State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China.
University of Chinese Academy of Sciences, 100049, Beijing, China.
Nat Commun. 2021 Nov 11;12(1):6502. doi: 10.1038/s41467-021-26693-y.
The observational records have shown a strengthening of the Pacific Walker circulation (PWC) since 1979. However, whether the observed change is forced by external forcing or internal variability remains inconclusive, a solid answer to more societal relevantly question of how the PWC will change in the near future is still a challenge. Here we perform a quantitative estimation on the contributions of external forcing and internal variability to the recent observed PWC strengthening using large ensemble simulations from six state-of-the-art Earth system models. We find the phase transition of the Interdecadal Pacific Oscillation (IPO), which is an internal variability mode related to the Pacific, accounts for approximately 63% (~51-72%) of the observed PWC strengthening. Models with sufficient ensemble members can reasonably capture the observed PWC and IPO changes. We further constrain the projection of PWC change by using climate models' credit in reproducing the historical phase of IPO. The result shows a high probability of a weakened PWC in the near future.
观测记录显示，自 1979 年以来，太平洋 Walker 环流（PWC）一直在增强。然而，观测到的变化是由外部强迫还是内部变率引起的，仍不确定。对于更与社会相关的问题，即 PWC 在不久的将来将如何变化，一个明确的答案仍然是一个挑战。在这里，我们使用来自六个最先进的地球系统模型的大集合模拟，对外部强迫和内部变率对最近观测到的 PWC 增强的贡献进行了定量估计。我们发现，与太平洋有关的内部变率模态——跨年代际太平洋振荡（IPO）的相位转变，约占观测到的 PWC 增强的 63%（约 51-72%）。具有足够集合成员的模型可以合理地捕捉到观测到的 PWC 和 IPO 变化。我们进一步通过气候模型在复制历史时期 IPO 方面的可信度来限制 PWC 变化的预测。结果表明，在不久的将来，PWC 减弱的可能性很高。
