Sensitivity of permafrost and season freezing evolution to regional
simulation of snow cover

Pavlova T.V., Nadyozhina E.D., Shkolnik I.M., Molkentin E.K.

Voeikov Main Geophysical Observatory
St. Petersburg, Russia

	Permafrost, seasonal ground freezing and seasonal snow-cover
	evolution are considered as cryospheric indicators of global
	climate change. The interaction between snow cover and ground
	thermal regime is one of the focus problems under the climate
	change. Spatial and temporal correspondence among snow cover
	and ground thermal evolution was examined using the ground
	heat transfer model (GHTM) and MGO regional climatic model
	(RCM). The GHTM employs multi-level one-dimensional heat
	transfer scheme; vegetation and snow cover over land are
	treated as additional model levels. The modified version of
	GHTM was developed accounting for snow density intra-seasonal
	evolution. The evolution of ground temperature distribution
	using daily RCM output data is analyzed. The RCM was run under
	IPCC A2 scenario of greenhouse gas and aerosols increase over
	the territory of Russia at 50 km horizontal resolution. The
	daily output allows to more correctly assess snow duration. We
	have compared the simulated snow cover with that derived from
	available standard observations and satellite data. There is a
	reasonable agreement between observation analysis and
	calculated characteristics. The focus of our investigations is
	the analysis of ground thermal conditions sensitivity to the
	modification in the calculation scheme. The effect of variable
	snow density on maximum seasonal thawing is mostly noticeable
	within the areas of discontinuous permafrost. In some regions
	of Central and Western Siberia the influence of variable snow
	density on seasonal cycle of temperature leads to the changes
	in thawing depth by 0.5-1 m. It is important to note that
	increase in thawing of about 1-1.5 m leads to seasonal
	freezing regime instead of season thawing and, therefore,
	considerable shift of the permafrost boundary northwards.

 	The analysis of interactions between various impacts on the
 	permafrost evolution for climatic regions in permafrost zone
 	was performed. The model projection of the near-surface
 	permafrost degradation was developed for several temporal
 	slices in 21st century using MGO RCM climatic data. It has
 	been found the permafrost boundaries migrate northwards slower
 	than seasonal freezing area significantly affecting the local
 	wetland ecosystems.