资源环境科技发展态势分析平台

The Walker circulation (WC) responds to CO₂ forcing at both short and long timescales. In climate models, the fast response accounts for a substantial portion of the total responses, but its mechanisms, particularly those pertaining to air-sea interactions, remain unclear. We find contrasting fast WC responses in the first two years of abrupt CO₂ forcing, determined by the models’ air-sea coupling strength in the equatorial Pacific. In models with a strong coupling, wind anomalies induced by the instantaneous land-sea thermal contrast trigger a Bjerknes feedback, leading to cooling in the equatorial Pacific and WC strengthening. The WC weakens gradually as the Bjerknes feedback wanes and the subsurface warm pool water migrates eastward as Kelvin waves. In models with a weaker coupling, the WC weakens monotonically. Our results suggest that the inter-model discrepancy in WC changes is associated with the uncertainty in the fast component.