Atlantic multidecadal variability modulates extratropical summer heatwaves

Journal article

Atlantic multidecadal variability (AMV) is a well-known mode of climate variability with well-understood impacts on several aspects of Northern Hemisphere climate. However, its impact on heatwaves, a type of heat extremes that is increasingly affecting human societies, remains less well understood. The influence of AMV on extratropical summer heatwaves in the Northern Hemisphere is analyzed with a suite of coupled climate model experiments from the Decadal Climate Prediction Project. Our analysis suggests that AMV exerts substantial influence on the heatwave frequency (HWF) and heatwave number (HWN) of heatwaves over subtropics and midlatitudes in the Northern Hemisphere. Compared to the widespread seasonal mean warming response, these heatwave hotspots are less expansive geographically. The warm AMV phase (AMV+) as opposed to the cold phase (AMV−) drives a global stationary wave anomaly that links hotspots of HWF and HWN increases over North America, North Africa, central/western Asia, and parts of East Asia. Such dynamic impacts of AMV on heatwaves are more significant than the thermodynamic impacts of a warmer ocean surface. Hence, mean surface warming alone due to the warming effects of AMV+ versus AMV− does not necessarily equate to more frequent heatwaves. Furthermore, precipitation and surface heat fluxe responses further amplify the HWF increases. By further comparing the tropical and extratropical portions of AMV imposed in model simulations, we emphasize that linear and nonlinear interactions of these features strongly shape the impacts of AMV. We further discuss the mechanisms for and causes of model-observation discrepancies and inter-model uncertainties in the influence of AMV on atmospheric circulation and summer heatwaves, in terms of atmospheric circulation response in North Atlantic-Europe and jet waveguide effects. This highlights some challenges in pinpointing the influence of AMV on heatwaves, and improved understanding of it is necessary for more accurate predictions and projections of heatwaves.

Authors: Ye, K; Woollings, T

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: IOP Publishing
• Journal: Environmental Research Letters
• Volume: 21
• Issue: 11
• Pages: 114001
• Article number: 114001
• Publication date: 2026-05-27
• Acceptance date: 2026-04-24
• DOI: 10.1088/1748-9326/ae6463
• EISSN: 1748-9326
• ISSN: 1748-9326
• Language: English
• Keywords: land surface and heat fluxes; heatwave; linear and nonlinear interactions; Atlantic multidecadal variability; atmospheric circulation