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![The Process of Thermokarst Lake Formation in Ice-rich Yedoma Permafrost. Stage I: Permafrost stage, Yedoma with major ice wedges. Stage II: Thaw processes lead to thermokarst lake formation. Stages III, IV: Thaw progression results in horizontal and vertical lake expansion. Figure based on data from [141,142].](publication/341048978/figure/fig1/AS:886003262820363@1588251047949/The-Process-of-Thermokarst-Lake-Formation-in-Ice-rich-Yedoma-Permafrost-Stage-I.png)
The Process of Thermokarst Lake Formation in Ice-rich Yedoma Permafrost. Stage I: Permafrost stage, Yedoma with major ice wedges. Stage II: Thaw processes lead to thermokarst lake formation. Stages III, IV: Thaw progression results in horizontal and vertical lake expansion. Figure based on data from [141,142].
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Permafrost covers a quarter of the northern hemisphere land surface and contains twice the amount of carbon that is currently present in the atmosphere. Future climate change is expected to reduce its near-surface cover by over 90% by the end of the 21st century, leading to thermokarst lake formation. Thermokarst lakes are point sources of carbon d...
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... thaw progression is generally rapid in the first years and slows down over time [44]. Overall, taliks facilitate rapid thaw beneath lakes and cause deeper carbon stocks to become bioavailable (Figure 1) [21,[47][48][49] [141,142]. ...
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... There has been a growing interest in how climate warming will affect northern wetlands here, because temperature increases can enhance evaporation rates, thaw permafrost, drain ponds, or initiate the development of new ponds. Warmer substrates can increase the thaw depth of water bodies, and temperature has an impact on vegetation growth and greenhouse gases, including water vapor, methane, and carbon dioxide (Negandhi et al., 2013;Andresen and Lougheed, 2015;Wrona et al., 2016;Zandt et al., 2020;Kreplin et al., 2021;Dyke and Sladen, 2022;Miner et al., 2022;Rehder et al., 2023). This study of pond thermal regimes at Polar Bear Pass (PBP) adds to this body of literature by evaluating the seasonal and inter-seasonal temperature regime of small tundra ponds ubiquitous to an extensive, low-gradient wetland in the Canadian High Arctic spanning warm and cool spring and summer. ...
This study evaluates the seasonal and inter-seasonal temperature regime of small tundra ponds ubiquitous to an extensive, low-gradient wetland in the Canadian High Arctic. Pond temperatures can modify evaporation and ground thaw rates, impact losses of greenhouse gases, and control the timing and emergence of insects and larvae critical for migratory-bird feeding habits. We focus our study on thaw ponds with a range of hydrologic linkages and sizes across Nanuit Itillinga, formerly known as Polar Bear Pass (PBP), Bathurst Island, and compare their thermal signals to other Arctic ponds. Pond temperatures and water levels were evaluated using temperature and water level loggers and verified by regular manual measurements. Other environmental data collected included microclimate, frost table depths, and water conductivity. Our results show that there is much variability in pond thermal regimes over seasons, years, and space. Cumulative relative pond temperatures were similar across years, with ponds normally reaching 10–15 °C for short to longer periods, except in 2013, which experienced a cold summer season during which pond temperatures never exceeded 5 °C. Pond frost tables and water conductivities respond to variable substrate conditions and pond thermal patterns. This study contributes to the ongoing discussion on climate warming and its impact on Arctic landscapes.
... For example, thaw lake cycles alter thermal regimes and moisture content in permafrost, leading to changes in ground stability and the formation of thermokarst features (Andresen & Lougheed, 2015;Jorgenson & Shur, 2007). These changes can affect vegetation patterns by modifying nutrient availability and soil conditions, influence wildlife habitats by altering landscape structure, and impact water flow patterns by changing drainage networks, thereby influencing the broader ecological and hydrological systems (Jones et al., 2022;Zandt et al., 2020). A recent study used satellite remote sensing to track lake drainage events across the entire northern permafrost region and revealed significant spatial heterogeneity in the distribution of drained lakes. ...
