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196 results on '"Christensen, T. R."'

1. Expert assessment of future vulnerability of the global peatland carbon sink

Author

Loisel, J., Gallego-Sala, A. V., Amesbury, M. J., Magnan, G., Anshari, G., Beilman, D. W., Benavides, J. C., Blewett, J., Camill, P., Charman, D. J., Chawchai, S., Hedgpeth, A., Kleinen, T., Korhola, A., Large, D., Mansilla, C. A., Müller, J., van Bellen, S., West, J. B., Yu, Z., Bubier, J. L., Garneau, M., Moore, T., Sannel, A. B. K., Page, S., Väliranta, M., Bechtold, M., Brovkin, V., Cole, L. E. S., Chanton, J. P., Christensen, T. R., Davies, M. A., De Vleeschouwer, F., Finkelstein, S. A., Frolking, S., Gałka, M., Gandois, L., Girkin, N., Harris, L. I., Heinemeyer, A., Hoyt, A. M., Jones, M. C., Joos, F., Juutinen, S., Kaiser, K., Lacourse, T., Lamentowicz, M., Larmola, T., Leifeld, J., Lohila, A., Milner, A. M., Minkkinen, K., Moss, P., Naafs, B. D. A., Nichols, J., O’Donnell, J., Payne, R., Philben, M., Piilo, S., Quillet, A., Ratnayake, A. S., Roland, T. P., Sjögersten, S., Sonnentag, O., Swindles, G. T., Swinnen, W., Talbot, J., Treat, C., Valach, A. C., and Wu, J.

Published
2021
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6. Rapid shift in greenhouse forcing of emerging arctic peatlands

Author

Christensen, T. R. (Torben R.), Scheller, J. (Johan), Scheel, M. (Maria), Rudd, D. A. (Daniel Alexander), Jackowicz-Korczynski, M. (Marcin), Mastepanov, M. (Mikhail), López-Blanco, E. (Efrén), Christensen, T. R. (Torben R.), Scheller, J. (Johan), Scheel, M. (Maria), Rudd, D. A. (Daniel Alexander), Jackowicz-Korczynski, M. (Marcin), Mastepanov, M. (Mikhail), and López-Blanco, E. (Efrén)

Abstract

In this study, we hypothesised that the actual development stage (i.e., current age of the ecosystem) is a determining factor for the magnitude of methane production and emissions in young, northern high-latitude peatlands. We demonstrate that the earliest development of peat soil imposes a sink-to-source shift in the greenhouse warming potential of emerging peatlands in response to climate change that holds feedback mechanisms of importance for short-term (< 100 years) climate warming.

Published
2023

7. Author Correction: Expert assessment of future vulnerability of the global peatland carbon sink

Author

Loisel, J., Gallego-Sala, A. V., Amesbury, M. J., Magnan, G., Anshari, G., Beilman, D. W., Benavides, J. C., Blewett, J., Camill, P., Charman, D. J., Chawchai, S., Hedgpeth, A., Kleinen, T., Korhola, A., Large, D., Mansilla, C. A., Müller, J., van Bellen, S., West, J. B., Yu, Z., Bubier, J. L., Garneau, M., Moore, T., Sannel, A. B. K., Page, S., Väliranta, M., Bechtold, M., Brovkin, V., Cole, L. E. S., Chanton, J. P., Christensen, T. R., Davies, M. A., De Vleeschouwer, F., Finkelstein, S. A., Frolking, S., Gałka, M., Gandois, L., Girkin, N., Harris, L. I., Heinemeyer, A., Hoyt, A. M., Jones, M. C., Joos, F., Juutinen, S., Kaiser, K., Lacourse, T., Lamentowicz, M., Larmola, T., Leifeld, J., Lohila, A., Milner, A. M., Minkkinen, K., Moss, P., Naafs, B. D. A., Nichols, J., O’Donnell, J., Payne, R., Philben, M., Piilo, S., Quillet, A., Ratnayake, A. S., Roland, T. P., Sjögersten, S., Sonnentag, O., Swindles, G. T., Swinnen, W., Talbot, J., Treat, C., Valach, A. C., and Wu, J.

Published
2021
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8. The future of tundra carbon storage in Greenland:sensitivity to climate and plant trait changes

Author

López-Blanco, E. (Efrén), Langen, P. L. (Peter L.), Williams, M. (Mathew), Christensen, J. H. (Jens Hesselbjerg), Boberg, F. (Fredrik), Langley, K. (Kirsty), Christensen, T. R. (Torben Røjle), López-Blanco, E. (Efrén), Langen, P. L. (Peter L.), Williams, M. (Mathew), Christensen, J. H. (Jens Hesselbjerg), Boberg, F. (Fredrik), Langley, K. (Kirsty), and Christensen, T. R. (Torben Røjle)

Abstract

The continuous change in observed key indicators such as increasing nitrogen deposition, temperatures and precipitation will have marked but uncertain consequences for the ecosystem carbon (C) sink-source functioning of the Arctic. Here, we use multiple in-situ data streams measured by the Greenland Ecosystem Monitoring programme in tight connection with the Soil-Plant-Atmosphere model and climate projections from the high-resolution HIRHAM5 regional model. We apply this modelling framework with focus on two climatically different tundra sites in Greenland (Zackenberg and Kobbefjord) to assess how sensitive the net C uptake will expectedly be under warmer and wetter conditions across the 21st century and pin down the relative contribution to the overall C sink strength from climate versus plant trait variability. Our results suggest that temperatures (5–7.7 °C), total precipitation (19–110 %) and vapour pressure deficit will increase (32–36 %), while shortwave radiation will decline (6–9 %) at both sites by 2100 under the RCP8.5 scenario. Such a combined effect will, on average, intensify the net C uptake by 9–10 g C m−2 year−1 at both sites towards the end of 2100, but Zackenberg is expected to have more than twice the C sink strength capacity of Kobbefjord. Our sensitivity analysis not only reveals that plant traits are the most sensitive parameters controlling the net C exchange in both sites at the beginning and end of the century, but also that the projected increase in the net C uptake will likely be similarly influenced by future changes in climate and existing local nutrient conditions. A series of experiments forcing realistic changes in plant nitrogen status at both sites corroborates this hypothesis. This work proves the unique synergy between monitoring data and numerical models to assist robust model calibration/validation and narrow uncertainty ranges and ultimately produce more reliable C cycle projections in understudied regions such as Gree

Published
2022

9. A mobile observatory powered by sun and wind for near real time measurements of atmospheric, glacial, terrestrial, limnic and coastal oceanic conditions in remote off-grid areas

Author

Rysgaard, S. (Søren), Bjerge, K. (Kim), Boone, W. (Wieter), Frandsen, E. (Egon), Graversen, M. (Michael), Høye, T. T. (Toke Thomas), Jensen, B. (Bjarne), Johnen, G. (Geoffrey), Jackowicz-Korczynski, M. A. (Marcin Antoni), Kerby, J. T. (Jeffrey Taylor), Kortegaard, S. (Simon), Mastepanov, M. (Mikhail), Melvad, C. (Claus), Mikkelsen, P. S. (Peter Schmidt), Mortensen, K. (Keld), Nørgaard, C. (Carsten), Poulsen, E. (Ebbe), Riis, T. (Tenna), Sørensen, L. (Lotte), Christensen, T. R. (Torben Røjle), Rysgaard, S. (Søren), Bjerge, K. (Kim), Boone, W. (Wieter), Frandsen, E. (Egon), Graversen, M. (Michael), Høye, T. T. (Toke Thomas), Jensen, B. (Bjarne), Johnen, G. (Geoffrey), Jackowicz-Korczynski, M. A. (Marcin Antoni), Kerby, J. T. (Jeffrey Taylor), Kortegaard, S. (Simon), Mastepanov, M. (Mikhail), Melvad, C. (Claus), Mikkelsen, P. S. (Peter Schmidt), Mortensen, K. (Keld), Nørgaard, C. (Carsten), Poulsen, E. (Ebbe), Riis, T. (Tenna), Sørensen, L. (Lotte), and Christensen, T. R. (Torben Røjle)

Abstract

Climate change is rapidly altering the Arctic environment. Although long-term environmental observations have been made at a few locations in the Arctic, the incomplete coverage from ground stations is a main limitation to observations in these remote areas. Here we present a wind and sun powered multi-purpose mobile observatory (ARC-MO) that enables near real time measurements of air, ice, land, rivers, and marine parameters in remote off-grid areas. Two test units were constructed and placed in Northeast Greenland where they have collected data from cabled and wireless instruments deployed in the environment since late summer 2021. The two units can communicate locally via WiFi (units placed 25 km apart) and transmit near-real time data globally over satellite. Data are streamed live and accessible from (https://gios.org). The cost of one mobile observatory unit is c. 304.000€. These test units demonstrate the possibility for integrative and automated environmental data collection in remote coastal areas and could serve as models for a proposed global observatory system.

Published
2022

10. Microbial community changes in 26,500-year-old thawing permafrost

Author

Scheel, M. (Maria), Zervas, A. (Athanasios), Jacobsen, C. S. (Carsten S.), Christensen, T. R. (Torben R.), Scheel, M. (Maria), Zervas, A. (Athanasios), Jacobsen, C. S. (Carsten S.), and Christensen, T. R. (Torben R.)

