Decadal Variability of Interacting Climate Subsystems in the Northern Hemisphere

加强对北半球年代际气候变化的了解是一个具有巨大社会意义的问题。该项目的目标是记录模拟的年代际变化，并在全球气候模型模拟中分析年代际气候变化的动力学。使用一种新的混合动力学/统计建模框架来研究年代际气候变化的动力学，并将它们与在较短的季节内到年际时间尺度上运行的气候过程联系起来，这项工作将深入了解气候系统的各种组成部分如何相互作用。研究人员假设，十年气候变化--定义为气候长期状态和变异性的突然变化，往往以十年为频率发生--是由于气候网络中同步状态的出现和可变耦合强度之间的相互作用，导致气候子系统的集体行为的结果。这一机制与同步混沌理论相一致，似乎是一种在气候系统中运行的非常强大的机制。它在仪器记录、强迫和非强迫气候模拟以及跨越几个世纪的代理记录中都有发现。在以年代际时间尺度为主的缓慢变化的大西洋子午线翻转环流(AMOC)的某些阶段，气候子系统同步/耦合其季节内‘节拍’的趋势似乎得到了加强。因此，这项工作将提供与综合气候模型模拟的耦合气候子系统有关的北半球气候可预测性的定量估计。

Improved understanding of Northern Hemisphere decadal climate variability is an issue of tremendous societal importance. The goal of this project is to document simulated decadal variability and to analyze the dynamics of decadal climate shifts in global climate model simulations. Using a novel hybrid dynamical/statistical modeling framework to study the dynamics of the decadal climate shifts and relate them to climate processes operating on shorter, intraseasonal-to-interannual time scales, this work will shed insights into how various components of the climate system interact. The researchers hypothesize that decadal climate shifts - defined as abrupt changes in the climates long-term state and variability that tend to happen with decadal frequency - arise as a result of collective behavior of climate subsystems due to interplay between occurrences of synchronized states and variable coupling strength within the climate network. This mechanism, which is consistent with the theory of synchronized chaos, appears to be a very robust mechanism operating in the climate system. It has been found in instrumental records, in forced and unforced climate simulations, as well as in proxy records spanning several centuries. The tendency for the climate subsystems to synchronize/couple their intra-seasonal 'beats' appears to be enhanced in certain phases of the slowly varying Meridional Overturning Circulation in the Atlantic (AMOC), which is dominated by the decadal time scales. This work will thus provide quantitative estimates of climate predictability in the Northern Hemisphere associated with the coupled climate subsystems simulated by comprehensive climate models.