The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform

Chrisanthi Avgerou - One of the best experts on this subject based on the ideXlab platform.

Walter C Oechel - One of the best experts on this subject based on the ideXlab platform.

  • An assessment of the carbon balance of Arctic tundra
    2016
    Co-Authors: A D Mcguire, Torben R Christensen, Daniel J Hayes, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, Peter M Lafleur, Paul A Miller, Walter C Oechel
    Abstract:

    Although Arctic tundra has been estimated to cover only 8 % of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990 and 2006 among observations, Regional and global applications of Process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of flux observations and inversion models indicate that the annual exchange of CO2 between Arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations suggests that Arctic tundra has acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 C warmer in the 2000s compared to the 1990s. The central estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Some of the Process models indicate that this occurred because net primary production increased more in response to warming than heterotrophic respiration. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from Arctic tundra have increased from the 1990s to 2000s because of the sensitivity of CH4 emissions to warmer temperatures. Based on our analyses of the estimates from observations, Process-based models, and inversion models, we estimate that Arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr−1 (uncertainty between a sink of 291 Tg C yr−1 and a source of 80 Tg C yr−1) and a source of CH4 to the atmosphere of 19 Tg C yr−1 (uncertainty between sources of 8 and 29 Tg C yr−1). The suite of analyses conducted in this study indicate that it is important to reduce uncertainties in Published by Copernicus Publications on behalf of the European Geosciences Union. 3186 A. D. McGuire et al.: Assessment of the carbon balance of Arctic tundra the observations, Process-based models, and inversions in order to better understand the degree to which Arctic tundra is influencing atmospheric CO2 and CH4 concentrations. The reduction of uncertainties can be accomplished through (1) the strategic placement of more CO2 and CH4 monitoring stations to reduce uncertainties in inversions, (2) improved observation networks of ground-based measurements of CO2 and CH4 exchange to understand exchange in response to disturbance and across gradients of climatic and hydrological variability, and (3) the effective transfer of information from enhanced observation networks into Process-based models to improve the simulation of CO2 and CH4 exchange from Arctic tundra to the atmosphere.

  • an assessment of the carbon balance of arctic tundra comparisons among observations Process models and atmospheric inversions
    Biogeosciences, 2012
    Co-Authors: A D Mcguire, Torben R Christensen, Daniel J Hayes, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, Peter M Lafleur, Paul A Miller, Walter C Oechel
    Abstract:

    Although Arctic tundra has been estimated to cover only 8 % of the global land surface, the large and po- tentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C ex- change in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990 and 2006 among observa- tions, Regional and global applications of Process-based ter- restrial biosphere models, and atmospheric inversion mod- els. Syntheses of flux observations and inversion models in- dicate that the annual exchange of CO2 between Arctic tun- dra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations sug- gests that Arctic tundra has acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty esti- mates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 C warmer in the 2000s compared to the 1990s. The cen- tral estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Some of the Process models in- dicate that this occurred because net primary production in- creased more in response to warming than heterotrophic res- piration. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from Arctic tundra have increased from the 1990s to 2000s because of the sensitivity of CH4 emissions to warmer tem- peratures. Based on our analyses of the estimates from ob- servations, Process-based models, and inversion models, we estimate that Arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr 1 (uncertainty between a sink of 291 Tg C yr 1 and a source of 80 Tg C yr 1 ) and a source of CH4 to the atmosphere of 19 Tg C yr 1 (uncertainty between sources of 8 and 29 Tg C yr 1 ). The suite of analyses conducted in this study indicate that it is important to reduce uncertainties in

  • An assessment of the carbon balance of Arctic tundra: comparisons among observations, Process models, and atmospheric inversions
    Biogeosciences, 2012
    Co-Authors: A D Mcguire, Torben R Christensen, Daniel J Hayes, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, Peter M Lafleur, Paul A Miller, Walter C Oechel
    Abstract:

    Abstract. Although Arctic tundra has been estimated to cover only 8% of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990 and 2006 among observations, Regional and global applications of Process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of flux observations and inversion models indicate that the annual exchange of CO2 between Arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations suggests that Arctic tundra has acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 °C warmer in the 2000s compared to the 1990s. The central estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Some of the Process models indicate that this occurred because net primary production increased more in response to warming than heterotrophic respiration. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from Arctic tundra have increased from the 1990s to 2000s because of the sensitivity of CH4 emissions to warmer temperatures. Based on our analyses of the estimates from observations, Process-based models, and inversion models, we estimate that Arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr−1 (uncertainty between a sink of 291 Tg C yr−1 and a source of 80 Tg C yr−1) and a source of CH4 to the atmosphere of 19 Tg C yr−1 (uncertainty between sources of 8 and 29 Tg C yr−1). The suite of analyses conducted in this study indicate that it is important to reduce uncertainties in the observations, Process-based models, and inversions in order to better understand the degree to which Arctic tundra is influencing atmospheric CO2 and CH4 concentrations. The reduction of uncertainties can be accomplished through (1) the strategic placement of more CO2 and CH4 monitoring stations to reduce uncertainties in inversions, (2) improved observation networks of ground-based measurements of CO2 and CH4 exchange to understand exchange in response to disturbance and across gradients of climatic and hydrological variability, and (3) the effective transfer of information from enhanced observation networks into Process-based models to improve the simulation of CO2 and CH4 exchange from Arctic tundra to the atmosphere.