Abstract

Northern permafrost soils store more than half of the global soil carbon. Frozen for at least two consecutive years, but often for millennia, permafrost temperatures have increased drastically in the last decades. The resulting thermal erosion leads not only to gradual thaw, resulting in an increase of seasonally thawing soil thickness, but also to abrupt thaw events, such as sudden collapses of the soil surface. These could affect 20% of the permafrost zone and half of its organic carbon, increasing accessibility for deeper rooting vegetation and microbial decomposition into greenhouse gases. Knowledge gaps include the impact of permafrost thaw on the soil microfauna as well as key taxa to change the microbial mineralization of ancient permafrost carbon stocks during erosion. Here, we present the first sequencing study of an abrupt permafrost erosion microbiome in Northeast Greenland, where a thermal erosion gully collapsed in the summer of 2018, leading to the thawing of 26,500-year-old permafrost material. We investigated which soil parameters (pH, soil carbon content, age and moisture, organic and mineral horizons, and permafrost layers) most significantly drove changes of taxonomic diversity and the abundance of soil microorganisms in two consecutive years of intense erosion. Sequencing of the prokaryotic 16S rRNA and fungal ITS2 gene regions at finely scaled depth increments revealed decreasing alpha diversity with depth, soil age, and pH. The most significant drivers of variation were found in the soil age, horizons, and permafrost layer for prokaryotic and fungal beta diversity. Permafrost was mainly dominated by Proteobacteria and Firmicutes, with Polaromonas identified as the most abundant taxon. Thawed permafrost samples indicated increased abundance of several copiotrophic phyla, such as Bacteroidia, suggesting alterations of carbon utilization pathways within eroding permafrost.

Published
2022

11. Earlier snowmelt may lead to late season declines in plant productivity and carbon sequestration in Arctic tundra ecosystems

Author

Zona, D. (Donatella), Lafleur, P. M. (Peter M.), Hufkens, K. (Koen), Bailey, B. (Barbara), Gioli, B. (Beniamino), Burba, G. (George), Goodrich, J. P. (Jordan P.), Liljedahl, A. K. (Anna K.), Euskirchen, E. S. (Eugénie S.), Watts, J. D. (Jennifer D.), Farina, M. (Mary), Kimball, J. S. (John S.), Heimann, M. (Martin), Göckede, M. (Mathias), Pallandt, M. (Martijn), Christensen, T. R. (Torben R.), Mastepanov, M. (Mikhail), López-Blanco, E. (Efrén), Jackowicz-Korczynski, M. (Marcin), Dolman, A. J. (Albertus J.), Belelli Marchesini, L. (Luca), Commane, R. (Roisin), Wofsy, S. C. (Steven C.), Miller, C. E. (Charles E.), Lipson, D. A. (David A.), Hashemi, J. (Josh), Arndt, K. A. (Kyle A.), Kutzbach, L. (Lars), Holl, D. (David), Boike, J. (Julia), Wille, C. (Christian), Sachs, T. (Torsten), Kalhori, A. (Aram), Song, X. (Xia), Xu, X. (Xiaofeng), Humphreys, E. R. (Elyn R.), Koven, C. D. (Charles D.), Sonnentag, O. (Oliver), Meyer, G. (Gesa), Gosselin, G. H. (Gabriel H.), Marsh, P. (Philip), Oechel, W. C. (Walter C.), Zona, D. (Donatella), Lafleur, P. M. (Peter M.), Hufkens, K. (Koen), Bailey, B. (Barbara), Gioli, B. (Beniamino), Burba, G. (George), Goodrich, J. P. (Jordan P.), Liljedahl, A. K. (Anna K.), Euskirchen, E. S. (Eugénie S.), Watts, J. D. (Jennifer D.), Farina, M. (Mary), Kimball, J. S. (John S.), Heimann, M. (Martin), Göckede, M. (Mathias), Pallandt, M. (Martijn), Christensen, T. R. (Torben R.), Mastepanov, M. (Mikhail), López-Blanco, E. (Efrén), Jackowicz-Korczynski, M. (Marcin), Dolman, A. J. (Albertus J.), Belelli Marchesini, L. (Luca), Commane, R. (Roisin), Wofsy, S. C. (Steven C.), Miller, C. E. (Charles E.), Lipson, D. A. (David A.), Hashemi, J. (Josh), Arndt, K. A. (Kyle A.), Kutzbach, L. (Lars), Holl, D. (David), Boike, J. (Julia), Wille, C. (Christian), Sachs, T. (Torsten), Kalhori, A. (Aram), Song, X. (Xia), Xu, X. (Xiaofeng), Humphreys, E. R. (Elyn R.), Koven, C. D. (Charles D.), Sonnentag, O. (Oliver), Meyer, G. (Gesa), Gosselin, G. H. (Gabriel H.), Marsh, P. (Philip), and Oechel, W. C. (Walter C.)

Abstract

Arctic warming is affecting snow cover and soil hydrology, with consequences for carbon sequestration in tundra ecosystems. The scarcity of observations in the Arctic has limited our understanding of the impact of covarying environmental drivers on the carbon balance of tundra ecosystems. In this study, we address some of these uncertainties through a novel record of 119 site-years of summer data from eddy covariance towers representing dominant tundra vegetation types located on continuous permafrost in the Arctic. Here we found that earlier snowmelt was associated with more tundra net CO₂ sequestration and higher gross primary productivity (GPP) only in June and July, but with lower net carbon sequestration and lower GPP in August. Although higher evapotranspiration (ET) can result in soil drying with the progression of the summer, we did not find significantly lower soil moisture with earlier snowmelt, nor evidence that water stress affected GPP in the late growing season. Our results suggest that the expected increased CO₂ sequestration arising from Arctic warming and the associated increase in growing season length may not materialize if tundra ecosystems are not able to continue sequestering CO₂ later in the season.

Published
2022

12. The ABCflux database:Arctic–boreal CO₂ flux observations and ancillary information aggregated to monthly time steps across terrestrial ecosystems

Author

Virkkala, A.-M. (Anna-Maria), Natali, S. M. (Susan M.), Rogers, B. M. (Brendan M.), Watts, J. D. (Jennifer D.), Savage, K. (Kathleen), Connon, S. J. (Sara June), Mauritz, M. (Marguerite), Schuur, E. A. (Edward A. G.), Peter, D. (Darcy), Minions, C. (Christina), Nojeim, J. (Julia), Commane, R. (Roisin), Emmerton, C. A. (Craig A.), Goeckede, M. (Mathias), Helbig, M. (Manuel), Holl, D. (David), Iwata, H. (Hiroki), Kobayashi, H. (Hideki), Kolari, P. (Pasi), López-Blanco, E. (Efrén), Marushchak, M. E. (Maija E.), Mastepanov, M. (Mikhail), Merbold, L. (Lutz), Parmentier, F. W. (Frans-Jan W.), Peichl, M. (Matthias), Sachs, T. (Torsten), Sonnentag, O. (Oliver), Ueyama, M. (Masahito), Voigt, C. (Carolina), Aurela, M. (Mika), Boike, J. (Julia), Celis, G. (Gerardo), Chae, N. (Namyi), Christensen, T. R. (Torben R.), Bret-Harte, M. S. (M. Syndonia), Dengel, S. (Sigrid), Dolman, H. (Han), Edgar, C. W. (Colin W.), Elberling, B. (Bo), Euskirchen, E. (Eugenie), Grelle, A. (Achim), Hatakka, J. (Juha), Humphreys, E. (Elyn), Järveoja, J. (Järvi), Kotani, A. (Ayumi), Kutzbach, L. (Lars), Laurila, T. (Tuomas), Lohila, A. (Annalea), Mammarella, I. (Ivan), Matsuura, Y. (Yojiro), Meyer, G. (Gesa), Nilsson, M. B. (Mats B.), Oberbauer, S. F. (Steven F.), Park, S.-J. (Sang-Jong), Petrov, R. (Roman), Prokushkin, A. S. (Anatoly S.), Schulze, C. (Christopher), St. Louis, V. L. (Vincent L.), Tuittila, E.-S. (Eeva-Stiina), Tuovinen, J.-P. (Juha-Pekka), Quinton, W. (William), Varlagin, A. (Andrej), Zona, D. (Donatella), Zyryanov, V. I. (Viacheslav I.), Virkkala, A.-M. (Anna-Maria), Natali, S. M. (Susan M.), Rogers, B. M. (Brendan M.), Watts, J. D. (Jennifer D.), Savage, K. (Kathleen), Connon, S. J. (Sara June), Mauritz, M. (Marguerite), Schuur, E. A. (Edward A. G.), Peter, D. (Darcy), Minions, C. (Christina), Nojeim, J. (Julia), Commane, R. (Roisin), Emmerton, C. A. (Craig A.), Goeckede, M. (Mathias), Helbig, M. (Manuel), Holl, D. (David), Iwata, H. (Hiroki), Kobayashi, H. (Hideki), Kolari, P. (Pasi), López-Blanco, E. (Efrén), Marushchak, M. E. (Maija E.), Mastepanov, M. (Mikhail), Merbold, L. (Lutz), Parmentier, F. W. (Frans-Jan W.), Peichl, M. (Matthias), Sachs, T. (Torsten), Sonnentag, O. (Oliver), Ueyama, M. (Masahito), Voigt, C. (Carolina), Aurela, M. (Mika), Boike, J. (Julia), Celis, G. (Gerardo), Chae, N. (Namyi), Christensen, T. R. (Torben R.), Bret-Harte, M. S. (M. Syndonia), Dengel, S. (Sigrid), Dolman, H. (Han), Edgar, C. W. (Colin W.), Elberling, B. (Bo), Euskirchen, E. (Eugenie), Grelle, A. (Achim), Hatakka, J. (Juha), Humphreys, E. (Elyn), Järveoja, J. (Järvi), Kotani, A. (Ayumi), Kutzbach, L. (Lars), Laurila, T. (Tuomas), Lohila, A. (Annalea), Mammarella, I. (Ivan), Matsuura, Y. (Yojiro), Meyer, G. (Gesa), Nilsson, M. B. (Mats B.), Oberbauer, S. F. (Steven F.), Park, S.-J. (Sang-Jong), Petrov, R. (Roman), Prokushkin, A. S. (Anatoly S.), Schulze, C. (Christopher), St. Louis, V. L. (Vincent L.), Tuittila, E.-S. (Eeva-Stiina), Tuovinen, J.-P. (Juha-Pekka), Quinton, W. (William), Varlagin, A. (Andrej), Zona, D. (Donatella), and Zyryanov, V. I. (Viacheslav I.)

