long-term Holocene ISM trends and the likely driving 55 mechanisms, higher frequency ISM variations have been more difficult to characterize 56 because there are comparatively few high-resolution records from the Third Pole (Chen et 57 al., 2015). The late Holocene is under represented by high-resolution paleoclimate 58 records in part because mean state aridity resulted in decreased resolution (e.g., Bird et 59 al., 2014) or depositional hiatuses in many ISM archives (Berkelhammer et al., 2012; 60 Morrill et al., 2006;Cai et al., 2012). The paucity of climate records detailing ISM 61 variability during the last few millennia limits our understanding of monsoon dynamics 62 during a time when climatic boundary conditions were generally similar to the present, 63 but perturbations in radiative and other forcings, including ocean-atmosphere processes, 64 produced widely recognized climatic events including: the Medieval Climate Anomaly 65 (MCA; 950-1250 AD) and Little Ice Age (LIA; 1450-1900 AD) (Mann et al., 2009). 66Paleoclimate records from the Third Pole that span at least part of the late 67Holocene suggest that within this period of general aridity there were regional scale 68Bird et al. (2016) Page 4 of 39 fluctuations in ISM precipitation, lake levels and temperature (Bird et al., 2014; 69 ...

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“…6h; Gasse et al, 1996). Increasing δ 18 O after 3.3 586 ka is interrupted at 2.4 ka by a period of steady to lower δ 18 O that lasted until 1.3 ka.…”

Section: Plateau 573mentioning

confidence: 99%

Late-Holocene Indian summer monsoon variability revealed from a 3300-year-long lake sediment record from Nir’pa Co, southeastern Tibet

et al. 2016

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“…Summaries of fluctuations of late Quaternary lake levels in Tibet and the desert margins of central Asia are provided in Fang (1991), Gasse et al (1991Gasse et al ( , 1996, Frenzel (1994), Pachur et al (1995), Tarasov et al (1996), Benn & Owen (1998), Qin & Yu (1998), Tarasov & Harrison (1998) and Wünnemann et al (1998). A discussion of the relationship between lake level changes, mountain glacier fluctuations and desert margins, and regional palaeoenvironmental changes in Central Asia is reviewed in Lehmkuhl & Haselein (2000).…”

Section: Tibetmentioning

confidence: 99%

Late Quaternary glaciation of Tibet and the bordering mountains: a review

Lehmkuhl¹,

Owen²

2005

Boreas

148

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Abundant glacial geologic evidence present throughout Tibet and the bordering mountains shows that glaciers have oscillated many times throughout the late Quaternary. Yet the timing and extent of glacial advances is still highly debated. Recent studies, however, suggest that glaciation was most extensive prior to the last glacial cycle. Furthermore, these studies show that in many regions of Tibet and the Himalaya glaciation was generally more extensive during the earlier part of the last glacial cycle and was limited in extent during the global Last Glacial Maximum (marine oxygen isotope stage 2). Holocene glacial advances were also limited in extent, with glaciers advancing just a few kilometers from their present ice margins. In the monsoon-influenced regions, glaciation appears to be strongly controlled by changes in insolation that govern the geographical extent of the monsoon and consequently precipitation distribution. Monsoonal precipitation distribution strongly influences glacier mass balances, allowing glaciers in high altitude regions to advance during times of increased precipitation, which are associated with insolation maxima during glacial times. Furthermore, there are strong topographic controls on glaciation, particular in regions where there are rainshadow effects. It is likely that glaciers, influenced by the different climatic systems, behaved differently at different times. However, more detailed geomorphic and geochronological studies are needed to fully explore regional variations. Changes in glacial ice volume in Tibet and the bordering mountains were relatively small after the global LGM as compared to the Northern Hemisphere ice sheets. It is therefore unlikely that meltwater draining from Tibet and the bordering mountains during the Lateglacial and early Holocene would have been sufficient to affect oceanic circulation. However, changes in surface albedo may have influenced the dynamics of monsoonal systems and this may have important implications for global climate change. Drainage development, including lake level changes on the Tibetan plateau and adjacent regions has been strongly controlled by climatic oscillations on centennial, decadal and especially millennial timescales. Since the Little Ice Age, and particularly during this century, glaciers have been progressively retreating. This pattern is likely to continue throughout the 21st century, exacerbated by human-induced global warming.

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“…Accordingly, lake sediments are being widely and thoroughly studied in this area, because there are more than 1000 lakes with areas greater than 1 km 2 present on the plateau [7]. Although these lakes provide many natural environmental archives for past environmental changes [8][9][10][11][12][13][14], the explanations of the proxies are still based on lake studies of the lowland or other areas. However, for lakes with complicated sedimentary environments, especially large lakes, it is essential to under-stand the spatial distribution and enrichment conditions of sediments when reconstructing the paleoclimate and paleoenvironment [15,16].…”

mentioning

confidence: 99%

The spatial distribution and sedimentary processes of organic matter in surface sediments of Nam Co, Central Tibetan Plateau

et al. 2012

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In this study, 67 surface sediment samples collected from Nam Co in central Tibet were analyzed for total carbon, total organic carbon and total nitrogen, and 51 of these samples were also analyzed for n-alkanes. The origin and spatial distribution of organic matter were then investigated using these proxies, and the control factors responsible for the spatial distribution patterns and paleolimnological significance were discussed. The results indicated that the origin of organic matter in surface sediment of Nam Co is consistent with the sources of n-alkanes, which were primarily submerged plants, followed by terrestrial plants, and then aquatic algae and bacteria. The organic matter in surface sediments of the lake showed typical spatial variability. Because of the great influence of underwater topography, river inputs and water quality, the spatial distribution of organic matter is enriched from the source to the deposit center. This spatial variability of organic matter in the lake indicates that the sediments in different areas have different sensitivities to environmental changes, which is important to reconstruction of paleoenvironments and paleoclimate using lake sediment cores.Tibetan Plateau, Nam Co, surface sediments, spatial distribution, sedimentary processes Citation:Wang Y, Zhu L P, Wang J B, et al. The spatial distribution and sedimentary processes of organic matter in surface sediments

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Holocene environmental changes in Bangong Co basin (Western Tibet). Part 4: Discussion and conclusions

Cited by 328 publications

References 17 publications

Late-Holocene Indian summer monsoon variability revealed from a 3300-year-long lake sediment record from Nir’pa Co, southeastern Tibet

Late-Holocene Indian summer monsoon variability revealed from a 3300-year-long lake sediment record from Nir’pa Co, southeastern Tibet

Late Quaternary glaciation of Tibet and the bordering mountains: a review

The spatial distribution and sedimentary processes of organic matter in surface sediments of Nam Co, Central Tibetan Plateau

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