New Insights Into Kuroshio Current Evolution Since the Last Deglaciation Based on Paired Organic Paleothermometers From the Middle Okinawa Trough

Abstract

As an important hydrological parameter in the upper ocean, the depth of the thermocline (DOT) in the Okinawa Trough (OT) is closely linked to air-sea interactions and Kuroshio Current (KC) intrusions. However, high-resolution DOT records in the OT since the last deglaciation have not been well reconstructed. In this study, we generated surface ((UK)-K-37') and shallow subsurface (TEX86H) temperature records from core M063-05, obtained from the middle OT, and reconstructed annual mean DOT variations since the last deglaciation based on vertical temperature gradients (Delta T (U37K'-TEX86H). The DOT variations in the OT are interpreted to be mainly driven by the KC, with a stronger KC resulting in a deeper DOT and a smaller Delta T (U37K'-TEX86H). In our reconstruction, the KC intensity increased gradually during the last deglaciation, with a reduction during the Younger Dryas, reached a maximum in the early Holocene, and then gradually declined during the middle to late Holocene. We also investigated the responses of the KC to high- and low-latitude climate systems. On orbital timescales, the evolution of the KC occurred in parallel to precession-induced El Nino-Southern Oscillation (ENSO) dynamics. On millennial timescales, fluctuations in the intensity of the KC during the last deglaciation suggest a dynamic link to the North Atlantic climate via the East Asian Monsoon. We propose that the Delta T between (UK)-K-37'- and TEX86H-based temperatures is a reliable indicator for high-resolution studies on the hydrographic structure of the OT and paleoceanographic evolution in the East China Sea.