Abstract

Past efforts to synthesize and quantify the magnitude and change in carbon dioxide (CO₂) fluxes in terrestrial ecosystems across the rapidly warming Arctic–boreal zone (ABZ) have provided valuable information but were limited in their geographical and temporal coverage. Furthermore, these efforts have been based on data aggregated over varying time periods, often with only minimal site ancillary data, thus limiting their potential to be used in large-scale carbon budget assessments. To bridge these gaps, we developed a standardized monthly database of Arctic–boreal CO₂ fluxes (ABCflux) that aggregates in situ measurements of terrestrial net ecosystem CO₂ exchange and its derived partitioned component fluxes: gross primary productivity and ecosystem respiration. The data span from 1989 to 2020 with over 70 supporting variables that describe key site conditions (e.g., vegetation and disturbance type), micrometeorological and environmental measurements (e.g., air and soil temperatures), and flux measurement techniques. Here, we describe these variables, the spatial and temporal distribution of observations, the main strengths and limitations of the database, and the potential research opportunities it enables. In total, ABCflux includes 244 sites and 6309 monthly observations; 136 sites and 2217 monthly observations represent tundra, and 108 sites and 4092 observations represent the boreal biome. The database includes fluxes estimated with chamber (19 % of the monthly observations), snow diffusion (3 %) and eddy covariance (78 %) techniques. The largest number of observations were collected during the climatological summer (June–August; 32 %), and fewer observations were available for autumn (September–October; 25 %), winter (December–February; 18 %), and spring (March–May; 25 %). ABCflux can be used in a wide array of empirical, remote sensing and modeling studies to improve understanding of the regional and temporal variability in CO₂ fluxes and to better es

Published
2022

13. Toward UAV-based methane emission mapping of Arctic terrestrial ecosystems

Author

Scheller, J. H. (Johan H.), Mastepanov, M. (Mikhail), Christensen, T. R. (Torben R.), Scheller, J. H. (Johan H.), Mastepanov, M. (Mikhail), and Christensen, T. R. (Torben R.)

Abstract

Methane is an important greenhouse gas, and emissions are expected to rise in Arctic wetland ecosystems when temperatures increase due to climate change. However, current emission estimates are associated with large uncertainties because methane shows high spatial variability. A central problem is that existing methods are often spatially restricted due to limitations in access, cost, power availability, and in need of high maintenance levels. Our study explores how a setup consisting of an unmanned aerial vehicle and a high-precision trace gas analyzer can complement well-established methods, like mobile flux chambers and eddy covariance towers, by providing independent maps of spatial variability in emissions at the landscape scale. In Zackenberg Valley, Northeast Greenland, we mapped concentration measurements from a high-precision trace gas analyzer with a reported precision of 0.6 parts per billion in a high-Arctic tundra fen ecosystem. We connected the analyzer via a long tube to a consumer-grade quadcopter, finding that the combined setup could differentiate near-surface methane concentrations of less than 5 parts per billion within a few meters under favorable weather conditions. Five of ten campaigns showed that relative methane concentration hot spots and cold spots significantly correlated with areas showing relatively high and low emissions (ranging from 1.40 to 7.4 mg m⁻² h⁻¹) during study campaigns in previous years. Concurrent measurements in a stationary automated chamber setup showed comparatively low methane emissions (~0.1 to 3.9 mg m⁻² h⁻¹) compared to previous years, indicating that a further improved UAV-analyzer setup could demonstrate clear differences in an ecosystem where methane emissions are generally higher. Calm conditions with some degree of air mixing near the surface were best suited for the mapping. Windy and wet conditions should be avoided, both for the reliability of the mapping and for safely navigating the unmanned aer

Published
2022

14. Radiation, soil water content, and temperature effects on carbon cycling in an alpine swamp meadow of the northeastern Qinghai–Tibetan Plateau

Author

Wei, J. (Junqi), Li, X. (Xiaoyan), Liu, L. (Lei), Christensen, T. R. (Torben Røjle), Jiang, Z. (Zhiyun), Ma, Y. (Yujun), Wu, X. (Xiuchen), Yao, H. (Hongyun), López-Blanco, E. (Efrén), Wei, J. (Junqi), Li, X. (Xiaoyan), Liu, L. (Lei), Christensen, T. R. (Torben Røjle), Jiang, Z. (Zhiyun), Ma, Y. (Yujun), Wu, X. (Xiuchen), Yao, H. (Hongyun), and López-Blanco, E. (Efrén)

Abstract

Predicted intensified climate warming will likely alter the ecosystem net carbon (C) uptake of the Qinghai–Tibetan Plateau (QTP). Variations in C sink–source responses to climate warming have been linked to water availability; however, the mechanisms by which net C uptake responds to soil water content in saturated swamp meadow ecosystems remain unclear. To explore how soil moisture and other environmental drivers modulate net C uptake in the QTP, field measurements were conducted using the eddy covariance technique in 2014, 2015, 2017, and 2018. The alpine swamp meadow presented in this study was a persistent and strong C sink of CO₂ (−168.0 ± 62.5 g C m⁻² yr⁻¹, average ± standard deviation) across the entire 4-year study period. A random forest machine-learning analysis suggested that the diurnal and seasonal variations of net ecosystem exchange (NEE) and gross primary productivity (GPP) were regulated by temperature and net radiation. Ecosystem respiration (Re), however, was found mainly regulated by the variability of soil water content (SWC) at different temporal aggregations, followed by temperature, the second contributing driver. We further explored how Re is controlled by nearly saturated soil moisture and temperature comparing two different periods featuring almost identical temperatures and significant differences on SWC and vice versa. Our data suggest that, despite the relatively abundant water supply, periods with a substantial decrease in SWC or increase in temperature produced higher Re and therefore weakened the C sink strength. Our results reveal that nearly saturated soil conditions during the growing seasons can help maintain lower ecosystem respiration rates and thus enhance the overall C sequestration capacity in this alpine swamp meadow. We argue that soil respiration and subsequent ecosystem C sink magnitude in alpine swamp meadows could likely be affected by future changes in soil hydrological conditions caused by permafrost degrada

Published
2022

16. Expert assessment of future vulnerability of the global peatland carbon sink (vol 11, pg 70, 2021)

Author

Loisel, J., Gallego-Sala, A. V., Amesbury, M. J., Magnan, G., Anshari, G., Beilman, D. W., Benavides, J. C., Blewett, J., Camill, P., Charman, D. J., Chawchai, S., Hedgpeth, A., Kleinen, T., Korhola, A., Large, D., Mansilla, C. A., Muller, J., van Bellen, S., West, J. B., Yu, Z., Bubier, J. L., Garneau, M., Moore, T., Sannel, A. B. K., Page, S., Valiranta, M., Bechtold, M., Brovkin, V., Cole, L. E. S., Chanton, J. P., Christensen, T. R., Davies, M. A., De Vleeschouwer, F., Finkelstein, S. A., Frolking, S., Galka, M., Gandois, L., Girkin, N., Harris, L. I., Heinemeyer, A., Hoyt, A. M., Jones, M. C., Joos, F., Juutinen, S., Kaiser, K., Lacourse, T., Lamentowicz, M., Larmola, T., Leifeld, J., Lohila, A., Milner, A. M., Minkkinen, K., Moss, P., Naafs, B. D. A., Nichols, J., O'Donnell, J., Payne, R., Philben, M., Piilo, S., Quillet, A., Ratnayake, A. S., Roland, T. P., Sjogersten, S., Sonnentag, O., Swindles, G. T., Swinnen, W., Talbot, J., Treat, C., Valach, A. C., and Wu, J.

Abstract

A Correction to this paper has been published: https://doi.org/10.1038/s41558-021-00991-1.

Published
2021
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17. Expert assessment of vulnerability of permafrost carbon to climate change

Author

Schuur, E. A. G., Abbott, B. W., Bowden, W. B., Brovkin, V., Camill, P., Canadell, J. G., Chanton, J. P., Chapin, III, F. S., Christensen, T. R., Ciais, P., Crosby, B. T., Czimczik, C. I., Grosse, G., Harden, J., Hayes, D. J., Hugelius, G., Jastrow, J. D., Jones, J. B., Kleinen, T., Koven, C. D., Krinner, G., Kuhry, P., Lawrence, D. M., McGuire, A. D., Natali, S. M., O’Donnell, J. A., Ping, C. L., Riley, W. J., Rinke, A., Romanovsky, V. E., Sannel, A. B. K., Schädel, C., Schaefer, K., Sky, J., Subin, Z. M., Tarnocai, C., Turetsky, M. R., Waldrop, M. P., Walter Anthony, K. M., Wickland, K. P., Wilson, C. J., and Zimov, S. A.

Published
2013
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18. Methane in Zackenberg Valley, NE Greenland:multidecadal growing season fluxes of a high-Arctic tundra

Author

Scheller, J. H. (Johan H.), Mastepanov, M. (Mikhail), Christiansen, H. H. (Hanne H.), and Christensen, T. R. (Torben R.)

