March 22: "State and Fate of Permafrost on a Changing Planet"

State and Fate of Permafrost on a Changing Planet

Abstract:

Permafrost has received much attention recently because surface temperatures are rising in most permafrost areas of the Earth, which may lead to permafrost thaw. Thawing of permafrost has been observed at the southern limits of the permafrost zone and this can lead to changes in ecosystems, in water and carbon cycles, and in infrastructure performance. If the current trends in climate continue, warming of permafrost will eventually lead to widespread permafrost thawing in the colder permafrost zones. There is however uncertainty concerning where this thawing will occur first, the rate of thaw and the consequences for Arctic, Subarctic and the global natural systems. Examination of past trends in permafrost conditions and distribution (especially during the last glacial-interglacial cycle) can facilitate better understanding of the possible rates and pathways of permafrost degradation in the future. The main reasons for this are: 1) the main present-day features in permafrost distribution both vertically and laterally were formed during the last 100,000 years and 2) we can expect that with persistent future climate warming, the first permafrost to begin to thaw will be the youngest Little Ice Age permafrost, followed by mid- and late-Holocene permafrost, and last to thaw would be the Late Pleistocene permafrost. This presentation will describe our knowledge of permafrost development in Eurasia during the last glacial-interglacial cycle.
To characterize the thermal state of permafrost, the International Permafrost Association launched its International Polar Year Project # 50, Thermal State of Permafrost (TSP). Ground temperatures are measured in existing and new boreholes within the global permafrost domain over a fixed time period in order to develop a snapshot of permafrost temperatures in both time and space. This data set will serve as a baseline against which to measure changes of near-surface permafrost temperatures and permafrost boundaries, to validate climate model scenarios, and for temperature reanalysis. The first results of the project based on data obtained from North America and Northern Eurasia are presented. Most of the observatories show a substantial warming during the last 20 years. The magnitude of warming varied with location, but was typically from 0.5 to 2°C at the depth of zero seasonal temperature variations in the permafrost. Thawing of the Little Ice Age permafrost is on-going at many locations. There are some indications that the late-Holocene permafrost started to thaw at some specific undisturbed locations in the European Northeast, in the Northwest Siberia, and in Alaska. Projections of possible changes in permafrost during the 21st century based on application of calibrated permafrost models are presented. The possible consequences of permafrost degradation are also discussed.