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摘要
This study presents bi-decadal scale pollen record of climate change from the Daotang Pond (36 degrees 57'35.4 N, 100 degrees 74'48.4 E; 3205 m a.s.l.). The pollen record situated 2 km southeast of Lake Qinghai in the north-eastern part of the Qinghai-Tibet Plateau (QTP) reveals a pattern of consequent changes in the alpine meadow and steppe vegetation throughout the last 1200 years. Due to its location at the interface of the East Asian Summer Monsoon (EASM) and the North Atlantic Westerlies, the Daotang record reacts sensitively even to minor changes in precipitation. Consequently, impact of both these major atmospheric circulation systems on the regional environments can be analysed and discussed along with the other climatic proxies from the region. The EASM impact was generally strong throughout the Medieval Warm Period (MWP), which lasted from the beginning of the record at 850 CE up to roughly 1400 CE. This time interval was characterised by a favourable warm and rather moist climate with a precipitation peak around 950 CE. However, two dry spells indicating irregular EASM weakening occurred around 1050-1150 CE and 1250-1400 CE. Westerlies dominated the atmospheric circulation during the Little Ice Age (LIA). This cold phase started around 1450 CE and lasted roughly until 1950 CE. It was characterised by a drier regional climate compared to the humid MWP, though lower evaporation due to decreased summer temperatures helped in keeping locally wet environment at the study site. Three dry and cold intervals are detected in the Daotang record at 1450-1550 CE, 1650-1700 CE and 1800-1850 CE, based on an exceptionally low Artemisia/Chenopodiaceae (A/C) pollen ratio and a generally low pollen concentration. After 1950 CE a shift towards a warmer and wetter climate occurred interrupted by a pronounced dry spell during the recent years.
- 出版日期2017-7-15
