A Millennial Scale Mid-Pleistocene Paleoclimate Record of Planktonic Foraminifera from the Northern South China Sea Site 1144

Planktonic foraminifera results from ODP Site 1144 in the northern South China Sea indicate that the Mid-Pleistocene climate transition is characterized by high-frequency changes on the millennial scale. In pace with glacial-interglacial cycles after the dominant glacial cyclicity shifted from 41 ka to 100 ka over the ~0.9 Ma, sudden increases in the abundance of cool-water planktonic foraminifera species became more evident. The SST variations estimated from transfer function show large decreases of up to 10 ℃ during the four major glacial periods of MIS22, 20, 18 and 16 between 0.9-0.6 Ma. Cooler conditions in glacial times also caused the thermocline depth to shoal in steps to a minimum of about 65 m at MIS20. Therefore, during the Mid-Pleistocene climate transition, the upper ocean water environment in the nouthern South China Sea was marked by δ¹⁸O values heavier than the last glacial maximum, a shoaled thermocline, and significant decrease to almost complete absence of several deep-water planktonic foraminiferal species, amplifying the paleoclimatic signals of SST contrasts between the northern and southern South China Sea and a strengthened winter monsoon on the millennial scale. Together with the E-W equatorial Pacific record, the N-S contrasts in the South China Sea demonstrate the significance of low latitude process in climate change.