The ESA funded two-year MethaneCAMP project addresses specifically satellite observations of methane (CH4) in the Arctic in support of the collaborative ESA-NASA Arctic Methane and Permafrost Challenge (AMPAC) initiative.  Up to now, satellite retrievals of methane have not been optimised for the high latitude conditions. Known challenges are 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. The goal of MethaneCAMP is to improve the observation capacity over polar regions by assessing and optimising methane retrievals at high northern latitudes. Furthermore, MethaneCAMP aims 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. Specifically, we will focus on Sentinel 5P/TROPMI, GOSAT, GOSAT-2 and IASI XCH4 observations and on few case studies of high spatial resolution instruments. In this presentation we review the preliminary results of MethaneCAMP project which are achieved in the first year 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 – first results, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17361, https://doi.org/10.5194/egusphere-egu23-17361, 2023.

Methane is a potent greenhouse gas that plays a significant role in the global climate system. High latitude methane is a particularly sensitive subject due to the uncertainty in future gas release due to multiple factors such as the thawing of permafrost and the evolution of wetland cover. Thus, these regions have the potential to significantly contribute to global warming. In this study, we present the results of the MAGIC2021 campaign, which was conducted in Lapland around Kiruna, Sweden in August 2021. The campaign included measurements with atmospheric air sampler AirCores on board weather balloons, three research aircraft equipped with in-situ sensors, and ground-based measurements of gas total columns using EM27/SUNs. We focus here on the combined measurements of 0-30 km profiles by AirCore and by ATR42 research aircraft to investigate sources of methane in the region. To this end, we employed back-trajectory Lagrangian models and conducted an in-depth comparison between model (ERA5, CAMS) and campaign data in a multi-species approach combining CH₄, CO₂ and CO. Our findings provide insight into the sources and transport of methane at high latitudes. They show that in order to properly study local sources of methane, it is mandatory to account for transported methane originating from regions as far as Northern Canada. Our work also highlights the importance of conducting in situ measurement campaigns like MAGIC2021, which provide valuable data for improving our understanding of atmospheric processes at high latitudes and informing the development of more accurate models and validate satellite retrievals. Plans for next campaigns will also be detailed.

How to cite: Langot, F., Crevoisier, C., Lauvaux, T., Guedj, A., Pernin, J., Berchet, A., Pison, I., and Wittig, S.: Natural methane emissions at high latitudes: A study through the MAGIC2021 measurements campaign, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13894, https://doi.org/10.5194/egusphere-egu23-13894, 2023.

Wetlands in the high northern latitudes are a major, yet poorly known contributor to the global methane (CH₄) budget. In wetlands, peat bogs and lakes, CH₄ is produced by organic degradation processes. These natural emissions are affected by climate change though, e.g. by changing temperatures and permafrost thaw. A better understanding is essential also for discussing the human role in the budget of this important greenhouse gas and mitigation options.

However, the data coverage in the region is still thin: accessibility is limited, satellite sensors struggle with the high solar zenith angle, difficult surface and thermodynamic conditions, or clouds. Corresponding emission inventories and models differ significantly, in the distribution as well as in the amount of emissions. Based in Kiruna/Sweden, the French MAGIC initiative addressed these knowledge gaps by bringing together a multitude of instruments on three research aircraft (Safire ATR-42, BAS Twin Otter, DLR Cessna) and various other platforms for measurements in northern Scandinavia in August 2021.

Here we focus on airborne in-situ measurements with the DLR Cessna. The suite of instruments aboard the aircraft included a meteorological sensor package, a Picarro, and an Aerodyne QCLS, providing CH₄,CO_2, C₂H_6, ¹³C(CH₄), temperature, H₂O, 3d-wind, all along the flight track.

The Cessna conducted 12 scientific flights in the region, which mostly targeted and scouted hotspots of CH₄ emissions indicated by wetland emission inventories. The flights were coordinated as often as possible with other airborne, ground-based and satellite platforms to allow for intercomparisons and for providing ground truth for remote sensing instruments. Estimating CH₄ emission fluxes is another major objective, which is challenging because of spatial and temporal heterogeneity of these area sources. To this end we tried a combination of different methods and flight patterns. We provide an overview of the measurements, discuss the different flight strategies and show first results of the analyses that are ongoing in the frame of the ESA MAGIC4AMPAC project.

How to cite: Gottschaldt, K.-D., Crevoisier, C., Fiehn, A., Fix, A., Hartung, K., Huntrieser, H., Jöckel, P., Kern, B., Kostinek, J., Markkanen, T., Mertens, M., Middleton, C., Pühl, M., Quatrevalet, M., Wooster, M., and Roiger, A.: Airborne in-situ observations of natural methane emissions in Scandinavia during MAGIC 2021, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15346, https://doi.org/10.5194/egusphere-egu23-15346, 2023.

