The landscapes in the discontinuous permafrost area of Western Siberia are unique objects for assessing the direct and indirect impact of permafrost on greenhouse gas fluxes. The aim of this study was to identify the influence of permafrost on the CO2 emission at the landscape and local levels. The CO2 emission from the soil surface with the removed vegetation cover was measured by the closed chamber method, with simultaneous measurements of topsoil temperature and moisture and thawing depth in forest, palsa, and bog ecosystems in August 2022. The CO2 emissions from the soils of the forest ecosystems averaged 485 mg CO2 m(-2) h(-1) and was 3-3.5 times higher than those from the peat soils of the palsa mound and adjacent bog (on average, 150 mg CO2 m(-2) h(-1)). The high CO2 emission in the forest was due to the mild soil temperature regime, high root biomass, and good water-air permeability of soils in the absence of permafrost. A considerable warming of bog soils, and the redistribution of CO2 between the elevated palsa and the bog depression with water flows above the permafrost table, equalized the values of CO2 emissions from the palsa and bog soils. Soil moisture was a significant factor of the spatial variability in the CO2 emission at all levels. The temperature affected the CO2 emission only at the sites with a shallow thawing depth.

Global warming has aggravated the problem of permafrost degradation, the long-term variation of which is not well estimated. In this study, a fully coupled hydrothermal dynamics cold region hydrologic model was used to quantify the historical spatial-temporal characteristics of permafrost degradation by estimating the depth to permafrost table (DPT), taliks in different subbasins, maximum frozen depth (MFD) for seasonally frozen ground (SFG), thaw date (TD), and annual number of frozen days (NFD) in the headwaters of the Yellow River (HWYR) in eastern High Mountain Asia. The model considered the taliks and successfully estimated four historical finescale permafrost maps. Permafrost degradation began with the enlargement of active layer thickness (ALT), formation of taliks, rise in the permafrost bottom, and merging of the permafrost table and bottom, and ended with a decrease in MFD. From 1980 to 2014, the permafrost area (PA) in the study area decreased by a total of 17,849 km2 at a rate of more than -7100 km2/decade (-5.8 %/decade). The mean DPT increased by 0.8 m at 31.76 cm/decade and more than 100 cm/decade at the grid scale. The absolute MFD (AMFD) decreased by 0.11 m at -14.47 cm/decade. The mean TD decreased by 14.28 days at -5.56 days/decade and more than -20 days/ decade at the grid scale. The mean NFD decreased by 25.51 days at -9.97 days/decade. The lowland area had a smaller NFD and an earlier TD than the mountainous area. Basins with a large air temperature (AT) and small elevation had a small DPT, MFD, TD, NFD, a large rate of decrease in TD and NFD, and increase in absolute DPT (ADPT), and a small rate of decrease in AMFD. The rates of increase in ADPT and decrease in AMFD were close to 0 when the change in AT was lower than 0.55 degrees C/decade.

The mechanisms of hydrological processes, biochemical cycles, and permafrost revolution, and the potential impacts of climate change on these, are still poorly quantified in alpine regions, partly due to a lack of understanding of soil water dynamics in the permafrost active layer. In this study, soil water in the active layer was monitored in-situ at nine sites, including wet meadow (WM), alpine meadow (AM), alpine steppe (AS), transitional area-steppe (TA-S), transitional area-meadow (TA-M), bare land (BL), extremely degraded wet meadow (EDWM), alpine steppe on south-facing slope (ASSF), and alpine meadow on north-facing slope (AMNF) regions. These sites are located in the hinterland of the Qinghai-Tibet Plateau (QTP). Ground-ice distributions and isotope variations under different alpine ecosystems were also examined. The results demonstrate that soil water content was low at 0.5-m depth and high at the surface and at 1.0-m depth in the soil profiles from the TA-S, BL, EDWM, ASSF, and AMNF sites. However, denser vegetation coverage masked the effects of the freeze thaw processes, which leading soil water content increased gradually with soil depth. Moreover, rainfall infiltration for recharging soil water in the lower layers was hampered due to the buffering action of mattic epipedons and the existence of clayed layers. Additionally, preferential flow often occurred in the degraded alpine meadows, which supplied deeper soil water. The Pearson correlation coefficients between soil water in the deeper layers and ground-ice were above 0.67 (significance < 0.05), suggesting that deep soil water had a stronger effect on the formation of ground-ice near the permafrost table than soil water at the surface and middle root layers. Furthermore, results from the analysis of isotopic tracers suggest that precipitation directly recharged more ground-ice near permafrost table at the EDWM, ASSF, and AWNF sites, but less so at the WM, AM, AS, and BL sites, due to greater evapotranspiration and land cover. These results provide insights into the effect future climate warming can have on ecological succession and regional hydrological processes.

