Description: Wetlands are the single largest natural source of atmospheric methane (CH4), a greenhouse gas, and occur extensively in the northern hemisphere. Large discrepancies remain between bottom-up and top-down estimates of northern CH4 emissions. To explore whether these discrepancies are due to poor representation of non-growing season CH4 emissions, we synthesized non-growing season and annual CH4 flux measurements from temperate, boreal, and tundra wetlands and uplands. Median non-growing season wetland emissions ranged from 0.9 g m-2 in bogs to 5.2 g m-2 in marshes and were dependent on moisture, vegetation, and permafrost. Annual wetland emissions ranged from 0.9 g m-2 y-1 in tundra bogs to 78 g m-2 y-1 in temperate marshes. Uplands varied from CH4 sinks to CH4 sources with a median annual flux of 0.0 ± 0.2 g m-2 y-1. The measured fraction of annual CH4 emissions during the non-growing season (observed: 13 to 47%) was significantly larger than was predicted by two process-based model ensembles, especially between 40-60º N (modeled: 4 to 17%). Constraining the model ensembles with the measured non-growing fraction increased total non-growing season and annual CH4 emissions. Using this constraint, the modeled non-growing season wetland CH4 flux from 〉40° north was 6.1 ± 1.5 Tg y-1, three times greater than the non-growing season emissions of the unconstrained model ensemble. The annual wetland CH4 flux was 37 ± 7 Tg y-1 from the data-constrained model ensemble, 25% larger than the unconstrained ensemble. Considering non-growing season processes is critical for accurately estimating CH4 emissions from high latitude ecosystems, and necessary for constraining the role of wetland emissions in a warming climate. This dataset contains the synthesis of measured flux data from the study.

Description: This dataset is a synthesis of published nitrous oxide (N2O) fluxes from permafrost-affected soils in Arctic, Antarctic, and Alpine permafrost regions. The data includes mean N2O flux rates measured under field (in situ) conditions and in intact plant-soil systems (mesocosms) under near-field conditions. The dataset further includes explanatory environmental parameters such as meteorological data, soil physical-chemical properties, as well as site and experimental information. Data has been synthesized from published studies (see 'Further details'), and in some cases the authors of published studies have been contacted for additional site-level information. The dataset includes studies published until 2019. We encourage linking additional N2O flux data from unpublished and future studies with similar metadata structure to this dataset, to produce a comprehensive, findable database for N2O fluxes from permafrost regions.

Description: This dataset merges nitrogen data from the Yedoma domain. It includes numerous fieldwork campaigns, which take place since 1998. In total 467 samples from the active layer (seasonally thawed layer), 175 samples from perennially frozen Holocene cover deposits, 479 samples from thermokarst deposits in drained thermokarst, 175 in-situ thawed, diagenetically (anaerobic microbial decomposition possible during unfrozen phase) altered Yedoma deposits (called Taberite), and 917 samples from frozen Yedoma deposits are included. Moreover it includes a NH4+ and NO3- quantification basing on of 658 samples, including 378 data points for NH4+ (active layer, 93; Holocene cover, 108; thermokarst sediment, 138; Taberite, 0; Yedoma deposit, 39) and 542 data points for NO3- (active layer, 94; Holocene cover, 137; thermokarst sediment, 119; Taberite, 6; Yedoma deposit, 186). The bootstrapping code we adjusted for this study is available from Zenodo (Jongejans & Strauss, 2020, doi:10.5281/zenodo.3734247). The code is published under a GNU General Public License v3.0. The included areal estimation of the Yedoma domain was used from the IRYP database (Strauss et al., 2022, doi:10.1594/PANGAEA.940078).

Description: This dataset includes two data tables of methane (CH4) fluxes measured in Arctic uplands. Dataset 1 contains CH4 fluxes measured at high temporal resolution (hourly fluxes) collected over two snow-free seasons (June–August; 2019, 2021) at Trail Valley Creek, an Arctic tundra site in the Western Canadian Arctic. Fluxes were measured with automated chambers installed in replication of six at three individual landcover vegetation units (Lichen, Shrub, Tussock) within dwarf-shrub dominated tundra. Site meteorological data are provided with the flux data at hourly resolution. Dataset 2 includes campaign-based, manual chamber measurements at sites displaying net CH4 uptake. These manual measurements were conducted during the growing season at typical, well-drained upland sites, which included, besides Trail Valley Creek, three additional sites in the Canadian and European Arctic (Havikpak Creek, Scotty Creek, Kilpisjärvi). Besides CH4 flux observations, dataset 2 contains measured greenhouse gas concentration profiles of CH4, carbon dioxide (CO2) and nitrous oxide (N2O) at 2 cm, 5 cm, 10 cm, and 20 cm soil depths, as well as site meteorological data. While wetlands are known CH4 emitters, drier arctic and boreal uplands may act as sinks of atmospheric CH4. The scope of the study and this dataset is to improve the spatial and temporal coverage of low CH4 emitting and sites displaying net CH4 uptake across the Arctic. Both datasets are meant as supplement to the published study, where further, detailed information on site conditions and methodology can be found.

