Strong and deep Atlantic meridional overturning circulation during the last glacial cycle
Strong and deep Atlantic meridional overturning circulation during the last glacial cycle
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DOI：
10.1038/nature14059
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发表时间：
2015-01-01
期刊：
影响因子：
64.8
通讯作者：
Deininger, M.
中科院分区：
文献类型：
--
作者：
Boehm, E.;Lippold, J.;Deininger, M.
在最后一次冰期循环（14万年前至今）期间，极端的、突然的北方半球气候振荡受到海洋环流和大气强迫变化的调制（1）。然而，大西洋纬向翻转环流（AMOC）的变化，这在控制从低到高纬度的热量传输和海洋CO2储存的作用，仍然是有限的限制超出末次冰期最大（2-4）。在这里，我们表明，一个深而有力的翻转环流模式持续了大部分的末次冰期循环，在大西洋的海洋环流占主导地位，而较浅的冰川模式与南方来源的沃茨填充深西北大西洋盛行在冰川盛期（3，5）。我们的研究结果是基于重建的强度和方向的AMOC在末次冰期周期从一个高分辨率的海洋沉积记录在北大西洋西部深处。两个独立的化学水示踪剂（Pa-231/Th-230和Nd-143/Nd-144的同位素比值）（6-8）的平行测量结果显示，在最后两次冰期终止期间，AMOC的响应是一致的，它们不受全球循环变化的直接影响。任何与这一配置的重大偏差，导致AMOC减速，都仅限于海因里希天文台灾难性冰山排放期间的百年尺度的漂移。北大西洋深水形成的严重和多百年削弱只发生在海因里希stadials接近冰川最大的冰覆盖率增加，可能是由于淡水输入增加。相比之下，AMOC是相对不敏感的亚千年融水脉冲在温暖的气候状态，和活跃的AMOC占上风，在Dansgaard-Oeschger interstadials（格陵兰温暖时期）。
Extreme, abrupt Northern Hemisphere climate oscillations during the last glacial cycle (140,000 years ago to present) were modulated by changes in ocean circulation and atmospheric forcing(1). However, the variability of the Atlantic meridional overturning circulation (AMOC), which has a role in controlling heat transport from low to high latitudes and in ocean CO2 storage, is still poorly constrained beyond the Last Glacial Maximum(2-4). Here we show that a deep and vigorous overturning circulation mode has persisted for most of the last glacial cycle, dominating ocean circulation in the Atlantic, whereas a shallower glacial mode with southern-sourced waters filling the deep western North Atlantic prevailed during glacial maxima(3,5). Our results are based on a reconstruction of both the strength and the direction of the AMOC during the last glacial cycle from a highly resolved marine sedimentary record in the deep western North Atlantic. Parallel measurements of two independent chemical water tracers (the isotope ratios of Pa-231/Th-230 and Nd-143/Nd-144)(6-8), which are not directly affected by changes in the global cycle, reveal consistent responses of the AMOC during the last two glacial terminations. Any significant deviations from this configuration, resulting in slowdowns of the AMOC, were restricted to centennial-scale excursions during catastrophic iceberg discharges of the Heinrich stadials. Severe and multicentennial weakening of North Atlantic Deep Water formation occurred only during Heinrich stadials close to glacial maxima with increased ice coverage, probably as a result of increased freshwater input. In contrast, the AMOC was relatively insensitive to sub-millennial meltwater pulses during warmer climate states, and an active AMOC prevailed during Dansgaard-Oeschger interstadials (Greenland warm periods).