SURFACE WATER TEMPERATURE CHANGES IN THE NORTHERN SOUTH CHINA SEA OVER LAST CA. 15 000 YEARS: EVIDENCE FROM MARINE DIATOMS

The relationship between the distribution of diatom taxa Thalassionema nitzschioides Grunow as well as its variety Thalassionema nitzschioides var. 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 var. parva/T. nitzschioides + nitzschioides var. parva, which is short for R_parva, 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 R_parva-SST index and stalagmite δ¹⁸O 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.