The role of the westerlies and orography in Asian hydroclimate since the late Oligocene
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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.
- Geology 7, 728–732 (2020). doi: 10.1130/G47400.1