Modern distribution patterns of planktonic foraminifera in the south China Sea and western Pacific: a new transfer technique to estimate regional sea-surface temperatures

We present 30 new planktonic foraminiferal census data of surface sediment samples from the South China Sea, recovered between 630 and 2883 m water depth. These new data, together with the 131 earlier published data sets from the western Pacific, are used for calibrating the SIMMAX-28 transfer function to estimate past sea-surface temperatures. This regional SIMMAX method offers a slightly better understanding of the marginal sea conditions of the South China Sea than the linear transfer function FP-12E, which is based only on open-ocean data. However, both methods are biased toward the tropical temperature regime because of the very limited data from temperate to subpolar regions. The SIMMAX formula was applied to sediment core 17940 from the northeastern South China Sea, with sedimentation rates of 20-80 cm/ka. Results revealed nearly unchanged summer temperatures around 28 degrees C for the last 30 ky, while winter temperatures varied between 19.5 degrees C in the last glacial maximum and 26 degrees C during the Holocene. During Termination 1A, the winter estimates show a Younger Dryas cooling by 3 degrees C subsequent to a temperature optimum of 24 degrees C during the Bolling/Allerod. Estimates of winter temperature differences between 0 and 100 m water depth document the seasonal variations in the thickness of the mixed layer and provide a new proxy for estimating past changes in the strength of the winter monsoon. (C) 1999 Elsevier Science B.V. All rights reserved.