A D Mcguire - One of the best experts on this subject based on the ideXlab platform.

  • An assessment of the carbon balance of Arctic tundra
    2016
    Co-Authors: A D Mcguire, Torben R Christensen, Daniel J Hayes, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, Peter M Lafleur, Paul A Miller, Walter C Oechel
    Abstract:

    Although Arctic tundra has been estimated to cover only 8 % of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990 and 2006 among observations, Regional and global applications of Process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of flux observations and inversion models indicate that the annual exchange of CO2 between Arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations suggests that Arctic tundra has acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 C warmer in the 2000s compared to the 1990s. The central estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Some of the Process models indicate that this occurred because net primary production increased more in response to warming than heterotrophic respiration. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from Arctic tundra have increased from the 1990s to 2000s because of the sensitivity of CH4 emissions to warmer temperatures. Based on our analyses of the estimates from observations, Process-based models, and inversion models, we estimate that Arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr−1 (uncertainty between a sink of 291 Tg C yr−1 and a source of 80 Tg C yr−1) and a source of CH4 to the atmosphere of 19 Tg C yr−1 (uncertainty between sources of 8 and 29 Tg C yr−1). The suite of analyses conducted in this study indicate that it is important to reduce uncertainties in Published by Copernicus Publications on behalf of the European Geosciences Union. 3186 A. D. McGuire et al.: Assessment of the carbon balance of Arctic tundra the observations, Process-based models, and inversions in order to better understand the degree to which Arctic tundra is influencing atmospheric CO2 and CH4 concentrations. The reduction of uncertainties can be accomplished through (1) the strategic placement of more CO2 and CH4 monitoring stations to reduce uncertainties in inversions, (2) improved observation networks of ground-based measurements of CO2 and CH4 exchange to understand exchange in response to disturbance and across gradients of climatic and hydrological variability, and (3) the effective transfer of information from enhanced observation networks into Process-based models to improve the simulation of CO2 and CH4 exchange from Arctic tundra to the atmosphere.

  • an assessment of the carbon balance of arctic tundra comparisons among observations Process models and atmospheric inversions
    Biogeosciences, 2012
    Co-Authors: A D Mcguire, Torben R Christensen, Daniel J Hayes, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, Peter M Lafleur, Paul A Miller, Walter C Oechel
    Abstract:

    Although Arctic tundra has been estimated to cover only 8 % of the global land surface, the large and po- tentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C ex- change in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990 and 2006 among observa- tions, Regional and global applications of Process-based ter- restrial biosphere models, and atmospheric inversion mod- els. Syntheses of flux observations and inversion models in- dicate that the annual exchange of CO2 between Arctic tun- dra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations sug- gests that Arctic tundra has acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty esti- mates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 C warmer in the 2000s compared to the 1990s. The cen- tral estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Some of the Process models in- dicate that this occurred because net primary production in- creased more in response to warming than heterotrophic res- piration. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from Arctic tundra have increased from the 1990s to 2000s because of the sensitivity of CH4 emissions to warmer tem- peratures. Based on our analyses of the estimates from ob- servations, Process-based models, and inversion models, we estimate that Arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr 1 (uncertainty between a sink of 291 Tg C yr 1 and a source of 80 Tg C yr 1 ) and a source of CH4 to the atmosphere of 19 Tg C yr 1 (uncertainty between sources of 8 and 29 Tg C yr 1 ). The suite of analyses conducted in this study indicate that it is important to reduce uncertainties in

  • An assessment of the carbon balance of Arctic tundra: comparisons among observations, Process models, and atmospheric inversions
    Biogeosciences, 2012
    Co-Authors: A D Mcguire, Torben R Christensen, Daniel J Hayes, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, Peter M Lafleur, Paul A Miller, Walter C Oechel
    Abstract:

