Statistics and characteristics of permafrost and ground‐ice distribution in the Northern Hemisphere

The recently published digital version of the International Permafrost Association (IPA) Circum‐Arctic Map of Permafrost and Ground Ice Conditions (the IPA map), together with ancillary data sets of the global land cover characteristics data base and the Global Land One‐kilometer Base Elevation data base, are used to investigate the distribution of permafrost and ground ice in the Northern Hemisphere. Our study indicates that permafrost underlies approximately 22.79 × 106 km2 or 23.9% of the exposed land area of the Northern Hemisphere. Permafrost extends from 26°N in the Himalayas to 84°N in northern Greenland. Approximately 70% of the permafrost is distributed between 45°N and 67°N. Generally, permafrost with high ice content (>20% by volume) and relatively thick overburden cover (>5 to 10 m) is found at high latitudes, representing approximately 8.57% of the total permafrost area, or 2.02% of the exposed land area of the Northern Hemisphere. Permafrost with low ice content (<10% by volume with either thick or thin overburden cover) occurs mainly in mountainous regions and high plateaus, representing approximately 66.5% of the total permafrost area or 15.8% of the exposed land area. Approximately 62% of the permafrost of the Northern Hemisphere is found below 500 m a.s.l. and about 10% occurs above 3000 m a.s.l. Based on the IPA map categories, the estimated volume of ground ice in the Northern Hemisphere is between 5.63 and 15.12 × 103 km3, corresponding to ∼2–4 cm sea level equivalent. Based on alternative assumptions, the volume of ground ice may be between 11.37 and 36.55 × 103 km3, which corresponds to 3–10 cm sea‐level equivalent.