In order to reliably predict the climate of our planet, and to help inform political conventions on greenhouse gas emissions such as the Paris Agreement of 2015, adequate knowledge of both natural and anthropogenic sources of the greenhouse gases Carbon dioxide (CO₂) and methane (CH₄) and their feedbacks is needed. Despite the recognized importance of this issue, our current understanding about sources and sinks of CO₂ and CH₄ is still inadequate. This is particularly true for the Arctic, where large wetlands and permafrost areas constitute the most relevant but least quantified ecosystems for the global carbon budget.

The CoMet 2.0 Arctic mission wants to help remedy this deficiency with a multi-disciplinary approach providing relevant measurements from Arctic regions using a suite of sophisticated scientific instrumentation onboard the German research aircraft HALO (High Altitude and LOng Range Research Aircraft, https://halo-research.de) to support state-of-the-art Earth System Models. At the same time, CoMet intends to support and improve current and future satellite missions, which still struggle to make high-quality measurements given the low sun elevation, low albedo, and adverse cloud conditions in the Arctic.

CoMet 2.0 Arctic (https://comet2arctic.de/) has successfully been conducted within a six-week intensive operation period from August 10th to September 16th, 2022 targeting greenhouse gas emissions from boreal wetlands and permafrost areas in the Canadian Arctic, from wildfires, and from anthropogenic emission sources such oil, gas, and coal extraction sites and landfills.

For that mission, HALO was equipped with a suite of remote sensing and in-situ instruments for the measurement of greenhouse gases and meteorological parameters. The remote sensing package comprised the CH₄ and CO₂ lidar CHARM-F (operated by DLR), the imaging spectrometer MAMAP2D-Light (operated by University of Bremen) and the hyperspectral imager specMACS (operated by LMU Munich). The remote sensors were supported by several in-situ instruments (operated by MPI Jena and DLR) to measure the main greenhouse gases and related trace species as well as an air sampler that collects air samples at flight level for later analysis (e.g. w.r.t. isotopes) in the laboratory. Furthermore, instruments to provide detailed information about the standard meteorological parameters (pressure, wind, humidity) were operated and several small meteorological sondes were launched in order to link those in-flight data to profiles.

A total of 135 flight hours including a test flight to landfills in Spain and transfer flights from Europe have been performed. 16 scientific flights took place out of Edmonton, Alberta, to various regions all over Canada.

CoMet 2.0 Arctic has partly been coordinated with the Arctic-Boreal Vulnerability Experiment field program by NASA (ABoVE, https://above.nasa.gov/). Both missions, ABoVE and CoMet 2.0 Arctic, are linked through the transatlantic initiative AMPAC (Arctic Methane and Permafrost Challenge, https://www.ampac-net.info/) that has recently been inaugurated by the US and European Space Agencies, NASA and ESA.

Thus, a valuable data set was acquired to help better understand the methane and carbon dioxide cycles in the Arctic and emissions from natural and anthropogenic sources.

How to cite: Fix, A., Bovensmann, H., Gerbig, C., Krautwurst, S., Gałkowski, M., Mathieu, Q., Fruck, C., Wolff, S., Reum, F., Waldmann, P., Ewald, F., Mayer, B., Jöckel, P., Kiemle, C., Miller, C. E., and the CoMet 2.0 Arctic team, A.: CoMet 2.0 Arctic: Carbon Dioxide and Methane Mission for HALO, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13301, https://doi.org/10.5194/egusphere-egu23-13301, 2023.

Land-terminating glaciers in Greenland and Iceland are sources of methane (CH₄) to the atmosphere^1,2,3. CH₄ is produced through microbial methanogenesis underneath the ice, transported dissolved in subglacial meltwater to the margin where the gas is emitted to the atmosphere via degassing⁴. However, sparse empirical data exist about the spatial distribution of subglacial CH₄ production and emission in other glaciated regions of the world, limiting our understanding of its regional and global importance in atmospheric carbon budgets and its possible role in the climate system.

In August 2022, we conducted fieldwork at three outlet glaciers - Dusty, Kluane and Donjek glaciers - of the St. Elias Icefields in Yukon, Canada, to investigate if these alpine glaciers are also sources of CH₄ emissions to the atmosphere. The glaciers were chosen due to the absence of proglacial lakes and the presence of meltwater upwellings at the glacier termini, which were accessed via helicopter.

In-situ extracted dissolved CH₄ and CO₂ concentrations were measured in the field with a portable greenhouse gas analyzer. Additionally, extracted gas was collected in exetainers for concentration measurements via gas chromatography and in Tedlar gas bags for stable carbon and hydrogen isotope analyses of CH₄ to decipher its origin. Further, water samples were collected for geochemical analyses. At Dusty glacier, we performed a high-intensity sampling campaign over 10 hours and continuous measurements of dissolved CH₄ concentrations with a custom-made low-cost and low-power dissolved CH₄ sensor⁵ to study changes in dissolved gas concentrations, stable isotopic signatures and water chemistry during the rising limb of the diurnal discharge curve.

