Rainfall changes over millennia are tracked

BEIJING－Chinese researchers have reconstructed precipitation changes of the past 12,000 years of a transition zone in North China's arid and semi-arid regions.

The East Asian summer monsoon, or EASM, variability is primarily influential for climate change in East Asia.

The lakes in the transition zone of North China's arid and semi-arid regions on the fringe of the monsoon are affected by the EASM. However, the pattern and mechanisms of the monsoon changed during the Holocene－the current geological epoch－that began approximately 11,650 years ago are still debated.

The researchers from Lanzhou University, the Chinese Academy of Sciences and Nantong University hoped to study the pattern and range of the EASM change over a longer time scale and predict the precipitation inside the transition zone.

They conducted a systematical geomorphologic survey along a closed-basin lake located on the southern Mongolian plateau and reconstructed the precipitation quantity at the lake over the past 12,000 years.

The research found that the monsoon dominated annual precipitation in the basin varied between 420 and 280 millimeters during the Holocene period, indicating a generally semi-arid environment on the southern Mongolian plateau. And the basin was broadly covered by open steppe vegetation throughout the Holocene.

Moreover, the EASM precipitation intensity increased from the early Holocene to the beginning of the mid-Holocene, followed by a decrease during the late Holocene, according to a research article recently published in the journal of Quaternary Science Reviews.

The results showed that the precipitation intensity of the EASM has generally decreased over the past 6,000 years. The researchers predicted that North China's arid and semi-arid regions would not witness any apparent precipitation increase in the future.

Xinhua