V.E. Romanovsky1, S.L. Smith2, H.H. Christiansen3,4, N. I. Shiklomanov5, D.A. Streletskiy5,
D.S. Drozdov6, N.G. Oberman7, A.L. Kholodov1, S.S. Marchenko1
1Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA
2Geological Survey of Canada, Natural Resources Canada, Ottawa, ON, Canada
3Geology Department, University Centre in Svalbard, UNIS, Norway
4Institute of Geography and Geology, University of Copenhagen, Denmark
5Department of Geography, George Washington University, Washington, DC, USA
6Earth Cryosphere Institute, Tyumen, Russia
7MIRECO Mining Company, Syktyvkar, Russia
November 26, 2013
- In 2013, new record high temperatures at 20 m depth were measured at two northernmost permafrost observatories on the North Slope of Alaska, in the Brooks Range, Alaska, and in the High Canadian Arctic, where measurements began in the late 1970s.
- During the last fifteen years (1998-2012), active-layer thickness has increased in the Russian European North, northern East Siberia and Chukotka.
- In 2012 in west Siberia, the active-layer thickness was the greatest observed since 1996, and in the Russian European North it was the greatest observed since measurements began in 1998.
The most direct indicators of changes in permafrost state are temperature and active layer thickness (ALT). Permafrost is ground that remains frozen for two or more years. The active layer is the top layer of soil and/or rock that thaws during the summer and freezes again during the fall. Permafrost temperature at a depth where seasonal temperature variations cease to occur can be used 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). Where continuous, year-round temperature measurements are available, the mean annual ground temperature (MAGT) at any depth within the upper 15 m of permafrost can be used as a measure of permafrost change. Such measurements can be obtained from boreholes, which now number ~600. A borehole inventory, including MAGTs for most of the boreholes are available online at http://nsidc.org/data/g02190.html.
Alaska: In 2013, new record high temperatures at 20 m depth were measured at some permafrost observatories on the North Slope of Alaska and in the Brooks Range (Fig. 62a), where measurements began in the late 1970s and early 1980s (Fig. 62b). The 20 m temperatures in 2013 were higher than in 2012 by 0.03°C at West Dock and Deadhorse (Fig. 62b) on the North Slope and by 0.06°C at Coldfoot (Fig. 62c) in the southern foothills of the Brooks Range. Permafrost temperatures at the other North Slope sites were exactly the same as in 2012, except for Happy Valley, where lower (by 0.06°C) temperatures than in 2012 were observed. At a depth of 20 m, temperature has increased since 2000 by +0.44°C per decade at West Dock, by +0.47°C per decade at Deadhorse, and by ~ +0.28°C per decade at Franklin Bluffs and Happy Valley (Fig. 62b). Permafrost temperatures in Interior Alaska (Fig. 62a) continued to decrease in 2013 (Fig. 62c), a cooling that dates back to 2007. Consequently, temperatures in 2013 at some sites in Interior Alaska were lower than those located further north, e.g., temperatures at College Peat and Birch Lake are now lower than at Old Man and Chandalar Shelf in the Brooks Range (Fig. 62). During the late 1980s, temperatures at College Peat and Birch Lake were 0.7°C higher than at Old Man and Chandalar Shelf, respectively.
Canada: In 2012 (the most recent year for which data are available), temperatures in the upper 25 m of ground at Alert, northernmost Ellesmere Island, were the highest since measurements began in 1978 (Fig. 63). At a depth of 15 m in borehole BH5, temperature has increased by ~ +1.5°C per decade since 2000, which is about +1°C higher than the rate for the entire record (Table 8). Even at a depth of 24 m, temperature has increased since 2000 at a rate approaching +1°C per decade (Table 8). Note that the rate of warming at Alert is greater than on the North Slope of Alaska.
|Location||Rate of change (°C/decade)||Rate of change (°C/decade)|
|Alert BH1 (24m)||0.28°C (1978-2012)||0.74°C (2000-2012)|
|Alert BH2 (24m)||0.32°C (1978-2012)||0.98°C (2000-2012)|
|Alert BH5 (15m)||0.48°C (1978-2012)||1.58°C (2000-2012)|
|Norman Wells (12 m)||0.17°C (1984-2012)||0.07°C (2000-2012)|
|Wrigley (10 m)||Insufficient data||0.2°C (2001-2012)|
Permafrost in the central Mackenzie River Valley in northwestern Canada continues to warm, but much more slowly than at Alert (Fig. 63, Table 8). Note also that permafrost in this region is much warmer than it is at Alert (Fig. 63). At depths of 10-12 m, ground temperature at Norman Wells and Wrigley has risen by 0.07-0.2°C per decade since 2000. At Norman Wells, the rate of warming has decreased during the last decade (Table 8).
