High-resolution records of sea surface temperature and salinity in the East China Sea in the last 14.2 ka: Implication from alkenone and its hydrogen isotopes

Palaeoceanographic environmental conditions in the East China Sea (ECS) shown as sea surface temperature (SST) and salinity (SSS) may reveal asynchronous hydroclimate changes from low-latitude warm ocean and East Asian monsoon (EAM). However, it remains unclear whether the SST and SSS in the ECS showed a notable response to the spatiotemporal patterns of hydroclimate with the synergistic impacts of the EAM and tropical ocean since the last deglaciation. The SST and SSS records based on alkenone and its hydrogen isotopes (δD_alkenone) with a high-resolution core from the ECS over the last 14 ka were analyzed to understand the forcing mechanisms on different timescales. Results indicate that the SST and SSS of the ECS fluctuated in millennial (～1500 a) and centennial (～750 a, ～350 a , and ～ 120 a) scales. During the last deglaciation and early Holocene, the Kuroshio was strengthened and carried relatively warm and salty seawater into the ECS, thus the SST and SSS were generally higher than normal ones. During the middle Holocene (9.0～5.0 kaBP), freshwater discharged into the ECS, followed by the regulation of its hydrodynamic circulations, which might create strong upper-ocean stratification, high and stable SST, and relatively low SSS. During 5.0~2.7 kaBP, the East Asian Winter Monsoon seemed to be strengthened, while the East Asian Summer Monsoon weakened, which enhanced the upwelling in the ECS due probably to the weakening of the Kuroshio, and subsequently led to the low SST and high SSS in the ECS. In the late Holocene, the surface water temperature and salinity in the ECS showed a decreasing trend, which was almost synchronous with the changes in the Kuroshio. This study presents new lights for further understanding of the low-latitude forcing on the paleoenvironmental evolution in marginal sea.