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Abstracts
SEARCH Open Science Meeting
October 27, 2003
Seattle, Washington, USA
Historical Changes in Seasonal Freeze and Thaw Depths in Russia
Oliver W. Frauenfeld1, Tingjun Zhang2, Roger G. Barry3, David Gilichinsky4
1National Snow and Ice Data Center/CIRES, University of Colorado, 449 UCB, Boulder, CO, 80309-0449, USA, Phone 303-735-0247, Fax 303-492-2468, oliverf@kryos.colorado.edu
2National Snow and Ice Data Center/CIRES, University of Colorado, 449 UCB, Boulder, CO, 80309-0449, USA, Phone 303-492-5236, Fax 303-492-2468, tzhang@nsidc.org
3National Snow and Ice Data Center/CIRES, University of Colorado, 449 UCB, Boulder, CO, 80309-0449, USA, Phone -303-492-5488, Fax 303-492-2468, rbarry@kryos.colorado.edu
4Soil Cryology Laboratory, Institute of Physico-Chemical and Biological Problems in Soil Sciences , Russian Academy of Sciences, Pushchino, Moscow Region, -, 142290, Russia, Phone (0967) 732604, Fax (0967) 790595, gilichin@issp.serpukhov.su
Seasonal freezing and thawing processes in cold regions play an exceedingly important role in ecosystem diversity, productivity, and the Arctic hydrological system in general. Furthermore, long-term changes in seasonal freeze and thaw depths are important indicators of climate change. Only sparse observational historical measurements of seasonal freeze and thaw depths are available in permafrost and seasonally frozen ground regions. However, soil temperature data are more readily and widely measured.
Using mean monthly soil temperature data for 240 stations located throughout Russia for 1930–1990, we have devised an interpolation method that determines the depth of the 0°C isotherm based on soil temperature data measured at various depths: 0.2 m, 0.4 m, 0.6 m, 0.8 m, 1.2 m, 1.6 m, 2.0 m, 2.4 m, and 3.2 m. This simple methodology works remarkably well and the relationship between the available measured annual maximum freeze and thaw depths and our interpolated values is almost perfectly 1:1, with a correlation coefficient (Pearson's R) greater than 0.97. Having verified the reliability of the interpolation methodology we are subsequently able to work with a greatly improved sample size of stations.
A comprehensive evaluation of these new data's long-term trends in Russia indicates that, in permafrost regions, active layer depths have been steadily increasing. In the period 1956–1990, during which time sample-sizes are of sufficient size for statistical analysis, the active layer exhibited a statistically significant deepening by approximately 11 cm. The changes in the seasonally frozen ground areas are even greater—the depth of the freezing layer has exhibited a statistically significant decrease, resulting in 33 cm less frozen ground in 1990 than in 1956. In general these changes indicate that, as temperatures have been increasing globally in recent decades, permafrost is thawing to a greater depth during the warm season while less of the ground is freezing during the cold season. Potential direct consequences of these trends are increased river runoff and changes in discharge throughout the Russian Arctic drainage basin.
Abstract Categories: Changes on Land
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