Status: this preprint is currently under review for the journal ESSD.
ABCFlux v2: Arctic–boreal CO2 and CH4 monthly flux observations and ancillary information across terrestrial and freshwater ecosystems
Anna-Maria Virkkala,Isabel Wargowsky,Judith Vogt,McKenzie A. Kuhn,Simran Madaan,Richard O'Keefe,Tiffany Windholz,Kyle A. Arndt,Brendan M. Rogers,Jennifer D. Watts,Kelcy Kent,Mathias Göckede,David Olefeldt,Gerard Rocher-Ros,Edward A. G. Schuur,David Bastviken,Kristoffer Aalstad,Kelly Aho,Joonatan Ala-Könni,Haley Alcock,Inge Althuizen,Christopher D. Arp,Jun Asanuma,Katrin Attermeyer,Mika Aurela,Sivakiruthika Balathandayuthabani,Alan Barr,Maialen Barret,Ochirbat Batkhishig,Christina Biasi,Mats P. Björkman,Andrew Black,Elena Blanc-Betes,Pascal Bodmer,Julia Boike,Abdullah Bolek,Frédéric Bouchard,Ingeborg Bussmann,Lea Cabrol,Eleonora Canfora,Sean Carey,Karel Castro-Morales,Namyi Chae,Andres Christen,Torben R. Christensen,Casper T. Christiansen,Housen Chu,Graham Clark,Francois Clayer,Patrick Crill,Christopher Cunada,Scott J. Davidson,Joshua F. Dean,Sigrid Dengel,Matteo Detto,Catherine Dieleman,Florent Domine,Egor Dyukarev,Colin Edgar,Bo Elberling,Craig A. Emmerton,Eugenie Euskirchen,Grant Falvo,Thomas Friborg,Michelle Garneau,Mariasilvia Giamberini,Mikhail V. Glagolev,Miquel A. Gonzalez-Meler,Gustaf Granath,Jón Guðmundsson,Konsta Happonen,Yoshinobu Harazono,Lorna Harris,Josh Hashemi,Nicholas Hasson,Janna Heerah,Liam Heffernan,Manuel Helbig,Warren Helgason,Michal Heliasz,Greg Henry,Geert Hensgens,Tetsuya Hiyama,Macall Hock,David Holl,Beth Holmes,Jutta Holst,Thomas Holst,Gabriel Hould-Gosselin,Elyn Humphreys,Jacqueline Hung,Jussi Huotari,Hiroki Ikawa,Danil V. Ilyasov,Mamoru Ishikawa,Go Iwahana,Hiroki Iwata,Marcin Antoni Jackowicz-Korczynski,Joachim Jansen,Järvi Järveoja,Vincent E. J. Jassey,Rasmus Jensen,Katharina Jentzsch,Robert G. Jespersen,Carl-Fredrik Johannesson,Chersity P. Jones,Anders Jonsson,Ji Young Jung,Sari Juutinen,Evan Kane,Jan Karlsson,Sergey Karsanaev,Kuno Kasak,Julia Kelly,Kasha Kempton,Marcus Klaus,George W. Kling,Natacha Kljun,Jacqueline Knutson,Hideki Kobayashi,John Kochendorfer,Kukka-Maaria Kohonen,Pasi Kolari,Mika Korkiakoski,Aino Korrensalo,Pirkko Kortelainen,Egle Koster,Kajar Koster,Ayumi Kotani,Praveena Krishnan,Juliya Kurbatova,Lars Kutzbach,Min Jung Kwon,Ethan D. Kyzivat,Jessica Lagroix,Theodore Langhorst,Elena Lapshina,Tuula Larmola,Klaus S. Larsen,Isabelle Laurion,Justin Ledman,Hanna Lee,A. Joshua Leffler,Lance Lesack,Anders Lindroth,David Lipson,Annalea Lohila,Efrén López-Blanco,Vincent L. St. Louis,Erik Lundin,Misha Luoto,Takashi Machimura,Marta Magnani,Avni Malhotra,Marja Maljanen,Ivan Mammarella,Elisa Männistö,Luca Belelli Marchesini,Phil Marsh,Pertti J. Martkainen,Maija E. Marushchak,Mikhail Mastepanov,Alex Mavrovic,Trofim Maximov,Christina Minions,Marco Montemayor,Tomoaki Morishita,Patrick Murphy,Daniel F. Nadeau,Erin Nicholls,Mats B. Nilsson,Anastasia Niyazova,Jenni Nordén,Koffi Dodji Noumonvi,Hannu Nykanen,Walter Oechel,Anne Ojala,Tomohiro Okadera,Sujan Pal,Alexey V. Panov,Tim Papakyriakou,Dario Papale,Sang-Jong Park,Frans-Jan W. Parmentier,Gilberto Pastorello,Mike Peacock,Matthias Peichl,Roman Petrov,Kyra St. Pierre,Norbert Pirk,Jessica Plein,Vilmantas Preskienis,Anatoly Prokushkin,Jukka Pumpanen,Hilary A. Rains,Niklas Rakos,Aleski Räsänen,Helena Rautakoski,Riika Rinnan,Janne Rinne,Adrian Rocha,Nigel Roulet,Alexandre Roy,Anna Rutgersson,Aleksandr F. Sabrekov,Torsten Sachs,Erik Sahlée,Alejandro Salazar,Henrique Oliveira Sawakuchi,Christopher Schulze,Roger Seco,Armando Sepulveda-Jauregui,Svetlana Serikova,Abbey Serrone,Hanna M. Silvennoinen,Sofie Sjogersten,June Skeeter,Jo Snöälv,Sebastian Sobek,Oliver Sonnentag,Emily H. Stanley,Maria Strack,Lena