祁连山东段全新世与现代水热组合特征研究

Study on Hydro-Thermal Characteristic of Eastern Qilian Mountains in Holocene and Present

位于祁连山北麓的扁都口和哈溪剖面记录了该地区的全新世气候变化。采用磁化率、有机碳含量和碳酸钙含量作为降水指标，其记录的水分变化与冰芯及其他记录的对比，显示了该地区全新世水热组合变化的特征。传统的大暖期鼎盛阶段并非本研究区的气候最宜期。５．２～４．０ｋａＢ．Ｐ．本区的环境相当优越，是气候最宜期。４．０ ｋａ Ｂ． Ｐ．存在一次比 ３．０ ｋａＢ． Ｐ．明显的气候恶化，地层和剖面记录突出。 ２． ０～１０ ｋａＢ． Ｐ．是低温下环境相对较好的时段。在本研究区，温度的升高和水分增加并非一致，超过一定的温度，环境的湿度反而有随之降低的趋势。现代气候的特征为过去气候变化提供了佐证。

Biandukou and Haxi section recorded climatic changes in Holocene, Eastern Qilian Mountains. Susceptibility, organic carbon content and CaCO_3 content are used as excellent proxies to summer monsoon, mainly the precipitation. Compared with the Dunde ice-core record, used as the thermal proxy, here we can rebuild the hydro-thermal characteristic in Holocene in this region. During the 7. 2 - 6. 0 Ka B. P., in eastern China and many other regions, climate characteristic was high temperature and high precipitation. But, in eastern Qilian Mountains, this period was not the optimum, it's only relatively suitable. The climate optimum took place during 5. 2 - 4. 0 ka B. P., not in the same time with Megathermal Maximum. Significant environment deterioration took place in 4. 0 ka B. P. and 3. 0 ka B. P., but the former was more distinct than the latter. So we took 4. 0 ka B. P. as the boundary of the middle Holocene and the late. Changes of ancient civilizations serviced as another proof for climatic changes. In 2. 0 - 1. 0 ka B. P., scores of climatic proxies showed another climate suitable period, but the leaching depth of CaCO_3 was shallow and the Dunde ice-core recorded the drop of temperature. Analysis of modern weather data shows that humidity has an incline to drop beyond a certain high temperature in arid and semi-arid region. While in subhumid regions, humidity increases with the increase of temperature and this may give the possibility of the assembly of high temperature and high humidity as now as in the middle Holocene(7. 2 - 6. 0 ka B. P. ). Environment qualities in arid and semi-arid regions mainly depend on water since it is the most important in all the factors. So temperature and humidity would not reach their maximum simultaneously in the studied area.