Significant SST differences between peak MIS5 and MIS1 along the low-latitude western North Pacific margin

Abstract

The peak period of marine isotope stage 5 (MIS5e) is the most recent warm period largely comparable to the present interglacial, marine isotope stage 1 (MIS1). The spatial variations in sea surface temperature (SST) between MIS5e and MIS1 can reveal the important differences in the effects of insolation and oceanographic conditions between the two warm periods, which in turns help refine global climate models. In order to quantify the differences, this study calculated the SST for the peak periods of MIS5e (c. 128-113 ka BP) and MIS1 (c. 8-3 ka BP) along the low-latitude western North Pacific margin (18 oN to 26 oN). Together with the previously published data from the South China Sea (9 oN to 19 oN), the results indicate a generally northwards decreasing trend in the two interglacial periods. This latitudinal SST trend in both peak MIS 1 and MIS 5e can be attributed to the strong influence of ocean currents in the studied region. Secondly, the average SST of peak MIS5e is 1.3 ± 0.2 °C higher than that of peak MIS1, suggesting a higher level of insolation during the previous interglacial. However, the above general pattern is complicated by the near-shore and offshore difference in the effects of winter monsoon on oceanic conditions around 20–22 oN. The coastal upwelling near 26 oN during peak MIS5e reduced the SST, whilst the SST was raised as the upwelling ceased during peak MIS1. Finally, the SSTs of the two warm periods are significantly higher than the present SST from 20 oN northwards, implying the influence of winter monsoon cold current in the Taiwan Strait.