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St. Lawrence Island in the Bering Strait has experienced a drastic increase in lake drainage since 2018, suggesting that the region may be reaching a critical environmental threshold or tipping point. This study used satellite images to track changes in over 3,000 lakes over two decades, discovering that warmer autumns with temperatures above 6°C greatly increase the chance of lakes draining. This indicates that the region's permafrost is becoming unstable due to higher temperatures. Permafrost thawing happens because the increased warmth causes the ice within the permafrost to melt, leading to the collapse and drainage of lakes. Such changes are important not only because they transform the local landscape but also because they can impact the people and wildlife depending on these lakes for survival. Understanding these patterns helps predict future changes and assists in preparing for and possibly preventing the negative impacts of these environmental changes. This study highlights how global warming can lead to significant changes in Arctic regions, which can have lasting effects on both the environment and human communities.
... The seasonal fluctuations of thermokarst lakes can affect the surrounding soil moisture and heat properties, leading to degradation of alpine meadow ecosystems [19]. Moreover, thermokarst lakes influence the stability of nearby infrastructure by conveying heat to the permafrost beneath embankments [20,21]. In the context of climate warming, it is anticipated that the hazards arising from thermokarst processes and permafrost degradation will intensify [22]. ...
Climate change is causing permafrost in the Qinghai–Tibet Plateau to degrade, triggering thermokarst hazards and impacting the environment. Despite their ecological importance, the distribution and risks of thermokarst lakes are not well understood due to complex influencing factors. In this study, we introduced a new interpretable ensemble learning method designed to improve the global and local interpretation of susceptibility assessments for thermokarst lakes. Our primary aim was to offer scientific support for precisely evaluating areas prone to thermokarst lake formation. In the thermokarst lake susceptibility assessment, we identified ten conditioning factors related to the formation and distribution of thermokarst lakes. In this highly accurate stacking model, the primary learning units were the random forest (RF), extremely randomized trees (EXTs), extreme gradient boosting (XGBoost), and categorical boosting (CatBoost) algorithms. Meanwhile, gradient boosted decision trees (GBDTs) were employed as the secondary learning unit. Based on the stacking model, we assessed thermokarst lake susceptibility and validated accuracy through six evaluation indices. We examined the interpretability of the stacking model using three interpretation methods: accumulated local effects (ALE), local interpretable model-agnostic explanations (LIME), and Shapley additive explanations (SHAP). The results showed that the ensemble learning stacking model demonstrated superior performance and the highest prediction accuracy. Approximately 91.20% of the total thermokarst hazard points fell within the high and very high susceptible areas, encompassing 20.08% of the permafrost expanse in the QTP. The conclusive findings revealed that slope, elevation, the topographic wetness index (TWI), and precipitation were the primary factors influencing the assessment of thermokarst lake susceptibility. This comprehensive analysis extends to the broader impacts of thermokarst hazards, with the identified high and very high susceptibility zones affecting significant stretches of railway and highway infrastructure, substantial soil organic carbon reserves, and vast alpine grasslands. This interpretable ensemble learning model, which exhibits high accuracy, offers substantial practical significance for project route selection, construction, and operation in the QTP.
... Similar to thermokarst gullies, the development of thermokarst lakes can accelerate soil organic matter decomposition, triggering a substantial CO 2 release into the atmosphere (Elder et al., 2018;Serikova et al., 2019;Yang et al., 2023). Meanwhile, permafrost thaw and increasing hydrological flow will deliver more labile C and nutrients into thermokarst lakes (In't Zandt et al., 2020;Vonk et al., 2015), which could further stimulate CO 2 production by accelerating DOC decomposition . More importantly, thermokarst lakes are regarded as foci of CH 4 release (Heslop et al., 2020). ...