    Abstract. Although Arctic tundra has been estimated to cover only 8% of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990 and 2006 among observations, Regional and global applications of Process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of flux observations and inversion models indicate that the annual exchange of CO2 between Arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations suggests that Arctic tundra has acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 °C warmer in the 2000s compared to the 1990s. The central estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Some of the Process models indicate that this occurred because net primary production increased more in response to warming than heterotrophic respiration. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from Arctic tundra have increased from the 1990s to 2000s because of the sensitivity of CH4 emissions to warmer temperatures. Based on our analyses of the estimates from observations, Process-based models, and inversion models, we estimate that Arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr−1 (uncertainty between a sink of 291 Tg C yr−1 and a source of 80 Tg C yr−1) and a source of CH4 to the atmosphere of 19 Tg C yr−1 (uncertainty between sources of 8 and 29 Tg C yr−1). The suite of analyses conducted in this study indicate that it is important to reduce uncertainties in the observations, Process-based models, and inversions in order to better understand the degree to which Arctic tundra is influencing atmospheric CO2 and CH4 concentrations. The reduction of uncertainties can be accomplished through (1) the strategic placement of more CO2 and CH4 monitoring stations to reduce uncertainties in inversions, (2) improved observation networks of ground-based measurements of CO2 and CH4 exchange to understand exchange in response to disturbance and across gradients of climatic and hydrological variability, and (3) the effective transfer of information from enhanced observation networks into Process-based models to improve the simulation of CO2 and CH4 exchange from Arctic tundra to the atmosphere.

  • An assessment of the carbon balance of arctic tundra: comparisons among observations, Process models, and atmospheric inversions
    Biogeosciences Discussions, 2012
    Co-Authors: A D Mcguire, Torben R Christensen, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, D. Hayes, P. Lafleur, Paul A Miller
    Abstract:

    Abstract. Although arctic tundra has been estimated to cover only 8% of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990–1999 and 2000–2006 among observations, Regional and global applications of Process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of the compilation of flux observations and of inversion model results indicate that the annual exchange of CO2 between arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations suggests that arctic tundra acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 °C warmer in the 2000s compared to the 1990s. The central estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from arctic tundra have increased from the 1990s to 2000s. Based on our analyses of the estimates from observations, Process-based models, and inversion models, we estimate that arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr−1 (uncertainty between a sink of 291 Tg C yr−1 and a source of 80 Tg C yr−1) and a source of CH4 to the atmosphere of 19 Tg C yr−1 (uncertainty between sources of 8 and 29 Tg C yr−1). The suite of analyses conducted in this study indicate that it is clearly important to reduce uncertainties in the observations, Process-based models, and inversions in order to better understand the degree to which Arctic tundra is influencing atmospheric CO2 and CH4 concentrations. The reduction of uncertainties can be accomplished through (1) the strategic placement of more CO2 and CH4 monitoring stations to reduce uncertainties in inversions, (2) improved observation networks of ground-based measurements of CO2 and CH4 exchange to understand exchange in response to disturbance and across gradients of hydrological variability, and (3) the effective transfer of information from enhanced observation networks into Process-based models to improve the simulation of CO2 and CH4 exchange from arctic tundra to the atmosphere.

Paul A Miller - One of the best experts on this subject based on the ideXlab platform.

  • An assessment of the carbon balance of Arctic tundra
    2016
    Co-Authors: A D Mcguire, Torben R Christensen, Daniel J Hayes, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, Peter M Lafleur, Paul A Miller, Walter C Oechel
    Abstract:

    Although Arctic tundra has been estimated to cover only 8 % of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990 and 2006 among observations, Regional and global applications of Process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of flux observations and inversion models indicate that the annual exchange of CO2 between Arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations suggests that Arctic tundra has acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 C warmer in the 2000s compared to the 1990s. The central estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Some of the Process models indicate that this occurred because net primary production increased more in response to warming than heterotrophic respiration. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from Arctic tundra have increased from the 1990s to 2000s because of the sensitivity of CH4 emissions to warmer temperatures. Based on our analyses of the estimates from observations, Process-based models, and inversion models, we estimate that Arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr−1 (uncertainty between a sink of 291 Tg C yr−1 and a source of 80 Tg C yr−1) and a source of CH4 to the atmosphere of 19 Tg C yr−1 (uncertainty between sources of 8 and 29 Tg C yr−1). The suite of analyses conducted in this study indicate that it is important to reduce uncertainties in Published by Copernicus Publications on behalf of the European Geosciences Union. 3186 A. D. McGuire et al.: Assessment of the carbon balance of Arctic tundra the observations, Process-based models, and inversions in order to better understand the degree to which Arctic tundra is influencing atmospheric CO2 and CH4 concentrations. The reduction of uncertainties can be accomplished through (1) the strategic placement of more CO2 and CH4 monitoring stations to reduce uncertainties in inversions, (2) improved observation networks of ground-based measurements of CO2 and CH4 exchange to understand exchange in response to disturbance and across gradients of climatic and hydrological variability, and (3) the effective transfer of information from enhanced observation networks into Process-based models to improve the simulation of CO2 and CH4 exchange from Arctic tundra to the atmosphere.

