China

Impact of the Tibetan Plateau

Rapid uplift during the late Cenozoic has shaped the landscape of the Tibetan Plateau and has drastically changed Chinas climate. Regional differences in geomorphology and local precipitation can result in different timing of glacial advances around the world. Currently, the Pacific Ocean monsoon dominates east China, while both the South Asia Monsoon and the mid-latitude Westerlies control the weather of the Himalaya and western China. The South Asia Monsoon dominates the southern part of Tibet, while the mid-latitude Westerlies dominate the northern part. These different climatic regimes have had important influences on the Quaternary glaciations.

The rise of the Himalayan Mountains and plateaus significantly increased worldwide erosion rates. Silicate weathering provides one of the major natural processes that remove CO2 from the atmosphere, in the process forming carbonates. Hence, the rise of the Himalaya and Tibetan Plateau could have contributed to the onset of Pleistocene glaciation by depleting atmospheric CO2, the most abundant greenhouse gas.

The Tibetan Plateau contains the largest ice mass on the Earth outside the polar regions. The Tibetan Plateau holds almost 37,000 catalogued glaciers, with a combined area of nearly 50,000 km2. These glaciers owe their existence to the rise of the Tibetan Plateau. They extend north into the arid and desert regions, feeding the Yellow and Yangtze rivers, which provide the main water resource for arid central Asia, and northeastern China. They also extend south into the warmer, wetter forests and concentrate around the Brahmaputra, Mekong, and Salween rivers, which provide needed water to both local residents and much of southeast Asia.

Coastal areas of China could suffer from sea-level rise due to melting of polar ice caps. On the Tibetan Plateau, however, the immediate response to the accelerating glacial retreat could be villages displaced as a consequence of lake expansion and disasters related to glacial lake outbursts and other floods. Severe water shortages may follow once the reservoir of glacial ice is depleted.

Paleoclimate Records

Until recently, researchers have found it difficult to compare the relative ages of Chinas Quaternary glaciations with each other, let alone with global ice ages. However, absolute numerical dating now allows China's glaciations to be placed into the pre-existing worldwide framework. Based on these new dating results, Yi Chaolu and others have determined that most Asian Quaternary glaciations in the last 100,000 years were synchronous with global glacial events. One glacial advance between 44,000 and 54,000 years ago in southeastern Tibet was not synchronous with global cooling, and might have been caused by greater precipitation during a locally colder period. Chinese [Page 195]researchers have identified more Quaternary glacial periods before the Wisconsin Glaciation than have been identified in other regions of the world. The uplift of Tibet during the Cenozoic could be responsible for these differences.

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