Estimates of the future methane (CH4) budget of northern permafrost landscapes remain highly uncertain with projections ranging from negligible to major CH4 releases to the atmosphere.

The German collaborative MOMENT project aims to address important gaps in process understanding of the high-latitude methane cycle using multi-scale methane flux observations in western Greenland linked to microbiological and biogeochemical laboratory studies. Through an innovative model-data integration framework, these novel datasets will be used to develop and evaluate land surface schemes of German Earth System Models (ESM) across terrestrial systems and multiple scales with the overarching goal to reduce uncertainties in future greenhouse gas projections.

We will introduce the overall project along with the innovations in experimental and observational techniques that facilitate observations at remote Arctic locations as well as in the lab. New remote sensing products allow for wall-to-wall mapping of structures on the finest scale across the Arctic, while novel computational infrastructure and modelling frameworks help with integration of all this information into next generation ESMs.

Selected preliminary results of the first field season and lab experiments will be highlighted.

How to cite: Sachs, T. and the the MOMENT project team: The MOMENT Project - Permafrost Research Towards Integrated Observation and Modelling of the Methane Budget of Ecosystems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21829, https://doi.org/10.5194/egusphere-egu24-21829, 2024.

The ESA funded MethaneCAMP project has focused on assessing, improving, and analysing satellite observations of methane (CH4) in the Arctic in support of the collaborative ESA-NASA Arctic Methane and Permafrost Challenge (AMPAC) initiative. 

Traditionally, the high latitude conditions have received minor attention when the satellite retrievals for methane have been optimised for global purposes as there has been known challenges caused by high solar zenith angles, low reflectivity over snow and ice, frequent cloudiness, varying polar vortex conditions and limited number of validation data sets. Now when the two-year MethaneCAMP project is finishing, we will demonstrate the recent improvements in the observation capacity over the polar regions by assessing and optimising methane SWIR and TIR retrievals at high northern latitudes. Moreover, the importance of AirCore reference observations of methane profiles in the varying polar vortex conditions will be highlighted.

We will analyse the long-term methane trends in the northern high latitudes and permafrost regions by using satellite observations and inverse modelling. We aim to demonstrate the potential of using satellite observations of methane together with modelling and surface observations in analysing spatial and temporal changes of the Arctic methane. Detection of methane hot spots will also be mentioned.

In MethaneCAMP project our focus has been on Sentinel 5P/TROPMI, GOSAT, GOSAT-2 and IASI XCH4 observations and GHGSat emission estimates. In this presentation we summarise the results of the project and discuss how the outcomes can be utilised in the AMPAC working group activities.

How to cite: Tamminen, J. and the MethaneCAMP project team: MethaneCAMP project – overview of results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20159, https://doi.org/10.5194/egusphere-egu24-20159, 2024.

Arctic permafrost has been identified as a critical element in the global climate system, since it stores a vast amount of carbon that is at high risk of being released under climate change. The feedbacks between permafrost carbon and climate change are moderated by complex interactions between physical, hydrological, biogeochemical, and ecological processes. Many of these are not well understood to date, and therefore also only rudimentarily represented in current Earth System Models (ESMs). A particular problem in this context is a scaling gap between processes and model grid.

The Q-ARCTIC project funded by the European Research Council (ERC) follows a synergetic approach by combining remote sensing and local-scale observations with modeling on scales from a few meters to hundreds of kilometers. The primary objective of Q-ARCTIC is to close the gap between process scales and the much coarser grid resolution of Earth System Models (ESMs), with a particular focus on the net effect of disturbance processes and associated changes in hydrology on the pan-Arctic scale. To close this gap, we developed new ESM modules representing subgrid through stochastic parameterizations, trained and evaluated with high-resolution remote sensing data and site-level observations.

