Highlights

• Main Authors: V. E. Romanovsky, S. L. Smith, H. H. Christiansen, N. I. Shiklomanov, D. S. Drozdov, N. G. Oberman, A. L. Kholodov, S. S. Marchenko
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2011
• Subjects: Arctic; Greenland; Svalbard; Active layer thickness; Chukotka; Ice; International Polar Year; IPY; north slope; permafrost; Alaska; Siberia
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.6988; http://www.lter.uaf.edu/pdf/1648_Romanovsky_Smith_2011.pdf

In 2011, new record high temperatures at 20 m depth were recorded at all permafrost observatories on the North Slope of Alaska, where measurements began in the late 1970s. During the last fifteen years, active-layer thickness has increased in the Russian European North, northern East Siberia, Chukotka, Svalbard and Greenland. Active-layer thickness on the Alaskan North Slope and in the western Canadian Arctic was relatively stable during 1995-2008. The most direct indicators of permafrost stability and changes in permafrost state are the permafrost temperature and the active layer thickness (ALT). Permafrost temperature measured at the depth where the seasonal variations in ground temperature cease to exist is best to use as an indicator of long-term change. This depth varies from a few meters in warm, ice-rich permafrost to 20 m and more in cold permafrost and in bedrock (Smith et al. 2010; Romanovsky et al. 2010a). However, if continuous year-around temperature measurements are available, the mean annual ground temperature (MAGT) at any depth within the upper 15 m can be used as a proxy of the permafrost temperature. The recently concluded International Polar Year (IPY 2007-2009) resulted in significant enhancement of the permafrost observing system in the Arctic; there are now ~575 boreholes (Fig. HTC23; Brown et al. 2010; Romanovsky et al. 2010a). A borehole inventory, including mean annual ground temperatures for most of these boreholes, is available online