Sea surface temperature records of core ZY2 from the central mud area in the South Yellow Sea during last 6200 years and related effect of the Yellow Sea Warm Current

Libo Wang,Dejiang Fan,Zuosheng Yang,Rongping Zhang,Meixun Zhao,Bangqi Hu

doi:10.1007/s11434-011-4442-y

Libo Wang, Dejiang Fan + Show 4 more

Open Access

https://doi.org/10.1007/s11434-011-4442-y

Copy DOI

Abstract

Sea surface temperature (SST) records in the South Yellow Sea during the last 6200 years are reconstructed by the unsaturation index of long-chain alkenones (U 37 K′ ) in sediment core ZY2 from the central mud area. The SST records varied between 14.1 and 16.5°C (15.6°C on average), with 3 phases: (1) A high SST phase at 6.2–5.9 cal ka BP; (2) A low and intensely fluctuating SST phase at 5.9–2.3 cal ka BP; and (3) A high and stable SST phase since 2.3 cal ka BP. Variation of the SST records is similar to intensity of the Kuroshio Current (KC), and corresponds well in time to global cold climate events. However, the amplitude of the SST response to cooling events was significantly different in different phases. The SST response to global cooling event was weak while the KC was strong; and the SST response was strong while the KC was weak. The difference in amplitude of the SST response is possibly caused by the modulation effect of the Yellow Sea Warm Current which acts as a shelf branch of the KC and a compensating current induced by the East Asia winter monsoon. The warm waters brought by the Yellow Sea Warm Current cushion the SST decrease induced by climate cooling, and both the Kuroshio and East Asian winter monsoon play important roles in the modulation mechanism. The SST records display a periodicity of 1482 years. The same period was found in the KC records, indicating that variation of the SST records in the central South Yellow Sea is strongly affected by KC intensity. The same period was also found in Greenland ice cores and North Atlantic and Arabian Sea sediment cores, showing a regional response of marine environmental variability in the East China Seas to that in the global oceans.

Highlights

Sea surface temperature records of core ZY2 from the central mud area in the South Yellow Sea during last 6200 years and related effect of the Yellow Sea Warm Current
Desiccation of the Taiwan Retreat Lake between 4.5 and 2.1 cal ka BP and reduction of its TOC content between 5.8 and 5.1 cal ka BP indicate summer monsoon weakening in these periods [34,35], which is consistent with the three low Sea surface temperature (SST) intervals (Figure 5b)
Studies of the Dunde ice core [37,38], Hongyuan peat [39] and historical documents [40,41] demonstrate climate cooling in the three low SST intervals

Summary

Lithology and chronology

Lithology of core ZY2 is homogeneous and mainly composed of grey, dark grey clay silt from the top down, with mean grain-size between 7.03 to 7.67Φ (7.42Φ on average). Grain-size distribution curves of the sediments are unimodal, indicating a stable sedimentary environment. The core has no sedimentation hiatus; sedimentation rates were 44 to 101 cm/ka based on AMS 14C data (Figure 2). Calendar age at the bottom layer of the core is about 6.2 cal ka BP. Because of sample measurement intervals, resolutions of grain-size time series of core ZY2 are about 18 years. Resolutions for SST are about 36 years in the top 36 cm of the core and 72 years below that depth

Sea surface temperature

Discussion

Response of the SST to the Kuroshio Current

Modulation effect of the Yellow Sea Warm Current to the SST

Conclusions