Our knowledge on permafrost carbon (C) cycle is crucial for understanding its feedback to climate warming and developing nature-based solutions for mitigating climate change. To understand the characteristics of permafrost C cycle on the Tibetan Plateau, the largest alpine permafrost region around the world, we summarized recent advances including the stocks and fluxes of permafrost C and their responses to thawing, and depicted permafrost C dynamics within this century. We find that this alpine permafrost region stores approximately 14.1 Pg (1 Pg=1015 g) of soil organic C (SOC) in the top 3 m. Both substantial gaseous emissions and lateral C transport occur across this permafrost region. Moreover, the mobilization of frozen C is expedited by permafrost thaw, especially by the formation of thermokarst landscapes, which could release significant amounts of C into the atmosphere and surrounding water bodies. This alpine permafrost region nevertheless remains an important C sink, and its capacity to sequester C will continue to increase by 2100. For future perspectives, we would suggest developing long-term in situ observation networks of C stocks and fluxes with improved temporal and spatial coverage, and exploring the mechanisms underlying the response of ecosystem C cycle to permafrost thaw. In addition, it is essential to improve the projection of permafrost C dynamics through in-depth model-data fusion on the Tibetan Plateau.
... Lakes contribute to a significant fraction of the global carbon budget (Bogard et al., 2019;Holgerson & Raymond, 2016;In't Zandt et al., 2020;Jia et al., 2022;Pierre et al., 2019;Raymond et al., 2013;Tan et al., 2017;Yan et al., 2018). However, there is considerable variability in the direction and magnitude of various types of lake CO 2 fluxes (Holgerson & Raymond, 2016;Li et al., 2021), and responses to climate change . ...
Dissolved inorganic carbon (DIC) sources, transportation, and transition in inland water bodies have been intensively studied due to their important role in the global carbon cycle. While glacier‐fed lakes play a crucial role in global carbon cycling, related studies are limited. In this study, we investigated the spatiotemporal variability of DIC in the maritime glacier‐fed lakes of the southeastern Tibetan Plateau, identifying the carbon sources and potential controlling factors of DIC pathways The results revealed significant temporal variations in DIC and δ¹³C‐DIC, with averages of 7.29 ± 0.45 mg C L⁻¹ and –8.6 ± 0.2‰ in summer, and 3.40 ± 0.54 mg C L⁻¹ and –7.4 ± 0.6‰ in winter, respectively. Temporal variations in DIC and δ¹³C‐DIC were mainly controlled by carbonates weathering and silicate weathering processes. The chemical weathering reactions facilitate the consumption of dissolved CO2. Undersaturated pCO2 (120.02 ± 29.18 μatm) relative to atmospheric equilibrium suggests considerable capacity for CO2 uptake within glacier‐fed lakes system. We estimated that the maritime glacier‐fed lakes in the southeastern Tibetan Plateau absorb a total of 9.6 ± 2.7 × 10⁻³ Tg C‐CO2 yr⁻¹, highlighting their significant contribution to the global carbon budget. The distinctive landscape of the glacier‐fed system and the vulnerable weathering environment result in seasonal and spatial variations of DIC concentration and δ¹³C‐DIC values, as well as the chemical weathering‐induced CO2 sink in glacier regions. Given the accelerated glacier retreat observed in this area, further studies on the temporal variability of DIC in the water column are urgently needed to identify the mechanisms driving the biogeochemical reactions inside glacier‐fed lake. Our study highlights the unrecognized role of maritime glacier‐fed lakes as CO2 sinks and emphasizes their significance in regional carbon budgets.
... Due to enhanced remote sensing imagery and classification algorithms, an improved survey and inventory is now possible and needed. An example of the relevance of such a dataset is the need for characterizing and monitoring the small water bodies in the boreal foresttundra ecozone, allowing to better understand their formation and roles of permafrost thaw (thermokarst) ponds in the biogeochemical carbon cycle (Negandhi et al., 2013;Heslop et al., 2020;Zandt et al., 2020). These numerous and widespread ponds result from abrupt permafrost thaw (Walter Anthony et al., 2018) and generally exhibit sizes below 0.01 km 2 and depths under 5 m, and are much more active biogeochemically than larger lakes (Abnizova et al., 2012;Bégin and Vincent, 2017;Arsenault et al., 2022). ...
