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摘要
Deciphering the evolution of global hydroclimate during the last deglaciation is of great significance for understanding the response of the climate system to the internal and external forces. Based on planktonic foraminiferal Globigerinodes ruber and Pulleniatina obliquiloculata shell Mg/Ca ratio obtained from core OKI02, we reconstructed a 19 000-year record of Sea Surface Temperature (SST) and Thermocline Water Temperature (TWT) to unveil the characteristics and process of upper water temperature in the Middle Okinawa Trough during the last deglaciation. The results imply that the SST was significantly low (about 23.7 ℃ on average) during the Last Glacial Maximum (LGM, about 19-18 ka BP), and was of obvious millennial-scale variation features during the last deglaciation. Heinrich Stadial 1(HS1), B?lling-Aller?d (B/A) and Younger Dryas (YD) events could be identified obviously in the record of SST.TWT shows a rising trend, with frequent and strong fluctuation since 19 ka BP. TWT is relatively low (about 20.3 ℃ on average) during the last deglaciation, without apparent significant millennial-scale changes. During the last deglaciation, the beginning time of SST rising in the Okinawa Trough was consistent with the SST record in high latitudes of the northern hemisphere, while lagged significantly behind SST record of the tropical western Pacific. Meanwhile, the SST change pattern in the Okinawa Trough was different from the continuous and stable warming process of the tropical western Pacific, but more similar to the climate change of the northern hemisphere high latitudes. In contrast, the warming time of TWT was earlier than that happened in the northern high latitudes but close to the tropical western Pacific. Moreover, the rising and fluctuating mode of TWT was different from the former and was more similar to the variation pattern of the tropical Pacific. The differentiated evolution of SST and TWT demonstrates that the influence of Atlantic Meridional Overturning Circulation (AMOC) on the atmospheric circulation may control the SST in the trough area through the changes of the East Asian winter monsoon. However, the tropical Pacific ENSO process probably plays an important role in the evolution of the regional TWT through the changes of the Kuroshio during the last deglaciation. The trend of the decoupling change in SST and TWT in the middle of the Okinawa Trough implies its intimate connection with high and low latitude oceans and climate change.
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