What question did this study set out to answer?

This research aims to understand how strong positive Arctic Oscillation conditions impact the persistence of Ural blocking events.

March 26, 2026Open Access

Enhanced persistence of Ural blocking under strong positive AO: the role of North Atlantic storm tracks and potential vorticity dynamics

Key Points

This research aims to understand how strong positive Arctic Oscillation conditions impact the persistence of Ural blocking events.
Analysis of Ural blocking events during varying magnitudes of the Arctic Oscillation.
Comparison of persistence durations under strong positive and weak positive AO conditions.
Examination of the role of North Atlantic storm tracks and thermodynamic feedback mechanisms.
Ural blocking events last significantly longer during strong positive Arctic Oscillation conditions (6.1 days compared to 4.7 days for weak positive AO).
Enhanced persistence is linked to organized North Atlantic storm tracks bringing heat and moisture to the Barents–Kara Sea.
Thermodynamic feedback from Arctic warming and sea ice loss weakens the potential vorticity gradient, stabilizing Ural blocking.

Abstract

Ural blocking (UB) and the associated Warm Arctic–Cold Eurasia (WACE) pattern are typically linked to the negative Arctic Oscillation (AO). However, robust UB events are surprisingly observed even during the positive AO phase, a condition generally expected to suppress blocking due to enhanced zonal flow. This study investigates how positive AO magnitude modulates UB persistence. We find that under strong positive AO conditions (AO > +1), UB events persist significantly longer (6.1 days) than weak positive AO (4.7 days). This enhanced persistence results from organized North Atlantic storm tracks that facilitate intense heat and moisture into the Barents–Kara Sea. The resulting Arctic warming and sea ice loss trigger a thermodynamic feedback loop that weakens the meridional potential vorticity (PV) gradient, effectively anchoring the UB system. Our findings reveal that strong positive AO paradoxically promotes persistent blocking through storm-PV coupling, offering critical insights for improving sub-seasonal predictions of Eurasian winter extremes.

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