614 / 2024-09-18 16:27:10

Climate impacts of the Atlantic Multidecadal Variability in pacemaker experiments

Atlantic Multidecadal Variability,decadal climate changes,numerical experiment

Atlantic Multidecadal Variability (AMV) significantly influences regional and global climate, as evidenced by observations and climate model simulations. While previous studies primarily utilized atmosphere-only models or coupled simulations with fixed AMV patterns, this research employs pacemaker experiments using time-varying observational North Atlantic sea surface temperature (NASST) records. By analyzing high-pass data, we demonstrate that AMV's global impact stems mainly from its tropical component, with ten ensemble members sufficiently distinguishing forced signals from internal variability. The response to a warm AMV anomaly unfolds in four stages: (1) warm pool warming and Indo-Western Pacific easterly anomalies driven by tropical Atlantic diabatic heating, (2) eastward propagation of equatorial thermocline anomalies, leading to La Niña-like conditions in the eastern Pacific after 7-10 months, (3) persistent La Niña conditions for 11-20 months via Bjerknes feedback and Aleutian low weakening through tropical teleconnections, and (4) emergence of a negative Pacific Decadal Oscillation pattern in the North Pacific after 21-25 months. These findings underscore the importance of incorporating time-varying SST observations in pacemaker experiments to fully capture complex inter-basin interactions.