Contrasted changes of sea-surface salinity in the southern and northern Okinawa Trough since the mid-Holocene

Abstract

A reconstruction of sea-surface salinity (SSS) in the southern Okinawa Trough (OT) since 6800 cal. yr BP has been presented in this study. We found that the SSS record increased gradually from the middle to late Holocene, indicating reduced summer precipitation in Taiwan. Our results also suggest regional patterns of SSS with SSS increasing in the southern OT and decreasing in the northern OT since the mid-Holocene. Observational data indicate that the SSS in the southern and northern OT are strongly affected by fluvial discharge from Taiwan and the Changjiang River, linked to summer precipitation in South and Central Eastern China, respectively. The contrasting changes in SSS from the OT since the mid-Holocene suggest different spatial patterns of precipitation, with decreasing summer precipitation in South China and increasing summer precipitation in central-eastern China due to the weakened East Asian Summer Monsoon (EASM) and solar insolation. The delayed seasonal transitions of the EASM, with a longer Meiyu stage and a shorter midsummer stage from the mid-Holocene to late Holocene, are consistent with the delayed northward migration of the westerlies in the late Holocene.