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 Chi 10 6 km(2) or 23.9% of the exposed land area of the Northern Hemisphere. Permafrost extends from 26(o)N in the Himalayas to 84(o)N in northern Greenland. Approximately 70% of the permafrost is distributed between 45 and 67(o)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 Chi 10(3) km(3), corresponding to similar to 2-4 cm sea level equivalent. Based on alternative assumptions, the volume of ground ice may be between 11.37 and 36.55 Chi 10(3) km(3), which corresponds to 3-10 cm sea-level equivalent.