Abstract

The carbon balance of high-latitude terrestrial ecosystems plays an essential role in the atmospheric concentration of trace gases, including carbon dioxide (CO₂) and methane (CH₄). Increasing atmospheric methane levels have contributed to ∼ 20 % of the observed global warming since the pre-industrial era. Rising temperatures in the Arctic are expected to promote the release of methane from Arctic ecosystems. Still, existing methane flux measurement efforts are sparse and highly scattered, and further attempts to assess the landscape fluxes over multiple years are needed. Here we combine multi-year July–August methane flux monitoring (2006–2019) from automated flux chambers in the central fens of Zackenberg Valley, northeast Greenland, with several flux measurement campaigns on the most common vegetation types in the valley to estimate the landscape fluxes over 14 years. Methane fluxes based on manual chamber measurements are available from campaigns in 1997, 1999–2000, and in shorter periods from 2007–2013 and were summarized in several published studies. The landscape fluxes are calculated for the entire valley floor and a smaller subsection of the valley floor, containing the productive fen area, Rylekærene. When integrated for the valley floor, the estimated July–August landscape fluxes were low compared to the single previous estimate, while the landscape fluxes for Rylekærene were comparable to previous estimates. The valley floor was a net methane source during July–August, with estimated mean methane fluxes ranging from 0.18 to 0.67 mg m⁻² h⁻¹. The mean methane fluxes in the fen-rich Rylekærene were substantially higher, with fluxes ranging from 0.98 to 3.26 mg m⁻² h⁻¹. A 2017–2018 erosion event indicates that some fen and grassland areas in the center of the valley are becoming unstable following pronounced fluvial erosion and a prolonged period of permafrost warming. Although such physical disturbance in the landscape can disrupt the current ecosystem–atmosphere flux patterns, even pronounced future erosion of ice-rich areas is unlikely to impact methane fluxes on a landscape scale significantly. Instead, projected changes in future climate in the valley play a more critical role. The results show that multi-year landscape methane fluxes are highly variable on a landscape scale and stress the need for long-term spatially distributed measurements in the Arctic.

Published
2021

19. Author Correction:Expert assessment of future vulnerability of the global peatland carbon sink (Nature Climate Change, (2021), 11, 1, (70-77), 10.1038/s41558-020-00944-0)

Author

Loisel, J., Gallego-Sala, A. V., Amesbury, M. J., Magnan, G., Anshari, G., Beilman, D. W., Benavides, J. C., Blewett, J., Camill, P., Charman, D. J., Chawchai, S., Hedgpeth, A., Kleinen, T., Korhola, A., Large, D., Mansilla, C. A., Müller, J., van Bellen, S., West, J. B., Yu, Z., Bubier, J. L., Garneau, M., Moore, T., Sannel, A. B.K., Page, S., Väliranta, M., Bechtold, M., Brovkin, V., Cole, L. E.S., Chanton, J. P., Christensen, T. R., Davies, M. A., De Vleeschouwer, F., Finkelstein, S. A., Frolking, S., Gałka, M., Gandois, L., Girkin, N., Harris, L. I., Heinemeyer, A., Hoyt, A. M., Jones, M. C., Joos, F., Juutinen, S., Kaiser, K., Lacourse, T., Lamentowicz, M., Larmola, T., Leifeld, J., Lohila, A., Milner, A. M., Minkkinen, K., Moss, P., Naafs, B. D.A., Nichols, J., O’Donnell, J., Payne, R., Philben, M., Piilo, S., Quillet, A., Ratnayake, A. S., Roland, T. P., Sjögersten, S., Sonnentag, O., Swindles, G. T., Swinnen, W., Talbot, J., Treat, C., Valach, A. C., and Wu, J.

Abstract

In the version of this Analysis originally published, the following affiliation for A. Lohila was missing: ‘Finnish Meteorological Institute, Climate System Research, Helsinki, Finland’. This affiliation has now been added, and subsequent affiliations renumbered accordingly, in the online versions of the Analysis.

Published
2021
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20. Multiple ecosystem effects of extreme weather events in the Arctic

Author

Christensen, T. R. (T. R.), Lund, M. (M.), Skov, K. (K.), Abermann, J. (J.), López-Blanco, E. (E.), Scheller, J. (J.), Scheel, M. (M.), Jackowicz-Korczynski, M. (M.), Langley, K. (K.), Murphy, M. J. (M. J.), Mastepanov, M. (M.), Christensen, T. R. (T. R.), Lund, M. (M.), Skov, K. (K.), Abermann, J. (J.), López-Blanco, E. (E.), Scheller, J. (J.), Scheel, M. (M.), Jackowicz-Korczynski, M. (M.), Langley, K. (K.), Murphy, M. J. (M. J.), and Mastepanov, M. (M.)

Abstract

The Arctic is getting warmer and wetter. Here, we document two independent examples of how associated extreme precipitation patterns have severe implications for high Arctic ecosystems. The events stand out in a 23-year record of continuous observations of a wide range of ecosystem parameters and act as an early indication of conditions projected to increase in the future. In NE Greenland, August 2015, one-quarter of the average annual precipitation fell during a 9-day intensive rain event. This ranked number one for daily sums during the 1996–2018 period and caused a strong and prolonged reduction in solar radiation decreasing CO₂ uptake in the order of 18–23 g C m⁻², a reduction comparable to typical annual C budgets in Arctic tundra. In a different type of event, but also due to changed weather patterns, an extreme snow melt season in 2018 triggered a dramatic gully thermokarst causing rapid transformation in ecosystem functioning from consistent annual ecosystem CO₂ uptake and low methane exchange to highly elevated methane release, net source of CO₂, and substantial export of organic carbon downstream as riverine and coastal input. In addition to climate warming alone, more frequent occurrence of extreme weather patterns will have large implications for otherwise undisturbed tundra ecosystems including their element transport and carbon interactions with the atmosphere and ocean.

Published
2021

21. Establishment of a cross-European field site network in the ALARM project for assessing large-scale changes in biodiversity

Author

Hammen, V. C., Biesmeijer, J. C., Bommarco, R., Budrys, E., Christensen, T. R., Fronzek, S., Grabaum, R., Jaksic, P., Klotz, S., Kramarz, P., Kröel-Dulay, G., Kühn, I., Mirtl, M., Moora, M., Petanidou, T., Pino, J., Potts, S. G., Rortais, A., Schulze, C. H., Steffan-Dewenter, I., Stout, J., Szentgyörgyi, H., Vighi, M., Vujic, A., Westphal, C., Wolf, T., Zavala, G., Zobel, M., Settele, J., and Kunin, W. E.

Published
2010
Full Text
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22. Expert assessment of future vulnerability of the global peatland carbon sink

Author

Loisel, J., Gallego-Sala, A. V., Amesbury, M. J., Magnan, G., Anshari, G., Beilman, D. W., Benavides, J. C., Blewett, J., Camill, P., Charman, D. J., Chawchai, S., Hedgpeth, A., Kleinen, T., Korhola, A., Large, D., Mansilla, C. A., van Bellen, S., West, J. B., Yu, Z., Bubier, J. L., Garneau, M., Moore, T., Sannel, A. B. K., Page, S., Bechtold, M., Brovkin, V., Cole, L. E. S., Chanton, J. P., Christensen, T. R., Davies, M. A., De Vleeschouwer, F., Finkelstein, S. A., Frolking, S., Ga?ka, M., Gandois, L., Girkin, N., Harris, L. I., Heinemeyer, A., Hoyt, A. M., Jones, M. C., Joos, F., Juutinen, S., Kaiser, K., Lacourse, T., Lamentowicz, M., Larmola, T., Leifeld, J., Lohila, A., Milner, A. M., Minkkinen, K., Moss, P., Naafs, B. D. A., Nichols, J., Payne, R., Philben, M., Piilo, S., Quillet, A., Ratnayake, A. S., Roland, T. P., Sonnentag, O., Swindles, G. T., Swinnen, W., Talbot, J., Treat, C., Valach, A. C., and Wu, J.

Subjects
Environmental Science (miscellaneous), Social Sciences (miscellaneous)
Abstract

© 2020, The Author(s), under exclusive licence to Springer Nature Limited. The carbon balance of peatlands is predicted to shift from a sink to a source this century. However, peatland ecosystems are still omitted from the main Earth system models that are used for future climate change projections, and they are not considered in integrated assessment models that are used in impact and mitigation studies. By using evidence synthesized from the literature and an expert elicitation, we define and quantify the leading drivers of change that have impacted peatland carbon stocks during the Holocene and predict their effect during this century and in the far future. We also identify uncertainties and knowledge gaps in the scientific community and provide insight towards better integration of peatlands into modelling frameworks. Given the importance of the contribution by peatlands to the global carbon cycle, this study shows that peatland science is a critical research area and that we still have a long way to go to fully understand the peatland–carbon–climate nexus.

