Decadal predictions of the cooling and freshening of the North Atlantic in the 1960s and the role of ocean circulation
Decadal predictions of the cooling and freshening of the North Atlantic in the 1960s and the role of ocean circulation
复制标题
DOI：
10.1007/s00382-014-2115-7
复制
发表时间：
2014-03
期刊：
影响因子：
4.6
通讯作者：
J. Robson;R. Sutton;Doug M. Smith
中科院分区：
文献类型：
--
作者：
J. Robson;R. Sutton;Doug M. Smith
1960年代，北大西洋海面温度（SST）迅速冷却。北大西洋副极地环流（SPG）的冷却幅度最大，并与SPG的快速清新相一致。在这里，我们分析后报的20世纪60年代北大西洋冷却与英国气象局的十年预测系统（DePreSys），这是初始化使用的观测。结果表明，DePreSys捕获的提前几年的时间观察到的冷却和清新的北大西洋SPG。DePreSys还捕获了更广泛的北大西洋SST的变化以及更广泛区域的地表气候影响，例如冬季大气环流和海冰范围的变化。我们发现，初始化的一个非常弱的大西洋经向翻转环流（AMOC），因此弱向北的热量输送，是至关重要的DePreSys预测所观察到的冷却的大小。当海洋观测数据没有被同化时，这种非常弱的AMOC就不会被捕获（即它不是本模式中的强迫响应）。SPG的淡化也主要是由DePreSys中的海洋盐输运变化决定的;特别是，模拟平流淡水异常类似于大盐度异常是关键。因此，DePreSys认为海洋动力学在20世纪60年代北大西洋的冷却中发挥了重要作用，并且这一事件是可以预测的。
In the 1960s North Atlantic sea surface temperatures (SST) cooled rapidly. The magnitude of the cooling was largest in the North Atlantic subpolar gyre (SPG), and was coincident with a rapid freshening of the SPG. Here we analyze hindcasts of the 1960s North Atlantic cooling made with the UK Met Office’s decadal prediction system (DePreSys), which is initialised using observations. It is shown that DePreSys captures—with a lead time of several years—the observed cooling and freshening of the North Atlantic SPG. DePreSys also captures changes in SST over the wider North Atlantic and surface climate impacts over the wider region, such as changes in atmospheric circulation in winter and sea ice extent. We show that initialisation of an anomalously weak Atlantic Meridional Overturning Circulation (AMOC), and hence weak northward heat transport, is crucial for DePreSys to predict the magnitude of the observed cooling. Such an anomalously weak AMOC is not captured when ocean observations are not assimilated (i.e. it is not a forced response in this model). The freshening of the SPG is also dominated by ocean salt transport changes in DePreSys; in particular, the simulation of advective freshwater anomalies analogous to the Great Salinity Anomaly were key. Therefore, DePreSys suggests that ocean dynamics played an important role in the cooling of the North Atlantic in the 1960s, and that this event was predictable.