Last summer, I saved this Guardian article for future use. It reported that climate scientists were predicting harsh winters due to the decreasing Arctic sea ice. 2012 saw a record low in Arctic sea ice area, 50% below the long-term average. Sea ice volume had even decreased by 80%. This winter’s annual maximum extent of Arctic sea ice was the sixth-lowest on record.
The impacts of decreasing Arctic sea ice were inter alia analysed in a study by the Potsdam Institute for Climate Impact Research (PIK) in 2009 already and are further discussed by Stefan Rahmstorf in German blog posts here and here. When the study came out Rahmstorf opined that it was a modeling prediction that remained to be tested empirically. Several years with low sea ice and subsequent harsh winters later, the theory seems to be holding up rather well.
In nuce (if I got this correct), according to the PIK researchers, less sea ice means more heat being absorbed by the Arctic Ocean, which facilitates the development of a high-pressure area in the Arctic, which then transports cold air from Siberia to Europe. And as the cold air traverses large ice-free water areas, it absorbs huge amounts of humidity, which results in the huge amounts of snow we have seen.
Thanks to the same high pressure area Greenland is currently enjoying unseasonably warm weather. Averaged out across the Northern hemisphere, March has so far been a bit warmer than in recent years.