Follow the decline in Arctic sea ice in this animation adapted from NASA showing the yearly maximum and minimum sea ice extents from 1999 to 2016. In the Arctic, sea ice forms when ocean water freezes into sheets of ice each winter, grows dramatically, and then retreats in the summer. The sea ice typically reaches its maximum extent in March of each year and its minimum extent in September. Satellites have monitored sea ice growth and retreat since 1979. Arctic sea ice has declined over this time, with the downward trend steepening in the 21st century. The period represented by this time series includes the 10 lowest minimum extents ever recorded in the Arctic.
To view the Background Essay, Teaching Tips, and Student Handouts for this animation, go to Support Materials below. This resource was developed through WGBH’s Bringing the Universe to America’s Classrooms project, in collaboration with NASA. Click here for the full collection of resources.