Strom,Patrick Sullivan,Ryan Sullivan,Anna Sytiuk,Torbern Tagesson,Pierre Taillardat,Julie Talbot,Suzanne E. Tank,Mario Tenuta,Irina Terenteva,Frederic Thalasso,Antoine Thiboult,Halldor Thorgeirsson,Fenix Garcia Tigreros,Margaret Torn,Amy Townsend-Small,Claire Treat,Alain Tremblay,Carlo Trotta,Eeva-Stiina Tuittila,Merritt Turetsky,Masahito Ueyama,Muhammad Umair,Aki Vähä,Lona van Delden,Maarten van Hardenbroek,Andrej Varlagin,Ruth K. Varner,Elena Veretennikova,Timo Vesala,Tarmo Virtanen,Carolina Voigt,Jorien E. Vonk,Robert Wagner,Katey Walter Anthony,Qinxue Wang,Masataka Watanabe,Hailey Webb,Jeffrey M. Welker,Andreas Westergaard-Nielsen,Sebastian Westermann,Jeffrey R. White,Christian Wille,Scott N. Williamson,Scott Zolkos,Donatella Zona,and Susan M. Natali
Abstract. Measurements of surface-atmosphere carbon dioxide (CO2) and methane (CH4) fluxes have been relatively sparse across the Arctic tundra and boreal biomes, causing significant uncertainties in carbon budget estimates from the region. While the availability of Arctic-boreal carbon flux data has increased substantially over the past decade, the data have remained spread across different repositories, scientific articles, and unpublished sources, making it difficult to leverage. Here we present a new dataset of monthly Arctic-boreal carbon fluxes (ABCFlux v2) across terrestrial (wetlands and uplands) and freshwater (lakes and rivers) ecosystems compiled from previous syntheses including the Arctic-boreal CO2 flux database (ABCFlux v1), the Boreal-Arctic Wetland and Lake Methane Dataset (BAWLD-CH4), and the Global River Methane Database (GRiMeDB). In addition, we consider data from general-purpose (e.g., Zenodo) and flux network repositories, literature, and site principal investigators. The dataset includes surface-atmosphere CO2 fluxes of gross primary production (GPP), ecosystem respiration (Reco), and net ecosystem exchange (NEE), alongside CH4 fluxes. For aquatic ecosystems, we split CH4 fluxes into diffusive and ebullitive flux pathways, and included potential emissions from transient storage in the water column (“storage fluxes”), alongside CO2 and CH4 concentrations dissolved in the surface water. Fluxes are measured through a variety of methods including chamber and eddy covariance techniques alongside bubble traps, ice-surveys, and concentration-based turbulence-driven modelling in aquatic ecosystems. The monthly flux data are reported together with supporting methodological and environmental metadata. The resulting ABCFlux v2 has 23,656 flux site-months, 8,182 concentration site-months, and 199 seasonal observations from 1,024 sites, and includes 55,560 reported fluxes (i.e. sum of GPP, Reco, NEE, and CH4 fluxes) from the years 1984 to 2024. The majority of monthly observations occurred after 1999. Wetlands had the highest number of site-month observations (8,641), followed by boreal forest (6,981), lotic ecosystems (6,275), lentic ecosystems (3,725) and upland tundra (3,308). Measurements of CO2 dominated the dataset across most ecosystem types (25,101) except for lentic ecosystems, where CH4 flux site-months (3,024) were more frequent than CO2 flux site-months (2,858). Overall, ABCFlux v2 includes 158 % more site-months for terrestrial CO2 flux data compared to ABCFlux v1. Integrating and updating BAWLD-CH4 flux data from growing season averages to monthly fluxes resulted in 5,671 site-months of chamber CH4 data compared to 762 site-years. This collaborative initiative, involving contributions from over 260 researchers, provides a comprehensive overview of the current state of the Arctic-boreal carbon flux network and its data, and serves as an important step in reducing uncertainties in Arctic-boreal carbon budgets and in enhancing our understanding of climate feedbacks. The data can be accessed at ORNL DAAC at https://doi.org/10.3334/ORNLDAAC/2448 (Virkkala et al., 2025b).
