末次间冰期以来北欧海南部洋流变动对大西洋经向翻转流及气候的影响：陆源与自生组分钕同位素证据

The Nordic Sea is source region of the North Atlantic Deep Water and the key area for the meridional thermohaline exchange between the Arctic and Atlantic Oceans. Hence, the Sea usually is used as the “window” to observe the interaction of current and climate. Three core sediments were collected from the southern Nordic Sea at important locations and depth. Sediment is sampled from the cores at same interval. Then, these sediment samples are measured grain distribution, and divided into four sub-samples, such as >63μm, 63-30μm, 30-10μm and<10μm, according to sensitive grain-size of hydrodynamic condition. The crusts of foraminifer are separated from the subsamples (>63μm) and analyzed the δ18O and dating (AMS14C). The subsamples (63-30μm) and few 30-10μm subsamples also be leached to separate the authigenic Fe-Mn oxide faction, and then leachate determined it for the compositions of elements and Nd isotope. The residue and subsample (<10μm) are used to extract terrigenous silicate to analyze mineral assemblages, element compositions and Nd isotopes. We deeply analyze and discuss all the data, and compare the difference among three cores. The objectives of this program are: to build temporal frame; to identify the provenances of silicate debris and the dynamical features of surface and deep waters based on changes of provenances of debris since the Last Interglacial; to clarify inflow of Atlantic Water (Irminger Current and Norwegian Current) inflow and outflow of Overflow Water (Denmark Strait Overflow Water and Iceland-Scotland Overflow Water) for the Nordic Sea since the Last Interglacial. The results above will take advantage to understand dynamical features of the southern Nordic Sea and the interactional mechanism of the Atlantic Meridional Overturning Circulation and global climate.

北欧海作为北大西洋深层水源地、北冰洋-大西洋经向温盐循环枢纽，是认识洋流变异对全球气候影响的天然“窗口”。课题筛选北欧海南部洋流变异关键部位和水深的3根柱样为研究对象，分析柱样不同层位的粒度特征，结合颗粒物水动力敏感性，将不同层位沉积物样品划分为>63、63-30、30-10和<10μm子样。>63μm子样用于有孔虫δ18O和14C同位素定年数据，建立年代格架；选择淋滤63-30和少量30-10μm子样外包自生铁锰膜，测定滤液元素和Nd同位素组成；残留相与<10μm子样分别纯化所含陆源硅酸盐，分析矿物、元素及Nd同位素。在年龄框架中，<10μm子样硅酸盐数据结合δ18O用于指示区内表层水体中大西洋水输入强度变化；滤液与残留相指标指示海区溢出水量的波动，以揭示北大西洋深层水产率变动。综合分析3根柱样数据，依据北欧海动力性质变化，探究末次间冰期以来大西洋经向翻转流变异对全球气候的影响。

北欧海作为北大西洋深层水源地、北冰洋-大西洋经向温盐循环枢纽，是认识洋流变异对全球气候影响的天然“窗口”。课题在采用有孔虫δ18O和AMS14C同位素定年方法构建北欧海3站岩芯年代格架的基础上，对沉积物碎屑组分进行Sr-Nd同位素、元素和矿物组成测定，对沉积物自生组分进行Sr-Nd同位素、元素组成分析，以揭示末次间冰期以来北欧海沉积物来源变化和深层水演化与北大西洋深层水的内在联系，探究大西洋径向翻转流对全球气候的响应。综合分析沉积物碎屑组分Sr-Nd同位素和元素地球化学表明，末次间冰期以来冰岛冰盖、斯堪的纳维亚冰盖和斯瓦尔巴德-巴比伦冰盖的涨缩以及大西洋表层水输入强弱驱动着北欧海沉积物物质来源变化。通过沉积物自生组分Nd同位素和元素地球化学特征的变化，重建了末次冰期以来北欧海深水演化。MIS2期间，北欧海深水（NSDW）与北大西洋水的交换强度弱，全新世NSDW水变率主要受北大西洋水在北欧海深部对流的控制。拉布拉多海水（LSW）和北欧海溢出水（ISOW）以“跷跷板”模式制约北大西洋深水（NADW），海因里希事件发生的冰川循环阶段可能不是控制北大西洋深水对淡水释放响应的主要控制因素，而淡水输入位置、大小和通量同样重要。