Interaction between Atlantic cyclones and Eurasian atmospheric blocking drives wintertime warm extremes in the high Arctic

Abstract. Atmospheric blocking can influence Arctic weather by diverting the mean westerly flow and steering cyclones polewards, bringing warm, moist air to high latitudes. Recent studies have shown that diabatic heating processes in ascending warm conveyor belt branch of extratropical are relevant dynamics. This leads question extent which associated with mid-latitude may high-latitude drive events. In this study we investigate dynamics behind 50 extreme events wintertime high-Arctic temperature anomalies during 1979–2016. Classifying based on occurrence within three selected sectors, find 30 these a block over Urals, featuring negative upper-level potential vorticity (PV) central Siberia north Ural Mountains. Lagrangian back-trajectory calculations show almost 60 % parcels making up PV experience lifting (median 11 K) 6 d prior block. Further, 70 heated trajectories undergo maximum compact region North Atlantic, temporally taking place between 1 before arriving region. We also anomalously cyclone activity (on average five 5 window) sector northwest main domain. addition, 10 Scandinavia. Around back started from blocks heating, Atlantic but generally closer time arrival further upstream relative blocking. suggests that, addition ability guide northwards, play significant role providing low-PV via moist-diabatic processes. emphasizes importance mutual interactions Eurasian for extremes.