We will present novel results based on in-situ observations that characterize prominent Arctic disturbance features, and satellite remote sensing products investigating fine scale (few meters) patterns in Arctic landscapes that are undergoing modifications linked to climate change. Targets investigated include for example sinking surfaces, wetness gradients in heterogeneous landscapes, or drained lake basins. Assimilation of these new datasets supported the development of new ESM model components that successfully capture the statistics of small-scale features, e.g. depressions linked to sinking surfaces, or surface water bodies that form when soil ice melts. Our results demonstrate that the ability to project the response of the high-latitude water, energy and carbon cycles to rising global temperatures may strongly depend on the ability to adequately represent the soil hydrology in permafrost affected regions.

How to cite: Göckede, M., Brovkin, V., Bartsch, A., and Heimann, M. and the Q-Arctic Team: Q-Arctic: A synergetic approach to observe and model pan-Arctic interactions between hydrology and carbon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14659, https://doi.org/10.5194/egusphere-egu24-14659, 2024.

The vulnerability of Arctic permafrost to climate change is evident, with anticipated widespread enhanced thawing under climate warming. This process may release substantial amounts of organic carbon. The positive feedback mechanism resulting from accelerated thaw and increased carbon emission is suspected to be a potential tipping element, possibly occurring within the 1.5 °C global warming range of the Paris Agreement. The consequences of Arctic permafrost thaw extend beyond carbon release, with the capability to drastically alter Earth's surface in Northern high latitudes.

This study employs high-resolution Large Eddy Simulations to investigate the impact of changing surfaces in the Arctic region on the neutrally stratified Atmospheric Boundary Layer. Utilizing a stochastic land cover model based on Gaussian Random Fields, representative permafrost landscapes are classified by distinct surface features. Experiments varying the areal fraction and surface correlation length of these surface features reveal significant insights into the sensitivity of the boundary layer to surface heterogeneity.

Key findings include a substantial impact of areal fraction of open water bodies on aggregated sensible heat flux at the blending height, suggesting a potential feedback mechanism: The smaller the areal fraction of open water bodies, the greater the sensible heat flux, the warmer the surface. Additionally, the blending height is significantly influenced by the correlation length of surface features. A longer surface correlation length leads to an increased blending height, highlighting the relevance of this metric for land surface models focused on Arctic permafrost.

How to cite: Schlutow, M. and Göckede, M.: Interaction of the Atmospheric Boundary Layer with degrading Arctic permafrost: A numerical study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9594, https://doi.org/10.5194/egusphere-egu24-9594, 2024.

As global temperatures continue to rise, a key uncertainty of terrestrial carbon (C) climate feedback is the rates of C loss upon abrupt permafrost thaw. This type of thawing - termed thermokarst - may in turn accelerate or dampen the response of microbial degradation of soil organic matter and carbon dioxide (CO₂) release to climate warming. However, such impacts have not yet been explored in experimental studies. Here, by experimentally warming three thermo-erosion gullies in an upland thermokarst site combined with incubating soils from another five thermokarst-impacted sites on the Tibetan Plateau, we investigate whether and how abrupt permafrost thaw would influence the responses of soil CO₂ release to climate warming. Our results show that warming-induced increase in soil CO₂ release is higher in thermokarst features than the adjacent non-thermokarst landforms. This larger warming response is mainly attributed to the lower substrate quality and higher abundance of microbial functional genes for recalcitrant C degradation in thermokarst-affected soils. Taken together, our study provides experimental evidence that abrupt permafrost thaw aggravates the warming-associated soil CO₂ loss, which will exacerbate the positive soil C-climate feedback in permafrost-affected regions under future warming scenarios.

How to cite: Yang, Y., Wang, G., and Peng, Y.: Intensified warming effects on soil respiration upon thermokarst formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2979, https://doi.org/10.5194/egusphere-egu24-2979, 2024.

The northern circumpolar permafrost region contains up to half of the global soil carbon pool and twice as much carbon as currently is in the atmosphere. At the same time, the Arctic is rapidly warming due to climate change, causing the permafrost to thaw. There is a risk that substantial amounts of soil organic carbon (SOC) may be released into the atmosphere as greenhouse gases during this process. This makes permafrost carbon a potentially strong climate feedback that could further amplify global warming.

