Thermal State of Permafrost in North America: A Contribution to the International Polar Year

The permafrost monitoring network in the polar regions of the Northern Hemisphere was enhanced during the International Polar Year (IPY), and new information on permafrost thermal state was collected for regions where there was little available. This augmented monitoring network is an important legacy of the IPY, as is the updated baseline of current permafrost conditions against which future changes may be measured. Within the Northern Hemisphere polar region, ground temperatures are currently being measured in about 575 boreholes in North America, the Nordic region and Russia. These show that in the discontinuous permafrost zone, permafrost temperatures fall within a narrow range, with the mean annual ground temperature (MAGT) at most sites being higher than 28C. A greater range in MAGT is present within the continuous permafrost zone, from above 18C at some locations to as low as 158C. The latest results indicate that the permafrost warming which started two to three decades ago has generally continued into the IPY period. Warming rates are much smaller for permafrost already at temperatures close to 08C compared with colder permafrost, especially for ice-rich permafrost where latent heat effects dominate the ground thermal regime. Colder permafrost sites are warming more rapidly. This improved knowledge about the permafrost thermal state and its dynamics is important for multidisciplinary polar research, but also for many of the 4 million people living in the Arctic. In particular, this knowledge is required for designing effective adaptation strategies for the local communities under warmer climatic conditions.

Permafrost Thermal State in the Polar Northern Hemisphere during the International Polar Year 2007–2009: a Synthesis

Vladimir E. Romanovsky,1* Sharon L. Smith 2 and Hanne H. Christiansen 31 Geophysical Institute, University of Alaska Fairbanks, USA2 Geological Survey of Canada, Natural Resources Canada, Ottawa, Ontario, Canada3 Geology Department, University Centre in Svalbard, UNIS, Norway

ABSTRACT A snapshot of the thermal state of permafrost in northern North America during the International Polar Year (IPY) was developed using ground temperature data collected from 350 boreholes. More than half of these were established during IPY to enhance the network in sparsely monitored regions. The measurement sites span a diverse range of ecoclimatic and geological conditions across the continent and are at various elevations within the Cordillera. The ground temperatures within the discontinuous permafrost zone are generally above 38C, and range down to 158C in the continuous zone. Ground temperature envelopes vary according to substrate, with shallow depths of zero annual amplitude for peat and mineral soils, and much greater depths for bedrock. New monitoring sites in the mountains of southern and central Yukon suggest that permafrost may be limited in extent. In concert with regional air temperatures, permafrost has generally been warming across North America for the past several decades, as indicated by measurements from the western Arctic since the 1970s and from parts of eastern Canada since the early 1990s. The rates of ground warming have been variable, but are generally greater north of the treeline. Latent heat effects in the southern discontinuous zone dominate the permafrost thermal regime close to 08C and allow permafrost to persist under a warming climate. Consequently, the spatial diversity of permafrost thermal conditions is decreasing over time.

Copyright # 2010 John Wiley & Sons; Ltd.KEY WORDS: permafrost; ground temperature regime; climate change; permafrost thaw; active layer; International Polar Year; Arctic regions

Paper published at: PERMAFROST AND PERIGLACIAL PROCESSESPermafrost and Periglac. Process. 21: 106–116 (2010) Published online in Wiley InterScience ( DOI: 10.1002/ppp.689

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Project Permafrost with Frontier scientist Vladimir E. Romanovsky