Paleotemperature variation in the South China Sea and the displacement of the Intertropical Convergence Zone during the last 30 kyrs

We have generated paleotemperature records from Cores MD97-2146 and MD 97-2151 during the last 30 kyrs to understand the latitudinal displacement of the intertropical convergence zone (ITCZ) in the western Pacific warm pool region. The paleotemperatures were estimated by TEX86 paleothermometry. The age depth models were created by calendar ages converted from AMS C-14 ages of planktonic foraminifera. At MD97-2146 in the northern South China Sea, TEX86-derived temperature was about 23°C in the last glacial maximum (21 ka), dropped to 20°C at 17 ka, rose to 26°C at 14.5 ka, dropped again to 25°C at 12 ka, followed by temperature rise to 28°C at 11.5 ka and subsequent gradual increase to 29°C until 7 ka. The changing pattern resembles the pattern of Greenland temperatures. At MD97-2151 in the southern South China Sea, TEX86-derived temperature was about 24°C from 21 ka to 15ka and dropped to 23°C at 14.5 ka, followed by temperature rise to 27°C at 11.5 ka and subsequent gradual increase to 30°C until 5 ka. The changing pattern resembles the pattern of Antarctic temperatures. The changing patterns of TEX86-derived temperature during the last deglaciation are more similar to those of foraminiferal Mg/Ca ratio in nearby cores than to alkenone UK37’. The TEX86-derived temperatures in core-top samples agree with the summer sea surface temperatures, suggesting that the TEX86 reflects the summer temperatures in the South China Sea. According to the TEX86-derived temperatures, the northern site was warmer than the southern site in the Bølling/Allerød period, and the former was cooler than the latter in the Oldest Dryas period. In modern setting, the northern South China Sea is warmer than the southern South China Sea in summer season when the ITCZ shifts north, and the former is cooler than the latter in winter season when the ITCZ shifts south. By analogy with this modern setting, we suggest that the ITCZ shifted north in the Bølling/Allerød period and south in the Oldest Dryas period. The similar trends were reported in the Atlantic Ocean and South America, suggesting that the ITCZ displacement during the last deglaciation was synchronous across the Atlantic and the western Pacific regions.