Currently, only a few studies attempted to quantify this permafrost carbon on a global scale. Despite the advances in estimating how much SOC is stored in the northern circumpolar permafrost region, there are still large uncertainties. Modelling permafrost carbon is particularly challenging due to the scarce availability of reference datasets on SOC content and great subsurface variability in the Arctic environment caused by cryoturbation. The high lateral (i.e. horizontal) and vertical (i.e. along the soil profile) variability results in several obstacles when mapping SOC in permafrost regions.

While previous studies on modelling permafrost carbon focused on quantifying its spatial heterogeneity, they lacked in capturing the complex (vertical) distribution of SOC as a function of depth. Furthermore, they often rely on discrete models to estimate the spatial variation. In this work, we focus on providing more accurate high-resolution, continuous global maps of permafrost SOC density using a 3D digital soil mapping approach. Digital soil mapping has shown to be a valuable tool in mapping SOC, as it can better capture the continuous variation of soil properties. Here, we used a random forest machine learning model to predict SOC based on a number of spatial variables representing soil forming factors (such as topographic attributes, climate, carbon age and land cover). The reference dataset that we used to train the model consists of soil profile observations from the permafrost region of the Northern Hemisphere, excluding alpine permafrost. We harmonised this dataset from existing databases and recent studies that provide information on carbon content from soil core measurements. Information on the bulk density was needed to calculate the SOC density and estimated for missing observations using pedotransfer functions. Results indicate that 3D modelling of permafrost carbon produces substantially different results than conventional 2D approaches. Furthermore, accounting for the vertical variation in SOC improves the prediction accuracy.

How to cite: Röseler, F., Treat, C., and Heuvelink, G.: Geospatial modelling of soil organic carbon density in 3D across the northern circumpolar permafrost region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8527, https://doi.org/10.5194/egusphere-egu24-8527, 2024.

Wildfires over permafrost put perennially frozen carbon at risk. However, burned area and wildfire carbon emissions from biomass burning over the diverse range of permafrost regions have not been revealed. Here, we show that continuous permafrost was a major contribution to wildfire expansion and carbon emission in the pan-Arctic over the last two decades. Burned area and wildfire carbon emissions dramatically increased over continuous permafrost during the last two decades, but decreased in other permafrost regions. Accelerating wildfire emission from continuous permafrost region is the single largest contribution to the increased emissions in northern permafrost regions. The share of permafrost in global wildfire CO₂ emissions grew from 2.42% in 1997 to 20.86% in 2021. Wildfire expansion is closely linked to an increased soil moisture deficit, considering wildfires there combust more than 90% of belowground fuel. Continuous permafrost experiences more severe fire-induced degradation. Active layer thickening following wildfires over continuous permafrost lasts more than three decades to reach a maximum of more than triple the pre-fire thickness. These findings highlight expansion of wildfires and acceleration of fire-induced carbon emission from continuous permafrost region, which disturbs organic carbon stock, accelerates the positive feedback between permafrost degradation and climate warming.

How to cite: Zhu, X., Jia, G., and Xu, X.: Expansion of wildfires and their impact on carbon emissions over pan-Arctic permafrost, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2291, https://doi.org/10.5194/egusphere-egu24-2291, 2024.

Regressive thaw slumps (RTSs) are permafrost landforms formed by the thawing of ice-rich permafrost or the melting of massive ground ice. The West Siberian Arctic (Yamal and Gydan peninsulas) is an area with widespread distribution of RTSs due to continuous permafrost and massive tabular ground ice close to the surface. The initiation of RTS in the region strongly affects the environment by altering vegetation and topography and releasing carbon. Roads and railways are also affected by RTS occurrence.  

