Palynological evidence for a southward shift of the North Atlantic Current at ~2.6 Ma during the intensification of late Cenozoic Northern Hemisphere glaciation
Palynological evidence for a southward shift of the North Atlantic Current at ~2.6 Ma during the intensification of late Cenozoic Northern Hemisphere glaciation
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DOI：
10.1002/2013pa002543
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发表时间：
2014-06
期刊：
影响因子：
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通讯作者：
J. Hennissen;M. Head;S. Schepper;J. Groeneveld
中科院分区：
文献类型：
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作者：
J. Hennissen;M. Head;S. Schepper;J. Groeneveld
利用两个地点跨越第四纪基底的~260 kyr间隔的甲藻孢囊组合和有孔虫地球化学，对北大西洋海流（NAC）在北方半球冰川作用（iNHG）加强期间的位置进行了评估：北大西洋东部深海钻探项目现场610在目前的NAC和北大西洋中部综合大洋钻探计划的路径地点U1313位于亚热带环流。稳定同位素和有孔虫Mg/Ca分析证实了海洋同位素阶段（MIS）G7-G6过渡（2.74 Ma）附近的冷却。然而，甲藻孢囊Perculodinium centrocarpum sensu Wall和Dale（1966年）的持续优势表明北大西洋东部的NAC活跃了14万年。在MIS 104（~2.60 Ma），一个深刻的甲藻孢囊组合营业额表明NAC关闭在北大西洋东部，这意味着北极上空的大气压力升高，并在西风带，将驱动NAC由此产生的转变。这些研究结果挑战了最近的建议，有没有显着的南迁的NAC或北极锋在iNHG期间，并揭示了一个基本的气候重组附近的基地的第四纪。
The position of the North Atlantic Current (NAC) during the intensification of Northern Hemisphere glaciation (iNHG) has been evaluated using dinoflagellate cyst assemblages and foraminiferal geochemistry from a ~260 kyr interval straddling the base of the Quaternary System from two sites: eastern North Atlantic Deep Sea Drilling Project Site 610 in the path of the present NAC and central North Atlantic Integrated Ocean Drilling Program Site U1313 in the subtropical gyre. Stable isotope and foraminiferal Mg/Ca analyses confirm cooling near the marine isotope stage (MIS) G7–G6 transition (2.74 Ma). However, a continued dominance of the dinoflagellate cyst Operculodinium centrocarpum sensu Wall and Dale (1966) indicates an active NAC in the eastern North Atlantic for a further 140 kyr. At MIS 104 (~2.60 Ma), a profound dinoflagellate cyst assemblage turnover indicates NAC shutdown in the eastern North Atlantic, implying elevated atmospheric pressure over the Arctic and a resulting shift in the westerlies that would have driven the NAC. These findings challenge recent suggestions that there was no significant southward shift of the NAC or the Arctic Front during iNHG, and reveal a fundamental climatic reorganization near the base of the Quaternary.