Published
2020

23. The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

Author

Pastorello, G. (Gilberto), Trotta, C. (Carlo), Canfora, E. (Eleonora), Chu, H. (Housen), Christianson, D. (Danielle), Cheah, Y.-W. (You-Wei), Poindexter, C. (Cristina), Chen, J. (Jiquan), Elbashandy, A. (Abdelrahman), Humphrey, M. (Marty), Isaac, P. (Peter), Polidori, D. (Diego), Ribeca, A. (Alessio), van Ingen, C. (Catharine), Zhang, L. (Leiming), Amiro, B. (Brian), Ammann, C. (Christof), Arain, M. A. (M. Altaf), Ardo, J. (Jonas), Arkebauer, T. (Timothy), Arndt, S. K. (Stefan K.), Arriga, N. (Nicola), Aubinet, M. (Marc), Aurela, M. (Mika), Baldocchi, D. (Dennis), Barr, A. (Alan), Beamesderfer, E. (Eric), Marchesini, L. B. (Luca Belelli), Bergeron, O. (Onil), Beringer, J. (Jason), Bernhofer, C. (Christian), Berveiller, D. (Daniel), Billesbach, D. (Dave), Black, T. A. (Thomas Andrew), Blanken, P. D. (Peter D.), Bohrer, G. (Gil), Boike, J. (Julia), Bolstad, P. V. (Paul V.), Bonal, D. (Damien), Bonnefond, J.-M. (Jean-Marc), Bowling, D. R. (David R.), Bracho, R. (Rosvel), Brodeur, J. (Jason), Bruemmer, C. (Christian), Buchmann, N. (Nina), Burban, B. (Benoit), Burns, S. P. (Sean P.), Buysse, P. (Pauline), Cale, P. (Peter), Cavagna, M. (Mauro), Cellier, P. (Pierre), Chen, S. (Shiping), Chini, I. (Isaac), Christensen, T. R. (Torben R.), Cleverly, J. (James), Collalti, A. (Alessio), Consalvo, C. (Claudia), Cook, B. D. (Bruce D.), Cook, D. (David), Coursolle, C. (Carole), Cremonese, E. (Edoardo), Curtis, P. S. (Peter S.), D'Andrea, E. (Ettore), da Rocha, H. (Humberto), Dai, X. (Xiaoqin), Davis, K. J. (Kenneth J.), De Cinti, B. (Bruno), de Grandcourt, A. (Agnes), De Ligne, A. (Anne), De Oliveira, R. C. (Raimundo C.), Delpierre, N. (Nicolas), Desai, A. R. (Ankur R.), Di Bella, C. M. (Carlos Marcelo), di Tommasi, P. (Paul), Dolman, H. (Han), Domingo, F. (Francisco), Dong, G. (Gang), Dore, S. (Sabina), Duce, P. (Pierpaolo), Dufrene, E. (Eric), Dunn, A. (Allison), Dusek, J. (Jiri), Eamus, D. (Derek), Eichelmann, U. (Uwe), ElKhidir, H. A. (Hatim Abdalla M.), Eugster, W. (Werner), Ewenz, C. M. (Cacilia M.), Ewers, B. (Brent), Famulari, D. (Daniela), Fares, S. (Silvano), Feigenwinter, I. (Iris), Feitz, A. (Andrew), Fensholt, R. (Rasmus), Filippa, G. (Gianluca), Fischer, M. (Marc), Frank, J. (John), Galvagno, M. (Marta), Gharun, M. (Mana), Gianelle, D. (Damiano), Gielen, B. (Bert), Gioli, B. (Beniamino), Gitelson, A. (Anatoly), Goded, I. (Ignacio), Goeckede, M. (Mathias), Goldstein, A. H. (Allen H.), Gough, C. M. (Christopher M.), Goulden, M. L. (Michael L.), Graf, A. (Alexander), Griebel, A. (Anne), Gruening, C. (Carsten), Gruenwald, T. (Thomas), Hammerle, A. (Albin), Han, S. (Shijie), Han, X. (Xingguo), Hansen, B. U. (Birger Ulf), Hanson, C. (Chad), Hatakka, J. (Juha), He, Y. (Yongtao), Hehn, M. (Markus), Heinesch, B. (Bernard), Hinko-Najera, N. (Nina), Hoertnagl, L. (Lukas), Hutley, L. (Lindsay), Ibrom, A. (Andreas), Ikawa, H. (Hiroki), Jackowicz-Korczynski, M. (Marcin), Janous, D. (Dalibor), Jans, W. (Wilma), Jassal, R. (Rachhpal), Jiang, S. (Shicheng), Kato, T. (Tomomichi), Khomik, M. (Myroslava), Klatt, J. (Janina), Knohl, A. (Alexander), Knox, S. (Sara), Kobayashi, H. (Hideki), Koerber, G. (Georgia), Kolle, O. (Olaf), Kosugi, Y. (Yoshiko), Kotani, A. (Ayumi), Kowalski, A. (Andrew), Kruijt, B. (Bart), Kurbatova, J. (Julia), Kutsch, W. L. (Werner L.), Kwon, H. (Hyojung), Launiainen, S. (Samuli), Laurila, T. (Tuomas), Law, B. (Bev), Leuning, R. (Ray), Li, Y. (Yingnian), Liddell, M. (Michael), Limousin, J.-M. (Jean-Marc), Lion, M. (Marryanna), Liska, A. J. (Adam J.), Lohila, A. (Annalea), Lopez-Ballesteros, A. (Ana), Lopez-Blanco, E. (Efren), Loubet, B. (Benjamin), Loustau, D. (Denis), Lucas-Moffat, A. (Antje), Lueers, J. (Johannes), Ma, S. (Siyan), Macfarlane, C. (Craig), Magliulo, V. (Vincenzo), Maier, R. (Regine), Mammarella, I. (Ivan), Manca, G. (Giovanni), Marcolla, B. (Barbara), Margolis, H. A. (Hank A.), Marras, S. (Serena), Massman, W. (William), Mastepanov, M. (Mikhail), Matamala, R. (Roser), Matthes, J. H. (Jaclyn Hatala), Mazzenga, F. (Francesco), McCaughey, H. (Harry), McHugh, I. (Ian), McMillan, A. M. (Andrew M. S.), Merbold, L. (Lutz), Meyer, W. (Wayne), Meyers, T. (Tilden), Miller, S. D. (Scott D.), Minerbi, S. (Stefano), Moderow, U. (Uta), Monson, R. K. (Russell K.), Montagnani, L. (Leonardo), Moore, C. E. (Caitlin E.), Moors, E. (Eddy), Moreaux, V. (Virginie), Moureaux, C. (Christine), Munger, J. W. (J. William), Nakai, T. (Taro), Neirynck, J. (Johan), Nesic, Z. (Zoran), Nicolini, G. (Giacomo), Noormets, A. (Asko), Northwood, M. (Matthew), Nosetto, M. (Marcelo), Nouvellon, Y. (Yann), Novick, K. (Kimberly), Oechel, W. (Walter), Olesen, J. E. (Jorgen Eivind), Ourcival, J.-M. (Jean-Marc), Papuga, S. A. (Shirley A.), Parmentier, F.-J. (Frans-Jan), Paul-Limoges, E. (Eugenie), Pavelka, M. (Marian), Peichl, M. (Matthias), Pendall, E. (Elise), Phillips, R. P. (Richard P.), Pilegaard, K. (Kim), Pirk, N. (Norbert), Posse, G. (Gabriela), Powell, T. (Thomas), Prasse, H. (Heiko), Prober, S. M. (Suzanne M.), Rambal, S. (Serge), Rannik, U. (Ullar), Raz-Yaseef, N. (Naama), Reed, D. (David), de Dios, V. R. (Victor Resco), Restrepo-Coupe, N. (Natalia), Reverter, B. R. (Borja R.), Roland, M. (Marilyn), Sabbatini, S. (Simone), Sachs, T. (Torsten), Saleska, S. R. (Scott R.), Sanchez-Canete, E. P. (Enrique P.), Sanchez-Mejia, Z. M. (Zulia M.), Schmid, H. P. (Hans Peter), Schmidt, M. (Marius), Schneider, K. (Karl), Schrader, F. (Frederik), Schroder, I. (Ivan), Scott, R. L. (Russell L.), Sedlak, P. (Pavel), Serrano-Ortiz, P. (Penelope), Shao, C. (Changliang), Shi, P. (Peili), Shironya, I. (Ivan), Siebicke, L. (Lukas), Sigut, L. (Ladislav), Silberstein, R. (Richard), Sirca, C. (Costantino), Spano, D. (Donatella), Steinbrecher, R. (Rainer), Stevens, R. M. (Robert M.), Sturtevant, C. (Cove), Suyker, A. (Andy), Tagesson, T. (Torbern), Takanashi, S. (Satoru), Tang, Y. (Yanhong), Tapper, N. (Nigel), Thom, J. (Jonathan), Tiedemann, F. (Frank), Tomassucci, M. (Michele), Tuovinen, J.-P. (Juha-Pekka), Urbanski, S. (Shawn), Valentini, R. (Riccardo), van der Molen, M. (Michiel), van Gorsel, E. (Eva), van Huissteden, K. (Ko), Varlagin, A. (Andrej), Verfaillie, J. (Joseph), Vesala, T. (Timo), Vincke, C. (Caroline), Vitale, D. (Domenico), Vygodskaya, N. (Natalia), Walker, J. P. (Jeffrey P.), Walter-Shea, E. (Elizabeth), Wang, H. (Huimin), Weber, R. (Robin), Westermann, S. (Sebastian), Wille, C. (Christian), Wofsy, S. (Steven), Wohlfahrt, G. (Georg), Wolf, S. (Sebastian), Woodgate, W. (William), Li, Y. (Yuelin), Zampedri, R. (Roberto), Zhang, J. (Junhui), Zhou, G. (Guoyi), Zona, D. (Donatella), Agarwal, D. (Deb), Biraud, S. (Sebastien), Torn, M. (Margaret), Papale, D. (Dario), Pastorello, G. (Gilberto), Trotta, C. (Carlo), Canfora, E. (Eleonora), Chu, H. (Housen), Christianson, D. (Danielle), Cheah, Y.