There is still no complete understanding of the true RTS distribution and its environmental controls in the West Siberian Arctic because of the remote location of the region. A remote sensing technique can be used to enhance our understanding of the characteristics of RTS over a large area. However, automated mapping of RTSs has certain limitations, including the lack of ground truth data, the large number of false-positive detections, and the ambiguity in interpretation. Moreover, the polycyclic nature of RTS development leads to a very complex spatial aggradation with numerous overlapping or nested RTSs. This poses additional challenges for mapping.

Based on theoretical and field studies, we developed a classification to capture the main morphological and environmental parameters of RTS nature visible on satellite imagery. To minimize false-positive detections we performed in-detail manual mapping of the RTSs in West Siberia using multiple sources including the ESRI satellite base map, Google Earth satellite base map, and Yandex Maps satellite base map. Each point was classified by several parameters: morphology, spatial aggradation, concurrent cryogenic processes, terrain position, and attachment to the base level. Field experience and data at the key sites, as well as a helicopter-based inventory, helped to perform verification and estimate accuracy.

We identified more than 4000 RTSs. The spatial distribution of identified RTSs demonstrates clusters over the western Yamal Peninsula and central-northern Gydan Peninsula. This research aims at a comprehensive analysis of the spatial distribution of classified RTS concerning regional geological, climate, and other available environmental data. Our results are valuable for understanding the nature of this widespread phenomenon in the Arctic.

How to cite: Nesterova, N., Tarasevich, I., Leibman, M., Kizyakov, A., Nitze, I., and Grosse, G.: Modern spatial distribution of diverse retrogressive thaw slumps in West Siberia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2165, https://doi.org/10.5194/egusphere-egu24-2165, 2024.

The northern high latitudes are warming much faster than the rest of the planet. While gradual thaw of permafrost is accounted for in the recent generation of the Earth System Models (ESMs), consequences of the abrupt thaw of permafrost and the subsequent greenhouse gas release are not yet taken into consideration. However, an abrupt thaw of very small fraction of the northern permafrost region can lead to significant carbon release and subsequent global warming (Turetsky et al. 2020).

An in-depth analysis of fine-scale permafrost subsidence processes is crucial for improved representation of abrupt thawing in simulations. Currently, permafrost subsidence is only taken into consideration in a few models, where subsidence is described in a deterministic process-based approach. This approach overlooks the high spatial heterogeneity in fine-scale permafrost processes.

Recent advancements in satellite technology allow the acquisition of Interferometric Synthetic Aperture Radar (InSAR) data on permafrost vertical displacement at meter-scale resolution. We conducted a case study on the Yamal Peninsula, Russia, where we compare permafrost subsidence data from Sentinel-1 with various potential driving factors, including climate forcing data from ERA5-Land and geomorphology data from MERIT Hydro. A statistical approach is taken to analyse the relationships between different factors and their contributions to permafrost subsidence. The results demonstrate the high heterogeneity of permafrost subsidence in the form of probability distribution functions at ESM-scale resolution. Eventually, our study aims to obtain a parameterization for pan-Arctic permafrost subsidence that can be implemented into the ICON-ESM in order to close the gap in permafrost modelling between process- and ESM-scale.

Reference: Turetsky, M.R., Abbott, B.W., Jones, M.C. et al. Carbon release through abrupt permafrost thaw. Nat. Geosci. 13, 138–143 (2020). https://doi.org/10.1038/s41561-019-0526-0

How to cite: Liu, Z., Widhalm, B., Bartsch, A., Kleinen, T., and Brovkin, V.: Statistical Modelling of Permafrost Subsidence Based on High-resolution InSAR Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17224, https://doi.org/10.5194/egusphere-egu24-17224, 2024.