Description: This dataset includes campaign-based, manual chamber measurements at sites displaying net methane (CH4) uptake. These manual measurements were conducted during the growing season at typical, well-drained upland sites, which included, besides Trail Valley Creek, three additional sites in the Canadian and European Arctic (Havikpak Creek, Scotty Creek, Kilpisjärvi). Besides CH4 flux observations, the dataset contains measured greenhouse gas concentration profiles of CH4, carbon dioxide (CO2) and nitrous oxide (N2O) at 2 cm, 5 cm, 10 cm, and 20 cm soil depths, as well as site meteorological data.

Description: Northern peatlands have accumulated large stocks of organic carbon (C) and nitrogen (N), but their spatial distribution and vulnerability to climate warming remain uncertain. Here, we used machine-learning techniques with extensive peat core data (n 〉 7,000) to create observation-based maps of northern peatland C and N stocks, and to assess their response to warming and permafrost thaw. We estimate that northern peatlands cover 3.7 ± 0.5 million km2 and store 415 ± 150 Pg C and 10 ± 7 Pg N. Nearly half of the peatland area and peat C stocks are permafrost affected. Using modeled global warming stabilization scenarios (from 1.5 to 6 °C warming), we project that the current sink of atmospheric C (0.10 ± 0.02 Pg C⋅y−1) in northern peatlands will shift to a C source as 0.8 to 1.9 million km2 of permafrost-affected peatlands thaw. The projected thaw would cause peatland greenhouse gas emissions equal to ∼1% of anthropogenic radiative forcing in this century. The main forcing is from methane emissions (0.7 to 3 Pg cumulative CH4-C) with smaller carbon dioxide forcing (1 to 2 Pg CO2-C) and minor nitrous oxide losses. We project that initial CO2-C losses reverse after ∼200 y, as warming strengthens peatland C-sinks. We project substantial, but highly uncertain, additional losses of peat into fluvial systems of 10 to 30 Pg C and 0.4 to 0.9 Pg N. The combined gaseous and fluvial peatland C loss estimated here adds 30 to 50% onto previous estimates of permafrost-thaw C losses, with southern permafrost regions being the most vulnerable.

Description: The Arctic is warming at twice the rate of the rest of the globe. While it has been increasingly highlighted that thawing permafrost accelerates soil organic matter decomposition, research on biogeochemical N cycling is still underrepresented. Arctic nitrous oxide (N2O) emissions have long been assumed to have a negligible climatic impact but recently increasing evidence has emerged of N2O hotspots in the Arctic. Even in small amounts, N2O has the potential to contribute to climate change due to it being nearly 300 times more potent at radiative forcing than CO2. Therefore, the ‘NOCA’ project aims to establish the first circumarctic N2O budget. Following intensive N2O flux sampling campaigns at primary sites within Northern Russia and soil N2O concentration measurements from secondary sites across the Arctic, we are now entering the phase of spatial extrapolation. Challenges to overcome are the small-scale heterogeneity of the landscape and incorporating small features that can function as N2O hotspots. Therefore, as a first step in upscaling the N2O fluxes, high resolution imagery is needed. We show here novel high-resolution 3D imagery from an unmanned aerial vehicle (UAV), which will be used to upscale N2O fluxes from plot to landscape scale by linking ground-truth N2O measurements to vegetation maps. This approach will first be applied to the East cliff of Kurungnakh Island in the Lena River Delta of North Siberia and is based on 2019 sampling campaign data. Kurungnakh Island is characterized by ice- and organic-rich Yedoma permafrost that is thawed by fluvial thermo-erosion forming retrogressive thaw slumps in various stages of activity. Overall, 20 sites were sampled along the cliff and inland, covering the significant topographic and vegetative characteristics of the landscape. The data from this scale will provide the basis for extrapolating, by using a stepwise upscaling approach, to the regional and finally circumarctic scale, allowing a first rough estimate of the current climate impact of N2O emissions from permafrost affected soils. Available international circumarctic data from this and past projects will be synthesized with an Arctic N2O database under development for use in future ecosystem and process-based climate model simulations.

