One significant change in the Arctic region in recent years has been the rapid decline in perennial sea ice. Perennial sea ice, also known as multi-year ice, is the portion of the sea ice that survives the summer melt season. Perennial ice may have a life-span of nine years or more and represents the thickest component of the sea ice; perennial ice can grow up to 4 meters thick. By contrast, first year ice that grows during a single winter is generally at most 2 meters thick.
This animation shows the Arctic sea ice age for the week of the minimum ice extent for each year, depicting the age in different colors. Younger sea ice, or first-year ice, is shown in a dark shade of blue while the ice that is 5 or more years old is shown as white. A color scale identifies the age of the intermediary years. A bar graph displayed in the lower right corner quantifies the area covered by the ice in each age category on the day of the annual minimum. In addition, memory bars shown in green portray the maximum annual value for each age range seen since Jan. 1, 1984, on the day of the annual minimum.