In situ field studies in thawing permafrost regions have shown that C emissions resulting from organic carbon (OC) decomposition depend among others on the variability in soil water content, which can be directly related to microtopography. A more precise assessment of the evolution of permafrost C emissions as a function of thermokarst development requires high-resolution quantification of thermokarst-affected areas, as lowland thermokarst development induces fine-scale spatial variability (~ 50 – 100 cm). Here, we investigate a gradient of lowland thermokarst development at Stordalen mire, Abisko, Sweden, from well-drained undisturbed palsas to inundated fens, which have undergone ground subsidence. We produced orthomosaics and digital elevation models from very-high resolution (10 cm) UAV photogrammetry as well as a spatially continuous map of soil electrical conductivity (EC) based on Electromagnetic Induction (EMI) measurements performed in September 2021. In conjunction, we measured in situ the soil water content from the different stages of thermokarst development at the same period. The soil EC values are contrasted along the gradient in line with contrasts observed in the landscape classification derived from the orthomosaics and digital elevation models: palsas are flat areas with low soil EC (drier), whereas fens are subsided areas with higher EC (water-saturated). Areas in the course of degradation (transition zones) are well identified based on their higher slope, and broad range of EC. Importantly, these transition zones are only detected using a very fine spatial scale (i.e., 10 cm) coupled to information on the microtopography. Compared to a set of previously collected orthomosaics and digital elevation models, our results show an acceleration of thermokarst development in this area with a rate of palsa decline 4 to 10 times greater in 2019-2021 than in 2000-2014.

How to cite: Thomas, M., Moenaert, T., du Bois d’Aische, É., Villani, M., Hirst, C., Lundin, E., Jonard, F., Lambot, S., Van Oost, K., Vanacker, V., Giesler, R., Mörth, C.-M., and Opfergelt, S.: Detecting lowland thermokarst development by UAV remote sensing in the Stordalen mire, Abisko, Sweden , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-559, https://doi.org/10.5194/egusphere-egu24-559, 2024.

The surface energy budget plays a critical role in terrestrial hydrologic and biogeochemical cycles. Nevertheless, its highly spatial heterogeneity across different vegetation types is still missing in the land surface model, ORCHIDEE-MICT (ORganizing Carbon and Hydrology in Dynamic EcosystEms–aMeliorated Interactions between Carbon and Temperature). In this study, we describe the representation of a multi-tiling energy budget in ORCHIDEE-MICT and assess its short and long-term impacts on energy, hydrology, and carbon processes. We found that: 1) With the specific values of surface properties for each vegetation type, the new version presents warmer surface and soil temperatures, wetter soil moisture, and increased soil organic carbon storage across the Northern Hemisphere. 2) Despite reproducing the absolute values and spatial gradients of surface and soil temperatures from satellite and in-situ observations, the considerable uncertainties in simulated soil organic carbon and hydrologic processes prevent an obvious improvement of temperature bias existing in the original ORCHIDEE-MICT. 3) The simulated continuous permafrost area (15.2 Mkm2) and non-continuous permafrost area (3.1 Mkm2) are comparative to observation-based datasets from Brown et al. (2002) (10.8 Mkm2 for continuous and 4.6 Mkm2 for non-continuous) and Obu et al. (2019) (11.5 Mkm2 for continuous and 5.3 Mkm2 for non-continuous). Consequently, the new version will facilitate various model-based permafrost studies in the future. 

How to cite: Xi, Y., Qiu, C., Zhang, Y., Zhu, D., Peng, S., Hugelius, G., Chang, J., Salmon, E., and Ciais, P.: Improving the simulation of permafrost extent by representing the multi-tiling energy budgets in ORCHIDEE-MICT model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17812, https://doi.org/10.5194/egusphere-egu24-17812, 2024.

Climate warming enables easier access and operation in the Arctic, fostering industrial and urban development. However, there is no comprehensive pan-Arctic overview of industrial and urban development, which is crucial for the planning of sustainable development of the region. In this study, we utilize satellite derived artificial light at night (ALAN) data to quantify the hotspots and the development of human activity across the Arctic from 1992 – 2013. We find that out of 16.4 million km² analyzed a total area of 839,710 km² (5.14%) is lit by human activity with an annual increase of 4.8%. The European Arctic and the oil and gas extraction regions in Russia and Alaska are hotspots of ALAN with up to a third of the land area lit, while the Canadian Arctic remains dark to a large extent. On average, only 15% of lit area in the Arctic contains human settlement, indicating that artificial light is largely attributable to industrial human activity. With this study, we provide a new, standardized approach to spatially assess human industrial activity across the Arctic, independent from economic data. Our results provide a crucial baseline for sustainable development and conservation planning across the highly vulnerable Arctic region.

