末次冰消期以来东亚季风演化：来自东海和北黄海沉积孢粉记录

IOCAS-IR > 海洋环流与波动重点实验室

	末次冰消期以来东亚季风演化：来自东海和北黄海沉积孢粉记录
其他题名	EVOLUTION OF THE EAST ASIAN MONSOON SINCE THE LAST DEGLACIATION:SPOROPOLLEN RECORDS IN THE EAST CHINA SEA AND THE NORTH YELLOW SEA
	陈金霞
学位类型	博士
	2008-06-07
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	东亚季风副热带高压热带辐合带东海北黄海孢粉
摘要	本论文通过对冲绳海槽南部的MD05-2908孔、北黄海的B-U35、B-U41、B-L44孔和北黄海的299份表层样中的孢粉组成、堆积速率、有机碳氮同位素的综合研究，分析了北黄海的孢粉来源、传播动力和途径，并与其它古气候记录对比，重建了末次冰消期以来东亚季风的演化。 MD05-2908孔孢粉组合特征显示6800-3800a BP间气候温暖干燥，其间存在着两次明显的温度降低、湿度增加阶段，即6800-6600a BP和5800-4850a BP；3800a BP以后，气候变得比较寒冷湿润，中世纪暖期和小冰期分别位于990-480a BP和480-230a BP。北黄海表层孢粉百分含量等值线图显示北黄海不同海域孢粉来源不同，北黄海东部海域(123.5°E以东的陆架区域)孢粉主要来源于鸭绿江；北黄海中部海域(123.5°E-122.6°E的陆架区域)孢粉来源比较复杂，既有来自辽东半岛、沿海岛屿、山东半岛，还有由黄海暖流携带而来的；北黄海西部海域(122.6°E以西的陆架区域)孢粉以黄海沿岸流携带而来的黄河来源的为主。北黄海表层孢粉百分含量等值线图还显示，北黄海东部海域孢粉分布主要受鸭绿江冲淡水影响，波浪和潮汐的作用较弱；北黄海中部海域孢粉分布受黄海暖流和辽东沿岸流的分支共同影响；黄海暖流与黄海沿岸流在山东半岛东北部相遇，形成一逆时针方向的涡旋，该涡旋控制着北黄海西部海域孢粉的分布。 B-U35孔、B-U41和B-L44孔孢粉组合特征显示，12830-12350a BP时气候寒冷干燥，植被以旱生草本植物为主，时间上可能对应YD事件；12350-10100a BP时植被以针叶林为主，林下生长着大量蕨类植物，气候寒冷湿润，可能对应着YD事件；10100-6600a BP时植被以落叶阔叶林为主，伴生大量旱生草本植物，气候温暖干燥；6600-5000a BP时植被以针叶-落叶阔叶混交林为主，旱生草本植物含量下降，相对上一阶段温度有所降低，但气候更湿润，可能对应全新世最佳期；5000-4000a BP时针叶林所占比例扩大，温度再次降低，湿度变化不明显；4000-500a BP旱生草本植物含量增加，气候寒冷干燥；500a BP-至今，受人类活动影响，植被遭到严重破坏。 B-U35孔和B-U41孔淡水水生植物花粉百分含量曲线显示11750a BP以来黄河河口地区沼泽湿地面积几经变化。10100-6600a BP时沼泽湿地范围在上一阶段的基础上进一步扩大；6600-2850a BP间沼泽湿地大面积缩小，水生植物属种式微；2850a BP之后黄河河口地区沼泽湿地面积再次扩大，水生植物重新繁盛。 MD05-2908孔蕨类孢子百分含量被用来作为中国东南部季风演化的代用指标。结果显示6800-3800a BP时夏季风较强，其间有两次夏季风减弱阶段，分别位于6800-6600a BP和5800-4850a BP，3800a BP以来，夏季风明显减弱，此期的夏季风减弱除受太阳辐射量的减少影响外，可能还与El Nino的频繁爆发有关。 B-U35孔和B-U41孔蒿属、藜科、麻黄科百分含量被用来作为中国中北部夏季风演化的代用指标。研究表明，11750a BP以来东亚夏季风强度在10100-6600a BP时，显著加强，6600a BP左右，夏季风开始减弱，4000a BP以后夏季风显著减弱。将MD05-2908孔、B-U35孔和B-U41孔夏季风代用指标进行对比发现，中晚全新世以来中国南-北湿度变化特征正好相反，东亚夏季风强度变化以及由此引起的雨锋的南进北撤可能是导致中国不同区域中晚全新世以来降雨量不同的主要原因。
其他摘要	In this study a giant gravity core MD05-2908 from the south Okinawa Trough (SOT), two shorter cores B-U35 and B-U41 from the north Yellow Sea (NYS) and hundreds of surface sediment samples were used to trace the original of material and the climatic variation histories since the last deglaciation. Palynological analysis, together with organic geochemistry methods such as carbon and nitrogen isotopic composition and elemental ratios were hired as proxies for climate changes and source indicators. Combined with AMS14C dating technique, we reconstructed the evolution history of the East Asian Monsoon since the last deglaciation. The major conclusions are as follows: The palynological records in core MD05-2908 reveal that the climate was relatively warm and dry during 6800-3800a BP，two cold and humid intervals between 6800-6600a BP and 5800-4850a BP punctuated this warm period. After 3800a BP, the climate became colder and wetter. Maps of pollen percentage isopolls of the NYS reveal that the sporopollen is mainly come from Yalu in the east of NYS, and the distribution of pollen is controlled by the diluted water of Yalu; the east branch of the Yellow Sea Warm Current(YSWC) and a branch of the coastal current along the Liaodong peninsula control the distribute of pollen in the central of NYS; the west branch of YSWC impacts with the western coast of the Yellow Sea, a cyclonic eddy is generated over the west of NYS, and the eddy control the distribute of pollen at here. The palynological records in core B-U35、B-U41 reveal that the last deglaciation ended at 10100a BP, the climate cold and wet during the last deglaciation; the climate of early Holocene(10100-6600a BP) warm and dry, after 6600a BP, the temperature begin decline, the precipitation is abundance between 6600 to 4000a BP, after 4000a BP, the precipitation decreasing. The significant change in arboreal and herbaceous pollen after 800a BP reflects widespread intensive human influence. The spore content at MD05-2908 core were adopted as proxies for East Asian monsoon evolution. The spore record shows that the East Asian monsoon intensity between 6800-3800a BP, two weaken intervals between 6800-6600a BP and 5800-4850a BP punctuates this strength period. After 3800a BP, the East Asian monsoon obviously weakening, this may have been produced by the combined effects of the decrease of the insolation and the density at El Nino frequencies. The percentage of Compositae,Chenopodiaceae and Ephedraceae at cores B-U35 and B-U41 were adopted as proxies for East Asian monsoon evolution. The conclusion suggested that the East Asian monsoon obviously intensified during 10100-6600a BP, while since 6600a BP, the East Asian monsoon become weaker and after 4000a B.P. the East Asian monsoon sharply decreased. Compared the East Asian summer monsoon records derived from pollen and spore proxies in the East China Sea and the North Yellow Sea, we found that they show the contrary trend. The humidity in south and north part of China shows reverse characters. Which may be cased by the intensity variation of the East Asian summer monsoon and its related rain-front latitudinal migration.
页数	134
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/313
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	陈金霞. 末次冰消期以来东亚季风演化：来自东海和北黄海沉积孢粉记录[D]. 海洋研究所. 中国科学院海洋研究所,2008.

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