30~10ka云南高山湖泊高分辨率生物记录与气候突变事件

通过对云南泸沽湖高分辨率沉积指标序列(硅藻、枝角类和孢粉)的对比分析,初步揭示了水生生物(硅藻、枝角类和水生孢粉)对末次冰盛期期间气候变化的快速响应过程.结果表明,硅藻群落组成首先响应末次冰盛期时期的开始变冷,枝角类滞后,水生孢粉则表现为渐进的响应过程.然而,泸沽湖沉积硅藻记录对末次冰期以来的短时间尺度气候快速变化的Heinrich和新仙女木事件并未有响应,揭示气候事件判别的准确性取决于指标直接响应气候的特征以及多指标的综合对比.综合西南季风区云南不同海拔湖泊沉积记录(硅藻、孢粉、摇蚊等)获得的2万年以来数据及序列表明,末次冰期千年尺度的气候突变事件( Heinrich 1、 B?lling/Aller?d暖期和新仙女木YD冷事件)在整个西南季风系统中都有反映,且气候事件变化区间及幅度存在区域差异,其根本原因是受不同气候系统、复杂地形(青藏高原)的制约.

The monsoon evolution and abrupt climate events recorded in high-resolution biological records from the alpine lakes of Yunnan during 30~10ka

Lugu Lake is located in the boundary between Yunnan and Sichuan provinces in Southwest China, on the southeast margin of the Tibetan Plateau with 2685 m a.s.l. It is a sub-tropical, deep, alpine lake and affected by southwest monsoons from the Indian Ocean. The climate in this region is temperate with distinct dry and wet seasons. The continuous sedimentary cores were recovered using UWITEC piston corer from Lugu Lake (LG08 core:18 m and LG10 core:9 m) at a water depth of 69.3 m in the central part of Lugu Lake (27°43'08.4"N, 100° 46' 33.9"E). 695 diatom samples and 168 cladoceran samples from Lugu Lake were analyzed. The present study mainly focused on the time interval 30.0~10.0 cal.ka B. P.(corresponding to 10.0~4.5 m depth in the sediment core), which had a stable sediment deposition rate (0.32 mm/a). These diatoms, cladoceran and pollen records spanning ca. 30 ka reveal different response processes of aquatic organisms (diatoms, cladocerans and pollen) to climate change during the Last Glacial Maximum (LGM). The results show that the aquatic biological organisms (cladocerans and diatoms) showed more rapid responses to cooling at the start and warming at the end of the LGM than aquatic pollen, and the aquatic pollen showed a gradual response process. The cooling associated with the LGM seems to have been first perceived by the diatoms, with a short lag by cladocerans and a gradual response by aquatic pollen. However, the sedimentary records (diatom, cladoceran and pollen) from Lugu lake sediments did not respond to the short-time abrupt climate change, e.g. the Heinrich events and Younger Dryas (YD) event. The synchronous changes of biological proxies (diatom, cladoceran and pollen) at 18.0~19.0 cal.ka B. P. indicated that the initial strengthening of southwest monsoon in Southwest China started at 18.0~19.0 cal.ka B. P. Compared with other data and sequences obtained from the sedimentary records of lakes at different altitudes (diatoms, pollen, chironomids, etc) in southwest monsoon region of Yunnan over 30 ka, it is demonstrated that the millennium abrupt climate events (Heinrich 1, B?lling/Aller?d warm period and YD cold event) are reflected in the southwest monsoon system, manifesting as cold and dry climatic conditions. However, there are regional differences in the timing, range and magnitude of biological proxies' response to abrupt climate events, which may be caused by the buffering effects of Qinghai-Tibetan Plateau, movement of ITCZ and weakening effect of underlying surface.