Russia: Permafrost temperature has increased by 1-2°C in northern Russia during the last 30 to 35 years (Romanovsky et al. 2010b). This is similar to the warming observed in Alaska during the same period. In the Polar Ural, for example, temperatures at 15 m depth at colder permafrost sites have been increasing by ~ +0.5°C per decade since the late 1980s (Fig. 64, ZS-124, R-92, and R57 sites). At the same time, at the warmer permafrost site, KT-16A, the warming has been much less pronounced (Fig. 64). At some warmer permafrost sites a slight cooling has been observed since 2009 (sites ZS-124 and KT-16a (Fig. 64).
Nordic area: There are limited long-term permafrost temperature records for the Nordic area. A few of these were initiated at the end of the 1990s, and since then temperature has increased at rates of +0.4 to +0.7°C/decade in the highlands of southern Norway, northern Sweden and Svalbard, with the largest warming in Svalbard and in northern Scandinavia (Isaksen et al. 2011; Christiansen et al. 2010).
Active Layer Thickness
In 2012 (the most recent year for which data are available), a majority of Alaska and Russian regions reported higher ALT values relative to the 1995-2012 average (Fig. 65). On the North Slope of Alaska, for example, ALT was on average 6% higher than the 1995-2012 average of 0.47 m. Compared to 2011, however, it was about 2% lower. In Interior Alaska ALT has been relatively unchanged since 2007, when it reached a maximum; the 2012 ALT values were slightly higher than 2011 and close to those of 2007-2010. Sites on the Seward Peninsula, westernmost Alaska mainland, showed much lower (by 20%) ALT values in 2012 relative to the long-term mean of 1999-2012.
A large increase in ALT was observed in West Siberia during 2009-2012, with 2012 ALT values being the highest (10% higher than 1995-2012 mean or 1.2 m) since 1996. A more or less continuous thickening of the active layer has been reported for Russian European North locations (Kaverin et al. 2012), where ALT in 2012 was the highest since observations began in 1998. Central Siberian locations also report the highest ALT values since observations began, in this case in 2005. In 2012 in eastern Siberia, ALT was 10% lower than in 2011 and all sites had lower ALT than the 1996-2012 average of 0.6 m. In 2012 in Chukotka (Russian Far East), ALT values were about 3% higher than in 2011, but overall there has been a progressive decrease in ALT since 2007, when it reached a maximum since observations began in 1994.
A progressive increase in ALT has been observed in some Nordic countries, e.g., in the Abisko area of Sweden since the 1970s, with an accelerated rate after 1995 that resulted in disappearance of permafrost in several mire landscapes (e.g., Åkerman and Johansson 2008, Callaghan et al. 2010). The increase in thaw propagation ceased during 2007-2010, coincident with drier summer conditions (Christiansen et al. 2010). Increases in ALT since the late 1990s have been observed on Svalbard and Greenland, but these are not spatially and temporally uniform (Christiansen et al. 2010).
Åkerman, H. J., and M. Johansson, 2008: Thawing permafrost and thicker active layers in sub-arctic Sweden. Permafr. Periglacial Proc., 19, 279-292.
Callaghan, T. V., F. Bergholm, T. R. Christensen, C. Jonasson, U. Kokfelt, and M. Johansson, 2010: A new climate era in the sub-Arctic: Accelerating climate changes and multiple impacts, Geophys. Res. Lett.,37, L14705, doi:10.1029/2009GL042064.
Christiansen, H. H., and 17 others, 2010: The Thermal State of Permafrost in the Nordic area during the International Polar Year, Permafr. Periglacial Proc., 21, 156-181.
Isaksen, K., R. S. Oedegård, B. Etzelmüller, C. Hilbich, C. Hauck, H. Farbrot, T. Eiken, H. O. Hygen, and T. F. Hipp, 2011: Degrading mountain permafrost in southern Norway: spatialand temporal variability of mean ground temperatures, 1999-2009, Permafr. Periglacial Proc., 22, 361-377.
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Romanovsky, V. E., S. L. Smith, and H. H. Christiansen, 2010a: Permafrost Thermal State in the Polar Northern Hemisphere during the International Polar Year 2007-2009: a synthesis. Permafr. Periglacial Proc., 21, 106-116.
Romanovsky, V. E., and 11 others, 2010b: Thermal State of Permafrost in Russia. Permafr. Periglacial Proc., 21, 136-155.
Romanovsky, V., N. Oberman, D. Drozdov, G. Malkova , A. Kholodov, and S. Marchenko, 2012: Permafrost, [in "State of the Climate in 2010"]. Bull. Amer. Meteor. Soc., 93 (7), S137-S138.
Smith, S. L., V. E. Romanovsky, A. G. Lewkowicz, C. R. Burn, M. Allard, G. D. Clow, K. Yoshikawa, and J. Throop, 2010: Thermal State of Permafrost in North America—A Contribution to the International Polar Year. Permafr. Periglacial Proc., 21, 117-135.
Smith, S. L., J. Throop, and A. G. Lewkowicz, 2012: Recent changes in climate and permafrost temperatures at forested and polar desert sites in northern Canada. Can. J. Earth Sci., 49, 914-924.