... These numerous and widespread ponds result from abrupt permafrost thaw (Walter Anthony et al., 2018) and generally exhibit sizes below 0.01 km 2 and depths under 5 m, and are much more active biogeochemically than larger lakes (Abnizova et al., 2012;Bégin and Vincent, 2017;Arsenault et al., 2022). Throughout their life span, they show diverse optical and morphological dynamics and are biogeochemical hotspots for the release of carbon dioxide (CO 2 ), nitrous oxide (N 2 O) and especially methane (CH 4 ), from permafrost to the atmosphere, through microbial and photochemical transformations (Breton et al., 2009;Edwards et al., 2009;Vonk et al., 2015;Zandt et al., 2020). Accounting for the role of these ponds is increasingly important due to permafrost warming, which generates more thaw ponds, potentially increasing greenhouse gas emissions (Holgerson and Raymond, 2016;Kuhn et al., 2018;Heslop et al., 2020). ...
Small water bodies (< 0.01 km2) showing diverse limnological properties occur in great abundance across the boreal forest and tundra landscapes of the Arctic and Subarctic. However, their classification, geographical distribution and collective importance for water, heat, nutrient, contaminant and carbon cycles are still poorly constrained. One important step for better understanding the role and evolution of small water bodies in the fast-changing northern landscapes is to develop image analysis protocols that allow their automatic remote sensing detection, delineation and inventory. In this study, we set an image analysis protocol (High Latitude Water – HLWATER V1.0) based on a trained supervised Mask R-CNN deep learning model over PlanetScope imagery for the automatic detection and delineation of small lakes and ponds that were absent in existing datasets. Most of our training dataset comprised water bodies smaller than 0.01 km2 (97%) and spanned a wide range of environmental and hydrological settings, from the sporadic to the continuous permafrost zones of Canada. The model was tested as a fully autonomous approach for eastern Hudson Bay, Nunavik (Subarctic Canada), a region that poses challenges for water remote sensing given the abundance and variety of small water bodies. These are mainly permafrost thaw and glacial basin ponds in the boreal forest-tundra in challenging optical settings influenced by vegetation or topography shadowing, or revealing peat water logging, fen and bog pond conditions. A multi-scale validation approach was developed using water body delineations from PlanetScope imagery and ultra-high resolution orthomosaics from Unoccupied Aerial Systems. This procedure allowed a sub-pixel assessment and identified the limitations and strengths of the trained model for detecting small and large water bodies. The results varied according to different landscape units, with mean Intersection over Union (IoU) 0.5 F1 Scores of 0.53 to 0.71 and mean F1 Scores of 0.62 to 0.95. Considering 166 m2 as the minimum pond size detection threshold, the IoU 0.5 F1 Scores were 0.7 to 0.91 and F1 Scores were 0.76 to 0.83, evaluated by comparing the model results with ultra-high resolution manual delineations. The image analysis protocol and trained model show high potential for extension to other boreal forest-tundra regions of the Arctic and Subarctic, allowing for detailed inventories of optically and morphologically diverse small water bodies over large areas of the circumpolar North.
... Even though it is certain that water-logged conditions in degraded permafrost soils, e.g., as a consequence of adjacent thermokarst development, significantly enhance the deepening of the active layer compared to well-drained permafrost-degraded soils (Nitzbon et al. 2020), the shift in SOM stabilization processes in degraded permafrost soils is often not considered in the current discussion. Furthermore, a potential long-term perspective with ongoing climate warming is not only considering permafrost degradation with more water-saturated soils, but also that more lakes and wetlands could disappear due to drainage (in't Zandt et al. 2020;Jones et al. 2022). An evaluation of contrasting permafrost degradation landscapes under dry and wet conditions is still lacking more field evidence to resolve the fate of SOM during permafrost degradation. ...
