Blocking ridges occur naturally, but are uncommon over Greenland this time of year. According to NOAA's Climate Prediction Center, blocking near the longitude of Greenland (50°W) only occurs about 2% of the time in the fall. These odds rise to about 6% in winter and spring. As I discussed in an April post, Arctic sea ice loss tied to unusual jet stream patterns, three studies published in the past year have found that the jet stream has been getting stuck in unusually strong blocking patterns in recent years. These studies found that the recent record decline in Arctic sea ice could be responsible, since this heats up the pole, altering the Equator-to-pole temperature difference, forcing the jet stream to slow down, meander, and get stuck in large loops. The 2012 Arctic sea ice melt season was extreme, with sea ice extent hitting a record lows. Could sea ice loss have contributed to the blocking ridge that steered Sandy into New Jersey? It is possible, but we will need to much more research on the subject before we make such a link, as the studies of sea ice loss on jet stream patterns are so new. The author of one of the new studies, Dr. Jennifer Francis of Rutgers, had this say in a recent post by Andy Revkin in his Dot Earth blog: "While it’s impossible to say how this scenario might have unfolded if sea-ice had been as extensive as it was in the 1980s, the situation at hand is completely consistent with what I’d expect to see happen more often as a result of unabated warming and especially the amplification of that warming in the Arctic."