5:15 PM - 7:15 PM
[MIS06-P04] Reconstruction of Kuroshio current variability over the last 20,000 years using oxygen isotope and Mg/Ca proxies of benthic foraminifera in Okinawa Trough
Keywords:Kuroshio, Paleoclimate, Okinawa Trough, Last glaciation maximum
The variation of Kuroshio Current plays a critical role in Japanese society, influencing both population growth in the past and climate condition. Despite of its dynamics, the trace of the current is quite controversial as a reduction in the amount of Kuroshio current entering the Okinawa Trough was found during the Last Glaciation Maximum (LGM), around 20 ka BP. This event was primarily ascribed to two factors: the presence of a land bridge and the temperature anomaly of the Pacific Ocean. Variability reconstruction of Kuroshio Current is crucial to mitigate the climate effect caused by the phenomenon.
This study was conducted to reconstruct the Kuroshio Current variability over the last 20 ka utilizing benthic foraminifera Uvigerina peregrina taken from KS 22-4 PC02 from section 1 to 3 core sample collected off the Okinawa Trough. The total core sample depth is 212.4 cm and was analyzed at 1 cm intervals to obtain high-resolution results. This study utilized oxygen isotopes, Mg/Ca ratios, and radiocarbon dating to enhance the accuracy of paleoclimate reconstruction. We also calculate the oxygen isotope of seawater, bottom water temperature, sand percentage and linear sedimentation rate (LSR).
The oxygen isotope values show an increasing trend with age, and Mg/Ca ratio follows the same pattern. The bottom water temperature ranges from 4 to 8°C, while the oxygen isotope composition of seawater exhibits a simultaneous relationship with the oxygen isotope values in foraminifera. The concurrent increase in oxygen isotope values and the Mg/Ca ratio between 5 and 10 ka BP is particularly notable, as it coincides with the Holocene Thermal Maximum, which likely influenced regional oceanographic conditions, including changes in salinity and freshwater input into the ocean. The bottom water temperature is slightly higher compared to the PC02 CTD measurement, which recorded approximately 5°C. Additionally, sand percentage also increased during this period, supported by a significant rise in the Linear Sedimentation Rate (LSR) between 5 and 6 ka BP, followed by a slight decrease until 10 ka BP.
These findings highlight the complexity of paleoclimate interpretation and the importance of considering factors such as Holocene Thermal Maximum and sedimentation dynamics. For further work, this research will extend to the end of section 3, around 20 ka BP with a more comprehensive approach to paleoceanographic and paleoclimatic analysis.
This study was conducted to reconstruct the Kuroshio Current variability over the last 20 ka utilizing benthic foraminifera Uvigerina peregrina taken from KS 22-4 PC02 from section 1 to 3 core sample collected off the Okinawa Trough. The total core sample depth is 212.4 cm and was analyzed at 1 cm intervals to obtain high-resolution results. This study utilized oxygen isotopes, Mg/Ca ratios, and radiocarbon dating to enhance the accuracy of paleoclimate reconstruction. We also calculate the oxygen isotope of seawater, bottom water temperature, sand percentage and linear sedimentation rate (LSR).
The oxygen isotope values show an increasing trend with age, and Mg/Ca ratio follows the same pattern. The bottom water temperature ranges from 4 to 8°C, while the oxygen isotope composition of seawater exhibits a simultaneous relationship with the oxygen isotope values in foraminifera. The concurrent increase in oxygen isotope values and the Mg/Ca ratio between 5 and 10 ka BP is particularly notable, as it coincides with the Holocene Thermal Maximum, which likely influenced regional oceanographic conditions, including changes in salinity and freshwater input into the ocean. The bottom water temperature is slightly higher compared to the PC02 CTD measurement, which recorded approximately 5°C. Additionally, sand percentage also increased during this period, supported by a significant rise in the Linear Sedimentation Rate (LSR) between 5 and 6 ka BP, followed by a slight decrease until 10 ka BP.
These findings highlight the complexity of paleoclimate interpretation and the importance of considering factors such as Holocene Thermal Maximum and sedimentation dynamics. For further work, this research will extend to the end of section 3, around 20 ka BP with a more comprehensive approach to paleoceanographic and paleoclimatic analysis.