Received: 02 Oct 2025 – Discussion started: 20 Oct 2025
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Dear Drs. Virkkala, Wargowsky, Vogt, and Kuhn, and co-authors,
I had the pleasure of reading a draft of your manuscript, co-authored with Dr. June Skeeter, entitled ABCFlux v2: Arctic–boreal CO2 and CH4 monthly flux observations and ancillary information across terrestrial and freshwater ecosystems as a part of the required internal review of publications process here at the Department of Natural Resources Canada’s Geological Survey of Canada.
From my perspective I think it is great! Thank you all and your co-authors for your hard work. I think this will be very well cited.
I really only have one suggestion and it is with regard to sub-classification of thaw described on Page 55:
"We further divide the thaw category into 13 categories: active layer detachment, active layer thickening, gradual thaw, ice-wedge degradation, palsa thaw, retrogressive thaw slumps, river bank erosion, subsidence, talik formation, thaw lake, thaw pond, thermokarst, thermokarst mounds with talik."
I think this can be simplified, and here I provide some discussion as to why and provide suggestions on how to do so in my comment. It’s only very a minor part of the work done, but many people are thinking about permafrost thaw, and so this little bit should be more precise. My comments and suggestions are as follows:
-River bank erosion should just be classified as higher-level erosion. It is due to hydro-mechanical processes and not thaw. Mechanical erosive processes also contribute to lateral expansion of thermokarst lakes for example, but this list does not include lake shoreline erosion. -Active-layer thickening relates to top-down thaw, so does the highly related subsidence, which is a function of active-layer thickening in the presence of ground ice. Active layer-thickening in fine-grained deposits that are frost susceptible (e.g., lacustrine and many morainal deposits) typically results in subsidence and the rate of AL thickening is comparatively slow due to latent heat required to melt ground ice. Active-layer thickening in coarse-grained sediments such as sands and gravels (e.g., glaciofluvial outwash) typically results in comparatively fast increase in AL thickness over time and little to no subsidence as such sediments are not usually associated with near-surface ground ice. Active-layer thickening in areas with exposed bedrock result in no subsidence, and comparatively rapid AL thickening due to very low ground ice contents, but substantial changes to local hydrology cmay occur with implications on drainage and biological functions. I suggest “active layer thickening” and “subsidence” could be meaningfully categorized as “active-layer thickening with subsidence” and “active-layer thickening without subsidence” -Gradual thaw is not a type of thaw that indicates any sort of genetic origin, and can relate to of several different processes. Talik formation is typically a slow process for example, as is thaw lake expansion. Gradual thaw is not that helpful if the intent is to assign a disturbance. I would delete this sub-category and reassign sites to more relevant thaw categories. -”Palsa thaw” is presumably a form of top-down thaw leading to active-layer thickening with subsidence, probably also accompanied by lateral permafrost degradation. Collapse of peatlands also occurs with active layer thickening and typically accompanied by lateral degradation. Palsa thaw might be included in a more general peatland sub-class.
