Climate change and response in bottom water circulation and sediment provenance in the Central Arctic Ocean since the Last Glacial
Climate change and response in bottom water circulation and sediment provenance in the Central Arctic Ocean since the Last Glacial
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DOI：
10.1016/j.chemgeo.2016.02.019
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发表时间：
2016-06
期刊：
影响因子：
3.9
通讯作者：
A. Meinhardt;K. Pahnke;P. Böning;B. Schnetger;H. Brumsack
中科院分区：
文献类型：
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作者：
A. Meinhardt;K. Pahnke;P. Böning;B. Schnetger;H. Brumsack
本文通过Nd、Sr同位素组成的研究，比较了末次冰期北冰洋深水环流和沉积物来源的模式与现代的情况（143 Nd/144 Nd，表示为εNd，87 Sr/86 Sr）以及元素组成（锰、钙、镁、无机碳总量），包括来自若干北冰洋海盆和海脊的11个沉积物岩心。表层沉积物的自生特征意味着北大西洋深层水源和全新世晚期的环流体系，大部分是均匀的，ε Nd值为− 10.9至− 10.3。LG沉积物的自生ε Nd值总体上变化较大（− 13.9至− 7.4）。较低的值具体发生在Amerasian和阿蒙森盆地，记录增强流的深沃茨从马卡罗夫盆地阿蒙森盆地可能通过罗蒙诺索夫岭intra-basin.In碎屑物源区，沉积在核心位置的成岩物质不能明确分配到不同的源区的基础上，其放射性同位素组成，但代表了不同的混合物。然而，美亚海盆表层沉积物的Nd和Sr同位素特征以北极西部源区为主（εNd= − 12.8至− 11.0; 87 Sr/86 Sr = 0.7214 ~ 0.7251），而欧亚盆地表层沉积物则以欧亚源为主（εNd= − 10.9 ~ − 9.7，87 Sr/86 Sr = 0.7178 ~ 0.7299），这与以前的研究结果一致。研究沉积物的体元素模式（Ca，Mg，TIC）支持这些差异的物源。LG样品显示出相同的趋势，在加拿大盆地具有低εNd（− 16.1至− 13.7）和高87 Sr/86 Sr（0.7294），在欧亚盆地沉积物中具有较高的εNd（− 12.6至− 8.8）和较低的87 Sr/86 Sr（0.7154至0.7249）。然而，LG样品的ε Nd和87 Sr/86 Sr值大多比地表样品低且更不均匀。我们的地球化学研究表明，LG期间的深水团的整体循环模式受卤水形成的局部影响，但总体上与今天相似。从LG的成岩物质的同位素组成是不同的现代，大概是由于较短的运输途径的成岩物质北冰洋，因为较低的海平面和暴露的货架在LG。然而，成岩馏分仍然代表了混合物从几个来源。
In this study, Arctic Ocean patterns of deep water circulation and sediment provenance during the Last Glacial (LG) were compared with the recent situation by investigating the Nd and Sr isotopic composition (143Nd/144Nd, expressed as εNd,87Sr/86Sr) of the leachable and lithogenic sediment fractions as well as the elemental composition (Mn, Ca, Mg, total inorganic carbon (TIC)) on a spatially extended scale encompassing 11 sediment cores from several Arctic Ocean basins and ridges.The leachable, authigenic signature of the surface sediments implies a North Atlantic deep water source and a late Holocene circulation regime that leads to well-mixed, mostly uniform, εNdvalues of − 10.9 to − 10.3. Sediments from the LG have overall more variable authigenic εNdvalues (− 13.9 to − 7.4). Lower values specifically occur in the Amerasian and Amundsen Basins, documenting an enhanced flow of deep waters from the Makarov Basin to the Amundsen Basin probably via the Lomonosov Ridge intra-basin.In terms of detrital provenance areas, the lithogenic material deposited at the core locations cannot be unambiguously assigned to distinct source areas based on its radiogenic isotope composition, but represents a diverse mixture. Nevertheless, the Nd and Sr isotope signatures of surface sediments from the Amerasian Basin are dominated by western Arctic sources (εNd= − 12.8 to − 11.0;87Sr/86Sr = 0.7214 to 0.7251), while Eurasian Basin surface sediments are dominated by Eurasian sources (εNd= − 10.9 to − 9.7,87Sr/86Sr = 0.7178 to 0.7299), which is in agreement with previous studies. Bulk element patterns (Ca, Mg, TIC) of the studied sediments support these differences in provenance. The LG samples show the same trends with low εNd(− 16.1 to − 13.7) and high87Sr/86Sr (0.7294) in the Canada Basin, and higher εNd(− 12.6 to − 8.8) and lower87Sr/86Sr (0.7154 to 0.7249) in the Eurasian Basin sediments. However, LG samples have mostly lower and more heterogenous εNdand87Sr/86Sr values than the surface samples.Our geochemical study shows that the overall circulation pattern of the deep water masses during the LG was locally influenced by brine formation but was generally similar to today. The isotopic composition of the lithogenic material from the LG is different from modern times, presumably due to shorter transport pathways of lithogenic material to the Arctic Ocean because of a lower sea level and exposed shelves during the LG. Nevertheless, the lithogenic fraction still represents a mixture from several sources.