Low-latitude control on sea surface temperatures in the middle Okinawa Trough over the last 3.6 kyr

Core OKI-152 is one of the best-dated late Holocene cores from the middle Okinawa Trough. The chronological framework and high resolution of this core can help better interpret the paleoclimatology and paleoceanography at centennial-millennial timescales. This core has been analyzed using the alkenone unsaturation index (U-37(K ')) to determine the sea surface temperatures over the last 3.6 kyr. Temperatures obtained from the core-top sample and the 3.6-kyr-averaged temperatures correspond well to the mean annual sea surface temperature (SST) at this location. The SSTs were lower during three periods in 3.6-2.7, 2.0-1.0, and 0.6-0 cal kyr BP, which corresponded to the Neoglacial Period, Dark Age Cold Period, and Little Ice Age, respectively. The variations in the U-37(K ')-derived SSTs in core OKI-152 were not correlated with the high-latitude North Atlantic climate but were synchronous with those of the western Pacific and the El Nino Southern Oscillation (ENSO) variability at low latitudes. When compared with SST signals from the southern Okinawa Trough, the differences in the SST (Delta SST) between the southern and middle Okinawa Trough over the past 3.6 kyr were mainly controlled by the input of freshwater from Taiwan. This result indicates that the East Asian monsoon could influence the SSTs in the Okinawa Trough by modulating precipitation. Modern observations, paleoceanographic proxies, and modeling studies are needed to further understand the interactions among the Okinawa Trough, Pacific Ocean, and East Asian monsoon system.