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PERMAFROST - Seventh International Conference
Poster Abstracts, 1998
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RESPONSE OF THE CRYOLITHOZONE IN YAKUTIA TO CLIMATE
CHANGE
N.I. Shender, A.S. Tetelbaum and Yu.B. Skachkov
Melnikov Permafrost Institute SB RAS, Yakutsk.
The problems of the sensitivity of the thermal regime of frozen ground in Yakutia to the
fluctuations (yearly and long-term) of such climate elements as air temperature ta and its components,
average summer (W s) and winter (W w) temperatures, snow cover thickness and density, are
considered. The regional characteristics of the air thermal regime are analyzed on the basis of the
data of meteorological observations and the results of the global atmospheric circulation simulation at
doubled CO2 concentration (GFDL, GISS, NGAR, OSU, UKMO). The latter allowed the estimation of
the spatial distribution of future air temperature increases.
It is shown that within the regional mainland ta varies from -4.4 to -18.0°C, whereas W s ranges
from 5,000 to 46,000 degree-hours. At doubling atmospheric CO 2 concentration, these characteristics
will fluctuate in the range of -1.3 to -13.5°C and 10,000-64,000 degree-hours, respectively. It is
noteworthy that the future climate have a changed degree of continentality compared to the presentday`s, with some increase in the central and eastern, considerable decrease in the northern, and
slight decrease in the western and, partially, southern regions. ta and Ws will increase by an average
of 3.7°C, 4.5°C, 6.0°C, 3.1°C and 14,500, 15,000, 5,000, and 18,000 degree-hours, respectively.
A numerical simulation of ground temperatures in Yakutia for equilibrium values has shown that
the average annual temperature of rocks now varies from 1.8 to -14°C. In the future its range will be
5 to -9.3°C. At the same time the average rock temperature increase will be 5.1°C in the north, 3.2°C
in the south, 5.7°C in the east, and 4.2°C in Central Yakutia.
The concept of the coefficient (k ) of permafrost sensitivity to climate warming is introduced.
Numerically it expresses the value of the soil temperature increase per degree of increase of the air
temperature. The calculations show that K averages is 0.85 for the north, 1.03 for the south, 1.14 for
the central area, and 1.27 for the east of the region studied. The latter means that the sensitivity to
climate warming is lowest in Yakutian Arctic and highest in its eastern and central areas.
In our opinion, the southern border of permafrost distribution in Eastern Siberia should be
considered to be the -2.5°C mean annual air isotherm, and of the continuous permafrost, about -7.5°C.
The equilibrium model of the soil temperature regime predicts the movement of the borders further
northward: to -7.0°C and -13°C, respectively. However, as this model does not take into account the
actual time of the system operation, it is able to reveal only some of various patterns of the
temperature regime formation in the soils of the region; hence, it does not give an idea what actually
will happen with the actual soil temperature increase in the region when the climate is warmer. The
calculations have been done for climate conditions in Yakutsk for the period up to the year 2060.
Three options have been considered.
Option 1. The air thermal characteristics change linearly. As a result of this change in upper
boundary conditions, the inertia of the thermal field of perennially frozen ground decreases it by 2733%.
Option 2. Yearly fluctuations of air thermal characteristics, snow thickness and density, are
imposed upon linearity. The calculations show that yearly fluctuations of these elements also decrease
the cryolithozone response to climate warming.
Option 3 should be considered summarizing, as it takes into account the increasing trend of air
temperature due to CO2 doubling and natural historic fluctuations of the climate elements: air
temperature characteristics taken through the harmonic analysis of the Yakutsk example, in
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The 7th International Permafrost Conference
particular, show climate warming for 1995-2020 and its sharp cooling by the middle of the next
century. The conditions of this option reduce the soil temperature increase acquired by equilibrium
models by the total of 54%. Extrapolating the results to the entire territory of Yakutia, we arrive at the
following scenario: the coefficients of permafrost sensitivity to climate warming and of the average
annual soil temperature increase by 2060 will be, respectively, 0.39 and 2.3°C in the north; 0.47 and
1.5°C in the south; 0.58 and 2.6°C in the east; and 0.52 and 1.9°C in Central Yakutia.
Finally, taking into account the delayed response of the climate system to CO 2 concentration
increase, the authors conclude that the soil warming will hardly exceed 0.5-1.5°C by the end of the
calculation period. The ÇÊclimate optimumÊÈ predicted for 1995-2020, when yearly air temperatures
can exceed long-term annual by 2-3.5°C, can be more dangerous for permafrost in the region.
Extended Abstracts
191