ESA — Long-term satellite record details permafrost thaw Frozen Arctic soils are set to release vast amounts of greenhouse gases to the atmosphere as they continue to thaw in coming decades. To aid in understanding the scale and speed of this climate process, researchers have released a new permafrost dataset. By definition, permafrost is ground that continuously remains below 0°C (32°F) for two or more years, located on land or under the ocean, however, much of the sub-surface ground in the Arctic polar regions has been frozen since the last ice age. Close to 25 percent of the Northern Hemisphere is underlain by permafrost, including 85 percent of Alaska, Greenland, Canada, and Siberia. It can also be located on mountaintops, such as the Andes and exposed land in Antarctica in the Southern Hemisphere.