The Central Asian region is located between the Greater Khingan Range and the Loess Plateau in the east, and the Caspian Sea in the west. It is characterized by an arid climate, extensive inland drainage basins with many lakes, and mountain systems with glaciers.
Recent data indicates that during the Last Glacial Maximum (LGM), most lakes in Central Asia had higher water levels compared to the present. This applies to large lakes such as the Aral Sea, the Balkhash, and the Ysyk-Kol, as well as smaller mountain lakes in the Tien Shan, Pamir, and Tibet. These lakes receive precipitation from westerlies.
However, lakes in the eastern rimland, such as Lake Qinghai and lakes in Inner Mongolia, which receive precipitation from summer East Asian monsoons, did not follow this pattern and had lower lake levels during the LGM. Lake Manas in the Junggar Basin also experienced lowered lake levels, potentially due to reduced runoff from the surrounding mountains.
The evidence suggests that most Central Asian lakes had higher water levels during the LGM, despite the region having more xerophytic (a plant adapted for life and growth with a limited water supply) vegetation compared to the present. Pollen data support this information for Tibet, Pamir, and Tien Shan.
The aridification of Central Asia is further supported by the intensity of loess accumulation during the LGM in the eastern part of the region (Loess Plateau) and the western part (piedmonts of Tien Shan and Pamir Mountains), indicating synchronous aridification across different areas of Central Asia. This aridification was caused by the strengthening of the winter Siberian anticyclone, weakened westerlies, and East Asian summer monsoons.
The difference between vegetation conditions and lake levels during the LGM can be explained by the dependence of lake levels on runoff from melting snow and glaciers in the mountains. Studies in the Mongun Tayga area (Tyva Republic, Russian Federation, Lake Hyargas Nuur basin) suggest a 30% decrease in precipitation during the LGM, accompanied by increased snow accumulation due to lower temperatures in the mountains.
These unique conditions led to a cryo-aridification climate, where vegetation degraded due to reduced precipitation, while lake levels rose due to increased runoff from the mountains.
In terms of land, for the most part, Central Asia had 3 types of land coverage:
1. Steppe-tundra
2. Polar and alpine desert
3. Temperate desert
So, the Central Asian land was mostly deserted, which is why the vegetation coverage was of the kind that did not require much water.
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