The age of Arctic sea ice can be determined using satellite observations and drifting buoy records to track the movement of ice floes, and can be a rough indicator for ice thickness.
This NOAA PMEL animation shows the age of the ice at the end of each winter since 1987. Paler colors indicate older ice, with light blue indicating 4-year ice to white indicating very old ice.
In the 1980’s, 26% of the Arctic winter ice pack consisted of thick ice built up over multiple years. After 2007, older ice diminishes rapidly and is replaced by younger ice. Starting in 2011, very old ice remains only along the Canadian coast.
At the end of winter 2014, only 10% of the ice pack was old ice, less than half the amount in the early 1980’s, and very old ice has become more rare. Learn more about Arctic Sea ice in 2014 in the Sea Ice article in the 2014 Arctic Report Card and visit PMEL's Arctic Research Page.