摘要
深海氧同位素（MIS） 6.5期是古气候演化的一个特殊时期.其太阳辐射强度显著高于全新世,但当时冰量较大,全球气候整体处于冰期环境;此现象支持全球气候变化主要受控于全球冰量.然而,来自中国石笋氧同位素异常偏负,指示东亚季风区湿润程度已达间冰期水平,支持东亚夏季风直接受太阳辐射所驱动.为理解以上冲突,本研究选取黄土高原沉积序列为研究对象,考察东亚夏季风是否可能在MIS 6.5期发生扩展,理解东亚季风区对太阳辐射的响应关系.研究结果发现：MIS 6.5期黄土高原水分条件与MIS 3期类似,显著低于典型间冰期气候.MIS 6.5期与典型间冰期之间降水量的差别,由季风边界区向核心区呈现逐渐降低的趋势.东亚夏季风演化与太阳辐射变化并不完全一致.黄土高原西北部沉积序列记录的东亚夏季风演化包含有强烈的岁差周期和100ka周期,可能受全球冰量和低纬地区太阳辐射的共同影响.
Marine isotopic stage 6.5 is a period which presents strong solar irradiation and large volume of ice sheets. The global is significance of cold and dry climate. This phenomenon is one of powerful evidence to support that the ice volume is major forcing for climate evolution after Mid-Pleistocene, rather than solar irradiation. However, the oxygen isotope of Chinese stalagmite revealed East Asia is as humid as typical interglacial at that time, or even more humid. This result suggests that East Asian summer monsoon is corresponding to solar irradiation change rather than ice volume. In this study, JY （Jingyuan） and LT （Lingtai） loess-paleosol sequences have been selected to investigate the evolution of East Asian summer monsoon. JY （36.35~N, 104.6~E; altitude 2115m） site is located in northwest of Loess Plateau, near the Tengger desert, with high deposition rate and weak pedogenesis. JY loess- paleosol sequences presents more than 500m. In this study, we just sampled in upper layer about 80.7m, including from the t-Iolocene loess to the bottom of the $2, 10cm interval sampling. Samples were dried in the laboratory, and measurement of the grain size and magnetic susceptibility. The time series of the profile is obtained by orbital tuning methods, firstly, comparing the grain size parameter of loess-paleosol sequences and the benthic 8180 curve （LR04） to get age control points, and then linear interpolation between each adjacent two age control points. LT （35.07~N, 107.65~E; altitude 1350m） site is located in the south of Loess Plateau, with lower relatively lower deposition rate and stronger pedogenesis, and the detailed profile description and data are modified from reference [ 16]. The magnetic susceptibility recovered paleorainfall suggested that MIS 6.5 present similar climatic condition with MIS 3, and much dryer than typical interglacial. The difference between MIS 6.5 and typical interglacial is increasing in northwestward in Chinese Loess Plateau. The East Asian summer monsoon evoluti
出处
《第四纪研究》
CAS
CSCD
北大核心
2015年第6期1402-1411,共10页
Quaternary Sciences
基金
国家自然科学基金项目（批准号：41401046）资助
关键词
黄土
磁化率
东亚夏季风
太阳辐射
loess, magnetic susceptibility, East Asian summer monsoon, solar irradiation
