Changes in the water-thermal regime of permafrost swamps in Western Siberia in response to climate warming

Changes in the water-thermal regime of swamps in the permafrost zone of Western Siberia are considered. Two types of swamps are prevalent in the study area: frost mound bogs (southern half of the area) and polygonal bogs (northern half of the area). The boundary between these swamps types is blurred and approximately matches the Polar Circle line. Detailed studies of the water-thermal regime of swamps in this area were carried out from 1971 to 1991 within the framework of the West Siberian expedition of the State Hydrological Institute. The present work uses a mathematical model of frost mound and polygonal bogs, which was developed based on the results of these studies. Daily meteorological data, specifically daily data on air temperature, precipitation totals and total and lower cloudiness from 23 stations are used as input parameters of the model. The duration of observations of meteorological stations ranges from 90 to 140 years. The mentioned period is divided into 2 parts, before and after 1978. All calculations were limited to the warm period, the boundaries of which are the transitions of average daily air temperature through 0 °C.

The results of calculations indicate a widespread increase in the average warm period air temperature values, from 0.3 °C in the south to 1.6 °C in the north of the territory. In the warmest years (2.5% probability of exceeding) this increase in the south of the zone is 1.5 °C and in the extreme north is 3.5 °C. The greatest changes in the parameters of the water-thermal regime can be traced in the increase of the peat deposit thawing depth. In average, the maximum thawing increased by 4-5 cm, and in the warmest years by 7-10 cm. For the north of polygonal bogs, the difference in thawing depth in some years increases dramatically and reaches 16 cm. At the same time, it should be noted that the calculated thawing depth often exceeds the peat deposit thickness, especially in the northern part of polygonal bogs. In such cases, the peat deposit thawing values should be considered as potential.

It is supposed that changes in the water-thermal regime of frost mound and polygonal bogs will contribute to the sequential evolution of the micro-landscape structure. The displacement of the boundaries of different types of swamps is complicated by orographic obstacles, primarily by the Siberian Uvals and requires a full-scale reorganization of the hydrographic network and structure of micro-landscapes.