Quantifying the influence of Barents-Kara sea ice loss on Ural blocking

Arctic amplification has been linked to significant changes in mid-latitude weather patterns, including the increasing frequency and persistence of extreme weather events. This study investigates the influence of Barents-Kara (BK) sea-ice variability on wintertime Ural blocking and its role in Eurasian cold temperature anomalies. Using ERA5 reanalysis data, we analyse Ural blocking frequency and persistence based on two commonly used blocking indices (an absolute geopotential height reversal index and an anomaly-based index method). The relationships between BK sea ice, Ural blocking, and Eurasian surface temperature are examined within a causal network framework, accounting for ENSO as a potential common driver by including it as a covariate and by stratifying the analysis by ENSO phase. We find that Ural blocking events occur more frequently and persist longer during winters with reduced BK sea ice. Although, results are sensitive to blocking index but remain qualitatively consistent and robust across indices. Composite analyses show a characteristic warm-Arctic/cold-Eurasia temperature pattern during Ural blocking events, which is amplified during winters with low BK sea ice and La Niña conditions. To assess whether Ural blocking is influenced by specific Arctic background conditions, we further classify winters into Deep and Shallow Arctic warming regimes over the Barents-Kara region. We find that Ural blocking occurs more frequently and is more persistent under Deep Arctic warming states, leading to a stronger cold-Eurasia temperature response compared to Shallow warming regimes. By statistically quantifying the relationships between Arctic sea ice, Ural blocking, and Eurasian temperature variability, this work advances the understanding of Arctic-midlatitude interactions.

Keywords: Arctic Amplification, Ural blocking, Barents-Kara sea ice, ENSO, Blocking indices, Blocking frequency and persistence, Eurasian cold winters.