Decomposition of the Grainsize Component and Its Climate Implication from Lake Barkol, Xinjiang
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摘要: 选择位于西风影响区的天山东段巴里坤湖湖泊岩芯样品，对沉积物粒度组分进行经验正交函数（EOF）分解，并探讨各分量的环境意义。结果显示，EOF1组分与沉积物粒度小于2 μm组分相关系数达0.64以上，并与代表区域有效湿度的碳酸盐氧同位素指标有很好的对应关系，故将EOF1解译为区域有效湿度的替代指标。EOF2组分与粒级为45~138 μm的颗粒相关系数大于0.65，且该粒级范围与区域降尘概率曲线的粗颗粒部分相似，可能指示区域风沙强度。通过EOF分解所得到的两个组分显示中全新世为有效湿度较低、风沙活动较强的时段，这一结果与发生在以蒙古高原北部为中心的区域中全新世干旱事件有较好的对应关系。同时，西伯利亚高压的加强所导致的西风环流和冬季风的增强为风沙活动提供了较好的动力基础，因此亚洲内陆干旱区的干旱化和风动力条件的加强很可能是导致该区域中全新世风沙活动增强的主导因素。Abstract: A 426 cm core from Lake Barkol, eastern Tian Shan, provides the evidence of Holocene climate in Westerly dominated Asia. Here, we present a grainsize component series decomposed by empirical orthogonal function and the chronology is based on radio carbon dating. The results show that the EOF1 component has a high correlation coefficient (0.64) with the volume percentage of the component less than 2 μm, furthermore it is similar to the evolution pattern of oxygen isotope from carbonate which is a proxy indicating the regional effective moisture, so the EOF1 component is an indicator of the effective moisture in the region. Modern dust grainsize analysis from Barkol shows a peak percentage around 61.2 μm. Coincidently, the EOF2 component has a high positive correlation coefficient with the grainsize ranging from 45 to 138 μm, which suggests that the EOF2 indicates the regional dust activity. EOF results suggested that the effective moisture was low and the dust activity was strong in midHolocene, which was consistent with the midHolocene arid interval occurred in the northern Mongolia Plateau. The enhanced Siberia high intensified the Westerly circulation and winter monsoon, and which could be the main reason for the arid and dusty midHolocene climate in the research region.
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Key words:
- Lake Barkol /
- grainsize /
- empirical orthogonal function /
- Holocene /
- effective moisture /
- dust activity
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