How to cite: Akandil, C., Plekhanova, E., Rietze, N., Oehri, J., Roman, M. O., Wang, Z., Radeloff, V., and Schaepman-Strub, G.: Artificial light at night reveals hotspots and rapid development of industrial activity in the Arctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4091, https://doi.org/10.5194/egusphere-egu24-4091, 2024.

The temperature dynamics of permafrost is crucial for ecosystem processes in the ice-free areas of the Antarctic Peninsula, where a strong long-term warming trend with an increase of 3.4 ºC in the mean annual air temperature since 1950 has been recorded (Turner et al., 2020). The consequences of this warming on past and future permafrost degradation are still not fully understood, mainly due to the sparse spatial coverage and short time span of borehole data, only available after the mid to late 2000’s (Vieira et al., 2010; Bockheim et al., 2013). The Cryogrid Community Model is an adaptable toolbox for simulating the ground thermal regime and the ice/water balance for permafrost (Westermann et al., 2017, 2022). The modular structure allows combinations of classes that represent the snow conditions and the subsurface materials. Here, permafrost temperatures from the 13 m depth King Sejong Station borehole (KSS), from Barton Peninsula, King George Island were used to assess the performance of Cryogrid and the quality of ERA5 forcing. For evaluating model performance, the setup was firstly used in its basic version with the GROUND_freeW_ubtf class, which considers a temperature boundary condition, for which air temperatures from KSS were used. Modifications to the stratigraphy and parameters were performed to achieve the strongest correlations and lower Mean Absolute Errors (MAE) between the simulated and observed ground temperature at nine depth levels. This approach allowed for the definition of the stratigraphy and parameters later used with the GROUND_freeW_seb_snow class, in which the surface energy balance scheme is included. The results show that ERA5 air temperature underestimates the records from KSS, especially during the summer, impacting the representation of surface warming. This deviation was corrected using linear regression corrected temperatures. The Cryogrid modelling results indicate an overestimation of the ground temperature during the thawing season and an underestimation during the freezing season, being the difference more pronounced at the surface. A strong correlation was shown between the simulated and measured ground temperatures in KSS down to 6 m depth (r>0.9) with MAE ranging from 0.4 to 0.9 ºC. Below 6 m the correlation weakens to 0.45 (13 m depth) due to differences in heat propagation and lack of temperature oscillation on the records when compared with the simulation. However, MAE values are residual, ranging from 0.1 to 0.2 ºC. The active layer thickness was overestimated in about 1 m. This research was funded by the project THAWIMPACT (FCT2022.06628.PTDC) and by CEG/IGOT (UIDP/00295/2020). Joana Baptista is funded by the FCT with a doctoral grant (2021.05119.BD).

How to cite: Baptista, J., Vieira, G., Westermann, S., and Lee, H.: Cryogrid modelling of permafrost temperature in the Maritime Antarctic (Barton Peninsula, King George Island), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17398, https://doi.org/10.5194/egusphere-egu24-17398, 2024.

This study assesses the escalating vulnerability of Arctic coastal communities due to the combined impacts of coastal erosion and permafrost warming. With the Arctic experiencing heightened temperatures, coastal permafrost areas face increased instability, endangering vital infrastructures. The study focuses on a pan-Arctic evaluation of settlements and infrastructures at risk, enhancing the existing Arctic coastal infrastructure dataset (SACHI) to include road types, airstrips, and artificial water reservoirs.

