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. Recent studies suggested significant impacts of borealcryosphere changes on wintertime air stagnation and haze pollution extremesin China. However, the underlying mechanisms of such a teleconnectionrelationship remains unclear. Here we use the Whole Atmosphere CommunityClimate Model (WACCM) to investigate dynamic processes leading toatmospheric circulation and air stagnation responses to Arctic sea icechanges. We conduct four climate sensitivity experiments by perturbing seaice concentrations (SIC) and corresponding sea surface temperature (SST) inautumn and early winter over the whole Arctic and three subregions in theclimate model. The results indicate distinct responses in circulationpatterns and regional ventilation to the region-specific Arctic changes,with the largest increase of both the probability (by 132 %) and theintensity (by 30 %) of monthly air stagnation extremes being found in theexperiment driven by SIC and SST changes over the Pacific sector of theArctic (the East Siberian and Chukchi seas). The increased air stagnationextremes are mainly driven by an amplified planetary-scale atmosphericteleconnection pattern that resembles the negative phase of the Eurasian(EU) pattern. Dynamical diagnostics suggest that convergence of transienteddy forcing in the vicinity of Scandinavia in winter is largely responsiblefor the amplification of the teleconnection pattern. Transient eddyvorticity fluxes dominate the transient eddy forcing and produce abarotropic anticyclonic anomaly near Scandinavia and wave train propagationacross Eurasia to the downstream regions in East Asia. The piecewisepotential vorticity inversion analysis reveals that this long-rangeatmospheric teleconnection of Arctic origin takes place primarily via themiddle and upper troposphere. The anomalous ridge over East Asia in themiddle and upper troposphere worsens regional ventilation conditions byweakening monsoon northwesterlies and enhancing temperature inversions nearthe surface, leading to more and stronger air stagnation and pollutionextremes over eastern China in winter. Ensemble projections based onstate-of-the-art climate models in the Coupled Model Intercomparison ProjectPhase 6 (CMIP6) corroborate this teleconnection relationship betweenhigh-latitude environmental changes and midlatitude weather extremes,though the tendency and magnitude vary considerably among each participatingmodel.

Atmospheric teleconnection processes linking winter air stagnation and haze extremes in China with regional Arctic sea ice decline