Normally the Hudson Bay in Canada is frozen over by November. However, that did not happen until mid January this winter. Why did this occur? Normally the Arctic Oscillation (AO) traps cold air over the North Pole. This year the AO was weaker than normal. It allowed cold air to spill southward, while allowing warm air to move northward. Thus heavy snow fell in North America and Europe, and areas like Hudson Bay had a lower ice levels this year.
This image shows the average Arctic sea ice concentration for January 2011, based on observations from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA’s Aqua satellite. Blue indicates open water; white indicates high sea ice concentrations; and turquoise indicates loosely packed sea ice. The yellow line shows the average sea ice extent for January from 1979 through 2000.
via : Record Low Arctic Sea Ice Extent for January @ NASA Earth Observatory Image of the Day