By analyzing coastline change rates from 2000 to 2020, alongside permafrost ground temperature and active layer thickness trends from the ESA Permafrost Climate Change Initiative datasets, the research identifies settlements at risk for the years 2030, 2050, and 2100. The accuracy of the dataset is rigorously evaluated. Results indicate that by 2100, 23% of coastal settlements will face the impacts of coastal erosion. Projections based on linear trends suggest an 8°C increase in coastal permafrost ground temperature and a 0.9-meter growth in active layer thickness by the same year.

Crucially, the study reveals that 65% of all infrastructures and settlements will be affected by permafrost warming within the range of 5-15°C, with 35% experiencing active layer thickening between 1-5 meters. This research marks the first regional-scale identification of settlements at risk from coastal erosion along Arctic and permafrost-dominated coasts in the northern hemisphere. The findings emphasize the urgency of adapting to current and future environmental changes to mitigate the deterioration of living conditions in permafrost coastal settlements. Immediate action is imperative to counteract these challenges and ensure the resilience of these vulnerable communities.

How to cite: Tanguy, R., Bartsch, A., Nitze, I., Irrgang, A., Petzold, P., Widhalm, B., von Baeckmann, C., Boike, J., Martin, J., Efimova, A., Vieira, G., Heim, B., Wieczorek, M., Grosse, G., and Ehrich, D.: Vulnerability assessment of Arctic coastal communities to the effects of coastal erosion and permafrost warming., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15989, https://doi.org/10.5194/egusphere-egu24-15989, 2024.

Arctic permafrost is a critical global tipping element in a warming climate. Annually, the erosion of coastal permafrost discharges an estimated 5 to 14 Tg of organic carbon (OC) into the Arctic Ocean. Although this previously stored OC has the potential to be reintroduced into the atmosphere, thus accelerating human-induced climate change, little is known about the benthic remineralization processes of permafrost OC after erosion and redeposition on the ocean floor. Our research quantified fluxes of dissolved inorganic carbon (DIC) and analyzed its isotopic composition of nearshore sediments in the Canadian Beaufort Sea, specifically off Herschel Island. Our findings showed a DIC release of 0.217 mmo/m²/d, with an average signature of δ¹³C = -22.44 ± 72 ‰ and F¹⁴C = 0.548 ± 0.007. Utilizing a model that combines two carbon isotopes, we estimate that approximately 38 ± 10% of the released DIC is a result of subsurface degradation of redeposited permafrost OC, with an additional 15 ± 12% originating from redeposited active layer OC. Additionally, isotopic endmember analysis was utilized on bacterial membrane lipids from live sedimentary bacteria to determine the relative utilization of OC sources in bacterial communities within shallow subsurface sediment (<25 cm). Our results indicate that, on average, these communities obtain 73 ± 10% of their OC from recent marine primary production, 11 ± 6% from permafrost OC, and 16 ± 11% from active layer OC. This study is the first direct quantitative assessment of the release of permafrost OC into the active carbon cycle after it has been redeposited on the ocean floor, as far as we know. The data suggest that the redeposited permafrost OC is easily accessible and utilized by subsurface bacteria. Considering the immense size and vulnerability of the eroding coastal permafrost OC pool, 27 to 53% of it contributing to benthic DIC fluxes could have a prolonged effect on the world's climate, worsening the climate emergency.

How to cite: Ruben, M., Hefter, J., Gentz, T., Schubotz, F., Wei, B., Liu, B., Fritz, M., Irrgang, A. M., von Jackowski, A., Geibert, W., and Mollenhauer, G.: Quantifying permafrost organic carbon remineralization after redeposition on the ocean floor, using  δ13C and F14C., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-149, https://doi.org/10.5194/egusphere-egu24-149, 2024.

Rapidly rising temperatures in the Arctic cause thaw of permafrost and increase coastal erosion that mobilizes permafrost-derived organic carbon (OC) into coastal waters. In the water column, permafrost-OC may either degrade and thus, enhance climate warming by adding greenhouse gases to the atmosphere or settle on the seabed and be buried in the sediments. In this study, we focused on the composition and degradation of particulate OC (POC) within the flocculation (nepheloid) layer - a turbulent layer close to seabed that holds a high amount of suspended sediments/particles and transports them across the vast Siberian Arctic shelves. More importantly, previous studies have shown that permafrost-OC, exported to the Arctic Ocean via coastal erosion, is largely carried in the POC fraction of the flocculation layer.