-Thermokarst mound formation almost always accompanies ice-wedge degradation, so separating the two may not be necessary. -"Talik formation" accompanies permafrost degradation associated with development of thaw lakes/ponds, and also top-down thaw associated with active-layer development/permafrost degradation in ice-poor surficial materials, so it accompanies different thaw processes and might not be that instructive to keep as a stand-alone sub-category. -Thermokarst as a standalone sub-category is not that helpful because it is a blanket term that principally includes (Kokelj and Jorgenson, 2013, Permafrost and Periglac. Process., 24: 108–119, DOI: 10.1002/ppp.1779): “(1) hillslope processes, including retrogressive thaw slumps, active-layer detachment slides (ALDS) and thermal erosion gullies; (2) thaw lake processes [PDM: includes ponds], including lake expansion, drainage and lake basin evolution; and (3) wetland processes, including peatland collapse and the development of bogs and fens.” I suggest reassigning sites from “Thermokarst” to other more meaningful thaw sub-categories.
-Due to the challenges in precisely categorizing one type of thermokarst versus another in the current list, the authors may want to consider simplifying things (e.g., fire is not further classified according to burn severity). I suggest the following: Active layer detachment sliding, retrogressive thaw slumping, ice-wedge degradation with mound formation, ice-wedge degradation without mound formation, active layer thickening with subsidence, active-layer thickening without subsidence, active-layer thickening with talik formation, thaw lake/pond expansion, peatland collapse [this includes peatland degradation where thaw settlement is accompanied by lateral permafrost degradation such as palsa degradation or peat plateau degradation (with resect to this data set the difference is basically a matter of scale) and development of bogs and fens]. -The authors could simplify things even further and simply sub-classify thaw according to predominant processes driving thaw: hillslope processes, thaw lake processes, wetland processes, active layer thickening.
Other than that, I noticed just a few minor things that you probably would have fixed anyway:
Page 62: I'd reference Table 8 for the first time here: "Our annual NEE estimates (Table 8) showed a clear sink-to-source transition from net ... "
Page 62: I'd reference Table 8 again here: "Annual CH4 fluxes (Table 8) demonstrated the ..."
Page 62: Other captions for Figures and Tables that show "tundra" include a sentence like: "The terrestrial tundra class characterizes non-wetland ecosystems in the tundra biome (i.e., dry and moist tundra). "
Best regards,
Peter D. Morse, Ph.D.