In-situ measured CH₄ and CO₂ concentrations yielded significantly elevated CH₄ and depleted CO₂ levels in the meltwater of all three glaciers. Discrete gas samples confirmed dissolved CH₄ concentrations 45x, 135x and 250x above the atmospheric equilibrium concentration (3.6 nmol L^-1) in the meltwater of Dusty, Kluane and Donjek glaciers, respectively. First measurements of stable carbon and hydrogen isotope values of CH₄ showed enrichment in ¹³C, while ²H was depleted compared to atmospheric CH₄, at all sites, likely originating from a thermogenic source or caused by bacterial CH₄ oxidation. Water analyses showed an alkaline environment enriched in carbonates and DOC, in contrast to more acidic waters from glaciers in Greenland and Iceland.

These first measurements demonstrate that the subglacial meltwaters from glaciers in the St. Elias Icefields are net sources of CH₄ and net sinks of CO₂ to the atmosphere. Our findings indicate that CH₄ emissions from subglacial environments under alpine glaciers may be a more common phenomenon than previously thought, and a potential cause for remotely sensed CH₄ concentrations anomalies over glaciated regions. However, more alpine glaciers and outlets from the Greenland Ice Sheet need to be studied to evaluate this link and provide the needed ground truthing for satellite sensors in high latitudes.

1. Christiansen & Jørgensen (2018) DOI 10.1038/s41598-018-35054-7

2. Lamarche-Gagnon et al. (2019) DOI 10.1038/s41586-018-0800-0

3. Burns et al. (2018) DOI 10.1038/s41598-018-35253-2

4. Christiansen et al. (2021) DOI 10.1029/2021JG006308

5. Sapper et al. (2022) DOI:10.5194/egusphere-egu22-9972

How to cite: Sapper, S. E., Juncher Jørgensen, C., Schroll, M., Keppler, F., and Riis Christiansen, J.: First measurement of methane emissions from Canadian glaciers in the Yukon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12327, https://doi.org/10.5194/egusphere-egu23-12327, 2023.

Spatio-temporal patterns of methane (CH₄) and carbon dioxide (CO₂) release from natural sources needs to be better understood across the Arctic region. Climate change in the Arctic is occurring at a pace that may be 2 to 4 times the global average, and existing measurements derive from a limited number of field sites, and most originate during the growing season although important studies show that release continues during winter. The Mackenzie River Delta in the western Canadian Arctic holds thin and destabilizing permafrost, high organic content soils, a high proportion of wetlands, and vast natural gas occurrences at depth, all of which create high methane potential. In the present study, we conducted atmospheric CH₄ and CO₂ measurements using a mobile laboratory equipped with a greenhouse gas analyzer during the summer and winter. We also visited known aquatic and terrestrial CH₄ flux hotspots, including pingos, lakes, river channels and wetlands, where we measured concentration transects and stable carbon isotope (¹³C-CH₄) values to characterize CH₄source and spatial pattern. Source stable carbon isotope (δ¹³C-CH₄) signatures at hotspots ranged from -42 to -88 ‰ δ¹³C-CH₄. Active surface microbial production was responsible for at least 4 of the 8 hotspots investigated, indicating that microbial production may be responsible for a greater number of CH₄ hotspots than is indicated by previous studies in the region. Mobile surveys showed that shrubland, grassland and deep water were the most important ecosystems for CH₄ and CO₂ production during the wintertime and that low lying areas of the Delta had the highest atmospheric mixing ratios of CH₄.

How to cite: Wesley, D., Dallimore, S., MacLeod, R., Sachs, T., and Risk, D.: Characterization of atmospheric methane release at hotspots in the outer Mackenzie River Delta, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10711, https://doi.org/10.5194/egusphere-egu23-10711, 2023.

Large stores of carbon frozen in the Arctic as permafrost are under threat of thawing as temperatures in the Arctic increase at a rate four times that of the global mean. This study uses recent atmospheric data from the North Slope of Alaska and Northeast Siberia to provide the most up-to-date assessment of emissions and trends from these two major high-latitude regions.

We use two methods to quantify emissions and assess trends across different seasons: 1) Using 35 years of data from Barrow, Alaska, a wind sector method that quantifies trends in emissions by calculating concentration enhancements over background using wind direction to identify the land sector (first used in Sweeney et al., 2016), and 2) using Barrow data and recent data from three Siberian stations, an inversion method with the high-resolution atmospheric transport model NAME that quantifies both emissions and trends from these regions. We use results from these two approaches to quantify the temperature sensitivity (Q10) of soils based on correlations between surface air and ground temperatures with methane emissions.