To study flocculation layer dynamics, sediment cores were collected using a multicorer device from the East Siberian Sea, Laptev Sea, and Kara Sea onboard R/V Akademik Mstistlav Keldysh in 2020. The overlying water of the sediment cores was stirred under controlled conditions to mimic sediment resuspension. The entrained suspended sediments were collected and incubated for two weeks (in the dark) to assess their susceptibility to degradation. During the incubation, dissolved O₂, POC, dissolved OC (DOC), dissolved inorganic carbon and δ¹³C of each carbon pool were measured at set time points. Additionally, to better understand sediment entrainment and degradation, sediment physical properties, including grain size and mineral-specific surface area, and macromolecular composition were determined.

Our preliminary results show that stirring largely entrains the smallest sediment particles, while it seems not to influence sediment macromolecular composition suggesting that none of the compound classes such as polysaccharides or aromatic compounds are preferentially entrained. Our incubation data show losses in dissolved O₂ suggesting microbial degradation, however, instead of decreases in the OC pools, especially POC shows increases combined with increases or decreases in DOC. These carbon dynamics likely result from interactions between different carbon pools such as adsorption of DOC to particles and/or leaching of POC to the DOC pool. With accelerated coastal erosion and increase in storminess in the Arctic Ocean due to sea ice loss, understanding dynamics of the flocculation layer and degradation of permafrost-OC on the Arctic sea shelves is becoming even more important to better constrain their potential climate impact.  

How to cite: Keskitalo, K., Mann, P., Tesi, T., van Dongen, B., Martens, J., Semiletov, I., Dudarev, O., Gustafsson, Ö., and Vonk, J.: Degradation and composition of organic carbon in the flocculation layer on the Laptev, East Siberian, and Kara seas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19404, https://doi.org/10.5194/egusphere-egu24-19404, 2024.

The stability and spatial distribution of subsea permafrost across the Arctic continental shelves play a pivotal role in our understanding of global warming. Serving as a significant carbon store, this permafrost has the potential to release greenhouse gases when it thaws, significantly influencing the global climate. This study is dedicated to a comprehensive investigation of the extent and state of submarine permafrost within the Arctic, with a particular focus on the comparative analysis of subsea permafrost development along the continental shelves of the Beaufort and East Siberian Seas. This research enhances our grasp of Arctic subsea permafrost's current variability and its role in global warming processes. To map the extent of subsea permafrost, we utilized multichannel seismic data from the Beaufort Sea (2014) and East Siberian Sea (2016, 2019), collected by the IBRV Araon. Employing a full waveform inversion approach, we precisely determined the seafloor permafrost's velocity structure, offering insights into its depth and state. The research reveals pronounced regional variations in the development of subsea permafrost on Arctic continental shelves. In particular, the continental shelf of the Beaufort Sea is characterized by a densely concentrated distribution of subsea permafrost extending to depths of up to 600 meters. In contrast, the continental shelf of the East Siberian Sea is dominated by permafrost that has thawed significantly, reaching depths of around 400 meters. These different regional patterns may be influenced by a number of factors, including the proximity of the shelf to the coast, the influence of ocean currents, the geological composition of the seabed and the prevailing thermal conditions. These findings suggest that the highly variable nature of submarine permafrost across the Arctic shelf is crucial to understanding warming induced changes in Arctic submarine permafrost and the potential for greenhouse gas release through permafrost dissociation.

How to cite: Jin, Y. K., Kang, S.-G., Choi, Y., Kim, S., and Hong, J. K.: Regional Variations of Subsea Permafrost Development on the Arctic Continental Shelves: A comparative analysis of the Beaufort and East Siberian Seas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5198, https://doi.org/10.5194/egusphere-egu24-5198, 2024.