Punctuated Shutdown of Atlantic Meridional Overturning Circulation during Greenland Stadial 1.
Punctuated Shutdown of Atlantic Meridional Overturning Circulation during Greenland Stadial 1.
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DOI：
10.1038/srep25902
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发表时间：
2016-05-19
影响因子：
4.6
通讯作者：
Wacker L
中科院分区：
文献类型：
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作者：
Hogg A;Southon J;Turney C;Palmer J;Bronk Ramsey C;Fenwick P;Boswijk G;Friedrich M;Helle G;Hughen K;Jones R;Kromer B;Noronha A;Reynard L;Staff R;Wacker L
格陵兰1期（GS-1，约12.9至11.65 kyr cal BP）是北大西洋冷却的时期，被认为是由北美淡水径流引起的，导致北大西洋经向翻转环流（AMOC）持续减少，导致两半球之间的反相温度响应（“两极跷跷板”）。在这里，我们利用亚化石新西兰贝壳杉报告第一个安全的日期，十年分辨率的大气放射性碳（14 C）记录跨越GS-1。通过将南、北方半球树轮14 C记录与海洋14 C序列精确比对，我们记录了在该阶段中两个相对较短的AMOC崩溃时期，约12，920 - 12，640 cal BP和12，050 - 11，900 cal BP。此外，我们的数据显示，在GS-1之前，半球间大气14 C偏移接近于零，在大约12，660 cal BP达到“近现代”值之前，与两个半球翻转的同步恢复和南大洋通风的增加一致。因此，GS-1的持续北大西洋冷却并不是由长期的AMOC减少驱动的，而是可能由于极锋向赤道迁移，减少了西南气团向高纬度的平流。我们的研究结果表明，相反的半球温度趋势是由大气遥相关驱动的，而不是AMOC变化。
The Greenland Stadial 1 (GS-1; ~12.9 to 11.65 kyr cal BP) was a period of North Atlantic cooling, thought to have been initiated by North America fresh water runoff that caused a sustained reduction of North Atlantic Meridional Overturning Circulation (AMOC), resulting in an antiphase temperature response between the hemispheres (the ‘bipolar seesaw’). Here we exploit sub-fossil New Zealand kauri trees to report the first securely dated, decadally-resolved atmospheric radiocarbon (14C) record spanning GS-1. By precisely aligning Southern and Northern Hemisphere tree-ring 14C records with marine 14C sequences we document two relatively short periods of AMOC collapse during the stadial, at ~12,920-12,640 cal BP and 12,050-11,900 cal BP. In addition, our data show that the interhemispheric atmospheric 14C offset was close to zero prior to GS-1, before reaching ‘near-modern’ values at ~12,660 cal BP, consistent with synchronous recovery of overturning in both hemispheres and increased Southern Ocean ventilation. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but probably due to an equatorward migration of the Polar Front, reducing the advection of southwesterly air masses to high latitudes. Our findings suggest opposing hemispheric temperature trends were driven by atmospheric teleconnections, rather than AMOC changes.