Climate variability on centennial timescales has often been linked to internal variability of the Atlantic Meridional Overturning Circulation (AMOC). However, due to the scarceness of suitable paleoclimate proxies and long climate model simulations, large uncertainties remain on the magnitude and physical mechanisms driving centennial-scale AMOC variability. For these reasons, we perform a systematic multi-model comparison of centennial-scale AMOC variability in pre-industrial control simulations of state-of-the-art global climate models. Six out of nine models in this study exhibit a statistically significant mode of centennial-scale AMOC variability. Our results show that freshwater exchanges between the Arctic Ocean and the North Atlantic provide a plausible driving mechanism in a subset of models, and that AMOC variability can be amplified by ocean–sea ice feedbacks in the Labrador Sea. The amplifying mechanism is linked to sea ice cover biases, which could provide an observational constraint for centennial-scale AMOC variability.

中文翻译：

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受北极-北大西洋相互作用和海冰偏差影响的 CMIP6 模型中大西洋经向翻转环流的百年尺度变率


百年时间尺度上的气候变率通常与大西洋经向翻转环流 （AMOC） 的内部变率有关。然而，由于合适的古气候替代物和长期气候模式模拟的稀缺，驱动百年尺度 AMOC 变率的幅度和物理机制仍然存在很大的不确定性。出于这些原因，我们在最先进的全球气候模型的工业前控制模拟中对百年尺度的 AMOC 变率进行了系统的多模型比较。本研究的 9 个模型中有 6 个表现出具有统计学意义的百年尺度 AMOC 变异性模式。我们的结果表明，北冰洋和北大西洋之间的淡水交换在模型子集中提供了一种合理的驱动机制，并且 AMOC 变异性可以被拉布拉多海的海冰反馈放大。放大机制与海冰覆盖偏差有关，这可能为百年尺度的 AMOC 变率提供观测约束。