-W. (You-Wei), Poindexter, C. (Cristina), Chen, J. (Jiquan), Elbashandy, A. (Abdelrahman), Humphrey, M. (Marty), Isaac, P. (Peter), Polidori, D. (Diego), Ribeca, A. (Alessio), van Ingen, C. (Catharine), Zhang, L. (Leiming), Amiro, B. (Brian), Ammann, C. (Christof), Arain, M. A. (M. Altaf), Ardo, J. (Jonas), Arkebauer, T. (Timothy), Arndt, S. K. (Stefan K.), Arriga, N. (Nicola), Aubinet, M. (Marc), Aurela, M. (Mika), Baldocchi, D. (Dennis), Barr, A. (Alan), Beamesderfer, E. (Eric), Marchesini, L. B. (Luca Belelli), Bergeron, O. (Onil), Beringer, J. (Jason), Bernhofer, C. (Christian), Berveiller, D. (Daniel), Billesbach, D. (Dave), Black, T. A. (Thomas Andrew), Blanken, P. D. (Peter D.), Bohrer, G. (Gil), Boike, J. (Julia), Bolstad, P. V. (Paul V.), Bonal, D. (Damien), Bonnefond, J.-M. (Jean-Marc), Bowling, D. R. (David R.), Bracho, R. (Rosvel), Brodeur, J. (Jason), Bruemmer, C. (Christian), Buchmann, N. (Nina), Burban, B. (Benoit), Burns, S. P. (Sean P.), Buysse, P. (Pauline), Cale, P. (Peter), Cavagna, M. (Mauro), Cellier, P. (Pierre), Chen, S. (Shiping), Chini, I. (Isaac), Christensen, T. R. (Torben R.), Cleverly, J. (James), Collalti, A. (Alessio), Consalvo, C. (Claudia), Cook, B. D. (Bruce D.), Cook, D. (David), Coursolle, C. (Carole), Cremonese, E. (Edoardo), Curtis, P. S. (Peter S.), D'Andrea, E. (Ettore), da Rocha, H. (Humberto), Dai, X. (Xiaoqin), Davis, K. J. (Kenneth J.), De Cinti, B. (Bruno), de Grandcourt, A. (Agnes), De Ligne, A. (Anne), De Oliveira, R. C. (Raimundo C.), Delpierre, N. (Nicolas), Desai, A. R. (Ankur R.), Di Bella, C. M. (Carlos Marcelo), di Tommasi, P. (Paul), Dolman, H. (Han), Domingo, F. (Francisco), Dong, G. (Gang), Dore, S. (Sabina), Duce, P. (Pierpaolo), Dufrene, E. (Eric), Dunn, A. (Allison), Dusek, J. (Jiri), Eamus, D. (Derek), Eichelmann, U. (Uwe), ElKhidir, H. A. (Hatim Abdalla M.), Eugster, W. (Werner), Ewenz, C. M. (Cacilia M.), Ewers, B. (Brent), Famulari, D. (Daniela), Fares, S. (Silvano), Feigenwinter, I. (Iris), Feitz, A. (Andrew), Fensholt, R. (Rasmus), Filippa, G. (Gianluca), Fischer, M. (Marc), Frank, J. (John), Galvagno, M. (Marta), Gharun, M. (Mana), Gianelle, D. (Damiano), Gielen, B. (Bert), Gioli, B. (Beniamino), Gitelson, A. (Anatoly), Goded, I. (Ignacio), Goeckede, M. (Mathias), Goldstein, A. H. (Allen H.), Gough, C. M. (Christopher M.), Goulden, M. L. (Michael L.), Graf, A. (Alexander), Griebel, A. (Anne), Gruening, C. (Carsten), Gruenwald, T. (Thomas), Hammerle, A. (Albin), Han, S. (Shijie), Han, X. (Xingguo), Hansen, B. U. (Birger Ulf), Hanson, C. (Chad), Hatakka, J. (Juha), He, Y. (Yongtao), Hehn, M. (Markus), Heinesch, B. (Bernard), Hinko-Najera, N. (Nina), Hoertnagl, L. (Lukas), Hutley, L. (Lindsay), Ibrom, A. (Andreas), Ikawa, H. (Hiroki), Jackowicz-Korczynski, M. (Marcin), Janous, D. (Dalibor), Jans, W. (Wilma), Jassal, R. (Rachhpal), Jiang, S. (Shicheng), Kato, T. (Tomomichi), Khomik, M. (Myroslava), Klatt, J. (Janina), Knohl, A. (Alexander), Knox, S. (Sara), Kobayashi, H. (Hideki), Koerber, G. (Georgia), Kolle, O. (Olaf), Kosugi, Y. (Yoshiko), Kotani, A. (Ayumi), Kowalski, A. (Andrew), Kruijt, B. (Bart), Kurbatova, J. (Julia), Kutsch, W. L. (Werner L.), Kwon, H. (Hyojung), Launiainen, S. (Samuli), Laurila, T. (Tuomas), Law, B. (Bev), Leuning, R. (Ray), Li, Y. (Yingnian), Liddell, M. (Michael), Limousin, J.-M. (Jean-Marc), Lion, M. (Marryanna), Liska, A. J. (Adam J.), Lohila, A. (Annalea), Lopez-Ballesteros, A. (Ana), Lopez-Blanco, E. (Efren), Loubet, B. (Benjamin), Loustau, D. (Denis), Lucas-Moffat, A. (Antje), Lueers, J. (Johannes), Ma, S. (Siyan), Macfarlane, C. (Craig), Magliulo, V. (Vincenzo), Maier, R. (Regine), Mammarella, I. (Ivan), Manca, G. (Giovanni), Marcolla, B. (Barbara), Margolis, H. A. (Hank A.), Marras, S. (Serena), Massman, W. (William), Mastepanov, M. (Mikhail), Matamala, R. (Roser), Matthes, J. H. (Jaclyn Hatala), Mazzenga, F. (Francesco), McCaughey, H. (Harry), McHugh, I. (Ian), McMillan, A. M. (Andrew M. S.), Merbold, L. (Lutz), Meyer, W. (Wayne), Meyers, T. (Tilden), Miller, S. D. (Scott D.), Minerbi, S. (Stefano), Moderow, U. (Uta), Monson, R. K. (Russell K.), Montagnani, L. (Leonardo), Moore, C. E. (Caitlin E.), Moors, E. (Eddy), Moreaux, V. (Virginie), Moureaux, C. (Christine), Munger, J. W. (J. William), Nakai, T. (Taro), Neirynck, J. (Johan), Nesic, Z. (Zoran), Nicolini, G. (Giacomo), Noormets, A. (Asko), Northwood, M. (Matthew), Nosetto, M. (Marcelo), Nouvellon, Y. (Yann), Novick, K. (Kimberly), Oechel, W. (Walter), Olesen, J. E. (Jorgen Eivind), Ourcival, J.-M. (Jean-Marc), Papuga, S. A. (Shirley A.), Parmentier, F.-J. (Frans-Jan), Paul-Limoges, E. (Eugenie), Pavelka, M. (Marian), Peichl, M. (Matthias), Pendall, E. (Elise), Phillips, R. P. (Richard P.), Pilegaard, K. (Kim), Pirk, N. (Norbert), Posse, G. (Gabriela), Powell, T. (Thomas), Prasse, H. (Heiko), Prober, S. M. (Suzanne M.), Rambal, S. (Serge), Rannik, U. (Ullar), Raz-Yaseef, N. (Naama), Reed, D. (David), de Dios, V. R. (Victor Resco), Restrepo-Coupe, N. (Natalia), Reverter, B. R. (Borja R.), Roland, M. (Marilyn), Sabbatini, S. (Simone), Sachs, T. (Torsten), Saleska, S. R. (Scott R.), Sanchez-Canete, E. P. (Enrique P.), Sanchez-Mejia, Z. M. (Zulia M.), Schmid, H. P. (Hans Peter), Schmidt, M. (Marius), Schneider, K. (Karl), Schrader, F. (Frederik), Schroder, I. (Ivan), Scott, R. L. (Russell L.), Sedlak, P. (Pavel), Serrano-Ortiz, P. (Penelope), Shao, C. (Changliang), Shi, P. (Peili), Shironya, I. (Ivan), Siebicke, L. (Lukas), Sigut, L. (Ladislav), Silberstein, R. (Richard), Sirca, C. (Costantino), Spano, D. (Donatella), Steinbrecher, R. (Rainer), Stevens, R. M. (Robert M.), Sturtevant, C. (Cove), Suyker, A. (Andy), Tagesson, T. (Torbern), Takanashi, S. (Satoru), Tang, Y. (Yanhong), Tapper, N. (Nigel), Thom, J. (Jonathan), Tiedemann, F. (Frank), Tomassucci, M. (Michele), Tuovinen, J.-P. (Juha-Pekka), Urbanski, S. (Shawn), Valentini, R. (Riccardo), van der Molen, M. (Michiel), van Gorsel, E. (Eva), van Huissteden, K. (Ko), Varlagin, A. (Andrej), Verfaillie, J. (Joseph), Vesala, T. (Timo), Vincke, C. (Caroline), Vitale, D. (Domenico), Vygodskaya, N. (Natalia), Walker, J. P. (Jeffrey P.), Walter-Shea, E. (Elizabeth), Wang, H. (Huimin), Weber, R. (Robin), Westermann, S. (Sebastian), Wille, C. (Christian), Wofsy, S. (Steven), Wohlfahrt, G. (Georg), Wolf, S. (Sebastian), Woodgate, W. (William), Li, Y. (Yuelin), Zampedri, R. (Roberto), Zhang, J. (Junhui), Zhou, G. (Guoyi), Zona, D. (Donatella), Agarwal, D. (Deb), Biraud, S. (Sebastien), Torn, M. (Margaret), and Papale, D. (Dario)

