A multi-model comparison of Atlantic multidecadal variability
A multi-model comparison of Atlantic multidecadal variability
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DOI：
10.1007/s00382-014-2056-1
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发表时间：
2014-11-01
期刊：
影响因子：
4.6
通讯作者：
Volodin, Evgeny
中科院分区：
文献类型：
--
作者：
Ba, Jin;Keenlyside, Noel S.;Volodin, Evgeny
对大西洋年代际变化进行了多模式分析，目的如下：调查与观测的相似性；评估Delworth等人提出的机制中不同要素的强度和相对重要性。(J Clim 6：1993-2011,1993)(以下简称D93)；并将模式差异与平均系统误差联系起来。这项分析是通过来自10个CGCM的长时间控制模拟进行的，这些CGCM的长度从500年到3600年不等。在大多数模式中，北大西洋平均海表温度(SST)的变化在几十年的时间尺度上表现出相当大的威力，但具有不同的周期性。中纬度地区海温变化最大，与仪器短记录一致。尽管模型配置存在很大差异，但我们发现模型之间在流程方面存在相当大的一致性。在十个模式中，有八个模式的中纬度SST变化与大西洋经向翻转环流(AMOC)的波动显著相关，这表明与向北的热量输送变化有关。与这一联系一致的是，AMOC最弱的三个模式在北大西洋具有最大的冷SST偏差。模式中AMOC与北大西洋涛动在年代际时间尺度上不存在线性关系。对D93机制的关键要素的分析揭示如下：大多数模式提供了强有力的证据，表明高纬冬季混合先于AMOC变化。然而，冬季对流的区域在不同的模式中有所不同。在大多数模式中，对流区盐度引起的密度异常往往导致AMOC，而温度引起的密度异常只在一个模式中导致AMOC。然而，分析表明，盐度在大多数模式中可能扮演着非常重要的角色，因为它们相关对流区的冷温度偏差。在大多数模式中，亚极涡旋的变化往往会导致AMOC的变化，而且这种关系在超过一半的模式中表现得很强。
A multi-model analysis of Atlantic multidecadal variability is performed with the following aims: to investigate the similarities to observations; to assess the strength and relative importance of the different elements of the mechanism proposed by Delworth et al. (J Clim 6: 1993-2011, 1993) (hereafter D93) among coupled general circulation models (CGCMs); and to relate model differences to mean systematic error. The analysis is performed with long control simulations from ten CGCMs, with lengths ranging between 500 and 3600 years. In most models the variations of sea surface temperature (SST) averaged over North Atlantic show considerable power on multidecadal time scales, but with different periodicity. The SST variations are largest in the mid-latitude region, consistent with the short instrumental record. Despite large differences in model configurations, we find quite some consistency among the models in terms of processes. In eight of the ten models the mid-latitude SST variations are significantly correlated with fluctuations in the Atlantic meridional overturning circulation (AMOC), suggesting a link to northward heat transport changes. Consistent with this link, the three models with the weakest AMOC have the largest cold SST bias in the North Atlantic. There is no linear relationship on decadal timescales between AMOC and North Atlantic Oscillation in the models. Analysis of the key elements of the D93 mechanisms revealed the following: Most models present strong evidence that highlatitude winter mixing precede AMOC changes. However, the regions of wintertime convection differ among models. In most models salinity-induced density anomalies in the convective region tend to lead AMOC, while temperatureinduced density anomalies lead AMOC only in one model. However, analysis shows that salinity may play an overly important role in most models, because of cold temperature biases in their relevant convective regions. In most models subpolar gyre variations tend to lead AMOC changes, and this relation is strong in more than half of the models.