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Researchers reveal drier mid-Holocene in Tarim Basin linked to poleward displacement of westerly jet

A research team led by Prof. An Zhisheng and Prof. Zhou Weijian from the Institute of Earth Environment of the Chinese Academy of Sciences (CAS) developed an innovative approach to examining the contrasting hydroclimate impacts of summer monsoons and westerly circulation in the hyper-arid Asian interior since the middle Holocene.

The findings are in the journal Communications Earth & Environment.

The Tarim Basin, home to the Taklamakan Desert—the world's second-largest shifting sandy desert—has long experienced extremely arid conditions, with annual precipitation below 50 mm, mostly concentrated in the summer months.

Using high-precision dating techniques, the researchers analyzed multiple climate proxies—such as grain size, geochemical elements, and isotopes—from high-resolution loess records in the central Kunlun Mountains. This allowed them to conduct a comprehensive study of hydrological and climatic changes in the Tarim Basin over the past 8,000 years.

They found that during the mid-Holocene (8.2–4.2 ka BP, ka BP = thousand years before the present), precipitation in the region sharply decreased due to the poleward shift of the subtropical westerly jet. This shift reduced precipitation in the surrounding mountain ranges, lowering downstream runoff.

Simultaneously, the northward movement of the westerly jet allowed more tropical moisture to enter the Tarim Basin, increasing summer rainfall events. However, despite these localized increases, the overall climate remained relatively dry.

This study suggests that a meridional shift in the westerly jet, driven by changes in mid- and high-latitude temperature gradients during the boreal summer, plays a crucial role in regulating average water availability in the region.

Its interaction with the Asian summer monsoon further influences these dynamics. These findings offer valuable insights into past climatic dynamics in arid areas and provide trend-based projections for future hydrological and climatic changes under warming scenarios.