The Effect of Increasing Active Layer Depth on the Changes in Water Budgetin the Cryolithozone
Under the influence of perennial dynamics of soil summer thawing depth, the upper layer of permafrost periodically thaws and becomes part of the soil profile in the cryolithozone. In this case, the horizon, which is either frozen or thawn, and has a thickness of several tens of centimeters, displays an elevated ice content (moisture). This horizon between the lower boundary of the active layer and the permafrost is named “protective layer” and functions like a buffer that hinders thawing of ice complex with its high ice content. The study of moisture using soil-regime methods and budget calculations showed that the “protective layer” of permafrost in sandy and loamy soils (1.5–5 m depth) contains from 25 to 60 mm of moisture in each 10-cm of frozen soils under different types of forests in Central Yakutia. The increase in the seasonal thawing depth of frozen soils under conditions of global changes and anthropogenic impacts (forest fires, destruction of forest cover, etc.) causes a degradation of the “protective layer”. The purpose of this article is to show the effect of increasing seasonal thawing depth of soils on the water content changes in permafrost territories due to the release of moisture preserved in the protective layer in the context of global climate change. It was revealed that with an increase in the seasonal thawing depth, a protective layer will release a significant amount of moisture conserved by permafrost, which causes changes in the water budget of the cryolithozone. As calculations show, with an increase in the soil seasonal thawing depth by 20–30 cm on the interfluve areas, the volume of moisture entering into the basins of nearby alases and rivers from frozen soils is estimated as 60 000–90 000 m3/km2. The obtained results can be used in modeling and forecasting the dynamics of the cryolithozone environment under the global climate change.