WATER MASS AND THAW DEPTH RELATIONSHIP WITHIN CENTRAL SIBERIA.

The permafrost region represents about 25% of the northern hemisphere (23×106 km2) and covers about 63% of the area of the Russian Federation (10×106 km2). Arctic and sub-arctic territories are particularly sensitive to temperature variations. Permafrost ground temperature has increased by 0.3-2.0°C in northern Russia during the last four decades. This will result in permafrost thawing and changes in water balance. Until 2050, the thaw depth in the northern part of Siberia could increase by more than 50%. The remote sensing technique is useful in the studies of permafrost area. Remotely sensed gravity measurements from the GRACE (Gravity Recovery and Climate Experiment) mission allowed identifying of significant decrease of water mass in ice regions. The aim of this investigation was to reveal relationships between active layer changes and water mass anomalies extracted from GRACE data in the cryolithozone of Central Siberia. Six test sites with available active layer data were investigated. Correlation analysis was carried out to determine relationships of the thaw depth with equivalent water thickness anomalies (EWTA). June EWTA significantly correlates with the thaw depth in July on the Samoilov Island (r = 0.82, p < 0.03). This means that an increasing amount of water in soil results in a better transfer of heat to the frozen soils, thus can result in thawing at greater depth. Depending on site mean thaw depth values positively correlates with April, May, June and August EWTA (r = 0.72-0.98, p < 0.05). For Igarka site, the negative correlation of thaw depth in September with August EWTA was revealed (r = -0.99, p < 0.1). This is opposed to the observed on Samoilov Island, and probably, explained by differences in hydrological regimes. [ABSTRACT FROM AUTHOR]