【作者】 陈碧珊；

【导师】 潘安定；

【作者基本信息】 广州大学 ， 自然地理学， 2010， 硕士

【摘要】 尕海湖是位于青藏高原东北部、德令哈盆地的一内陆封闭性湖泊,对气候变化响应非常敏感,是研究区域环境对全球变化响应的理想地点。本文利用在尕海湖西北岸获得的DG02孔岩芯沉积物样品的粒度、磁化率(平均年代分辨率为37a)和孢粉(平均年代分辨率为65a)等多气候代用指标的综合分析,重建尕海湖全新世以来的古气候环境演化历史,并同周边及其他区域气候记录进行广泛的对比,探讨该地区全新世以来可能的气候变化驱动机制。全新世以来,尕海湖地区的古气候大致经历了以下3个主要气候变化阶段:①在11400～7910cal aB.P.期间,对应早全新世。研究区气候整体冷湿,大致分为两个阶段,早期在结束新仙女木冷事件之后,气温有所回升,降水增加;后期气温有所降低,降水量仍较高,气候相对冷湿。②在7910～5110cal aB.P.期间,研究区气候暖湿,水热组合条件最好,是本区域真正意义上的气候适宜期。③在5110～230cal aB.P.期间,研究区气候整体冷干,大致分为三个阶段,早期气候冷干;中期,气温稍有回升,气候温干;后期,气候表现为冷湿。同时在全新世期间发生8.2cal KaB.P.、6.4cal kaB.P.、5.8cal kaB.P.、5.2cal kaB.P.、2.6cal kaB.P.和1.2cal kaB.P.等6次快速变冷或变干事件。总的来看,尕海湖地区全新世以来的气候变化历史同季风边缘区的一些气候记录基本上是一致的,但是由于不同气候记录的敏感性以及不同区域气候客观上存在的地区性差异,使得一些具体的变化细节对比可能出现一定的差别。另外,考虑到不同气候记录的样品分析精度、定年精度等方面存在一定的差异,对全新世期间一些重要气候事件的确认与对比还有赖于开展更多的高精度年代序列和提高样品分析精度。根据孢粉共存分析法重建该地区全新世以来多气候参数的变化序列,结果显示各参数的共存区间为:年均温(2.2～8℃)、年均降水量(131～363mm)、最冷月均温(-15.8～-8℃)、最热月均温(18.5～23℃)、平均最小月降水量(2～3mm)、平均最大月降水量(26.4～88.4mm)、大于5℃的有效积温(1578～2458℃·d)、相对湿度(49～57%)。尕海湖全新世时期的气候与现代气候类型整体上保持一致,但在全新世不同时期气候有微小的波动,中全新世(7910～5110cal aB.P.)年均温达到最高,而在5110 cal aB.P.后开始变冷,并逐步趋向现代的温度。全新世降水量总体上比现代降水量多,早全新世(11400～7910cal aB.P.)降水量最高,此后降水量逐渐降低,并在晚全新世逐渐出现干旱化。尕海湖位于季风边缘区,全新世以来气候在不同时期受到西风环流、亚洲夏季风等影响,与低纬热带海洋地区的海-气相互作用也具有一定的联系,但最重要的气候驱动因素可能还是太阳辐射的变化,包括地球气候系统复杂的、非线性的相互作用与反馈过程。更多还原

【Abstract】 Gahai Lake is a closed inland lake, which is located in the northeast Delingha Basin, Qinghai—Tibet Plateau. It is very sensitive in the response to climate change and is the ideal location to study the regional environment response to global change. Based on comprehensive analysis of granularity, magnetic susceptibility (average resolution is 37a) and pollen (average resolution is 65a ) in DG02 core obtained from the west-northern margin of Gahai Lake, and compared with the climate records from the adjacent areas, this article reconstructed the Holocene climate and discussed the possible climate change-driven mechanism in the study area.Gahai Lake had gone through three major paleclimate stage in the Holocene. The first stage was from 11400 to 7910cal aB.P., which was corresponding to early Holocene. The climate was cold and wet, which can be divided into two periods. The early period was at the end of the Younger Dryas cold event, with inceasing temperature and precipitation. In the late period the temperature decreased slightly but the precipitation is still high, which means the climate was relative wet and cold. The second stage was from 7910 to 5110cal aB.P., with the climate of warm and wet, and the combinations of the heat and precipitation in this region were best of all epoch, which was actually the Holocene optimum. The third stage was from 5110 to 230cal aB.P., with the climate of cold and dry as a whole, which can be divided into three periods. In the early period, the climate was cold and wet. In the second period, the temperature recovered slightly and the climate was warm and dry. Later, the climate was cold and wet. At the same time, it had six cold or dry events in 8.2cal kaB.P., 6.4cal kaB.P., 5.8cal kaB.P., 5.2cal kaBP, 2.6cal kaB.P. and 1.2 cal kaB.P. in the Holocene.Climate change in the Gahai Lake since Holocene was similar to the record of marginal zone of monsoon, but there were some differences of details in the climate change, due to different sensitivity of climate proxy and the regional climate. Taking into account the different precision of climate proxy, dating precision et al, the affirmation of some key Holocene climate events would depend on more accurate data of chronology and samples.Based on the Coexistence Approach that reconstructed Holocene climate, the result showed the coexistence intervals of each parameter: mean annual temperature(2.2～8℃), mean annual precipitation(131～363mm), mean temperature of the coldest month(-15.8～-8℃), mean temperature of the warmest month(18.5～23℃), mean minimum monthly precipitation(2～3m), mean maximum monthly precipitation (26.4～88.4mm), growing-day degrees above 5℃(1578～2458℃·d), mean relative humidity(49～57%). The Holocene climate overall consisted with modern climate types in Gahai Lake, but it had small fluctuations at different periods. The highest annual average temperature reached the highest in Mid-Holocene(7910～5110 cal aB.P.), but it began cold at 5110cal aB.P. and gradually become a modern temperature. Precipitation in Holocene was more than modern time’s. Precipitation was the most in early Holocene(11400～7910cal aB.P.) and then the precipitation gradually deceased and then emerged drought in the late Holocene(5110～230cal aB.P.).Gahai Lake, which is located in the monsoon marginal, may be influenced by westerly circulation and the Asian summer monsoon at different stage in the Holocene, and also contacts with the low latitude air–sea interactions of the tropical ocean regions.更多还原