Permafrost soils in the northern hemisphere are known to harbor large amounts of soil organic matter (SOM). Global climate warming endangers this stable soil organic carbon (SOC) pool by triggering permafrost thaw and deepening the active layer, while at the same time progressing soil formation. But depending, e.g., on ice content or drainage, conditions in the degraded permafrost can range from water-saturated/anoxic to dry/oxic, with concomitant shifts in SOM stabilizing mechanisms. In this field study in Interior Alaska, we investigated two sites featuring degraded permafrost, one water-saturated and the other well-drained, alongside a third site with intact permafrost. Soil aggregate- and density fractions highlighted that permafrost thaw promoted macroaggregate formation, amplified by the incorporation of particulate organic matter, in topsoils of both degradation sites, thus potentially counteracting a decrease in topsoil SOC induced by the permafrost thawing. However, the subsoils were found to store notably less SOC than the intact permafrost in all fractions of both degradation sites. Our investigations revealed up to net 75% smaller SOC storage in the upper 100 cm of degraded permafrost soils as compared to the intact one, predominantly related to the subsoils, while differences between soils of wet and dry degraded landscapes were minor. This study provides evidence that the consideration of different permafrost degradation landscapes and the employment of soil fractionation techniques is a useful combination to investigate soil development and SOM stabilization processes in this sensitive ecosystem.
... On the other hand, CH4 production potentials over 96 days were several orders of magnitude higher than in undisturbed PF samples. This may be due 420 to proliferation of a highly productive methanogenetic community over time, but also due to additional nutrient input from surrounding non-PF fens or bogs (In ' T Zandt et al., 2020). ...
Permafrost soils are undergoing rapid thawing due to climate change and global warming. Permafrost peatlands are especially vulnerable since they are located near the southern margin of the permafrost domain in the discontinuous and sporadic permafrost zones. They store large quantities of carbon (C) which, upon thawing, are decomposed and released as carbon dioxide (CO2), methane (CH4) or dissolved organic carbon (DOC). This study compares carbon degradation in three permafrost peatland ecosystems in Finnmark, Norway, which represent a well-documented chronosequence of permafrost formation. Peat cores from active layer, transition zone and permafrost zone were thawed under controlled conditions and incubated for up until 350 days under initially-oxic or anoxic conditions while measuring CO2, CH4 and DOC production. Carbon degradation varied among the three peat plateaus but showed a similar trend over depth with largest CO2 production rates in the top of the active layer and in the permafrost. Despite marked differences in peat chemistry, post-thaw CO2 losses from permafrost peat throughout the first 350 days in the presence of oxygen reached 67–125 % of those observed from the top of the active layer. CH4 production was only measured after a prolonged anoxic lag phase in samples from transition zone and permafrost, but not in active layer samples. CH4 production was largest in thermokarst peat sampled next to decaying peat plateaus. DOC production by active layer samples throughout 350 days incubation exceeded gaseous C loss (up to 23-fold anoxically), whereas little DOC production or uptake was observed for permafrost peat after thawing. Taken together, permafrost peat in decaying Norwegian peat plateaus degrades at rates similar to active layer peat, while highest CH4 production can be expected after inundation of thawed permafrost material in thermokarst ponds.
... This emission is attributed to the rapid availability of organic matter in the freshly thawed soil, providing substance for microbial mineralization processes. As a result, it leads to a positive feedback loop amplifying climate warming (Serikova et al., 2019;In't Zandt et al., 2020). Contrary to previous understanding, recent evidence indicates that permafrost thaw can also induce extensive drying of wetlands. ...
