Sea ice is an important part of Arctic and Antarctic ecosystems, providing habitat for primary producers such as algae and plankton to thrive. Mariners hoping to safely navigate polar waters must also pay close attention to sea ice. To properly understand changes in sea ice over time, scientists need robust data about its age—meaning how long sea ice has remained frozen—in the world’s polar oceans.

Sea ice forms and grows in the autumn and winter, and melts in the spring and summer. Sea ice that has existed less than a year is called first-year ice. Sea ice that has survived at least one melt season is multiyear ice. Multiyear ice tends to be thicker and more resistant to melting than first-year ice.

Since the start of the satellite record in 1979, Arctic sea ice has declined. This has created a trend away from older, thicker sea ice toward younger, thinner sea ice that is more prone to melting. Satellite instruments can estimate the age of sea ice by measuring the emissivity of the ice at different wavelengths. 

NASA’s Earth observation datasets include sea ice characteristics, thickness, and concentration measurements. These data help scientists better understand polar ecosystems, the effects of climate change, and risks to Arctic shipping.