Coverage of ice across land or a waterbody can be measured by either its area or extent. Area is the amount of ice covering a region or waterbody. Extent is the total space covered by at least 15% ice. Scientists studying ice from space-based platforms often prefer using the extent measurement. This is because their microwave instruments can see well through clouds and winter darkness but at times may have trouble discerning between ocean water and meltwater on the surface of ice in summer. This confusion between ocean and meltwater can lead to miscalculations of ice area. The scientific community also has greater agreement on how to measure ice extent than it does area, and the way ice extent is counted in platform imagery has reduced day-to-day variability.

NASA data can be used for measuring ice extent to aid in understanding weather and global climate patterns, monitoring habitat health in the cryosphere, and for the safety and planning of human activities. 

Learn more about near real-time ice extent data for shipping provided by NASA's Land, Atmosphere Near real-time Capability for Earth observation (LANCE).