Variability of the Denmark Strait Overflow during the Last Glacial Maximum
Variability of the Denmark Strait Overflow during the Last Glacial Maximum
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末次盛冰期丹麦海峡溢流的变化
DOI：
10.1111/j.1502-3885.2006.tb01112.x
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发表时间：
2006
期刊：
影响因子：
2.2
通讯作者：
H. Erlenkeuser
中科院分区：
文献类型：
--
作者：
C. Millo;M. Sarnthein;A. Voelker;H. Erlenkeuser
今天，丹麦海峡溢流(DSO)补偿了北大西洋洋流向北流动的挪威和伊尔明格支流，这些支流驱动了北欧热泵。在末次冰盛期，冰盖收缩了丹麦海峡的开口，此外还有冰的升降/均衡效应，使其深度(今天的∼630m)减少了∼130m。这些因素，加上水团南北密度梯度的减小，预计将限制甚至逆转末次冰盛期的DSO强度。为了更好地约束这些边界条件，我们首次提出了冰川DSO的重建，使用了丹麦海峡北部和南部地点的四个新的和四个已公布的底栖生物和浮游生物稳定同位素记录。底栖动物δ18O和δ13C最大值的时空分布表明，在σ0∼2 8.7~2 8.4/2 8.1的中层水层，存在由北向南的密度梯度，表明末次盛冰期北欧海区存在高密度、高透气性的水。然而，中大西洋海脊顶部极高的底栖生物DSO13C值表明，冰岛南部还有一个冰川北大西洋中水的对流单元，然而，该对流单元的密度却低得多(σ0∼28.1)。水密度的南北梯度可能意味着，冰川DSO像今天一样指向南方，并向伊尔明格盆地冰川北大西洋深水输送。
The Denmark Strait Overflow (DSO) today compensates for the northward flowing Norwegian and Irminger branches of the North Atlantic Current that drive the Nordic heat pump. During the Last Glacial Maximum (LGM), ice sheets constricted the Denmark Strait aperture in addition to ice eustatic/isostatic effects which reduced its depth (today ∼630 m) by ∼130 m. These factors, combined with a reduced north‐south density gradient of the water‐masses, are expected to have restricted or even reversed the LGM DSO intensity. To better constrain these boundary conditions, we present a first reconstruction of the glacial DSO, using four new and four published epibenthic and planktic stable‐isotope records from sites to the north and south of the Denmark Strait. The spatial and temporal distribution of epibenthic δ18O and δ13C maxima reveals a north‐south density gradient at intermediate water depths from σ0∼28.7 to 28.4/28.1 and suggests that dense and highly ventilated water was convected in the Nordic Seas during the LGM. However, extremely high epibenthic δ13C values on top of the Mid‐Atlantic Ridge document a further convection cell of Glacial North Atlantic Intermediate Water to the south of Iceland, which, however, was marked by much lower density (σ0∼28.1) The north‐south gradient of water density possibly implied that the glacial DSO was directed to the south like today and fed Glacial North Atlantic Deep Water that has underthrusted the Glacial North Atlantic Intermediate Water in the Irminger Basin.