HR: 1340h
AN: GC23A-0985    [Abstracts]
TI: Modeling the Effect of Organic Layer and Water Content on Permafrost Dynamics in the Northern Hemisphere
AU: * Marchenko, S
EM: ffssm1@uaf.edu
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk drive, Fairbanks, AK 99775-7320, United States
AU: Rmanovsky, V
EM: ffver@uaf.edu
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk drive, Fairbanks, AK 99775-7320, United States
AB: Climate projections for the 21st century indicate that there could be a pronounced warming and degradation of permafrost with a corresponding shift in landscape processes. Therefore, we expect a further degradation of permafrost in the Arctic and sub-Arctic regions. In order to simulate the distribution and temperatures of permafrost and active layer thickness for the entire Northern Hemisphere permafrost domain, the equilibrium model GIPL1.1 has been developed. GIPL1.1 is a spatially distributed model of permafrost based on an approximate analytical solution of soil freezing and thawing, which includes an estimation of thermal offset due to the difference of frozen and thawed soil thermal properties. GIPL1.1 model also accounts effectively for the effects of snow cover, vegetation, soil moisture, and soil thermal properties. Comparison between calculated distribution of permafrost temperatures using GIPL1.1 model and the International Permafrost Association (IPA) permafrost map shows a very good agreement. For this study we used three different GIPL1.1 runs, each driven by the same boundary conditions but with different soil properties. The control run takes into account the organic matter layer and the thawing/freezing of soil water. For the second simulation, the presence of water was also taken into account, but the organic soil properties were replaced by the mineral soil properties throughout the entire calculated domain. The third simulation was performed only for the mineral soil that contains no water. All three simulations were implemented for two time intervals. For the present-day climatic conditions, the CRU2 data set with 0.5° by 0.5° latitude/longitude resolution was used. The future climate scenario was derived from the MIT-2D climate model output for the 21st century. Results of permafrost modeling show significant differences between the all three runs in both spatial distribution of permafrost and in permafrost temperatures. These results show that incorrect treatment of soil properties (the lack of organic matter) has much greater influence on ground temperatures and permafrost distribution than the incorrectly prescribed soil water content. The difference in mean value of the mean annual ground temperature (MAGT) for the total 40,423 grid points for the entire Northern Hemisphere for the present time reached 2.6°C that corresponds to the permafrost area reduction by 6.8 million km². In case of incorrectly prescribed soil water content, much greater discrepancies were found in the active layer thickness evaluation. These discrepancies grew dramatically when MAGT values were approaching 0°C.
DE: 0702 Permafrost (0475)
DE: 0706 Active layer
DE: 0772 Distribution
DE: 0798 Modeling
DE: 1621 Cryospheric change (0776)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting