NASA
Nasa: Artic Sea Ice Continues to Decline
Great animation showing the transformation of Artic sea ice can be found here. Different explanations of this phenominon are also offered on this site.
University Corporation for Atmospheric Research
Ucar: Why the Polar Vortex Keeps Breaking Out of the Arctic
Why does the Polar Vortex keep breaking out of the Arctic? Surprisingly, warming global temperatures play a role.