Age distribution of Arctic sea ice, 2019. Map based on satellite data showing sea ice in the Arctic in August near its minimum level for 2019. The ice is shaded according to its age, which ranges from over four years (white) to less than a year (darker grey). Ice that is present for more than a year is known as multi-year ice or perennial ice. It starts off around 2 metres thick, but can reach a thickness of over nine metres. The decline in perennial ice in the Arctic is an indication of climate change. A key to the shading and the distribution by age is at top right. This data was obtained using a variety of satellite sensors, and is provided by the National Snow and Ice Data Center (NSIDC). For a map displaying the data for 1987, see image C048/5024.