The Evolving Role of External Forcing in North Atlantic SST Variability Over the Last Millennium
The Evolving Role of External Forcing in North Atlantic SST Variability Over the Last Millennium
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DOI：
10.1175/jcli-d-21-0338.1
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发表时间：
2022-01
影响因子：
4.9
通讯作者：
J. Klavans;A. Clement;M. Cane;Lisa N. MURPHYb
中科院分区：
文献类型：
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作者：
J. Klavans;A. Clement;M. Cane;Lisa N. MURPHYb
大西洋多年代际变率（AMV）影响大西洋盆地两侧的温度，降水和极端事件。以前的气候模式研究表明，当外部辐射强迫保持不变时，大尺度海洋和大气环流与海表温度异常有关，这些异常具有与观测到的AMV相似的特征。然而，有一个积极的辩论，这些内部波动驱动的耦合大气-海洋变率是否仍然影响AMV在我们的现代，人为强迫的气候在几十年的时间尺度。在这里，我们提供了证据，从多个大型合奏的气候模式，古重建，仪器观测的外部强迫在AMV中的作用越来越大。在1850年之前，主要来自火山的外部强迫解释了大约三分之一的AMV方差。1850年至1950年间，存在一个过渡期，外部强迫解释了AMV方差的一半，但火山强迫仅占其中的10%左右。1950年以后，外部强迫解释了四分之三的AMV方差。也就是说，外部强迫在AMV中的作用随着外部强迫变化的增加而增加，即使强迫来自不同的来源。当强迫相对稳定时，如在早期的模拟研究中，内部产生的AMV变化的百分比较高。
Atlantic Multidecadal Variability (AMV) impacts temperature, precipitation, and extreme events on both sides of the Atlantic basin. Previous studies with climate models have suggested that when external radiative forcing is held constant, the large-scale ocean and atmosphere circulation are associated with sea-surface temperature anomalies that have similar characteristics to the observed AMV. However, there is an active debate as to whether these internal fluctuations driven by coupled atmosphere-ocean variability remain influential to the AMV on multidecadal timescales in our modern, anthropogenically-forced climate. Here we provide evidence from multiple large ensembles of climate models, paleo reconstructions, and instrumental observations of a growing role for external forcing in the AMV. Prior to 1850, external forcing, primarily from volcanoes, explains about one third of AMV variance. Between 1850 and 1950, there is a transitional period, where external forcing explains half of AMV variance, but volcanic forcing only accounts for about 10% of that. After 1950, external forcing explains three quarters of AMV variance. That is, the role for external forcing in the AMV grows as the variations in external forcing grow, even if the forcing is from different sources. When forcing is relatively stable, as in earlier modeling studies, a higher percentage of AMV variations are internally generated.