Location :Scientists Reveal Multi-scale Hydroclimatic Changes in the Winter Precipitation–dominated Central Asia over the Past 7800 Years
A recent study published in the PNAS reveals that western Central Asia has been experiencing a long-term drying trend for the past 7800 years. This discovery, based on the analysis of a stalagmite from the Fergana Valley in Kyrgyzstan, adds a critical piece to understanding the hydroclimatic patterns in Central Asia influenced by the westerlies.
Central Asia: Confronting Severe Ecological Challenges
Central Asia is among one of the most significant arid regions in the world. Especially with the acceleration of global warming, the region faces severe challenges such as accelerated glacier melting, shrinking lakes, and water scarcity. The shrinkage of the Aral Sea is being described as “one of the planet's worst environmental disasters”. Since these challenges exist, understanding the long-term hydroclimatic changes that have occurred throughout Central Asia during the Holocene is essential for predicting future precipitation trends and their potential impacts on social development.
Unveiling the Hydroclimatic history of Western Central Asia Over 7800 Years
To address these challenges, a joint research group led by Prof. TAN Liangcheng from the Institute of Earth Environment of the Chinese Academy of Sciences (CAS), utilized multiple proxies (δ18O, δ13C, and Sr/Ca) derived from the stalagmite, reconstructed a precisely dated and highly resolved hydroclimatic record in Western Central Asia.
“Our results suggest a long-term drying trend in Western Central Asia, contrasting sharply with the wetter conditions observed in Eastern Central Asia.” Dr. TAN explained. This disparity is attributed to the different reactions of winter and summer westerly jets to seasonal solar radiation changes. Since the Holocene, the reduced Northern Hemisphere summer insolation led to strengthened and southward shift of summer westerly jet, resulting in wetter trend in summer precipitation-dominated Eastern Central Asia. Conversely, in the winter precipitation-dominated Western Central Asia, influenced by the increased Northern Hemisphere winter insolation, the winter westerly jet stream moved northward accompanied by temperature rises, reducing Mediterranean storm activities and thus decreasing water vapor transport to Central Asia, leading to reduced winter precipitation and snowfall. “This implies the vast region may face continued precipitation reduction with the ongoing increase in winter solar radiation and global warming”, Dr. TAN emphasized.
Drought events: The profound impact on trans-Eurasian cultural exchanges.
Furthermore, the international team found significant quasi-periodic of 1400 years, 50-70 years, and 20-30 years, which may be related to the climate fluctuations of the North Atlantic, indicating a broader climatic interconnectedness. In particular, the identified centennial to decadal-scale droughts and pluvials periods could have profound impacts on the regional societies and trans-Eurasian cultural exchange. For instance, a severe drought approximately 5180-5820 years ago hindered the expansion of Central Asian culture and delayed the cultural development along the prehistoric Silk Road oasis route. After the great drought disaster, the gradual recovery of precipitation promoted the prosperity of the Bronze Age civilization in Central Asia, marked by the rise of the Bactria-Margiana Archaeological Complex. In addition, the expansion of the Persian Empire (550 BC to 330 BC) corresponded well with the pluvial period in the vast region in 2360 to 2500 years ago.
Experts in the field assert that the comprehensive climatic sequences uncovered in this study provide an unparalleled temporal resolution, shedding light on the complex climate dynamics of Central Asia. This discovery not only deepens our understanding of the regional hydroclimate history but also enhances the projections about how future climate change impact this ecologically sensitive area.
Contact: BAI Jie, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China. Email: baijie@ieecas.cn
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