Large‐scale circulation associated with moisture intrusions into the Arctic during winter

We examine the poleward transport of water vapor across 70°N during boreal winter in the ERA‐Interim reanalysis product, focusing on intense moisture intrusion events. We analyze the large‐scale circulation patterns associated with these intrusions and the impacts they have at the surface. A total of 298 events are identified between 1990 and 2010, an average of 14 per season, accounting for 28% of the total poleward transport of moisture across 70°N. They are concentrated over the main ocean basins at that latitude in the Labrador Sea, North Atlantic, Barents/Kara Sea, and Pacific. Composites of sea level pressure and potential temperature on the 2 potential vorticity unit surface during intrusions show a large‐scale blocking pattern to the east of each basin, deflecting midlatitude cyclones and their associated moisture poleward. The interannual variability of intrusions is strongly correlated with variability in winter‐mean surface downward longwave radiation and skin temperature averaged over the Arctic.