This is the best animation I’ve seen of changes in Arctic Sea Ice. The video clearly shows the dramatic seasonal changes in sea ice cover, as well as the general decline in sea ice extent. Perhaps most importantly it captures the reduction of old ice. The decline of multiyear ice reveals how weak the ice coverage has become, older ice that survives the summer provides stability by creating thicker and stronger ice. Thanks to NOAA Climate Services for putting this together:
The sea ice declines are accentuated by the albedo feedback. Open ocean water has a significantly darker surface than an ice covered sea and therefore absorbs much more of the sun’s heat than the reflective ice covering. This creates a positive feedback whereby the extra absorbed solar radiation triggers further sea ice melt.
A recent study in Nature suggests that both the duration and magnitude of the current decline in sea ice is seemingly unprecedented for the past 1450 years . An ice free Arctic in the summer may occur within the next 30 years .
There has been speculation of a possible Arctic sea-ice ‘tipping point’, whereby a threshold is reached such that sea-ice loss is irreversible leading to permanent ice free summers. However, recent modelling studies suggest this is not the case and that sea-ice recovery from a prescribed ice-free summer is possible within two years (see  and ).
A great resource for tracking sea ice changes and further reliable information on this topic is the National Snow & Ice Data Center (NSIDC) website.
There is also a free iphone app called Arctic Watch that uses data from the National Oceanic and Atmospheric Association (NOAA) and provides daily updates on Arctic sea ice area (you have to pay $0.99 for the Antarctic data).