Solar activity and the westerlies dominate decadal hydroclimatic changes over arid Central Asia

Yan, Dongsheng; Xu, Hai; Lan, Jianghu; Ke, Zhou; Ye, Yuanda; Zhang, Jixiao; An, Zhisheng; Yeager, Kevin M.

doi:10.1016/j.gloplacha.2018.12.006

Cited by 37 publications

(34 citation statements)

References 52 publications

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“…Wind fields further illustrate the dominance of the southern branch of westerlies during winter and spring and resulting southwesterly wind in the Pamirs over the studied time intervals (Figure S2a). In contrast, in summers the region is more dominated by the northern branch with northern winds (in agreement with computed back trajectories by Yan et al, ), which is an additional explanation for the lower precipitation compared to winter and spring.…”

Section: Resultssupporting

confidence: 90%

“…While westerlies dominated the local hydroclimate during the Holocene based on proxy evidence (Aichner et al, ; Yan et al, ), studies on glacial to interglacial climate in the region are mainly restricted to climate model simulations (Li et al, ; Zhang et al, ). Pre‐Holocene climatic records from Central Asia are limited to speleothems from Ton Cave (Uzbekistan) and Kesang Cave (Tien Shan, China) and loess sections from western Tajikistan, all located several hundreds of kilometers to the Northwest and East of the Central Pamirs, respectively (Cai et al, ; Cheng et al, ; Haggi et al, ; Figure ).…”

Section: Introductionmentioning

confidence: 99%

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Hydroclimate in the Pamirs Was Driven by Changes in Precipitation‐Evaporation Seasonality Since the Last Glacial Period

Aichner

Makhmudov²,

Rajabov³

et al. 2019

Geophysical Research Letters

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The Central Asian Pamir Mountains (Pamirs) are a high-altitude region sensitive to climatic change, with only few paleoclimatic records available. To examine the glacial-interglacial hydrological changes in the region, we analyzed the geochemical parameters of a 31-kyr record from Lake Karakul and performed a set of experiments with climate models to interpret the results. δD values of terrestrial biomarkers showed insolation-driven trends reflecting major shifts of water vapor sources. For aquatic biomarkers, positive δD shifts driven by changes in precipitation seasonality were observed at ca. 31-30, 28-26, and 17-14 kyr BP. Multiproxy paleoecological data and modelling results suggest that increased water availability, induced by decreased summer evaporation, triggered higher lake levels during those episodes, possibly synchronous to northern hemispheric rapid climate events. We conclude that seasonal changes in precipitation-evaporation balance significantly influenced the hydrological state of a large waterbody such as Lake Karakul, while annual precipitation amount and inflows remained fairly constant.Plain Language Summary Lakes in arid Central Asia are particularly susceptible to the rise and fall of lake levels as a consequence of climatic changes. To evaluate drivers behind this phenomenon, we developed a record of humidity and lake levels throughout the last 31,000 years from a high-altitude lake in the Pamir Mountains. Herefore, we combined hydrological and ecological reconstructions with climate model experiments. Results show that neither the enhanced inflow by melting glaciers nor the significantly increased precipitation amount was responsible for higher lake levels during the studied interval. Instead, reduced summer evaporation during cold episodes was the major trigger for lake transgressions. These fluctuations were driven by changes in radiative forcing (i.e., insolation and hence temperature change) as a consequence of changes in the Earth's orbit around the Sun. As such, our results suggest that a significant impact on lake levels in arid regions is also to be expected by the current anthropogenically driven global warming.

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Section: Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Hydroclimate in the Pamirs Was Driven by Changes in Precipitation‐Evaporation Seasonality Since the Last Glacial Period

Aichner

Makhmudov²,

Rajabov³

et al. 2019

Geophysical Research Letters

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“…The atmospheric 137 Cs fallout peak in the northern hemisphere occurred at 1963 AD (Robbins and Edgington, 1975), and this peak is widely used as a time marker of 1964 AD in lake sediments. Although the 1986 Chernobyl nuclear leak out may generate a 137 Cs peak in lake sediment, this peak can be hardly detected in northwestern China (Xu et al, 2010;Yu et al, 2017;Yan et al, 2019). The 137 Cs curve of the core BL13-1-4 shows no clear peak, suggesting considerable disturbance of the sediments in modern times.…”

