Variability of temperature regime in the ridge-hollow bog complex of the Mukhrino station

Introduction. Siberian bog ecosystems are among the world's largest carbon stores and play a critical role in global climate regulation through the long-term accumulation of organic matter in peat strata. The rate of carbon exchange in these ecosystems is largely controlled by climatic and hydrological conditions. However, the quantitative impact of specific hydrometeorological factors, including temperature, on the rate of carbon fluxes remains poorly understood. The temperature regime of organic bog soils is characterized by high inertia and smaller diurnal and seasonal variations compared to mineral soils, due to the high heat capacity of water and the low thermal conductivity of peat. This stability creates unique conditions for biota, but simultaneously increases the ecosystem's sensitivity to changes in the hydrological regime. In the context of modern climate change, studying the thermal characteristics of bogs is particularly relevant for assessing their functional state, stability, and predicting carbon balance dynamics. The aim of this study is a comprehensive analysis of long-term air temperature patterns in a wetland ecosystem using the Mukhrino research station in central Western Siberia as an example.

The study focused on typical raised bogs of the middle taiga subzone located within the Mukhrino research station (60°54' N, 68°42' E). The station is a unique model site with a distinct microtopography of a ridge-hollow complex. The study is based on a 12-year continuous microclimatic dataset (2012–2024) obtained using an automatic weather station. Measurements were conducted simultaneously on two key microtopographic elements: the ridge (a more drained, elevated structure) and the hollow (a depression with excessive moisture). To ensure reliability, the data underwent quality control procedures, including the identification and interpolation of minor gaps, as well as comparative calibration in 2024. Long-term (60-year) data from the Roshydromet weather station in Khanty-Mansiysk, as well as ERA5 Land global climate reanalysis data, were used to provide regional context and verify the data.

The analysis revealed pronounced spatiotemporal variability in temperature regimes, closely linked to microtopography and seasonal dynamics.

In winter (December–February), under clear anticyclonic conditions and weak insolation, more intense radiative cooling is observed in the hollow. Nighttime air temperatures in the hollow can be 2–4°C lower than on the ridge, where the regime is milder and more stable. In summer (June–August), the situation changes: the better-drained and less humid surface of the ridge warms more intensely. The average daily temperature on the ridge in July can exceed that of the natural wetland by 1–1.5°C. The daily temperature range on the ridge in summer is significantly higher (9–12°C) than in the wetland (3–5°C). In spring and fall, these differences even out.

A comparison of data from the Mukhrino station and the Khanty-Mansiysk weather station clearly revealed the urban "heat island" effect. In winter, temperatures in the city are consistently 2–3°C higher than in the natural wetland. Daily temperature ranges in the urban environment are also smoothed out (up to 6°C) compared to those in the wetland (10–12°C). In summer, the differences are minimal, and on clear days, the ridge can even be 0.5–1°C warmer than the city. Global reanalysis data demonstrate general synchronicity of climate trends with field measurements (the correlation coefficient between temperature series on the ridge and ERA5 was r = 0.78). However, systematic discrepancies were identified. ERA5 Land significantly smooths extreme values and daily amplitudes, which is due to its spatial resolution (~9 km²), which averages the heterogeneous landscape, and algorithmic filtering. In particular, nighttime temperature minimums on the ridge in winter (up to -35…-38 °C) are underestimated by 3–5 °C in the reanalysis, while daytime maximums in summer (up to +24…+26 °C) are underestimated by 4–6 °C. This indicates the inability of global models to adequately reflect the intense microclimatic processes within wetland landscapes. This study confirms that the temperature regime of Western Siberian raised bogs is characterized by a complex spatiotemporal organization determined by microtopography (ridge/hollow), underlying surface moisture, and regional climate trends. The significant discrepancies identified between local field measurements, urban weather station data, and global reanalyses highlight the critical importance of long-term local monitoring for a fundamental understanding of wetland ecosystem functioning. Only data with high spatial and temporal detail allows for the accurate assessment of extreme parameters necessary for verifying climate models, accurately calculating carbon balances, and developing scientifically based strategies for the conservation and adaptive management of these vulnerable and ecologically significant natural sites in the face of anthropogenic climate change.