Abstract

The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.

Published
2020

25. Multiple Ecosystem Effects of Extreme Weather Events in the Arctic

Author

Christensen, T. R., primary, Lund, M., additional, Skov, K., additional, Abermann, J., additional, López-Blanco, E., additional, Scheller, J., additional, Scheel, M., additional, Jackowicz-Korczynski, M., additional, Langley, K., additional, Murphy, M. J., additional, and Mastepanov, M., additional

Published
2020
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26. Modelling CH4 emissions from arctic wetlands: effects of hydrological parameterization

Author

Petrescu, A. M. R., Huissteden, J., Jackowicz-Korczynski, M., Yurova, A., Christensen, T. R., Patrick Crill, Bäckstrand, K., Maximov, T. C., and Hydrology and Geo-environmental sciences

Subjects
SDG 13 - Climate Action
Abstract

This study compares the CH4 fluxes from two arctic wetland sites of different annual temperatures during 2004 to 2006. The PEATLAND-VU model was used to simulate the emissions. The CH4 module of PEATLAND-VU is based on the Walter-Heimann model. The first site is located in northeast Siberia, Indigirka lowlands, Kytalyk reserve (70° N, 147° E) in a continuous permafrost region with mean annual temperatures of −14.3°C. The other site is Stordalen mire in the eastern part of Lake Torneträsk (68° N, 19° E) ten kilometres east of Abisko, northern Sweden. It is located in a discontinuous permafrost region. Stordalen has a sub arctic climate with a mean annual temperature of −0.7°C. Model input consisted of observed temperature, precipitation and snow cover data. In all cases, modelled CH4 emissions show a direct correlation between variations in water table and soil temperature variations. The differences in CH4 emissions between the two sites are caused by different climate, hydrology, soil physical properties, vegetation type and NPP. For Kytalyk the simulated CH4 fluxes show similar trends during the growing season, having average values for 2004 to 2006 between 1.29–2.09 mg CH4 m−2 hr−1. At Stordalen the simulated fluxes show a slightly lower average value for the same years (3.52 mg CH4 m−2 hr−1) than the observed 4.7 mg CH4 m−2 hr−1. The effect of the longer growing season at Stordalen is simulated correctly. Our study shows that modelling of arctic CH4 fluxes is improved by adding a relatively simple hydrological model that simulates the water table position from generic weather data. Our results support the generalization in literature that CH4 fluxes in northern wetland are regulated more tightly by water table than temperature. Furthermore, parameter uncertainty at site level in wetland CH4 process models is an important factor in large scale modelling of CH4 fluxes.

Published
2018
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27. Spatial variability of CO2 uptake in polygonal tundra: assessing low-frequency disturbances in eddy covariance flux estimates

Author

Pirk, N., Sievers, J., Mertes, J., Parmentier, F.-J. W., Mastepanov, M., and Christensen, T. R.

Subjects
lcsh:Geology, lcsh:QH501-531, lcsh:QH540-549.5, lcsh:QE1-996.5, lcsh:Life, lcsh:Ecology
Abstract

The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV) that mapped ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency) flux contributions were especially pronounced during snowmelt and introduced a large bias of −46 gC m−2 to the annual CO2 budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem). Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO2 in 2015 (−82 gC m−2). Due to differences in light-use efficiency, wetter areas with low-centered polygons sequestered 47 % more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2 K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink in polygonal tundra.

Published
2017

28. Biomass offsets little or none of permafrost carbon release from soils, streams, and wild␣re: an expert assessment

Author

Abbott, B. W., Jones, J. B., Schuur, E. A. G., Chapin, F. S., Bowden, W. B., Bret-Harte, M. S., Epstein, H. E., Flannigan, M. D., Harms, T. K., Hollingsworth, T. N., Mack, M. C., Mcguire, A. D., Natali, S. M., Rocha, A. V., Tank, S. E., Turetsky, M. R., Vonk, J. E., Wickland, K. P., Aiken, G. R., Alexander, H. D., Amon, R. M. W., Benscoter, B. W., Bergeron, Y., Bishop, K., Blarquez, O., Bond-Lamberty, B., Breen, A. L., Buffam, I., Cai, Y. H., Christopher Carcaillet, Carey, S. K., Chen, J. M., Chen, H. Y. H., Christensen, T. R., Cooper, L. W., Cornelissen, J. H. C., Groot, W. J., Deluca, T. H., Dorrepaal, E., Fetcher, N., Finlay, J. C., Forbes, B. C., French, N. H. F., Gauthier, S., Girardin, M. P., Goetz, S. J., Goldammer, J. G., Gough, L., Grogan, P., Guo, L. D., Higuera, P. E., Hinzman, L., Hu, F. S., Hugelius, G., Jafarov, E. E., Jandt, R., Johnstone, J. F., Karlsson, J., Kasischke, E. S., Kattner, G., Kelly, R., Keuper, F., Kling, G. W., Kortelainen, P., Kouki, J., Kuhry, P., Laudon, H., Laurion, I., Macdonald, R. W., Mann, P. J., Martikainen, P. J., Mcclelland, J. W., Molau, U., Oberbauer, S. F., Olefeldt, D., Pare, D., Parisien, M. A., Payette, S., Peng, C. H., Pokrovsky, O. S., Rastetter, E. B., Raymond, P. A., Raynolds, M. K., Rein, G., Reynolds, J. F., Robards, M., Rogers, B. M., Schadel, C., Schaefer, K., Schmidt, I. K., Shvidenko, A., Sky, J., Spencer, R. G. M., Starr, G., Striegl, R. G., Teisserenc, R., Tranvik, L. J., Virtanen, T., Welker, J. M., Zimov, S., Institute of Arctic Biology and Department of Biology & Wildlife, University of Alaska [Fairbanks] (UAF), Ecosystèmes, biodiversité, évolution [Rennes] (ECOBIO), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (LEHNA), Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE), McMaster University [Hamilton, Ontario], 955713, National Science Foundation, OPP-0806394, Office of Polar Programs, Future Forest (Mistra), SITES (Swedish Science Foundation), TOMCAR-Permafrost #277059, Marie Curie International Reintegration, Institute of Arctic Biology, Université de Rennes (UR)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Earth and Climate, Systems Ecology, Amsterdam Global Change Institute, Environmental Sciences, Tarmo Virtanen / Principal Investigator, and Environmental Change Research Unit (ECRU)

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, Biomass, F800, SEQUESTRATION, Permafrost, 01 natural sciences, FIRE, wildfire, Klimatforskning, Arctic, вечная мерзлота, Dissolved organic carbon, ECOSYSTEMS, SDG 13 - Climate Action, boreal, General Environmental Science, Total organic carbon, ARCTIC TUNDRA, CLIMATE-CHANGE, Carbon, Climate change, Miljövetenskap, Permafrost carbon cycle, Earth and Related Environmental Sciences, STORAGE, углеродный баланс, particulate organic carbon, Climate Research, permafrost carbon, Soil science, 010603 evolutionary biology, BOREAL FOREST, биомасса, Ecosystem, SDG 14 - Life Below Water, 1172 Environmental sciences, 0105 earth and related environmental sciences, INTERIOR ALASKA, coastal erosion, Hydrology, VULNERABILITY, NITROGEN DEPOSITION, Renewable Energy, Sustainability and the Environment, coastal erosion Supplementary material for this article is available, Public Health, Environmental and Occupational Health, Geovetenskap och miljövetenskap, 15. Life on land, dissolved organic carbon, Tundra, 13. Climate action, Soil water, Environmental science, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Environmental Sciences
Abstract

CT3 ; EnjS4; International audience; As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wild␣re, and hydrologic carbon ␣ux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identi␣ed water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous ␣ndings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%–85% of permafrost carbon release can still be avoided if human emissions are actively reduced.

Published
2016
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29. Modelling CH4 emissions from arctic wetlands: effects of hydrological parameterization

Author

Petrescu, A. M. R., van Huissteden, J., Jackowicz-Korczynski, M., Yurova, A., Christensen, T. R., Crill, P. M., Bäckstrand, K., Maximov, T. C., Department of Hydrology and Geo-Environmental Sciences [Amsterdam], Vrije Universiteit Amsterdam [Amsterdam] (VU), Lund Univ., Department of Physical Geography and Ecosystems Analysis, Stockholm Univ., Department of Geology and Geochemistry, the Russian Academy of Sciences [Moscow, Russia] (RAS), and EGU, Publication

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:QE1-996.5, lcsh:Life, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], lcsh:Geology, lcsh:QH501-531, [PHYS.ASTR.CO] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], lcsh:QH540-549.5, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, lcsh:Ecology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

This study compares the CH4 fluxes from two arctic wetland sites of different annual temperatures during 2004 to 2006. The PEATLAND-VU model was used to simulate the emissions. The CH4 module of PEATLAND-VU is based on the Walter-Heimann model. The first site is located in northeast Siberia, Indigirka lowlands, Kytalyk reserve (70° N, 147° E) in a continuous permafrost region with mean annual temperatures of −14.3°C. The other site is Stordalen mire in the eastern part of Lake Torneträsk (68° N, 19° E) ten kilometres east of Abisko, northern Sweden. It is located in a discontinuous permafrost region. Stordalen has a sub arctic climate with a mean annual temperature of −0.7°C. Model input consisted of observed temperature, precipitation and snow cover data. In all cases, modelled CH4 emissions show a direct correlation between variations in water table and soil temperature variations. The differences in CH4 emissions between the two sites are caused by different climate, hydrology, soil physical properties, vegetation type and NPP. For Kytalyk the simulated CH4 fluxes show similar trends during the growing season, having average values for 2004 to 2006 between 1.29–2.09 mg CH4 m−2 hr−1. At Stordalen the simulated fluxes show a slightly lower average value for the same years (3.52 mg CH4 m−2 hr−1) than the observed 4.7 mg CH4 m−2 hr−1. The effect of the longer growing season at Stordalen is simulated correctly. Our study shows that modelling of arctic CH4 fluxes is improved by adding a relatively simple hydrological model that simulates the water table position from generic weather data. Our results support the generalization in literature that CH4 fluxes in northern wetland are regulated more tightly by water table than temperature. Furthermore, parameter uncertainty at site level in wetland CH4 process models is an important factor in large scale modelling of CH4 fluxes.

