近海泥质沉积物敏感粒径作为冬季风强度指标的再研究：与器测数据的对比

RE-ANALYSIS OF SENSITIVE GRAIN SIZE OF COASTAL MUDDY SEDIMENTS AS PROXY OF WINTER MONSOON STRENGTH：COMPARISON WITH INSTRUMENTAL DATA

中国近海泥质沉积物敏感粒级的平均粒径已被广泛用于重建东亚冬季风强度,但目前敏感粒径序列与器测数据的对比研究较少,且近年不断有学者对一些区域泥质沉积物敏感粒径的指示意义提出不同观点.本文利用北黄海西部泥质区、南黄海中部泥质区和长江口泥质区的3根沉积柱,以210Pb、137Cs测年以及沉积物敏感粒级分析方法,分别获得了过去100余年三孔高分辨率敏感粒度组分的变化序列,并与器测西伯利亚高压数据进行对比.结果显示,3个泥质区沉积物敏感组分的平均粒径变化趋势不完全一致,其中南黄海中部与长江口泥质区沉积物敏感粒径序列具有较好的正相关关系,但与北黄海西部泥质区沉积物敏感粒径序列变化趋势相反;3条序列均与指示东亚冬季风强度的西伯利亚高压序列变化趋势不同.进一步分析表明,3条序列与冬季风指标序列变化不一致的原因可能在于：北黄海西部和南黄海中部泥质区沉积物为冷涡沉积,受沿岸流影响可能较小;长江口泥质区沉积物受河流径流等的影响较大.由此可见,泥质区沉积物的沉积特征受多种因素的影响,在利用泥质沉积物敏感粒级的平均粒径作为东亚冬季风强度的替代指标时需谨慎,应考虑沉积物所在区域的成因机制,尤其是环流体系及河流输沙等因素的影响.

Mean grain size of sensitive components in Chinese coastal muddy sediments has been widely used as a proxy for the East Asian winter monsoon （EAWM） intensity. However, few studies have focused on the comparison between sequences of sensitive grain size and instrumental data of EAWM intensity, and different views on the indication of sensitive grain size appeared continuously during the recent years. In the present study, three cores, including Core 35009 （35°00.15＇N, 123°29.75＇E; 75,8m in depth） from the central South Yellow Sea mud area, Core 38002 （37°59.92＇N, 122°30.21＇E; 49.2m in depth） from the west of the North Yellow Sea mud area and Core TO2 （31°40.34＇N, 122°60.06＇E; 42.1m in depth） from the mud area off the Changjiang Estuary, were studied through 210Pb and 137Cs chronology and sensitive grain size analysis. High-resolution sequences of the sensitive grain size during the past 100 years have been obtained and compared with the instrumental data of Siberian High index, which served as the indicator of EAWM intensity. The results showed that trends in sequences of mean grain size of sensitive components in three cores were different. Though grain size sequences of the sensitive components in cores 35009 and T02 were positively correlated, their trends are opposite to that in Core 38002. No significant correlation between each sequence and Siberian High index was found. Our further analysis indicated that sediments in the North Yellow Sea mud area and the central South Yellow Sea mud area might not be significantly influenced by coastal currents, and those in the mud area off the Changjiang Estuary should be influenced by river runoff. Thus it is suggested that mean grain size of the sensitive components of muddy sediments in some mud areas should be carefully used for reconstruction of winter monsoon strength, because it could be influenced by regional factors, such as circulation system and riverderived materials.