With the inclusion of atmospheric concentration data after 2015, we now show that land emissions from the North Slope of Alaska have been increasing since 2000, reflecting a change from previous analyses, which showed no significant increase in summertime methane emissions between 1986-2014 (Sweeney et al., 2016). We find significant emissions from the late shoulder season (Autumn-Winter), which has historically been undermeasured and underrepresented in models and emissions inventories, in this region of Alaska as well as two North-eastern Siberian locations, the Taymyr Peninsula and the East Siberian Lowlands. We show that emissions during this late-season have been growing over the past two decades at a rate similar to summer-time emissions.

Our results based on long-term atmospheric data can be used to show that important change is happening in the Arctic, with an increasing emissions trend and the presence of late shoulder season emissions.

How to cite: Ward, R. H., Ganesan, A. L., Sweeney, C., Miller, J., Goeckede, M., Laurila, T., Hatakka, J., Ivakhov, V., and Makshtas, A.: Increasing methane emissions from the North Slope of Alaska since 2000 and late Autumn-Winter emissions from multiple Arctic regions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7504, https://doi.org/10.5194/egusphere-egu23-7504, 2023.

Lakes and drained lake basins (DLB) are ubiquitous landforms in permafrost lowland regions, covering 50% to 75% of permafrost lowlands in parts of Alaska, Siberia, and Canada. Depending on the time passed since the drainage event, surface characteristics within the DLB such as surface roughness, vegetation, moisture and abundance of ponds may vary. The mosaic of vegetative and geomorphic succession within DLBs and the distinct differences between DLBs and surrounding areas can be discriminated with remote sensing and used to derive a landscape-scale classification. Previously published local and regional studies have demonstrated the importance of DLBs regarding carbon storage, greenhouse gas and nutrient fluxes, hydrology, geomorphology, and habitat availability. To help quantify these processes on a circumpolar scale and improve the representation of Arctic landscapes in large scale models, a circumpolar data set of DLBs distribution and DLB properties is needed.  Due to the inherent temporal characteristics of DLBs, such a data set also has the potential for space-for-time applications regarding landscape models. A pan-Arctic scale effort to map and further the understanding of DLBs in permafrost-regions is the outcome of work conducted within the International Permafrost Association (IPA) Action Group on DLBs, a bottom-up effort led by the scientific community that includes developing a first pan-Arctic drained lake basin data product based on multispectral remote sensing data (Landsat-8). Comprehensive mapping of DLBs areas across the circumpolar permafrost landscape and including field data into this approach will allow for future utilization of these data in pan-Arctic models, aid upscaling efforts and greatly enhance our understanding of DLBs in the context of permafrost landscapes. This will improve quantitative studies on landscape diversity, wildlife habitat, permafrost, hydrology, geotechnical conditions, high-latitude carbon cycling, and landscape vulnerability to climate change.

How to cite: Bergstedt, H., Jones, B., Bartsch, A., Farquharson, L., Wolter, J., Breen, A., Kanevsiy, M., Grosse, G., Roy-Léveillée, P., and von Baeckmann, C.: Mapping Drained Lake Basins on a circumpolar scale, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11626, https://doi.org/10.5194/egusphere-egu23-11626, 2023.

Gas hydrates are known to be an enormous potential energy resource that are accumulated worldwide, especially in the polar regions, and yet the estimates for this resource remain uncertain. In the Arctic region, methane emissions into the atmosphere are a substantial factor in global warming that poses a great danger to the environment. Previously, several studies have been conducted to estimate the gas hydrates in the Arctic to ease such problems despite the need for more data compared to conventional reserves. In the western continental margin of the Chukchi Plateau, the sea mound morphologies were first discovered, and gas hydrate samples were obtained via gravity coring during the first expedition in 2016. In the following expedition in 2018, an intensive gas hydrate exploration including the single-channel seismic survey was conducted in the area of mound morphologies and identified the local bottom simulating reflectors. Consequently, an extensive multichannel seismic survey was conducted in 2019 to investigate the geophysical characteristics of widely distributed gas hydrates in the western continental margin of the Chukchi Plateau. The objective of this study is to estimate the potential volume of gas hydrate resources in the Chukchi Plateau based on the geophysical data. From this study, the distribution of bottom-simulating reflectors and local gas hydrate saturations were derived from the geophysical data. The gas hydrate saturation model in this study area was constructed using the kriging method with few geological assumptions. Then, the total volume of gas hydrates in the western continental margin of the Chukchi Plateau was proposed. The results of this study will provide basic information on the estimates of gas hydrates in the western continental margin of the Chukchi Plateau and contribute to assessing the size of the associated volume of methane emissions due to global warming.

How to cite: Choi, Y., Kang, S.-G., Choi, Y., and Hong, J. K.: Estimation of potential gas hydrate resources based on the geophysical data in the western continental margin of the Chukchi Plateau, the Arctic Ocean, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5019, https://doi.org/10.5194/egusphere-egu23-5019, 2023.

