南海北部15ka BP以来表层海水温度变化:来自海洋硅藻的记录

SURFACE WATER TEMPERATURE CHANGES IN THE NORTHERN SOUTH CHINA SEA OVER LAST CA.15000 YEARS: EVIDENCE FROM MARINE DIATOMS

对西太平洋边缘海148个表层硅藻样品中菱形海线藻（Thalassionema nitzschioides）及其小形变种（Thalassionema nitzschioidesvar.parva）的分布与表层海水温度（SST）之间关系进行研究,将菱形海线藻小形变种与所有菱形海线藻百分含量的比值（简称硅藻Rparva值）视为温度指数,开展南海北部MD05-2904孔附近海域15kaBP以来表层海水温度变化研究。结果表明：（1）南海北部15 kaBP以来表层海水温度呈现明显的阶段性波动特点,即末次冰消期气候转暖过程中,12.9-11.5 kaBP前后温度略有下降,与新仙女木事件对应,全新世南海北部气候依次经历了升温期、高温期和降温期3个变化阶段;（2）全新世大暖期鼎盛期结束后,南海北部海水温度阶段下降,两次明显降温分别发生于4 kaBP前后和1.5 kaBP前后;（3）MD05-2904孔硅藻Rparva值时间序列曲线与董哥洞D4石笋δ18O曲线对比表明,南海北部表层海水温度变化与末次冰消期以来东亚季风强度变化关系较为密切。

The relationship between the distribution of diatom taxa Thalassionema nitzschioides Grunow as well as its variety Thalassionema nitzschioides vat. parva Heiden et Kolbe and surface water temperature （SST） was studied based on diatom analysis results from 148 surface sedimentary samples from the marginal seas of the West Pacific. The ratio of T. nitzschioides vat. parva / T. nitzschioides ＋ nitzschioides vat. parva, which is short for Rparva was regarded as a SST-index to document SST changes in core MD05-2904 from the northern South China Sea （SCS）. Three preliminary conclusions could be approached as follows： （1） SST changes were distinctively characteristic of stepwise fluctuations. A warming trend during the last deglaciation was punctuated by a slightly cooling event which corresponded to the Younger Dryas （YD）. The Holocene episode could be divided into three phases of warming, continuously high temperature and cooling. （2） Two remarkable cooling records were documented around 4 kaBP and 1.5 kaBP after the megathermal of the Holocene. （3） Comparison between time series of MD05-2904 diatom Rparva- SST index and stalagmite 8180 results from Dongge Cave, Guizhou Province suggested that changes in the East Asian Monsoon climate is synchronous with variations in the SST in the northern SCS since the last deglaciation and they might have a close correlation with each other.