Section: Resultsmentioning

confidence: 98%

“…After 1945, especially in the 1950s, nuclear tests were widely carried out in the world, which led to the rapid increase of atmospheric 137 Cs concentration. A rapid increase in 137 Cs activity from natural background (zero) was detected in a large number of undisturbed or weakly disturbed lake sediment cores, and this point was assigned as a time marker of 1952 AD, which is particularly evident in lakes in northwest China (e.g., Yu et al, 2017;Lan et al, 2018;Yan et al, 2019). The atmospheric 137 Cs fallout peak in the northern hemisphere occurred at 1963 AD (Robbins and Edgington, 1975), and this peak is widely used as a time marker of 1964 AD in lake sediments.…”

Section: Resultsmentioning

confidence: 99%

“…Precipitation in the lower reaches of the lake basin is relatively high; for example, it reaches ∼400 mm/a in the eastern part of Tianshan Mountain (Hu, 2004). Water vapor in the study area comes from the Atlantic, Mediterranean, and Caspian Sea water supply (Aizen et al, 2006;Chen et al, 2008;Xu et al, 2019b;Yan et al, 2019). Salinity of modern lake water is unevenly distributed, with a spatially increasing trend from west to east (Jiu et al, 1990).…”

Section: Background and Methodsmentioning

confidence: 99%

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Variable Late Holocene 14C Reservoir Ages in Lake Bosten, Northwestern China

Lan

et al. 2020

Front. Earth Sci.

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Radiocarbon (14 C) dating has been widely used in paleoclimate reconstruction. However, the reliability of the 14 C age in lake sediments is sensitive to the 14 C reservoir effect, especially for a lake in arid regions. In this study, we evaluated the 14 C reservoir ages under different hydroclimatic conditions over the past ∼2300 years in Lake Bosten, northwestern China, by comparing with different dating results and with multi-proxy indices of a vertical-down sediment core collected in this lake. The 14 C reservoir ages during ∼1800 to 650 BP (a dry interval) are estimated to be approximately 1170 years older than those during ∼650-100 BP and those during 2200-1800 BP (wet intervals). We proposed that variation in 14 C exchange rate between the dissolved CO 2 in lake water and CO 2 in the atmosphere, as well as the changing proportion of organic matter in the lake and the catchment, could have contributed to the variable 14 C reservoir ages in Lake Bosten. The result of this study suggests that the 14 C reservoir effect may be larger in dry periods than in wet periods in the arid/semi-arid area, which should be considered when establishing age models of lake sediment cores from these regions.

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Wind variability over the Caspian Sea, its impact on Caspian seawater level and link with ENSO

Arpe

Molavi-Arabshahi

Leroy

2020

Intl Journal of Climatology

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Newly available time series of 10‐m winds over last 60 years in the South Caspian Sea (CS) region show a remarkable shift in wind speed in 1995, that is also the year of maximum elevation of the Caspian Sea level (CSL). Our aim is to find the mechanisms linking these two features. This change is not only seen in the wind observations along the Southern CS coast, but also in the European Centre for Medium‐Range Weather Forecasts (ECMWF) reanalysis covering the Southern CS, leading there to an increase of evaporation after 1995. Due to wind increase, evaporation increases but does not lead to enhanced precipitation over the CS catchment area, the water seems to be lost to the east of the drainage basin for the water budget of the CS after 1995. This stopped the CSL rise and caused its post‐1995 fall. The connection between the wind speed and the trend of the CSL can also be seen for the 1977 low stand. Before 1977, the CSL was slightly dropping with relatively strong wind, then the wind speed fell and the CSL started to rise. The change of the wind seems to be induced by a teleconnection from El Niño‐Southern oscillation (ENSO). It is shown that ENSO impact is much stronger than that of North Atlantic oscillation (NAO), not only for the change of the CSL, but also for several key components of the CS water budget, like the Volga river discharge and wind speed. The wind speed is induced by ENSO, which is demonstrated by a shift of the jet stream over the CS area. This could be an explanative link between ENSO and CSL variability, but still needs further understanding. The NAO has a similar impact but to a lesser degree. When NAO and ENSO are working in the same direction, the CSL change is enhanced like from 1990 to 1995.

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Solar activity and the westerlies dominate decadal hydroclimatic changes over arid Central Asia

Cited by 37 publications

References 52 publications

Hydroclimate in the Pamirs Was Driven by Changes in Precipitation‐Evaporation Seasonality Since the Last Glacial Period

Hydroclimate in the Pamirs Was Driven by Changes in Precipitation‐Evaporation Seasonality Since the Last Glacial Period

Variable Late Holocene 14C Reservoir Ages in Lake Bosten, Northwestern China

Wind variability over the Caspian Sea, its impact on Caspian seawater level and link with ENSO

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