Carbonyl sulfide (OCS), the most abundant atmospheric sulfur-carrying gas, can contribute to regulating Earth’s radiative balance through forming sulfate aerosols. The bryophyte-dominated tundra lying over the ice-free Antarctica is an important terrestrial carbon sink and provides colonies for sea animals, such as penguins and seals, which remains hitherto unexplored concerning OCS biogeochemistry. Here, we measured OCS fluxes from the Antarctic tundra and coupled their fluxes to soil biogeochemical properties to explore OCS production and degradation processes. The bryophyte-dominated normal upland tundra was an OCS sink at -0.97 ± 0.57 pmol m^-2 s^-1, resulting from both bryophytes and OCS-metabolizing enzymes (e.g., carbon anhydrase, nitrogenase) secreted by soil microbes, such as Acidobacteria, Verrucomicrobia, Chloroflexi, and Mortierellomycota. In comparison, tundra within sea animal colonies was an OCS source up to 1.35 ± 0.38 pmol m^-2 s^-1, due to the input of organosulfur from sea animals and the animal-induced anaerobic soil environment, which promoted simultaneous abiotic OCS production in soil, and outweighed the biogenic OCS uptake by bryophytes and soil microbes. Furthermore, sea animal colonization shaped the soil microenvironment, affecting nutrient levels, pH and moisture, which may have reduced the abundances of OCS-metabolizing microbes and thereby OCS degradation and further unveiled concurrent OCS production. Basic calculation suggested that sea animals contribute about 107 metric tons yr^-1 of OCS-S to the atmosphere. The strength of this OCS source is expected to increase in response to Antarctic warming. Overall, tundra ecosystems are important interfaces for OCS exchange and sea animals exert an impact on the sulfur cycle in coastal Antarctica.

How to cite: Zhang, W., Zhu, R., Jiao, Y., Rhew, R. C., Sun, B., Rinnan, R., and Zhou, Z.: Sea animals promote carbonyl sulfide (OCS) emissions from Antarctic tundra, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10192, https://doi.org/10.5194/egusphere-egu23-10192, 2023.

High latitude peatlands are a significant source of atmospheric methane. Production, consumption and emission rates are spatially and temporally heterogeneous, resulting in a wide range of global estimates for the atmospheric budget of methane. Increasing temperatures in Arctic regions cause degradation of underlying permafrost, changing hydrology, vegetation and microbial communities, but the consequences of this for methane cycling, including stable methane isotopes, are poorly understood. We provide evidence of direct linkages between below ground methanogen communities and above ground plant communities that can be remotely sensed and used in model simulations to effectively predict methane and isotopic fluxes across the landscape. Combining remote sensing with biogeochemical modeling can be used to predict methane dynamics, including the fraction derived from hydrogenotrophic versus acetoclastic microbial methanogenesis. Applying this approach across heterogeneous discontinuous permafrost peatlands enables us to accurately predict isotopic emissions, which will help constrain the global role of Arctic methane emissions.

How to cite: Varner, R., Crill, P., Kuhn, M., Cronin, D., Palace, M., McCalley, C., Burke, S., Deng, J., Saleska, S., and Rich, V. and the A2A and EMERGE project teams: From Archaea to the atmosphere: linking above and belowground communities to scale methane and isotopic emissions across the Arctic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11027, https://doi.org/10.5194/egusphere-egu23-11027, 2023.

Wildfire is the most important disturbance agent in boreal forests. These disturbances play a major role in the boreal forest carbon cycle. They lead to direct CO₂ and CH₄ emissions during the active fire phase and to long-lasting post-fire impacts on net CO₂ and CH₄ fluxes through changes in forest structure and in microclimatic conditions. For example, a forest’s ability to minimise differences between land surface and air temperature can preserve permafrost and can lower soil temperatures and thus soil respiration. Fire and post-fire succession are linked to diverse changes in ecosystem function and structure shaping land-atmosphere interactions and, thus, forest microclimate for decades after the disturbance event. However, the mechanisms behind changes in boreal forest microclimate remain uncertain hampering our understanding of carbon cycle impacts of wildfires. Here, we analyse surface energy balance observations from 17 eddy covariance flux tower sites across fire disturbance chronosequences in the North American boreal biome to identify the main drivers of post-fire changes in land surface-air temperature gradients. We use 102 years of observations to quantify winter and summer changes in important ecosystem properties such as evaporative fraction, aerodynamic conductance, and albedo following stand-replacing fire disturbances. Then, we link changes in ecosystem properties to decadal changes in surface-air temperature gradients.

