Abrupt ice-age shifts in southern westerly winds and Antarctic climate forced from the north
Abrupt ice-age shifts in southern westerly winds and Antarctic climate forced from the north
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DOI：
10.1038/s41586-018-0727-5
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发表时间：
2018-11-29
期刊：
影响因子：
64.8
通讯作者：
Steig, Eric J.
中科院分区：
文献类型：
--
作者：
Buizert, Christo;Sigl, Michael;Steig, Eric J.
南半球的中纬度西风通过南大洋上涌（1）、与深海的碳交换（2）、Agulhas泄漏（印度洋沃茨进入大西洋）（3）以及可能的南极冰盖稳定性（4）在全球气候系统中发挥核心作用。南半球西风的经向移动被假设为（5，6）与热带辐合带（7）的移动平行发生，以响应Dansgaard-Oeschger（DO）事件-最后一个冰河时代的北大西洋气候突变事件。移动到南极洲西部的水分路径（8）与这一观点一致，但可能代表了热带强迫的太平洋遥相关模式（9）。南半球大气环流对溶解氧循环的全面响应及其对南极温度的影响仍不清楚（10）。在这里，我们使用五个冰芯同步通过火山标志显示，南极温度对溶解氧循环的响应可以理解为两种模式的叠加：一个空间均匀的海洋“两极跷跷板”模式，落后于北方半球气候约200年，和一个空间异质的大气模式，是同步的突发事件在北方半球。大气模态的温度异常与现今南方环形模态的变化相类似，而不是太平洋-南美模式。此外，氘过量记录表明，南半球西风在所有海洋盆地的阶段与北方气候的纬向一致迁移。我们的工作为理解北方半球气候突变引起的环南极温度变化提供了一个简单的概念框架。我们提供了南半球西风突然转变的观测证据，这些证据先前已经记录了全球海洋环流和大气二氧化碳的（1-3）后果。这些相互关联的变化突出表明，有必要从全球而不是纯粹从北大西洋的角度来看待溶解氧循环。
The mid-latitude westerly winds of the Southern Hemisphere play a central role in the global climate system via Southern Ocean upwelling(1), carbon exchange with the deep ocean(2), Agulhas leakage (transport of Indian Ocean waters into the Atlantic)(3) and possibly Antarctic ice-sheet stability(4). Meridional shifts of the Southern Hemisphere westerly winds have been hypothesized to occur(5,6) in parallel with the well-documented shifts of the intertropical convergence zone(7) in response to Dansgaard-Oeschger (DO) events-abrupt North Atlantic climate change events of the last ice age. Shifting moisture pathways to West Antarctica(8) are consistent with this view but may represent a Pacific teleconnection pattern forced from the tropics(9). The full response of the Southern Hemisphere atmospheric circulation to the DO cycle and its impact on Antarctic temperature remain unclear(10). Here we use five ice cores synchronized via volcanic markers to show that the Antarctic temperature response to the DO cycle can be understood as the superposition of two modes: a spatially homogeneous oceanic 'bipolar seesaw' mode that lags behind Northern Hemisphere climate by about 200 years, and a spatially heterogeneous atmospheric mode that is synchronous with abrupt events in the Northern Hemisphere. Temperature anomalies of the atmospheric mode are similar to those associated with present-day Southern Annular Mode variability, rather than the Pacific-South American pattern. Moreover, deuterium-excess records suggest a zonally coherent migration of the Southern Hemisphere westerly winds over all ocean basins in phase with Northern Hemisphere climate. Our work provides a simple conceptual framework for understanding circum-Antarctic temperature variations forced by abrupt Northern Hemisphere climate change. We provide observational evidence of abrupt shifts in the Southern Hemisphere westerly winds, which have previously documented(1-3) ramifications for global ocean circulation and atmospheric carbon dioxide. These coupled changes highlight the necessity of a global, rather than a purely North Atlantic, perspective on the DO cycle.