Permafrost

202
Climate Factors of Permafrost Regime and Their Change
in Northern Eurasia During Recent Decades
V.V.Popova, A.B. Shmakin
(Institute of Geography, Russian Academy of Sciences)
Abstract: Low-frequency variations of the surface air temperature (SAT) and snow
accumulation are recognized as major climate factors of permafrost regime changes. Daily data
of SAT and February snow depth for 1950-2001 in Northern Eurasia are examined in order to
study the response of permafrost thawing depth on recent changes of SAT and snow
accumulation. The listed parameters are calculated for the reference period of 1951-1980, as
well as for the period of contemporary warming (1989-2001). The periods were chosen
according to the variations of average annual air temperature in Russia, which has increased by
about 1°C, and its rise is statistically significant.
The spatial fields of the seasonal and annual SAT for the mentioned time periods are
plotted. Regions with its different trends during the contemporary warming are revealed. The
number of days with extremely strong frosts in winter decreases significantly in a large part of
Siberia. Analyses of snow depth principal components (PCs) indicate that within the Northern
Eurasia, there are several regions spatially homogeneous with respect to snow depth interannual
variations, respondent to certain atmospheric circulation modes. Temporal variability of snow
accumulation in each of the revealed regions differs by the share of low- and high-frequency
variations, as well as by the relation with recent global warming. First of all, it touches upon the
region between the White Sea and river Lena basin, where the snow depth variations are
described by PC1. Snow accumulation in that region is revealed to be associated with
circulation modes, also responsible for the recent changes of surface air temperature over the
Northern Eurasia. Strengthening of cyclonic activity, linked to positive phase of North Atlantic
Oscillation and enhanced westerlies, has to be considered as a major circulation factor of
positive trend of both temperature and snow accumulation since 1970s. Thus, over the major
portion of Siberia both increased SAT and snow accumulation seem to be affecting the
permafrost thawing depth. At the same time, relation of the anomalies of the annual SAT and
snow depth on one hand, and permafrost thawing depth on the other hand, demonstrates its
strong dependence on the types of landscape.
The study was supported by the Russian Foundation for Basic Research (grant
04-05-64745) and by INTAS (grant No. 03-51-5296).
Key words: permafrost, climate change, Northern Eurasia, atmospheric circulation, land cover
features