Reconciling two alternative mechanisms behind bi-decadal variability in the North Atlantic
Reconciling two alternative mechanisms behind bi-decadal variability in the North Atlantic
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DOI：
10.1016/j.pocean.2015.06.009
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发表时间：
2015-09
影响因子：
4.1
通讯作者：
P. Ortega;J. Mignot;D. Swingedouw;F. Sévellec;E. Guilyardi
中科院分区：
文献类型：
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作者：
P. Ortega;J. Mignot;D. Swingedouw;F. Sévellec;E. Guilyardi
了解北大西洋变率的优先时间尺度，通常与大西洋纬向翻转环流（AMOC），是十年预测的前景至关重要的。然而，从对气候模拟的分析中提出的各种各样的机制，可能取决于模型本身，激发了关于哪些过程在现实中发生的辩论。一个机制越来越受到关注，在理想化的模式和观测，是一个向西传播的地下浮力异常，影响AMOC通过一个盆地尺度的纬向密度梯度的强化，增强了向北的transportviathermal风平衡。在这项研究中，我们重新审视了控制模拟研究所皮埃尔-西蒙拉普拉斯耦合模型5A（IPSL-CM 5A），其特征在于一个强大的AMOC周期在20年，以前解释了上层海洋-大气-海冰耦合模式驱动对流活动的冰岛南部。我们的研究表明，这种机制建设性地与盆地范围内的传播在地下相互作用。这种建设性的反馈可以解释为什么在这个耦合模式中的年代际变率是如此强烈，与其他模式相比。
Understanding the preferential timescales of variability in the North Atlantic, usually associated with the Atlantic meridional overturning circulation (AMOC), is essential for the prospects for decadal prediction. However, the wide variety of mechanisms proposed from the analysis of climate simulations, potentially dependent on the models themselves, has stimulated the debate of which processes take place in reality. One mechanism receiving increasing attention, identified both in idealized models and observations, is a westward propagation of subsurface buoyancy anomalies that impact the AMOC through a basin-scale intensification of the zonal density gradient, enhancing the northward transportviathermal wind balance. In this study, we revisit a control simulation from the Institut Pierre-Simon Laplace Coupled Model 5A (IPSL-CM5A), characterized by a strong AMOC periodicity at 20 years, previously explained by an upper ocean–atmosphere–sea ice coupled mode driving convection activity south of Iceland. Our study shows that this mechanism interacts constructively with the basin-wide propagation in the subsurface. This constructive feedback may explain why bi-decadal variability is so intense in this coupled model as compared to others.