末次盛冰期以来苏拉威西海区上层海水对快速气候变化的响应

摘要

通过对苏拉威西海MD98-2178站位浮游有孔虫定量分析、表层浮游有孔虫Globigerinoides ruber壳体镁钙(Mg/ca)比值反演海表温度(SST),并结合表层和次表层浮游有孔虫氧、碳同位素,探讨末次盛冰期以来,苏拉威西海区温度、盐度、生产力、温跃层深度变化及其对快速气候变化的响应.研究发现:末次盛冰期苏拉威西海区,海表温度存在明显降温,较现代海表温度下降了2.9℃,但缺乏对快速气候波动明显响应.MD98-2178站位盐度、生产力以及温跃层深度等记录,则明显响应快速气候波动,在H1,YD等变冷事件期间,盐度变高、生产力上升、温跃层深度变浅,指示东亚冬季风加强,热带辐合带(ITCZ)南移以及印度尼西亚穿越流(ITF)减弱.末次盛冰期以来,MD98-2178站位属种组合、生产力、盐度以及温跃层深度在11kaB.P.左右存在明显的突变.且在南海、印尼海区普遍存在,指示了该海域在11kaB.P.左右存在霞要的气候变化过程.%The sea surface temperature ( SST) , sea surface salinity( SSS) , paleo-productivity and the depth of thermocline reconstructed by means of planktonic foraminiferal assemblages, Mg/Ca ratio of the surface dwelling planktonic foraminiferal shells ,and oxygen and carbon isotopes of the surface and subsurface dwellers via site MD98 -2178.which revealed that they have different responses to the rapid climate changes in late Quaternary. Calypso gravity core MD98-2178,located on the offshore of North Eastern Borneo(3. 62°N.118. 70°E; water depth in 1984m) .was recovered during R/V Marion Durfresne 111/IMAGES Ⅳ cruise in 1998. And the upper 12. 01m of the core ( total length : 35. 61m) . undisturbed light brown yellowish nannofossil and foraminifera-bearing clay, is the key study object in this paper. The age model for the upper 12. 01m of the core MD98-2178 was established on the basis of 12 AMS 14C dates measured in Leibniz Laboratory in KieI.Germany. The raw 14C dates were corrected by a 400-year reservoir effect and converted to calendar ages using Fairbanks0107 program. The upper 12. 01m of the core ,representing the sediment records from 20. 01kaB. P. to 1. 8kaB. P. , has a nearly 150-year average temporal resolution. During the last glacial maximum( LGM) , the SST in Sulawesi Sea decreased remarkably ( nearly 2. 9℃ ) compared with modern SST, but it could not show any obvious change during the rapid climate fluctuations.However,the SSS,paleo-productivity and the depth of thermocline at site MD98-2178 displayed obvious responses to the rapid climate changes. During the periods of Hl , YD ,8. 2ka cooling events , the increased salinity and paleoproductivity , and shoaled thermocline possibly indicated strengthened winter Asian Monsoon , southward shifted ITCZ and weakened Indonesian Throughflow. After LGM , the planktonic foraminiferal assemblage , paleo-productivity , sea surface salinity( SSS) and the depth of thermocline displayed obvious changes at 11kaB. P. , which simultaneously occurred in the South China Sea and Indonesian sea waters.reflect the similar climate change in the two regions.After 11kaB. P. , increased abundance of warm-water species, decreased abundance of cold-water species, deeper thermocline .decreased salinity and obvious decreased paleo-productivity were recorded in site MD98-2178 .which were similar in records of the South China Sea and Indonesian Sea. And SSS records, obviously decreased after llkaB. P.,in the South China Sea and Indonesian Sea possibly indicated numerous fresh water imported.which could be weakening the upper ocean water mixing and llkaB. P. climate change.