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

Palaeoceanographic environmental conditions (e.g., sea surface temperature (SST) and salinity (SSS)) of the East China Sea (ECS) may reveal asynchronous hydroclimate changes to those from both low-latitude warm ocean and East Asian monsoon (EAM). However, it remains unclear whether the SST and SSS in the ECS has shown a notable response to spatiotemporal patterns of hydroclimate with the synergistic impacts of the EAM and tropical ocean since the last deglaciation. In this study, the SST and SSS records based on alkenone and its hydrogen isotopes (delta D-alkenone) with a high-resolution core from the ECS over the last 14 kyr are presented here to understand forcing mechanisms on different timescales. Results indicate that the ECS experienced SST and SSS variability on different timescales. SST and SSS records of the ECS overprint a millennial period of similar to 1500 yrs., and centennial periods of similar to 750, similar to 350, and similar to 120 yrs. During the last deglaciation and early Holocene, as a result of a strengthened Kuroshio Current (KC) bringing relative warm and salty seawater into the ECS, the SST and SSS were generally higher than normal. During the middle Holocene (9.0-5.0 ka), amounts of freshwater discharged into the ECS, following a regulation of its hydrodynamic circulations. This situation may create strong upper-ocean stratification, resulting in high and stable SST and relatively low SSS. In the period from 5.0 to 2.7 ka, the East Asian Winter Monsoon seemed to strengthen, while the East Asian Summer Monsoon weakened, leading to enhancing the upwelling in the ECS. This pattern could have triggered a reduction in the KC, and subsequently led to low SST and high SSS in the ECS. In the late Holocene, ECS changes imitated the reduction in KC, acting as an indicator of warm equatorial Pacific. Therefore, the ECS has exhibited decreasing trends in SSS and SST during this period. This study presents new lights to further understand the role of low-latitude forcing on the paleoenvironmental evolution in the marginal sea.