We find that the summer daytime surface-air temperature gradient increases after the fire disturbance indicating reduced ability to cool the land surface during the warm summer months. However, in the winter, the daytime temperature gradient becomes smaller. Decreased aerodynamic conductance contributes mainly to the post-fire surface heating in the summer while increasing albedo mainly explains winter cooling. Evaporative fraction increases initially in the first few decades after the post-fire disturbance. However, during drought years, the evaporative fraction declines rapidly. Our results provide important insights into fire impacts on microclimatic conditions and ground thermal regimes in boreal forests and highlight the reduced capacity of post-fire forests to reduce land surface temperatures during heatwave events. The findings have the potential to contribute to a better mechanistic understanding of post-fire permafrost thaw and soil respiration changes.

How to cite: Helbig, M. and Daw, L.: Boreal forests on fire - Decadal wildfire impacts on boreal forest microclimate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3533, https://doi.org/10.5194/egusphere-egu23-3533, 2023.

Permafrost soils store vast amounts of carbon, twice as much as the atmosphere. With climate warming occurring at a rate three to four times the global average in Arctic-boreal ecosystems this carbon is at risk of being released to the atmosphere in the form of carbon dioxide or methane (hereby, carbon fluxes) exacerbating global climate warming. However, gaps in carbon flux data in high latitude ecosystems limit our ability to understand, upscale, model, and project carbon fluxes, which in turn limit our ability to set accurate emissions reduction targets to stay within globally agreed upon temperature thresholds such as 1.5 or 2°C. To address this, we are strategically expanding the informal Arctic-boreal carbon flux network through the installation of ~10 new eddy covariance sites and supporting expanded measurements (during winter and for CH₄) at existing sites. To guide site selection decision making, we are using a representativeness analysis of the current eddy covariance network, determining the Euclidean distance in environmental data space using key carbon flux drivers at a 1 km² resolution across the Arctic-boreal region (Pallandt et al., 2022). Analyses show a lack of representation in the high Arctic, Siberia, and Eastern Canada, and representation is substantially lower when considering only sites with year-round measurement or that measure methane, limiting our ability to estimate the full impact of carbon fluxes from the Arctic-boreal region. Additional consideration is given to logistical constraints, partnerships, and modeling gaps. Work has begun including a re-installation in Churchill, MB, and upgrades for year-round and additional instrumentation for 4 towers in Alberta and the Northwest Territories and a site in Iqaluit, NU. We will further synthesize existing network data to inform the Dynamic Vegetation [Model] Dynamic Organic Soil Terrestrial Ecosystem Model (DVM-DOS-TEM) model and use machine learning approaches to upscale Arctic-boreal carbon fluxes.

How to cite: Arndt, K. and Natali, S. and the Permafrost Pathways Flux Steering Committee: Strategic expansion of the Arctic-Boreal carbon flux network, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10643, https://doi.org/10.5194/egusphere-egu23-10643, 2023.

Wetlands play an important role in the carbon balance of the Arctic. All wetland types are characterized by an individual combination of hydrological conditions, soils, vegetation cover, etc. These characteristics influence their feedback with current and future climate conditions, and therefore also their greenhouse gas exchange processes. While most climate models distinguish only one or two types of wetlands, biogeographical approaches define at least ten types of wetlands in the Arctic.

Improving the representation of wetland ecology in carbon upscaling studies in the Arctic requires finding the balance between the diversity of wetlands, including their variability in responses to climate forcing, and the information that is commonly available to represent them in modelling frameworks. On the one hand, a larger number of classes allows a more precise description of the conditions and characteristics of the fluxes within each class. On the other hand, more classes also mean less information per class, and thus more gaps that need to be interpolated.

To support the development of a refined classification scheme, we first built a database on Arctic wetland characteristics, including measured carbon pools and fluxes, based on the available information from published studies. Our database covers the period 1988 – 2019, with observations for all seasons available. Most data was taken from flux chamber studies, since this technique allows to resolve the highly heterogeneous mosaic of landcover, environmental conditions, vegetation and consequently GHG fluxes that characterize large fractions of the Arctic. For all plots, general (coordinates, time of measurements, etc.), physical (pH, vegetation composition, water table, etc.) site characteristics and CH₄ and CO₂ fluxes were collected. However, for some of these parameters, data coverage turned out to be too sparse to complete analyses. For example, permafrost depth, pH, and water table level cover only 45, 15 and 34% of all available plots. To improve this situation, remotely-sensed data was included, allowing to equally cover all measurement points, albeit often with less accuracy.

Based on statistical processing using agglomerative hierarchical cluster analysis, we divided all observations into wetland categories based on their CO₂ and CH₄ flux signatures and the response to dominant environmental factors. We present the most successful classifications for different total numbers of classes, allowing to base the choice of scheme on the information that is available for a specific modelling study.

How to cite: Ivanova, K. and Goeckede, M.: Optimization of a classification scheme for Arctic wetlands to support carbon and energy flux upscaling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1905, https://doi.org/10.5194/egusphere-egu23-1905, 2023.

