Nonlinear responses of the winter warm Arctic-cold Eurasia pattern to multi-year La Niña

Abstract

Multi‐year La Niña events have been observed frequently and exert a significant influence on weather extremes in the mid‐high latitudes of the Northern Hemisphere. However, how different durations of La Niña affect winter surface air temperatures over the Arctic and Eurasia, specifically the warm Arctic‐cold Eurasia (WACE) pattern, remains poorly understood. Using reanalysis and model outputs, this study reveals that double‐year La Niña produces a WACE pattern with a strong cold anomaly over east‐central Eurasia, whereas triple‐ and single‐year events produce weaker thermal responses. Thus, the responses of winter Eurasian temperatures to triple‐, double‐, and single‐year La Niña events are nonlinear due to their association with changes in Ural‐Siberian blocking dynamics. Coupled model intercomparison project phase 6 (CMIP6) model outputs and CESM2 Pacific Pacemaker ensemble experiments, despite biases, broadly reproduce the observed nonlinearity and support the reanalysis results.