Published
2008

38. Assessing the spatial variability in peak season CO2 exchange characteristics across the Arctic tundra using a light response curve parameterization

Author

Mbufong, H. N., Lund, M., Aurela, M., Christensen, T. R., Eugster, W., Friborg, T., Hansen, B. U., Humphreys, E. R., Jackowicz-Korczynski, M., Kutzbach, L., Lafleur, P. M., Oechel, W. C., Parmentier, F. J. W., Rasse, D. P., Rocha, A. V., Sachs, T., van der Molen, M. K., Tamstorf, M. P., Mbufong, H. N., Lund, M., Aurela, M., Christensen, T. R., Eugster, W., Friborg, T., Hansen, B. U., Humphreys, E. R., Jackowicz-Korczynski, M., Kutzbach, L., Lafleur, P. M., Oechel, W. C., Parmentier, F. J. W., Rasse, D. P., Rocha, A. V., Sachs, T., van der Molen, M. K., and Tamstorf, M. P.

Published
2014

41. Assessing the spatial variability in peak season CO&lt;sub&gt;2&lt;/sub&gt; exchange characteristics across the Arctic tundra using a light response curve parameterization

Author

Mbufong, H. N., primary, Lund, M., additional, Aurela, M., additional, Christensen, T. R., additional, Eugster, W., additional, Friborg, T., additional, Hansen, B. U., additional, Humphreys, E. R., additional, Jackowicz-Korczynski, M., additional, Kutzbach, L., additional, Lafleur, P. M., additional, Oechel, W. C., additional, Parmentier, F. J. W., additional, Rasse, D. P., additional, Rocha, A. V., additional, Sachs, T., additional, van der Molen, M. K., additional, and Tamstorf, M. P., additional

Published
2014
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43. Ecosystem change and stability over multiple decades in the Swedish subarctic:complex processes and multiple drivers

Author

Callaghan, T. V., Jonasson, Charlotte, Thierfelder, T., Yang, Z., Hedenas, H., Johansson, Margareta, Molau, U., Bogaert, R. Van, Michelsen, A., Olofsson, J., Bokhorst, S., Phoenix, G., Bjerke, J. W., Tommervik, H., Christensen, T. R., Hanna, E., Koller, E. K., Sloan, V. L., Callaghan, T. V., Jonasson, Charlotte, Thierfelder, T., Yang, Z., Hedenas, H., Johansson, Margareta, Molau, U., Bogaert, R. Van, Michelsen, A., Olofsson, J., Bokhorst, S., Phoenix, G., Bjerke, J. W., Tommervik, H., Christensen, T. R., Hanna, E., Koller, E. K., and Sloan, V. L.

Published
2013

44. The Arctic

Author

Petersen, H., Meltofte, H., Rysgaard, S., Rasch, M., Jonasson, S., Christensen, T. R., Friborg, T., Søgaard, H., Pedersen, S. A., Jørgensen, A. M. K., Fenger, J., and Halsnæs, K.

Published
2001

45. Annual carbon gas budget for a subarctic peatland, northern Sweden

Author

Bäckstrand, Kristina, Crill, P. M., Jackowicz-Korczyñski, M., Mastepanov, M., Christensen, T. R., Bastviken, David, Bäckstrand, Kristina, Crill, P. M., Jackowicz-Korczyñski, M., Mastepanov, M., Christensen, T. R., and Bastviken, David

Abstract

Temperatures in the Arctic regions are rising, thawing permafrost and exposing previously stable soil organic carbon (OC) to decomposition. This can result in northern latitude soils, which have accumulated large amounts of OC potentially shifting from atmospheric C sinks to C sources with positive feedback on climate warming. In this paper, we estimate the annual net C gas balance (NCB) of the subarctic mire Stordalen, based on automatic chamber measurements of CO2 and total hydrocarbon (THC; CH4 and NMVOCs) exchange. We studied the dominant vegetation communities with different moisture and permafrost characteristics; a dry Palsa underlain by permafrost, an intermediate thaw site with Sphagnum spp. and a wet site with Eriophorum spp. where the soil thaws completely. Whole year accumulated fluxes of CO2 were estimated to 29.7, −35.3 and −34.9 gC m−2 respectively for the Palsa, Sphagnum and Eriophorum sites (positive flux indicates an addition of C to the atmospheric pool). The corresponding annual THC emissions were 0.5, 6.2 and 31.8 gC m−2 for the same sites. Therefore, the NCB for each of the sites was 30.2, −29.1 and −3.1 gC m−2 respectively for the Palsa, Sphagnum and Eriophorum site. On average, the whole mire was a CO2 sink of 2.6 gC m−2 and a THC source of 6.4 gC m−2 over a year. Consequently, the mire was a net source of C to the atmosphere by 3.9 gC m−2 (based on area weighted estimates for each of the three plant communities). Early and late snow season efflux of CO2 and THC emphasize the importance of winter measurements for complete annual C budgets. Decadal vegetation changes at Stordalen indicate that both the productivity and the THC emissions increased between 1970 and 2000. Considering the GWP100 of CH4, the net radiative forcing on climate increased 21% over the same time. In conclusion, reduced C compounds in these environments have high importance for both the annual C balance and climate.

Published
2010
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46. Ecosystem responses to increased precipitation and permafrost decay in subarctic Sweden inferred from peat and lake sediments

Author

Kokfelt, U., Rosén, P., Schoning, K., Christensen, T. R., Förster, J., Karlsson, J., Reuss, N., Rundgren, M., Callaghan, T. V., Jonasson, C., Hammarlund, D., Kokfelt, U., Rosén, P., Schoning, K., Christensen, T. R., Förster, J., Karlsson, J., Reuss, N., Rundgren, M., Callaghan, T. V., Jonasson, C., and Hammarlund, D.

Abstract

Recent accelerated decay of discontinuous permafrost at the Stordalen Mire in northern Sweden has been attributed to increased temperature and snow depth, and has caused expansion of wet minerotrophic areas leading to significant changes in carbon cycling in the mire. In order to track these changes through time and evaluate potential forcing mechanisms, this paper analyses a peat succession and a lake sediment sequence from within the mire, providing a record for the last 100 years, and compares these with monitored climate and active layer thickness data. The peat core was analysed for testate amoebae to reconstruct changes in peatland surface moisture conditions and water table fluctuations. The lake sediment core was analysed by near infrared spectroscopy to infer changes in the total organic carbon (TOC) concentration of the lake-water, and changes in delta C-13 and C, N and delta N-15 to track changes in the dissolved inorganic carbon (DIC) pool and the influence of diagenetic effects on sediment organic matter, respectively. Results showed that major shifts towards increased peat surface moisture and TOC concentration of the lake-water occurred around 1980, one to two decades earlier than a temperature driven increase in active layer thickness. Comparison with monitored temperature and precipitation from a nearby climate station indicates that this change in peat surface moisture is related to June-September (JJAS) precipitation and that the increase in lake-water TOC concentration reflects an increase in total annual precipitation. A significant depletion in C-13 of sediment organic matter in the early 1980s probably reflects the effect of a single or a few consecutive years with anomalously high summer precipitation, resulting in elevated DIC content of the lake water, predominantly originating from increased export and subsequent respiration of organic carbon from the mire. Based on these results, it was not possible to link proxy data obtained on peat and

Published
2009
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47. Annual cycles of methane emission from a subarctic peatland

Author

Jackowicz-Korczyňski, M., Christensen, T. R., Bäckstrand, K., Crill, P. M., Friborg, T., Mastepanov, M., Ström, L., Jackowicz-Korczyňski, M., Christensen, T. R., Bäckstrand, K., Crill, P. M., Friborg, T., Mastepanov, M., and Ström, L.

Abstract

Although much attention in recent years has been devoted to methane (CH4) emissions from northern wetlands, measurement based datasets providing full annual budgets are still limited in number. This study was designed to help fill the gap of year-round measurements of CH4 emissions from subarctic mires. We report continuous eddy correlation CH 4 flux measurements made during 2006 and 2007 over the Stordalen mire in subarctic Sweden (68°20'N, 19°03'E, alt. 351 m) using a cryocooled tunable diode laser (TDL). The landscape scale CH4 fluxes originated mainly from the permafrost free wet parts of the mire dominated by tall graminoid vegetation. The midseason average CH4 emission mean was 6.2±2.6 mg m-2 h-1. A detailed footprint analysis indicates an additional strong influence on the flux by the nearby the shallow Lake Villasjön (0.17 km2, max depth 1.3 m). A stable bimodal distribution of wind flow from either the easier or the west allowed separating the lake and mire vegetation signals. The midseason lake emission rates were as high as 12.3±3.3 mg m-2 h-1. Fluxes from a homogeneous area dominated by Eriophorum augustifolium agree well with automatic chamber measurements located in similar vegetation in the wet minerotrophic parts of the peatland. The high fluxes observed from this vegetation type are significant because the areal distribution of this source in the mire is expanding due to ongoing thawing of the permafrost. A simple peat temperature relationship with CH4 emissions was used to fill data gaps to construct a complete annual budget of CH4 fluxes over the studied area. The calculated annual CH4 emissions in 2006 and 2007 equaled 24.5 and 29.5 g CH4 m-2 y-1 respectively. These are considerably higher annual sums than what has earlier been estimated for this mire based on manual cha

Published
2009

48. Palsa mires- CO2 exchange from Stordalen mire

Author

Friborg, Thomas, Johansson, Paul Torbjörn, Jackowicz-Korcynski, M., Christensen, T. R., Crill, P. M., Friborg, Thomas, Johansson, Paul Torbjörn, Jackowicz-Korcynski, M., Christensen, T. R., and Crill, P. M.

Published
2008

50. Introduction

Author

Meltofte, H., Christensen, T. R., Elberling, Bo, Forchhammer, M. C., Rasch, M., Meltofte, H., Christensen, T. R., Elberling, Bo, Forchhammer, M. C., and Rasch, M.

Published
2008

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