Climate warming holds the potential to cause extensive drying of wetlands in the Arctic, but the warming-drying effects on belowground ecosystems, particularly micro-eukaryotes, remain poorly understood. We investigated the responses of soil micro-eukaryotic communities, including fungi, protists, and microbial metazoa, to decadal drainage manipulation in a Siberian wet tundra using both amplicon and shotgun metagenomic sequencing. Our results indicate that drainage treatment increased the abundance of both fungal and non-fungal micro-eukaryotic communities, with key groups such as Ascomycota (mostly order Helotiales), Nematoda, and Tardigrada being notably abundant in drained sites. Functional traits analysis showed an increase in litter saprotrophic fungi and protistan consumers, indicating their increased activities in drained sites. The effects of drainage were more pronounced in the surface soil layer than the deeper layer, as soils dry and warm from the surface. Marked compositional shifts were observed for both communities, with fungal communities being more strongly influenced by drainage-induced vegetation change than the lowered water table itself, while the vegetation effect on non-fungal micro-eukaryotes was moderate. These findings provide insights into how belowground micro-eukaryotic communities respond to the widespread drying of wetlands in the Arctic and improve our predictive understanding of future ecosystem changes.
... During thermokarst lake development, the concentrations of dissolved organic carbon (DOC), Fe, Al, Mn, and some divalent heavy metals in the water column decreases, while pH, and nitrate and phosphate concentrations increase (Manasypov et al., 2015(Manasypov et al., , 2020Pokrovsky et al., 2011). The processes associated with small lake formation, input of partly decomposed organics, and activity of microbial communities stimulate CO 2 and CH 4 production in lake sediments (In't Zandt et al., 2020;Vonk et al., 2015). In contrast, CH 4 emission decreases with an increase in the lake age and size (Bastviken et al., 2004;Shirokova et al., 2013); the underlying mechanisms, however, remain unclear. ...
... The SUVA 254 , a parameter indicating the DOC aromaticity (Edzwald & Tobiason, 1999;Matilainen et al., 2011;Minor & Stephens, 2008), showed that aromaticity increased with increasing lake size (Table 1, SUVA column), supporting the observed decreasing CO 2 production. DOC quality was used as a proxy of C availability for microbial decomposition (In't Zandt et al., 2020;Laurion et al., 2021;Shirokova et al., 2009). The CO 2 production, however, decreased 2-3 times with depth in the small and medium lakes (Figures 2a-c and 3a,c,d) according to the proposed dependency on C decomposability, which was not revealed by the SUVA 254 results. ...
Shallow thermokarst lakes are important sources of greenhouse gases (GHGs) such as methane (CH 4 ) and carbon dioxide (CO 2 ) resulting from continuous permafrost thawing due to global warming. Concentrations of GHGs dissolved in water typically increase with decreasing lake size due to coastal abrasion and organic matter delivery. We hypothesized that (i) CH 4 oxidation depends on the natural oxygenation gradient in the lake water and sediments and increases with lake size because of stronger wind‐induced water mixing; (ii) CO 2 production increases with decreasing lake size, following the dissolved organic matter gradient; and (iii) both processes are more intensive in the upper than deeper sediments due to the in situ gradients of oxygen (O 2 ) and bioavailable carbon. We estimated aerobic CH 4 oxidation potentials and CO 2 production based on the injection of ¹³ C‐labeled CH 4 in the 0–10 cm and 10–20 cm sediment depths of small (~300 m ² ), medium (~3000 m ² ), and large (~10 ⁶ m ² ) shallow thermokarst lakes in the West Siberian Lowland. The CO 2 production was 1.4–3.5 times stronger in the upper sediments than in the 10–20 cm depth and increased from large (158 ± 18 nmol CO 2 g ⁻¹ sediment d.w. h ⁻¹ ) to medium and small (192 ± 17 nmol CO 2 g ⁻¹ h ⁻¹ ) lakes. Methane oxidation in the upper sediments was similar in all lakes, while at depth, large lakes had 14‐ and 74‐fold faster oxidation rates (5.1 ± 0.5 nmol CH 4 ‐derived CO 2 g ⁻¹ h ⁻¹ ) than small and medium lakes, respectively. This was attributed to the higher O 2 concentration in large lakes due to the more intense wind‐induced water turbulence and mixing than in smaller lakes. From a global perspective, the CH 4 oxidation potential confirms the key role of thermokarst lakes as an important hotspot for GHG emissions, which increase with the decreasing lake size.