Fine scale three-dimensional (3D) permafrost distributions at the basin scale are currently lacking. They are needed to monitor climatic and ecosystem change and for the maintenance of infrastructure in cold regions. This paper determined the horizontal and vertical distributions of permafrost and its quantitative responses to climate warming in the High Asia region by constructing a quasi-3D model that couples heal transfer and water movement and is forced by spatially-interpolated air temperatures using an elevation-dependent regression method. Four air temperature scenarios were considered: the present stale and air temperature increases of 1, 2 and 3 degrees C A fine-scale permafrost map was constructed. The map considered taliks and local factors including elevation, slope and aspect, and agreed well with field observations. Permafrost will experience severe degradation with climate warming, with decreases in area of 36% per degree increase in air temperature, increases in the depth-to-permafrost table of 2.67 m per degree increase in air temperature, and increases in 15 m-depth ground temperatures of 125 degrees C per degree 'increase in air temperature. Permafrost is more vulnerable in and beside river valleys than in high mountains, and on sunny rather than shady slopes. These results provide an effective reference for permafrost prediction and 'infrastructure and ecosystem management in cold regions affected by global warming. (C) 2019 Elsevier B.V. All rights reserved.

Soil porewaters are a vital component of the ecosystem as they are efficient tracers of mineralweathering, plant litter leaching, and nutrient uptake by vegetation. In the permafrost environment, maximal hydraulic connectivity and element transport from soils to rivers and lakes occurs via supra-permafrost flow (i.e. water, gases, suspended matter, and solutes migration over the permafrost table). To assess possible consequences of permafrost thaw and climate warming on carbon and Green House gases (GHG) dynamics we used a substituting space for time approach in the largest frozen peatland of theworld. We sampled stagnant supra-permafrost (active layer) waters in peat columns of western Siberia Lowland (WSL) across substantial gradients of climate (-4.0 to -9.1 degrees C mean annual temperature, 360 to 600 mm annual precipitation), active layer thickness (ALT) (N300 to 40 cm), and permafrost coverage (sporadic, discontinuous and continuous). Weanalyzed CO2, CH4, dissolved carbon, and major and trace elements (TE) in 93 soil pit samples corresponding to several typical micro landscapes constituting theWSL territory (peat mounds, hollows, and permafrost subsidences and depressions). We expected a decrease in intensity of DOC and TE mobilization from soil and vegetation litter to the suprapermafrost waterwith increasing permafrost coverage, decreasing annual temperature and ALT along a latitudinal transect from 62.3 degrees N to 67.4 degrees N. However, a number of solutes (DOC, CO2, alkaline earth metals, Si, trivalent and tetravalent hydrolysates, and micronutrients (Mn, Co, Ni, Cu, V, Mo) exhibited a northward increasing trend with highest concentrations within the continuous permafrost zone. Within the substituting space for time climate change scenario and northward shift of the permafrost boundary, our results suggest that CO2, DOC, and many major and trace elements will decrease their concentration in soil supra-permafrost waters at the boundary between thaw and frozen layers. As a result, export of DOC and elements from peat soil to lakes and rivers of the WSL (and further to the Arctic Ocean) may decrease. (C) 2018 Elsevier B.V. All rights reserved.

Thawing permafrost on the Qinghai-Tibet Plateau (QTP) has great impacts on the local hydrological process by way of causing ground ice to thaw. Until now there is little knowledge on ground ice hydrology near permafrost table under a warming climate. This study applied stable tracers (isotopes and chloride) and hydrograph separation model to quantify the sources of ground ice near permafrost table in continuous permafrost regions of the central QTP. The results indicated that the ground ice near permafrost table was mainly supplied by active layer water and permafrost water, accounting for 58.9 to 87.0% and 13.0 to 41.1%, respectively, which implying that the active layer was the dominant source. The contribution rates from the active layer to the ground ice in alpine meadow (59 to 69%) was less than that in alpine steppe (70 to 87%). It showed well-developed hydrogeochemical depth gradients, presenting depleted isotopes and positive chemical gradients with depth within the soil layer. The effects of evaporation and freeze-out fractionation on the soil water and ground ice were evident. The results provide additional insights into ground ice sources and cycling near permafrost table in permafrost terrain, and would be helpful for improving process-based detailed hydrologic models under the occurring global warming. (C) 2018 Elsevier B.V. All rights reserved.

This study investigates whether the diurnal temperature cycle affects the geothermal regime on the Qinghai-Tibet Plateau. To separately characterize this effect, the impact of climatic warming on the ground's thermal regime is eliminated by setting the global warming rate to 0 degrees C/year. The diurnal temperature cycle at the natural ground surface is denoted as sinusoidal functions with amplitudes of 0, 5, 8, and 12 degrees C, respectively. A one-dimensional heat conduction model was utilized to compute the geo-temperature under the natural ground surface, eliminating the effect of geometric boundaries, such as the roadway's embankment, on the geothermal regime. The results show that the diurnal temperature cycle does affect the geothermal regime as (1) under the same mean annual ground temperature, the higher diurnal temperature fluctuation amplitude (DTFA) on the ground surface, the thinner the active layer; (2) the higher the DTFA, the colder the underlying soil. An analysis of the heat flow at the ground surface showed that the diurnal temperature cycle resulted in a net negative heat balance at the earth's surface. This heat loss induced by the diurnal temperature cycle cools the underlying soil. The results and analysis suggest that, currently, the documented numerical model which ignores the diurnal temperature cycle overestimates the warming of the underlying soil. This overestimation, if the DTFA at ground surface is 12 degrees C, would be up to 0.4 degrees C. Considering that pavement surface usually undergoes high diurnal temperature cycles, the impact of the DTFA on pavement subgrade's frost conditions and on the pavement deformation is simply discussed. Published by Elsevier B.V.