The Arctic is warming at a faster rate than the rest of the planet due to climate change. The warmer temperatures are causing, among other effects, the permafrost to thaw. When ice-rich permafrost thaws, thermokarst features form due to subsidence of the ground surface and the creation of dynamic depressions, basins, and lakes. As a result, the hydrological cycle in these latitudes is intensifying, causing an increase of nutrients and organic carbon in surface waters. Such impacts on freshwaters affect microbial community composition, and thus, these systems are good sentinels to study processes in primary ecological succession related to ecosystem processes such as productivity and greenhouse gas (GHG) emissions. This study aims to improve the current understanding of microbial processes leading to release of GHG in thermokarst lakes. To that end, we sampled a total of 12 thermokarst basins in August 2022 along a latitudinal gradient (67ºN - 69ºN) in the Northwestern Territories (Canada). The basins were selected so that half were in the taiga biome and half in the tundra biome. In addition, based on satellite images and in-field observations, half of the lakes sampled were in expansion and the other half were undergoing drainage. Water samples were collected for the analysis of GHGs (CH_4, CO₂, N₂O), major ions, dissolved nutrients (organic C, δ¹³C-DOC, organic and inorganic -N) and microbial community composition (16S rRNA gene metabarcoding). We used Ar-corrected gas saturation of each GHG as a proxy of net metabolic changes. Our first results show that both expanding and shrinking lakes were strongly oversaturated in CH₄ andCO₂, slightly saturated in N₂O, and slightly undersaturated in O₂, pointing out higher respiration activity than primary production. Microbial mineralization of organic matter was used as a proxy for GHG production. We found higher concentrations of dissolved organic C in shrinking lakes compared to expanding ones. Following the latitudinal gradient (i.e. biomes), higher temperatures were found in lakes sampled in the taiga compared to those located in tundra, together with deeper permafrost table depths. In surface waters, pH values and dissolved O₂ concentrations were significantly higher in tundra lakes compared to taiga lakes, probably as a result of lateral DOM fluxes in more productive ecosystems (i.e. boreal forests). Differences between microbial communities in both biomes are therefore expected, which we will verify once the ongoing sequencing analyses are available. Our study advances the current knowledge of GHG dynamics in thermokarst lakes and helps to predict future effects of climate change impacts in northern latitudes.

How to cite: Valiente, N., Grau, O., Martin, V., Janssens, I., Van de Putte, I., Dörsch, P., Schmidt, H., and Richter, A.: Greenhouse gas dynamics across a latitudinal gradient of thermokarst lakes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4338, https://doi.org/10.5194/egusphere-egu23-4338, 2023.

In the context of global climate change, permafrost thaw in northern high-latitude territories is becoming a major concern due to the vast amount of organic carbon that is stored within this region. To accurately predict the feedback between Arctic permafrost carbon pools and future climate change, detailed insight into current carbon cycle processes and their environmental controls is imperative. A highly valuable data source for this purpose are continuous observations of turbulent exchange fluxes of carbon (e.g. CO₂ and CH₄ fluxes) and energy (e.g. fluxes of sensible and latent heat) with the eddy-covariance technique, in combination with the monitoring of environmental parameters such as e.g. air or soil temperature and moisture, radiation,  atmospheric turbulence, water table levels, precipitation, and snow depth.

In this study, we evaluate the effect of drainage on vertical carbon fluxes and environmental parameters within a Northeast Siberian wet tundra permafrost ecosystem. Our experiment includes two co-located eddy-covariance sites, one reflecting disturbed conditions affected by a drainage system which was built in 2004, and the other as an undisturbed control site. Both towers were identically outfitted with eddy covariance instruments mounted on 5 m tall towers on the floodplain of the Kolyma River near Chersky (68.75 º N, 161.33º E) in Northeast Siberia, Russia. The dataset analyzed here covers the period from July 2013 to December 2021, including continuous coverage throughout the winter seasons. We present a statistical analysis of the long-term trends in the environmental parameters and surface-atmosphere exchange fluxes at both sites. In addition, we relate the carbon and heat fluxes at both sites in the spectral and temporal domain to the inter-annual variability in climate conditions, which include extremes in both summer (temperature, precipitation) and winter (snow cover) conditions. Finally, we show the annual carbon budget of both sites, with a specific focus on the long-term impact of the drainage on carbon cycle process.

How to cite: Bolek, A., Schlutow, M., El-Madany, T., Kolle, O., Heimann, M., and Goeckede, M.: Impact of the Long-Term Drainage on the Eddy-Covariance Fluxes in Northern High Latitude Permafrost Regions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5011, https://doi.org/10.5194/egusphere-egu23-5011, 2023.

