Solar forcing of North Atlantic surface temperature and salinity over the past millennium
Solar forcing of North Atlantic surface temperature and salinity over the past millennium
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DOI：
10.1038/ngeo2094
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发表时间：
2014-04-01
影响因子：
18.3
通讯作者：
Barker, Stephen
中科院分区：
文献类型：
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作者：
Moffa-Sanchez, Paola;Born, Andreas;Barker, Stephen
在过去的1000年里，北大西洋地区的气候和海洋状况出现了几次百年尺度的波动，其中包括从公元1450年到1850年左右的一个相对寒冷的时期，被称为小冰期（1）。这些变化可能与太阳辐照度的变化有关，并通过包括大西洋经向翻转环流在内的反馈作用被放大（2）。大西洋经向翻转环流回流分支的变化反映在冰岛南部混合层底部的水体性质上。在这里，我们利用从一个具有亚十年分辨率的海洋沉积岩芯中获取的有孔虫壳体的δO - 18和Mg/Ca比值的配对测量值，重建了该地区从公元818年到1780年的温跃层温度和盐度。重建的水文百年尺度变化与总太阳辐照度的变化相关。我们在对过去1000年气候的模拟中发现了类似的相关性。我们推断水文变化可能反映了与大气环流变化相关的亚极地环流强度的变化。具体来说，在模拟中，低太阳辐照度促进了频繁且持续的大气阻塞事件的发展，在这些事件中，北大西洋东部的一个准静止高压系统改变了西风的流动。我们得出结论，这个过程可能导致了小冰期期间欧洲有记录的连续寒冷冬季。
There were several centennial-scale fluctuations in the climate and oceanography of the North Atlantic region over the past 1,000 years, including a period of relative cooling from about AD 1450 to 1850 known as the Little Ice Age(1). These variations may be linked to changes in solar irradiance, amplified through feedbacks including the Atlantic meridional overturning circulation(2). Changes in the return limb of the Atlantic meridional overturning circulation are reflected in water properties at the base of the mixed layer south of Iceland. Here we reconstruct thermocline temperature and salinity in this region from AD 818 to 1780 using paired delta O-18 and Mg/Ca ratio measurements of foraminifer shells from a subdecadally resolved marine sediment core. The reconstructed centennial-scale variations in hydrography correlate with variability in total solar irradiance. We find a similar correlation in a simulation of climate over the past 1,000 years. We infer that the hydrographic changes probably reflect variability in the strength of the subpolar gyre associated with changes in atmospheric circulation. Specifically, in the simulation, low solar irradiance promotes the development of frequent and persistent atmospheric blocking events, in which a quasi-stationary high-pressure system in the eastern North Atlantic modifies the flow of the westerly winds. We conclude that this process could have contributed to the consecutive cold winters documented in Europe during the Little Ice Age.