On the role of Ural Blocking in driving the Warm Arctic–Cold Siberia pattern

We use reanalysis data to substantiate the role of Ural Blocking (UB) in driving the Warm Arctic‐Cold Siberia (WACS) pattern, which represents an anti‐correlation of surface temperature between the Barents‐Kara Seas and Central Asia. We confirm a robust link between UB and the WACS pattern on daily to sub‐seasonal timescales. UB controls the pace of the WACS; warming over the Barents‐Kara Seas and cooling over Central Asia peak 3‐5 days after the UB onset. The observed sea‐ice deficit over the Barents‐Kara Seas in the weeks prior to UB onset is not statistically significant when the long‐term trend in sea‐ice is removed. Thus, the sea‐ice deficit may not have a direct impact on UB occurrence but it develops as a delayed response to UB. The interannual variability of WACS is also strongly linked to UB. We identify an upward trend in wintertime UB in recent decades that accounts for a cooling rate of 1∘C/decade over Central Asia. Over the Barents‐Kara Seas, UB trends explain a small fraction of the warming, which is dominated by Arctic Amplification. Finally, the link between UB and the WACS is statistically robust over the ERA‐Interim period but weaker during the 1990s when the lowest activity of UB Episodes was observed.