Permafrost Extent in the Northern Hemisphere
Permafrost is defined as soil, rock, and any other subsurface Earth material that exists at or below 0 °C for two or more consecutive years. Current maps of permafrost in the Northern Hemisphere (20° N to 90° N) are based on a map compiled in 1997 by the International Permafrost Association (see original 1997 permafrost map below). This map contributes to a unified international dataset that depicts the distribution and properties of permafrost and ground ice. Colors indicate permafrost extent, estimated in percent area. A second map, updated on February 21, 2012, has been digitized and simplified to show continuous permafrost, discontinuous/sporadic permafrost, isolated patches of permafrost, as well as ice sheets and glaciers. Here the original map and a later digitized version have been adapted for diplay on the hyperwall.
While ground-based instruments can be used to obtain reliable measurements of permafrost at specific locations, it is difficult to make continuous measurements of permafrost because of its remoteness and vast distribution. Satellite observations from space, however, can cover broad areas and provide frequent measurements. The Soil Moisture Active Passive, or SMAP, mission is NASA’s first Earth-observing satellite mission designed to collect continuous global observations of surface soil moisture conditions as well as whether or not the water contained within the soil is frozen or thawed—called its freeze/thaw state—every 2-3 days at 3-40 km (~2-25 mi) spatial resolution. These data will help quantify the nature, extent, timing, and duration of landscape seasonal freeze/thaw state transitions as well as help detect permafrost thaw.
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GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 22.214.171.124.0