Permafrost temperature records: Indicators of climate change

Permafrost has received much attention recently because surface temperatures are rising in most permafrost areas of the Earth, bringing permafrost to the edge of widespread thawing and degradation. The thawing of permafrost that already occurs at the southern limits of the permafrost zone can generate dramatic changes in ecosystems and in infrastructure performance. In this article, we describe an emerging system for comprehensive monitoring of permafrost temperatures, a system which is needed for timely detection of worldwide changes in permafrost stability, and for predictions of negative consequences of permafrost degradation. Permafrost is rock, sediment, or any other Earth material with a temperature that remains below 0°C for two or more years. Permafrost zones occupy up to 24% of the exposed land area of the Northern Hemisphere (Figure 1) [Zhang et al., 2000]. Permafrost ranges from very cold (temperatures of −10°C and lower) and very thick (more than 500 m and as much as 1400 m) in the Arctic, to warm (within 1 or 2° of the melting point) and thin (several meters or less in thickness) in the sub‐Arctic.