Future warming of the Arctic not only threatens to destabilize the enormous pool of organic carbon accumulated in permafrost soils, but may also mobilize elements such as calcium (Ca) or silicon (Si). Little is known about the effects of Si and Ca on carbon cycle processes in soils from Siberia, the Canadian Shield or Alaska. We incubated five different soils for six months with different Ca and amorphous Si (ASi) concentrations. Our results show a strong decrease in soil CO2 production for all soils with increasing Ca concentrations. The ASi effect was not clear across the different soils used, with soil CO2 production increasing, decreasing or not being significantly affected depending on the soil type and if the soils were initially drained or waterlogged. Including Ca as a controlling factor for Arctic soil CO2 production rates may therefore reduce uncertainties in modelling future scenarios on how Arctic regions may respond to climate change. To project how biogeochemical cycling in Arctic ecosystems will be affected by climate change, there is a need for data on element availability. For this we analysed ASi, Si, Ca, iron (Fe), phosphorus (P), and aluminium (Al) availability from 574 soil samples from the circumpolar Arctic region. We show large differences in element availability among different lithologies and Arctic regions. We summarized these data in pan-Arctic element maps focussing on the top 100 cm of Arctic soil. Furthermore, we provide values for element availability for the organic and the mineral layer of the seasonally thawing active layer as well as for the uppermost permafrost layer. Our spatially explicit data on differences in the availability of elements between the different lithological classes and regions now and in the future will improve Arctic Earth system models for estimating current and future carbon and nutrient feedbacks under climate change.

How to cite: Stimmler, P. and Schaller, J.: Calcium and amorphous silica in Arctic soils: Estimating Pan-Arctic availabilities and importance for CO2 production, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13563, https://doi.org/10.5194/egusphere-egu23-13563, 2023.

Rapid warming is currently accelerating Arctic carbon cycling, including increased permafrost thaw and CO₂ production from soil organic matter decomposition, but also CO₂ uptake by plants. Plants can additionally stimulate soil organic matter decomposition near their roots, via the rhizosphere priming effect. In a recent modeling study, we showed that priming can accelerate Arctic soil carbon loss at a globally relevant rate, and spatial analysis pointed to large potential contributions from carbon-rich permafrost peatlands. At the same time, the high carbon content of peatlands might render them insusceptible to input of easily available organic compounds by plant roots, which is considered a key component of priming. We here investigated the susceptibility of permafrost peat soils to priming by plant compounds under aerobic conditions that resemble the dominant rooting zone. To that end, we combined a 30-week laboratory incubation of peat soils from five circum-Arctic locations, with a literature meta-analysis of priming studies of Arctic peat and mineral soils. The combined experimental and literature data showed substantially and significantly weaker priming susceptibility of peat than mineral soils. Organic carbon addition increased CO₂ production from soil organic matter in mineral, but not in peat soils. Organic nitrogen addition had a significant effect on both sample types, but that of peat was much weaker. These observations point at fundamental, mechanistic differences in the response of peat and mineral soil organic matter decomposition to changing carbon and nitrogen availability. In a new model sensitivity analysis, we show that insusceptibility of peatlands to priming would substantially reduce estimates of priming-induced carbon loss from the circum-Arctic. While our study suggests a limited effect of plant-released organic compounds on peat decomposition, it does not preclude a vegetation effect on decomposition under natural conditions. The large carbon stocks of circum-Arctic peatlands and expected changes in vegetation and drainage, call for increased efforts to quantify the combined effect of living plants on soil processes beyond carbon input.

How to cite: Wild, B., Monteux, S., Wendler, B., Hugelius, G., and Keuper, F.: Rhizosphere priming in a warming Arctic: Are peatlands insusceptible?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6128, https://doi.org/10.5194/egusphere-egu23-6128, 2023.

Groundwater is one of the largest continental carbon reservoirs and tightly linked to globally significant carbon fluxes such as uptake on land, evasion from inland waters and delivery to oceans. Despite emerging evidence that these fluxes are sensitive to environmental changes, long-term trends in groundwater carbon dynamics remain widely unknown. Here I show that dissolved inorganic carbon and carbon dioxide concentrations in groundwater have increased on average by 29% and 48%, respectively, across Sweden (55−68°N) during 1980−2020. I attribute these changes mainly to a partial recovery from historic atmospheric sulfate deposition and associated shifts in weathering pathways in acid-sensitive bedrock, but also to enhanced soil respiration as a likely consequence of climate and land use changes. The results highlight previously neglected significant long-term and large-scale dynamics in groundwater carbon cycling and have implications for the pathways and time scales through which carbon is cycled through the land - inland water - ocean continuum. The observed dynamics should be included in carbon cycle models for accurate evaluations and predictions of the effects of environmental changes on regional and global carbon fluxes.

How to cite: Klaus, M.: Rising carbon dioxide concentrations in Swedish groundwater during 1980−2020, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1265, https://doi.org/10.5194/egusphere-egu23-1265, 2023.