Research Scientist / Chercheur scientifique
Geological Survey of Canada | Natural Resources Canada | Government of Canada /
Commission géologique du Canada | Ressources naturelles Canada | Gouvernement du Canada
Adjunct Research Professor, Department of Geography and Environmental Studies, Carleton University
Associate Member, School of Graduate Studies, University of Lethbridge
Secretary, Canadian Permafrost Association (CPA) / l’Association canadienne du pergélisol (l’ACP)
Department of Geography & Environmental Studies, Carleton University, Ottawa, Canada
Jacqueline Hung
Woodwell Climate Research Center, Falmouth, MA, USA
Jussi Huotari
Faculty of Biological and Environmental Sciences, Ecosystems and Environment Research Programme, Lammi Biological Station, University of Helsinki, Lammi FI-16900, Finland
Masinotek Oy, Ensimmäinen Savu 2, Vantaa FI-01510, Finland
Hiroki Ikawa
National Agriculture and Food Research Organization, Japan
Danil V. Ilyasov
UNESCO Department "Environmental Dynamics and Global Climate Changes", Yugra State University, Khanty-Mansiysk, Russia
Mamoru Ishikawa
Faculty of Earth Environmental Science, Hokkaido University, Japan
Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark
Norwegian Institute for Nature Research (NINA), Oslo, Norway
Chersity P. Jones
Department of Earth Sciences and Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH
Anders Jonsson
Department of Ecology, Environment and Geoscience, Umeå University, Umeå, Sweden
Ji Young Jung
Korea Polar Research Institute, Incheon, South Korea
Sari Juutinen
Finnish Meteorological Institute, Finland
Evan Kane
College of Forest Resources and Environmental Science, Michigan Technological University, USA
Jan Karlsson
Department of Ecology, Environment and Geoscience, Umeå University, Umeå, Sweden
Sergey Karsanaev
Institute for Biological Problems of Cryolithozone of the Siberian Branch of the RAS - Division of Federal Research Centre "The Yakut Scientific Centre of the Siberian Branch of the Russian Academy of Sciences", Russia
Centre d’études nordiques (CEN), Université Laval, Québec, Canada
Universite du Quebec a Trois-Rivieres, Research Centre for Watershed-Aquatic ecosystem interactions (RIVE) , Canada
Trofim Maximov
Institute for Biological Problems of Cryolithozone of the Siberian Branch of the RAS - Division of Federal Research Centre "The Yakut Scientific Centre of the Siberian Branch of the Russian Academy of Sciences", Russia
Christina Minions
Woodwell Climate Research Center, Falmouth, MA, USA
Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
Roman Petrov
Institute for Biological Problems of Cryolithozone of the Siberian Branch of the RAS - Division of Federal Research Centre "The Yakut Scientific Centre of the Siberian Branch of the Russian Academy of Sciences", Russia
This dataset includes monthly measurements of carbon dioxide and methane exchange between land, water, and the atmosphere from over 1,000 sites in Arctic and boreal regions. It combines measurements from a variety of ecosystems, including wetlands, forests, tundra, lakes, and rivers, gathered by over 260 researchers from 1984–2024. This dataset can be used to improve and reduce uncertainty in carbon budgets in order to strengthen our understanding of climate feedbacks in a warming world.
This dataset includes monthly measurements of carbon dioxide and methane exchange between land,...
Dear Drs. Virkkala, Wargowsky, Vogt, and Kuhn, and co-authors,
I had the pleasure of reading a draft of your manuscript, co-authored with Dr. June Skeeter, entitled ABCFlux v2: Arctic–boreal CO2 and CH4 monthly flux observations and ancillary information across terrestrial and freshwater ecosystems as a part of the required internal review of publications process here at the Department of Natural Resources Canada’s Geological Survey of Canada.
From my perspective I think it is great! Thank you all and your co-authors for your hard work. I think this will be very well cited.
I really only have one suggestion and it is with regard to sub-classification of thaw described on Page 55:
"We further divide the thaw category into 13 categories: active layer detachment, active layer thickening, gradual thaw, ice-wedge degradation, palsa thaw, retrogressive thaw slumps, river bank erosion, subsidence, talik formation, thaw lake, thaw pond, thermokarst, thermokarst mounds with talik."
I think this can be simplified, and here I provide some discussion as to why and provide suggestions on how to do so in my comment. It’s only very a minor part of the work done, but many people are thinking about permafrost thaw, and so this little bit should be more precise. My comments and suggestions are as follows:
-River bank erosion should just be classified as higher-level erosion. It is due to hydro-mechanical processes and not thaw. Mechanical erosive processes also contribute to lateral expansion of thermokarst lakes for example, but this list does not include lake shoreline erosion.
