The role of the westerlies and orography in Asian hydroclimate since the late Oligocene

Rising mountains left Central Asia high and dry

23 December 2020

The aridification of Central Asia during the Cenozoic era (about 65 million years ago to the present) began when mountains grew tall enough to block rain-bearing westerly winds.

The Tian Shan and Pamir mountain ranges rise between the Himalayas and the Hindu Kush and are thought to have driven a drying out of Central Asia’s climate, but when and why this aridification began is still debated.

Now, a team that included researchers from Lanzhou University in China has studied sediment records from the windward (west) and leeward (east) of the Tian Shan-Pamir plateau and found that the Tajik basin to the west developed a wetter climate around 25 million years ago.

Through climate simulations, the researchers discovered that the east–west climate divide emerged around the time the mountains reached 3,000 metres — also roughly 25 million years ago — and began to trap moisture blown from the west, leaving drier conditions to the east.

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References

1. Geology 7, 728–732 (2020). doi: 10.1130/G47400.1