Sea surface temperature oscillations in southern Okinawa Trough during last 2700 years from ODP Hole 195-1202B

Most of the temperature reconstructions for the past two millennia are based on proxy data from various sites on land. Here we present a bidecadal resolution record of sea surface temperature (SST) in Southern Okinawa Trough for the past ca. 2700 years by analyzing tetraether lipids of planktonic archaea in the ODP Hole 1202B, a site under the strong influence of Kuroshio Current and East Asian monsoon. The reconstructed SST anomalies generally coincided with previously reported late Holocene climate events, including the Roman Warm Period, Sui-Tang dynasty Warm Period, Medieval Warm Period, Current Warm Period, Dark Age Cold Period and Little Ice Age. However, the Medieval Warm Period usually thought to be a historical analogue for the Current Warm Period has a mean SST of 0.6-0.8°C lower than that of the Roman Warm Period and Sui-Tang dynasty Warm Period. Despite an increase since 1850 AD, the mean SST in the 20th century is still within the range of natural variability during the past 2700 years. A close correlation of SST in Southern Okinawa Trough with air temperature in East China, intensity of East Asian monsoon and the El-Niño Southern Oscillation index has been attributed to the fluctuations in solar output and oceanic-atmospheric circulation.

过往两千年的多数温度重建研究均基于陆地区域不同测点的代用资料。本研究通过分析大洋钻探计划（Ocean Drilling Program，ODP）1202B钻孔站位中浮游古菌的四醚脂类，构建了过去约2700年冲绳海槽南部海表温度（sea surface temperature，SST）的二十年分辨率记录，该站位受黑潮（Kuroshio Current）与东亚季风（East Asian monsoon）的强烈影响。重建得到的海表温度距平序列与此前报道的全新世晚期气候事件基本吻合，包括罗马暖期、隋唐暖期、中世纪暖期、现代暖期、黑暗时代冷期与小冰期。不过，常被视为现代暖期历史类比物的中世纪暖期，其海表温度均值较罗马暖期与隋唐暖期低0.6~0.8℃。尽管自公元1850年以来海表温度有所上升，但20世纪的海表温度均值仍处于过去2700年的自然变率范围之内。冲绳海槽南部海表温度与中国东部气温、东亚季风强度以及厄尔尼诺-南方涛动指数（El-Niño Southern Oscillation index）的显著相关性，可归因于太阳辐出度波动与海气环流的变化。