
end of the summer thaw. In September 2007, Arctic sea-ice extent was the smallest area on
record since satellites began collecting measurements about 30 years ago. (a) Although a
cold winter allowed sea ice to cover much of the Arctic in the following months, this pair
of images shows the drastic change in conditions. On the right (February 2008), the ice pack
contained much more young ice than the long-term average (left). In the past, more ice sur-
vived the summer melt season and had an opportunity to thicken over the following win-
ter. The area and thickness of sea ice that survives the summer has been declining over