NASA / GSFC SVS / NSIDC / WORLD DATA CENTER FOR GLACIOLOGY / SCIENCE PHOTO LIBRARY NASA / GSFC SVS / NSIDC / WORLD DATA CENTER FOR GLACIOLOGY / SCIENCE PHOTO LIBRARY
Global permafrost layers. Cylindrical world map showing the permafrost and ground ice regions in the northern hemisphere in shades of purple. The four shades represent the following: sporadic permafrost (lightest colour), isolated permafrost (second lightest colour), discontinuous permafrost (second darkest colour) and continuous permafrost (darkest colour). Permafrost is permanently frozen ground that remains at or below the freezing point of water for at least two years. This date was obtained from the National Snow and Ice Data Center and the World Data Center for Glaciology. The visualisation was part of the Science On a Sphere project. This image was published in 2008.
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