Soil temperature regimes on the southern border of the zone of frozen bogs in Western Siberia

Abstract

Numto Nature Park (Western Siberia) is one of the southernmost locations of frozen peatlands. In 2019–2022, soil temperatures were measured there using an automatic monitoring system. The measurements were carried out for Murshik Hemic Cryic Histosol on flat palsa peatlands and frost mounds. The temperature for Folic Albic Podzol was measured for reference. The average annual temperature of the soil surface was found to be positive in all study areas: + 0.8 °C on the frost mound; +1.3 °C on the flat palsa peatlands; and + 4.5 °C in Folic Albic Podzol. The low temperature on the frost mound is due to the low snow cover, so the soil surface cools down to the minimum in winter. As for flat palsa peatlands, peat remains frozen all year round, starting from a depth of 0.5 m. On the frost mound, at the same time, the depth of seasonal thawing is 2 m. In winter, the frost penetration on the mound doesn't reach the permafrost table, revealing its probable degradation in case of further climate warming. According to the soil thermal regime classification, the soil on the frost mound falls into the category of long-term seasonally frozen soils, while high palsa peatlands nearby Nadym Town belong to the permafrost type. Data from the nearby meteorological station show a trend of rising air temperature and rainfall. An analysis of the soil temperature regime and the course of exogenous processes demonstrate that Murshik Hemic Cryic Histosol on high palsa peatlands is unstable. Permafrost persists there due to the low thickness of the snow cover on the peaks, which facilitates winter cooling. If the snow-cover height increases, permafrost is likely to melt there.