Permafrost

Response of Ice-rich Permafrost to Contemporary
Climate Warming and Surface Disturbance
P.P. Gavriliev, I.S. Ugarov and P.V. Efremov
(Melnikov Permafrost Institute, Siberian Branch, Russian Academy of Sciences)
Abstract: Based on the data from integrated monitoring investigations over the period of 1989
to 2005, the parameters of the active layer over the ice-rich permafrost containing thick wedge
ice (the ice-wedge complex) changed little, within the range of natural variation, in the natural
(undisturbed) landscapes. These observations add support to the views of a number of
well-known scientists who believe that, firstly, permafrost degradation in response to moderate
climatic warming is weak and, secondly, the permafrost in Central Yakutia shows thermal
stability to moderate climate warming.
In the areas of surface, soil and vegetation disturbances, however, a degradational situation
developed in the upper part of the ice-rich permafrost (upper 10-15 m) with the 5 to 35% loss of
cold resources and ground ice volumes over a short period of time (1989-2005) in response to
an increase in air temperature of 1.5 to 2.6°C. In places, permafrost temperatures at a depth of
10 m have warmed by 1-2°C.
In the disturbed landscapes located on the VI-VII terraces of the Lena River, the upper part
of the ice-rich permafrost thawed at a rate of 0.3-0.6 m in the years with anomalously warm
winters and warm, rainy summers (1996-1999 and 2005). Where the surface was disturbed, a
thawing trend of the ice-wedge complex ranged on average from 0.03 to 0.20 m/yr . At the
Dyrgabai site, the table of the permafrost with ice wedges lowered rapidly from 1.8 m in 1991
to 4.5 m in 2005. This triggered thermokarst, thermal erosion and other frost-related processes.
The influence of cryogenic processes on the response and inertia of the ice-wedge complex
is estimated to be high (mec=1.3-3 or greater) for typical geothermal conditions: mean annual
temperatures tm=-1° to -3°C and high ice contents (i=0.5-0.8). At some disturbed inter-alas sites,
a thawing trend of the ice-rich permafrost (∆hip) may exceed an increasing trend of seasonal
thaw (∆h) in natural (undisturbed) analogues by a factor of 3-15 or greater. This is explained by
a 1.5-3 times increase in snow accumulation in thaw settlements relative the background norm
and by the additional effect of intensified cryogenic processes. If thermokarst develops,
degradation of the ice-rich permafrost occurs at a faster rate under moderate climate warming.
These observations indicate that the response of permafrost to contemporary climate
warming and surface disturbance is not uniform. The problems requiring further research are
discussed.
Key words: Climate, ice-rich permafrost, landscapes, thermokarst
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