Description: Arctic nitrous oxide (N2O) emissions have long been assumed to have a negligible climatic impact but recently increasing evidence has emerged of N2O hotspots in the Arctic. Even in small amounts, N2O has the potential to contribute to climate change due to it being nearly 300 times more potent at radiative forcing than CO2. Therefore, the ‘NOCA’ project aims to establish the first circumarctic N2O budget. Following intensive N2O flux sampling campaigns at primary sites within Northern Russia and soil N2O concentration measurements from secondary sites across the Arctic, we are now entering the phase of spatial extrapolation. Challenges to overcome are the small-scale heterogeneity of the landscape and incorporating small features that can function as N2O hotspots. Therefore, as a first step in upscaling the N2O fluxes, high resolution imagery is needed. We show here novel high-resolution 3D imagery from an unmanned aerial vehicle (UAV), which will be used to upscale N2O fluxes from plot to landscape scale by linking ground-truth N2O measurements to vegetation maps. This approach will first be applied to the East cliff of Kurungnakh Island in the Lena River Delta of North Siberia and is based on 2019 sampling campaign data. Kurungnakh Island is characterized by ice and organic-rich Yedoma permafrost that is thawed by fluvial thermo-erosion forming retrogressive thaw slumps in various stages of activity. Overall, 20 sites were sampled along the cliff and inland, covering the significant topographic and vegetative characteristics of the landscape. The data from this scale will provide the basis for extrapolating, by using a stepwise upscaling approach, to the regional and finally circumarctic scale, allowing a first rough estimate of the current climate impact of N2O emissions from permafrost affected soils. Available international circumarctic data from this and past projects will be synthesized with an Arctic N2O database under development for use in future ecosystem and process-based climate model simulations

Description: Arctic soils and sediments are well known for their huge carbon stocks and the significant positive feedback carbon dioxide (CO2) and methane (CH4) emissions can have on climate change. However, the vast amounts of nitrogen (N) and possible emissions of the strong greenhouse gas nitrous oxide (N2O) from Arctic soils are much less considered in this context. Arctic soils have been neglected in global N2O accounting, since their N2O emissions were traditionally thought to be low due to the general N-limitation of biological processes. Recent results suggest, however, that this assumption is unwarranted and needs to be revised. Still, although we know about the risk for increasing N2O emissions from the Arctic with warming, data are available only from a handful of sites and we are lacking any estimate on the circumarctic N2O budget even under the present climate. This presentation will introduce our plan to produce the first circumarctic N2O budget, an important baseline scenario against which changes in circumarctic N2O emissions can be observed with ongoing warming and global change. In order to estimate the first circumarctic N2O budget, we synthesize existing data and organize large-scale surveys of N2O fluxes across the Circumarctic. In our synthesis effort, we collect published and unpublished data on N2O emissions and N2O soil gas concentrations and analyze the data for driving variables and mechanisms underlying the N2O fluxes from various sites with different soil and vegetation characteristics. In addition, we organize measurement campaigns (via the INTERACT remote access program) to quantify N2O fluxes across a wide variety of Arctic sites using a network of collaborator stations with simple, standardized methods, and combine this N2O screening with GIS approaches to scale up the N2O fluxes step-wise from plot to regional and circumarctic levels. Ultimately, these data will be combined with existing data-sets and archived in a database that will be made available for process modelers in order to develop and improve the performance N2O models for permafrost soils. N2O flux data were published in 21 articles from 16 Arctic sites. In the frame of this project, N2O flux measurements were conducted in 2018 at 18 study sites located in Russia, Scandinavia, Svalbard, Canada and Alaska. First analyses show that N2O is released from a range of environmentally distinct sites and at variable magnitudes with soil N content, soil C/N ratios, vegetation cover, water availability, and nutrient content likely playing significant roles. Ultimately, this project will not only provide a valuable input towards the first estimate of the circumarctic N2O budget but also towards understanding the controls of Arctic N2O fluxes which is necessary for future projections. There is urgent need for collaboration among partners in this effort and we would thus like to invite interested researchers to contribute with further published or unpublished data on N2O fluxes/concentrations from Arctic sites to support our synthesis effort. Scientists are also highly requested to sample additional N2O data from “their” Arctic sites with the simple methods introduced here, in order to help us filling large data gaps.

Description: Nitrogen regulates multiple aspects of the permafrost climate feedback, including plant growth, organic matter decomposition, and the production of the potent greenhouse gas nitrous oxide. Despite its importance, current estimates of permafrost nitrogen are highly uncertain. Here, we compiled a dataset of 〉2000 samples to quantify nitrogen stocks in the Yedoma domain, a region with organic-rich permafrost that contains ~25% of all permafrost carbon. We estimate that the Yedoma domain contains 41.2 gigatons of nitrogen down to ~20 metre for the deepest unit, which increases the previous estimate for the entire permafrost zone by ~46%. Approximately 90% of this nitrogen (37 gigatons) is stored in permafrost and therefore currently immobile and frozen. Here, we show that of this amount, ¾ is stored 〉3 metre depth, but if partially mobilised by thaw, this large nitrogen pool could have continental-scale consequences for soil and aquatic biogeochemistry and global-scale consequences for the permafrost feedback.