-Active-layer thickening relates to top-down thaw, so does the highly related subsidence, which is a function of active-layer thickening in the presence of ground ice. Active layer-thickening in fine-grained deposits that are frost susceptible (e.g., lacustrine and many morainal deposits) typically results in subsidence and the rate of AL thickening is comparatively slow due to latent heat required to melt ground ice. Active-layer thickening in coarse-grained sediments such as sands and gravels (e.g., glaciofluvial outwash) typically results in comparatively fast increase in AL thickness over time and little to no subsidence as such sediments are not usually associated with near-surface ground ice. Active-layer thickening in areas with exposed bedrock result in no subsidence, and comparatively rapid AL thickening due to very low ground ice contents, but substantial changes to local hydrology cmay occur with implications on drainage and biological functions. I suggest “active layer thickening” and “subsidence” could be meaningfully categorized as “active-layer thickening with subsidence” and “active-layer thickening without subsidence”
-Gradual thaw is not a type of thaw that indicates any sort of genetic origin, and can relate to of several different processes. Talik formation is typically a slow process for example, as is thaw lake expansion. Gradual thaw is not that helpful if the intent is to assign a disturbance. I would delete this sub-category and reassign sites to more relevant thaw categories.
-”Palsa thaw” is presumably a form of top-down thaw leading to active-layer thickening with subsidence, probably also accompanied by lateral permafrost degradation. Collapse of peatlands also occurs with active layer thickening and typically accompanied by lateral degradation. Palsa thaw might be included in a more general peatland sub-class.
-Thermokarst mound formation almost always accompanies ice-wedge degradation, so separating the two may not be necessary.
-"Talik formation" accompanies permafrost degradation associated with development of thaw lakes/ponds, and also top-down thaw associated with active-layer development/permafrost degradation in ice-poor surficial materials, so it accompanies different thaw processes and might not be that instructive to keep as a stand-alone sub-category.
-Thermokarst as a standalone sub-category is not that helpful because it is a blanket term that principally includes (Kokelj and Jorgenson, 2013, Permafrost and Periglac. Process., 24: 108–119, DOI: 10.1002/ppp.1779): “(1) hillslope processes, including retrogressive thaw slumps, active-layer detachment slides (ALDS) and thermal erosion gullies; (2) thaw lake processes [PDM: includes ponds], including lake expansion, drainage and lake basin evolution; and (3) wetland processes, including peatland collapse and the development of bogs and fens.” I suggest reassigning sites from “Thermokarst” to other more meaningful thaw sub-categories.
-Due to the challenges in precisely categorizing one type of thermokarst versus another in the current list, the authors may want to consider simplifying things (e.g., fire is not further classified according to burn severity). I suggest the following: Active layer detachment sliding, retrogressive thaw slumping, ice-wedge degradation with mound formation, ice-wedge degradation without mound formation, active layer thickening with subsidence, active-layer thickening without subsidence, active-layer thickening with talik formation, thaw lake/pond expansion, peatland collapse [this includes peatland degradation where thaw settlement is accompanied by lateral permafrost degradation such as palsa degradation or peat plateau degradation (with resect to this data set the difference is basically a matter of scale) and development of bogs and fens].
-The authors could simplify things even further and simply sub-classify thaw according to predominant processes driving thaw: hillslope processes, thaw lake processes, wetland processes, active layer thickening.
Other than that, I noticed just a few minor things that you probably would have fixed anyway:
Page 62: I'd reference Table 8 for the first time here: "Our annual NEE estimates (Table 8) showed a clear sink-to-source transition from net ... "
Page 62: I'd reference Table 8 again here: "Annual CH4 fluxes (Table 8) demonstrated the ..."
Page 62: Other captions for Figures and Tables that show "tundra" include a sentence like: "The terrestrial tundra class characterizes non-wetland ecosystems in the tundra biome (i.e., dry and moist tundra). "
Best regards,
Peter D. Morse, Ph.D.
Research Scientist / Chercheur scientifique
Geological Survey of Canada | Natural Resources Canada | Government of Canada /
Commission géologique du Canada | Ressources naturelles Canada | Gouvernement du Canada
Adjunct Research Professor, Department of Geography and Environmental Studies, Carleton University
Associate Member, School of Graduate Studies, University of Lethbridge
Secretary, Canadian Permafrost Association (CPA) / l’Association canadienne du pergélisol (l’ACP)