亚北极鄂霍次克海晚第四纪冰海沉积作用与水团变化历史

Changing histories of glaciomarine deposition and water masses in the subarctic Okhotsk Sea of Late Quaternary

  • 摘要: 亚北极鄂霍次克海是全球重要的碳汇之一,也是北太平洋中层水的主要源区,研究晚第四纪鄂霍次克海古环境变化及其影响因素对于理解亚极地海洋对气候变化的响应有重要意义。本文对鄂霍次克海南部科学院海隆ARC2-T00岩芯进行了粗组分、坠石、有孔虫丰度和CaCO3含量的统计与分析、底栖有孔虫Uvigerina spp.氧碳同位素测试等,并基于其底栖有孔虫Uvigerina spp.-δ18O和深海氧同位素曲线LR04-δ18O与相邻站位OS03-1 Uvigerina spp.-δ18O的对比,建立了该岩芯的地层年代框架。该研究表明,在MIS 6—MIS 2的大部分时期,鄂霍次克海南部主要沉积动力为西风、洋流及海冰;风尘堆积速率的变化指示西风带在冰期增强,间冰期减弱;海冰沉积堆积速率的变化表明,在冰期或冰段,海冰沉积受当时季节性海冰沉积中心带所处位置的影响较大;海冰和水团指标变化显示,鄂霍次克海南部此时为季节性海冰覆盖,鄂霍次克海中层水上部生成增强,中层水下部的盐度变化可能与宗谷暖流前伸体的输入、海冰形成析出的卤水下沉和太平洋深层水的侵入有关。

     

    Abstract: The subarctic Okhotsk Sea is one of the most important carbon sinks in the world and the main source areas of ​​North Pacific Intermediate Water (NPIW). The study of Late Quaternary paleoenvironmental changes of the ​​Okhotsk Sea and their effect factors are of great significance for understanding the responses of subpolar oceans to global climate change. Coarse fraction, drop stone, foraminiferal abundance, CaCO3 content, benthic foraminifera Uvigerina spp. oxygen and carbon isotopes in the core ARC2-T00 collected from the Academy of Sciences on Rise of Southern Okhotsk Sea are tested, counted or analyzed by the authors and then the stratigraphic chronology of the core is established based on the comparison of the benthic foraminifera Uvigerina spp.-δ18O, the global deep-sea oxygen isotope stacks LR04-δ18O and the adjacent site OS03-1 Uvigerina spp.-δ18O. The results indicate that, in the most intervals of MIS 6—2, the sedimentary dynamic mechanisms in the Southern ​​Okhotsk Sea are dominated by westerlies, ocean currents and sea ice. Changes in the accumulation rate of eolian dust indicate that the westerlies strengthened and weakened during the glacials and the interglacials, respectively. The variation in the accumulation rate of sea ice sediments illustrates that during the glacials, sea ice deposition was severely influenced by the location of the seasonal sea ice depositional center at that time. Meanwhile, as indicated by proxies of sea ice and water masses, the southern ​​Okhotsk Sea was covered by seasonal sea ice and the upper Okhotsk Sea Intermediate Water (uOSIW) production was strengthened. Salinity variation in lower Okhotsk Sea Intermediate Water (lOSIW) may be related to inflow of the Forerunner of Soya Warm Current Water (FSCW), brine rejection due to sea ice formation and intrusion of the Pacific Deep Water (PDW).

     

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