Vestnik MGTU (Mar 2024)
The main results of monitoring the power of the active layer at CALM sites of the Nadymsky object
Abstract
Monitoring of the thickness of the active layer within the lake-marsh type of terrain in the northern taiga was carried out at three sites organized in 1997, 2013 and 2022. In these areas, two types of tracts are distinguished: frozen peat bogs and swampy runoff hollows with a lowered roof of permafrost (the cross-section of the sites is the same type, the only difference is in the thickness of the peat). The work methodology complied with the unified protocol of the international CALM program. Additionally, the surface settlement was assessed (based on leveling from a local benchmark), geophysical studies were carried out and the temperature of the active layer rocks was measured at different gullies. In swampy runoff hollows, hollows with open water and on specific mineral spots within peat bogs, the depth of the permafrost roof is 3–10 m. At the boundaries of peat bogs and in swampy runoff hollows, the thawing depth exceeds 2 m, and on peat bogs it varies from 0.8 to 1.6 m depending on the thickness of the organic layer and the condition of the ground cover. On peatlands with an organic layer more than 1 m thick and a continuous ground cover, the depth of the seasonal thawing layer in some places does not exceed 0.4 m. These peatlands respond poorly to climate change. The depth of the permafrost roof within thin peat bogs (less than 0.5 m of peat) with oppressed vegetation cover is currently more than 2 m, marking the beginning of the replacement of the seasonally thawed layer with seasonally frozen and the formation of areas with a lowered permafrost roof. Monitoring of soil temperatures in such areas has showed that a random combination of climatic factors in individual years can lead to short-term (two years) new formation of permafrost or the merging of seasonal permafrost with permafrost. Thus, the formation of non-merging permafrost is of a reciprocating nature.
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