九州台古土壤S1记录的末次间冰期东亚夏季风变化
EASTERN ASIAN SUMMER MONSOON VARIATION DURING MIS5e AS RECORDED BY PALEOSOL S1 AT JIUZHOUTAI LOESS SECTION
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摘要: 对沉积速率较高的黄土高原西部地区九州台剖面S1古土壤的夏季风代用指标——磁化率、碳酸钙含量、色度进行了测量。综合分析结果表明,MIS5e开始前,夏季风有一次衰退事件,末次盛间冰期早期夏季风强于晚期,而中期夏季风强度相对较弱,然而这种变化是较为和缓的,并没有表现出类似GRIP冰心氧同位素的大幅度、快速变化,表明MIS5e期间东亚夏季风是相对稳定的。来自海洋的研究表明,西太平洋洋面温度(SST)和洋面高度在MIS5e早期和晚期相对较高,中期相对较低,证实了西太平洋环境变化和东亚夏季风强度之间存在成因上的联系。与先前有关全新世东亚夏季风研究结果的对比表明,MIS5e和全新世东亚夏季风演化具有一定的相似性,可能反映了低纬海洋和高纬大陆之间能量和物质交换对太阳辐射响应的某种内在机制。Abstract: Proxies of the Eastern Asian Summer Monsoon (EASM)-magnetic susceptibility depending on frequency,carbonate content and soil color of paleosol S1 of Jiuzhoutai loess-paleosol profile whose accumulative rate is high and which is located in western Chinese Loess Plateau have been measured. Synthesis analysis of the obtained data deduced a decline event of EASM at the beginning of MIS5e, and then the intensity of EASM increased quickly until the last interglacial. Early MIS5e EASM is stronger than the late MIS5e one, and the middle MIS5e is the weakest. The gentle change of MIS5e EASM has no characters of the abrupt change of GRIP oxygen isotope, suggesting the EASM is relative stable during MIS5e. The surface sea temperature and sea level in the west part of the Pacific is relatively high during early and late MIS5e and relatively low during middle MIS5e, consistent with the change of EASM, meaning that environmental change of the west part of the Pacific partly controlled the change of the EASM. Previous studies on Holocene EASM suggested that early Holocene EASM is stronger than late Holocene one, and middle Holocene is relatively dry. The same character of EASM change of MIS5e and Holocene may reveal the inherence mechanism of EASM change.