Take a second and watch older Arctic sea ice -- represented by white and lighter colors -- expand and retreat in this animation. By the end of the time-lapse, it's strikingly clear that older sea ice has declined dramatically since 1987.
Scientists refer to older ice as "multi-year" ice, meaning that it has survived at least one summer melting season and is thicker than younger ice. In this video, the older sea ice is represented by the lighter colors, with the color white signaling ice that is more than nine years old.
"Wind and ocean circulation patterns are conspiring with a warmer climate to reduce the amount of year-round (multi-year) ice, transforming the remaining ice into a younger, thinner version of its old self," explains NOAA.
A new study published this month found that the summer melting season has increased by about a month since 1979. Additionally, the maximum extent of Arctic sea ice at its annual low-point in September has decreased by 40 percent since the 1970s, report researchers at the Scripps Institution of Oceanography at the University of California, San Diego.