AMAP 2011 – The Arctic as a Messenger for Global Processes – Climate Change and Pollution, 4-6 May, 2011, Copenhagen, Denmark

Estimation of possible changes of active layer depth in North-East of Russia using climate change scenarios and deterministic-stochastic approach

Lyudmila Lebedeva, Olga Semenova

Understanding the effect of climate change in the permafrost is critical to assessing its various impacts on ecology, infrastructure, etc. The deterministic-stochastic approach can be used for effective quantifiable probabilistic evaluation of the effects of climate change on permafrost. Here the deterministic models distinguish between the processes in permafrost landscapes with different soil, vegetation, and snow properties, while the stochastic models provide stochastic meteorological input and a framework to link global climate models in a changing environment with the land surface components.
The goal of the research is to study the process of permafrost seasonal thawing/freezing, to improve the physical base of process representation in the deterministic model, and finally to assess the possible changes in permafrost properties (active layer depth, temperature, seasonal variations) of different landscapes of Eastern Siberia on the base deterministic-stochastic modelling using IPCC climate change scenarios. 
Two models developed in State Hydrological Institute of Russia were implemented in this study. The deterministic Hydrograph model is a distributed process-based runoff formation modelling system. The Stochastic Model of Weather provides simulated meteorological input for the Hydrograph model using the Monte-Carlo method. 
The study was conducted using the long-term observational data from small research watershed of Kolyma water-balance station situated within the upstream of Kolyma River (the North-East of Russia, 61º54’N, 147º25’E).  Three main types of landscapes considerably differing by soils and vegetation were studied; they are rock debris, open woods and swamp forest. 
The following key objectives were considered to project the permafrost conditions in North-Eastern Siberia according to climate change scenarios:
1) Assessment of deterministic hydrological model parameters using observed meteorological data as input.
2) Generation continuous series of daily meteorological data (30 years span) according the A1F1 and B1 IPCC climate change scenarios using the stochastic model.
3) Simulation the water and energy fluxes in the permafrost sites with randomly generated series of meteorological elements as forcing data using the deterministic model with historically derived parameters.
4) Assessment and comparison the changes of permafrost active layer properties within variable conditions and according different climate change scenarios. 
According to the modelling results the average active layer depth by 2030 projected with A1F1 input increases faster than with B1 one. The thawing depth in stone debris and swamp forest landscapes can reach 2.3 m and 1.05 m respectively according to A1F1 scenario and 2.05 m and 0.8 m respectively according to B1 scenario. Currently observed values are 1.6 m for debris rock and 0.6 m swamp forest. 
The study results including analysis of possible impact of active layer depth change on runoff will be presented. 
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