Persistent Nordic deep-water overflow to the glacial North Atlantic
Persistent Nordic deep-water overflow to the glacial North Atlantic
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DOI：
10.1130/g31677.1
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发表时间：
2011-06-01
期刊：
影响因子：
5.8
通讯作者：
Richards, D. A.
中科院分区：
文献类型：
--
作者：
Crocket, K. C.;Vance, D.;Richards, D. A.
北大西洋气候对格陵兰-冰岛-挪威海（GIN）的倾覆、深水通过格陵兰-冰岛-苏格兰海脊溢出到北大西洋以及温暖的地表水向北流动的补偿非常敏感。物理模型表明，在没有这种翻转的情况下，向北方半球的海洋热传输减少了50%，北大西洋开阔海面的温度降低了6摄氏度，冬季海冰极限向南迁移了45度。虽然模拟的平衡气候状态的末次盛冰期（LGM）表明没有GIN海洋溢出，这些模型结果的测试受到阻碍的沉积代理的模糊性。在这里，我们提出了一个底层水钕（Nd）同位素记录从罗卡尔槽调查在过去的43 k. y的循环沃茨的来源的变化。今天和整个全新世的大部分时间，水从GIN海，沿着水从北大西洋流（NAC）夹带在溢出，设置底层水Nd同位素组成的罗卡尔槽类似-10。我们的研究结果表明，这种情况的持久性回到末次冰期和以后的中期海洋同位素阶段3。周期性的放射性漂移打断了融水事件发生时的记录，这意味着要么继续GIN海洋溢出没有NAC夹带，或千年规模的中断南部水源水的溢出和变浅。我们的结论是，溢出至少间歇性存在于末次盛冰期，如果不是连续的，和GIN海仍然是一个源的深水北大西洋在最后一次冰期循环。
North Atlantic climate is very sensitive to overturning in the Greenland-Iceland-Norwegian (GIN) Seas, overflow of deep water into the North Atlantic via the Greenland-Iceland-Scotland Ridge, and compensating northward flow of warm surface water. Physical models suggest that, in the absence of such overturning, oceanic heat transport to the Northern Hemisphere is reduced by as much as 50%, open North Atlantic sea-surface temperatures are as much as 6 degrees C lower, and the winter sea-ice limit migrates as far south as 45 degrees N. Although simulations of the equilibrium climate state for the Last Glacial Maximum (LGM) suggest the absence of GIN Seas overflow, tests of these model results have been hampered by ambiguity in sedimentary proxies. Here we present a bottom-water neodymium (Nd) isotope record from the Rockall Trough to investigate changes in the sources of circulating waters over the past 43 k.y. Today and throughout most of the Holocene, water from the GIN Seas, along with water from the North Atlantic Current (NAC) entrained during overflow, sets the bottom-water Nd isotope composition of the Rockall Trough to similar to-10. Our results suggest the persistence of this scenario back into the LGM and beyond to mid-Marine Isotope Stage 3. Periodic radiogenic excursions punctuate the record at times of meltwater events, implying either continued GIN Seas overflow without NAC entrainment, or millennial-scale interruptions in the overflow and shoaling of Southern Source Water. We conclude that overflow was at least intermittently present during the LGM, if not continuous, and that the GIN Seas have remained a source of deep water to the North Atlantic during the last glacial cycle.