The impact of resolution on the adjustment and decadal variability of the Atlantic meridional overturning circulation in a coupled climate model
The impact of resolution on the adjustment and decadal variability of the Atlantic meridional overturning circulation in a coupled climate model
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DOI：
10.1007/s00382-012-1309-0
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发表时间：
2012-12-01
期刊：
影响因子：
4.6
通讯作者：
Sutton, Rowan T.
中科院分区：
文献类型：
--
作者：
Hodson, Daniel L. R.;Sutton, Rowan T.
大西洋经向翻转环流（MOC）的变化对气候产生重要影响，特别是在年代际尺度上。由于在解决所涉及的一些关键过程时缺乏保真度，耦合气候模型中的 MOC 模拟受到了影响，达到了未知的程度。迫切需要提高气候模型的分辨率和保真度，同时还需要评估分辨率的提高如何影响 MOC 等关键现象的模拟。在本研究中，我们通过比较同一模型的高分辨率和低分辨率版本，研究显着提高耦合气候模型（海洋和大气）分辨率对 MOC 变化模拟的影响。在这两个版本中，MOC 的年代际变化与从拉布拉多海沿西部深处边界向南传播的密度异常密切相关。我们证明，由于西边边界波的速度增加，MOC 调整在更高分辨率的模型中进行得更快。然而，大西洋海面温度对 MOC 变化的响应在两种分辨率上即使不是幅度上也相对稳健。 MOC 还在两个模型版本中激发了热带大西洋的海洋-大气耦合响应。在高分辨率模型中，但在低分辨率模型中，有证据表明，在 MOC 达到最大值 6 年后，北大西洋上空的温带大气发生了显着的响应。在这两个模型中，都有证据表明拉布拉多海的深层密度异常存在微弱的负反馈，因此 MOC 也存在微弱的负反馈（时间尺度约为十年）。我们的结果强调需要进一步开展工作来了解 MOC 的年代际变化及其在气候模型中的模拟。
Variations in the Atlantic meridional overturning circulation (MOC) exert an important influence on climate, particularly on decadal time scales. Simulation of the MOC in coupled climate models is compromised, to a degree that is unknown, by their lack of fidelity in resolving some of the key processes involved. There is an overarching need to increase the resolution and fidelity of climate models, but also to assess how increases in resolution influence the simulation of key phenomena such as the MOC. In this study we investigate the impact of significantly increasing the (ocean and atmosphere) resolution of a coupled climate model on the simulation of MOC variability by comparing high and low resolution versions of the same model. In both versions, decadal variability of the MOC is closely linked to density anomalies that propagate from the Labrador Sea southward along the deep western boundary. We demonstrate that the MOC adjustment proceeds more rapidly in the higher resolution model due the increased speed of western boundary waves. However, the response of the Atlantic sea surface temperatures to MOC variations is relatively robust-in pattern if not in magnitude-across the two resolutions. The MOC also excites a coupled ocean-atmosphere response in the tropical Atlantic in both model versions. In the higher resolution model, but not the lower resolution model, there is evidence of a significant response in the extratropical atmosphere over the North Atlantic 6 years after a maximum in the MOC. In both models there is evidence of a weak negative feedback on deep density anomalies in the Labrador Sea, and hence on the MOC (with a time scale of approximately ten years). Our results highlight the need for further work to understand the decadal variability of the MOC and its simulation in climate models.