Reorganization of the North Atlantic Oscillation during early Holocene deglaciation
Reorganization of the North Atlantic Oscillation during early Holocene deglaciation
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DOI：
10.1038/ngeo2767
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发表时间：
2016-07
影响因子：
18.3
通讯作者：
J. Wassenburg;S. Dietrich;J. Fietzke;J. Fohlmeister;K. Jochum;D. Scholz;D. Richter;A. Sabaoui;C. Spötl;G. Lohmann;M. Andreae;A. Immenhauser
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文献类型：
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作者：
J. Wassenburg;S. Dietrich;J. Fietzke;J. Fohlmeister;K. Jochum;D. Scholz;D. Richter;A. Sabaoui;C. Spötl;G. Lohmann;M. Andreae;A. Immenhauser
北大西洋涛动是北大西洋地区的主要气压模式，影响地中海、西北欧、格陵兰岛和亚洲的冬季气温和降水。描述冰岛和亚速尔群岛之间海平面气压差的指数与欧洲西北部和非洲西北部的偶极降水模式相关。随着格陵兰冰盖融化，北大西洋涛动将如何发展尚不清楚。过去的一个潜在的类比是全新世早期，在此期间，北大西洋周围的冰盖融化，地表水变得清新，影响了经向翻转环流的强度。在这里，我们提出了基于洞穴沉积物 δ18O 的非洲西北部全新世降雨记录，并将其与欧洲基于洞穴沉积物的降雨记录进行了比较。这两个记录在全新世早期呈正相关，随后在全新世中期转为反相关，类似于现代记录。根据我们对地球系统模型的模拟，我们认为向反相关的转变反映了由于劳伦太德冰盖的消亡而发生的大规模大气和海洋重组以及流向北大西洋的融水通量的大幅减少，这表明北大西洋涛动对冰盖融化具有潜在的敏感性。
The North Atlantic Oscillation is the dominant atmospheric pressure mode in the North Atlantic region and affects winter temperature and precipitation in the Mediterranean, northwest Europe, Greenland, and Asia. The index that describes the sea-level pressure difference between Iceland and the Azores is correlated with a dipole precipitation pattern over northwest Europe and northwest Africa. How the North Atlantic Oscillation will develop as the Greenland ice sheet melts is unclear. A potential past analogue is the early Holocene, during which melting ice sheets around the North Atlantic,freshened surface waters, affecting the strength of the meridional overturning circulation. Here we present a Holocene rainfall record from northwest Africa based on speleothem δ18O and compare it against a speleothem-based rainfall record from Europe. The two records are positively correlated during the early Holocene, followed by a shift to an anti-correlation, similar to the modern record, during the mid-Holocene. On the basis of our simulations with an Earth system model, we suggest the shift to the anti-correlation reflects a large-scale atmospheric and oceanic reorganization in response to the demise of the Laurentide ice sheet and a strong reduction of meltwater flux to the North Atlantic, pointing to a potential sensitivity of the North Atlantic Oscillation to the melting of ice sheets.