Quaternary upper ocean thermal gradient variations in the South China Sea: Implications for east Asian monsoon climate
Quaternary upper ocean thermal gradient variations in the South China Sea: Implications for east Asian monsoon climate
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DOI：
10.1029/2004pa001115
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发表时间：
2005-12
期刊：
影响因子：
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通讯作者：
Jun Tian;Pinxian Wang;Ronghua Chen;Xinrong Cheng
中科院分区：
文献类型：
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作者：
Jun Tian;Pinxian Wang;Ronghua Chen;Xinrong Cheng
[1]东亚季风气候对南海局地气候条件有着重要的影响。在这里，我们提出的结果，从3年的研究中，蛋白石的百分比，Pulleniatina pulliciloculata和Globigerinoides ruber的通量，有机碳通量，初级生产力的现代沉积物陷阱在冬季混合层深度最深时，都显示出最高值。亚表层居群P. acuiloculata与混合层居群G.在越南近海具有浅混合层的冷涡区，12个活塞岩心和一个大洋钻探计划（ODP）现场的岩心顶部样品中的红含量很大，约为0.6‰，但在缺乏冷涡的深混合层环境中，红含量降低。我们还提供了1.56万年的G. ruber和P. acetyloculata的化石，揭示了第四纪海洋上层温度梯度的变化。较低的Δδ 18 O（P-G）值表明，在大多数冰川事件中，混合层深度增加，可能是由于冬季季风风较强。相反，间冰期期间较高的Δδ 18 O（P-G）值表明混合层深度减少，因此冬季季风减弱。1143站δ 18 O（P-G）与1144站草本植物和蛋白石通量的比较表明，冰期和间冰期的变化分别受到较强和较弱的东亚冬季风的强烈影响。因此，至少从更新世开始，南海上层海洋热梯度变化就一直受到东亚冬季风的影响。
[1] The east Asian monsoon climate has an overwhelming influence on local climatic conditions of the South China Sea (SCS). Here we present results from a 3-year study of modern sediment traps from the central SCS in which the percentage of opal, the fluxes of Pulleniatina obliquiloculata and Globigerinoides ruber, the organic carbon flux, and primary productivity all show highest values during winter when the mixed layer depth is deepest. The δ18O difference (Δδ18O(P-G)) between the subsurface dwelling P. obliquiloculata and the mixed layer dwelling G. ruber in core top samples from 12 piston cores and one Ocean Drilling Program (ODP) site in the SCS is large, ∼0.6‰ in a cold eddy area with a shallow mixed layer off Vietnam, but is reduced in deep mixed layer settings lacking cold eddies. We also present 1.56 Myr-long isotope records of G. ruber and P. obliquiloculata from ODP site 1143 in the southern SCS that reveal upper ocean thermal gradient variations during the Quaternary. Lower Δδ18O(P-G) values indicate increased mixed layer depths over most glacial episodes, likely due to stronger winter monsoon winds. In contrast, higher Δδ18O(P-G) values during interglacial intervals suggest decreased mixed layer depths and thus weaker winter monsoon winds. Comparisons of Δδ18O(P-G) with the percentage of P. obliquiloculata at site 1143 and the percentage of herbs and opal flux at site 1144 demonstrate that glacial-interglacial variations were strongly influenced by stronger and weaker east Asian winter monsoons during glacials and interglacials, respectively. Therefore the upper ocean thermal gradient variations in the SCS have been consistently affected by the east Asian winter monsoon since at least the beginning of the Pleistocene.