  • an assessment of the carbon balance of arctic tundra comparisons among observations Process models and atmospheric inversions
    Biogeosciences, 2012
    Co-Authors: A D Mcguire, Torben R Christensen, Daniel J Hayes, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, Peter M Lafleur, Paul A Miller, Walter C Oechel
    Abstract:

    Although Arctic tundra has been estimated to cover only 8 % of the global land surface, the large and po- tentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C ex- change in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990 and 2006 among observa- tions, Regional and global applications of Process-based ter- restrial biosphere models, and atmospheric inversion mod- els. Syntheses of flux observations and inversion models in- dicate that the annual exchange of CO2 between Arctic tun- dra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations sug- gests that Arctic tundra has acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty esti- mates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 C warmer in the 2000s compared to the 1990s. The cen- tral estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Some of the Process models in- dicate that this occurred because net primary production in- creased more in response to warming than heterotrophic res- piration. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from Arctic tundra have increased from the 1990s to 2000s because of the sensitivity of CH4 emissions to warmer tem- peratures. Based on our analyses of the estimates from ob- servations, Process-based models, and inversion models, we estimate that Arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr 1 (uncertainty between a sink of 291 Tg C yr 1 and a source of 80 Tg C yr 1 ) and a source of CH4 to the atmosphere of 19 Tg C yr 1 (uncertainty between sources of 8 and 29 Tg C yr 1 ). The suite of analyses conducted in this study indicate that it is important to reduce uncertainties in

  • An assessment of the carbon balance of Arctic tundra: comparisons among observations, Process models, and atmospheric inversions
    Biogeosciences, 2012
    Co-Authors: A D Mcguire, Torben R Christensen, Daniel J Hayes, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, Peter M Lafleur, Paul A Miller, Walter C Oechel
    Abstract:

    Abstract. Although Arctic tundra has been estimated to cover only 8% of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990 and 2006 among observations, Regional and global applications of Process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of flux observations and inversion models indicate that the annual exchange of CO2 between Arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations suggests that Arctic tundra has acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 °C warmer in the 2000s compared to the 1990s. The central estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Some of the Process models indicate that this occurred because net primary production increased more in response to warming than heterotrophic respiration. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from Arctic tundra have increased from the 1990s to 2000s because of the sensitivity of CH4 emissions to warmer temperatures. Based on our analyses of the estimates from observations, Process-based models, and inversion models, we estimate that Arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr−1 (uncertainty between a sink of 291 Tg C yr−1 and a source of 80 Tg C yr−1) and a source of CH4 to the atmosphere of 19 Tg C yr−1 (uncertainty between sources of 8 and 29 Tg C yr−1). The suite of analyses conducted in this study indicate that it is important to reduce uncertainties in the observations, Process-based models, and inversions in order to better understand the degree to which Arctic tundra is influencing atmospheric CO2 and CH4 concentrations. The reduction of uncertainties can be accomplished through (1) the strategic placement of more CO2 and CH4 monitoring stations to reduce uncertainties in inversions, (2) improved observation networks of ground-based measurements of CO2 and CH4 exchange to understand exchange in response to disturbance and across gradients of climatic and hydrological variability, and (3) the effective transfer of information from enhanced observation networks into Process-based models to improve the simulation of CO2 and CH4 exchange from Arctic tundra to the atmosphere.

  • An assessment of the carbon balance of arctic tundra: comparisons among observations, Process models, and atmospheric inversions
    Biogeosciences Discussions, 2012
    Co-Authors: A D Mcguire, Torben R Christensen, Arnaud Heroult, Eugenie S Euskirchen, John S Kimball, Charles D Koven, D. Hayes, P. Lafleur, Paul A Miller
    Abstract:

    Abstract. Although arctic tundra has been estimated to cover only 8% of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990–1999 and 2000–2006 among observations, Regional and global applications of Process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of the compilation of flux observations and of inversion model results indicate that the annual exchange of CO2 between arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of Process-based model simulations suggests that arctic tundra acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 °C warmer in the 2000s compared to the 1990s. The central estimates of the observations, Process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Similarly, the observations and the applications of Regional Process-based models suggest that CH4 emissions from arctic tundra have increased from the 1990s to 2000s. Based on our analyses of the estimates from observations, Process-based models, and inversion models, we estimate that arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr−1 (uncertainty between a sink of 291 Tg C yr−1 and a source of 80 Tg C yr−1) and a source of CH4 to the atmosphere of 19 Tg C yr−1 (uncertainty between sources of 8 and 29 Tg C yr−1). The suite of analyses conducted in this study indicate that it is clearly important to reduce uncertainties in the observations, Process-based models, and inversions in order to better understand the degree to which Arctic tundra is influencing atmospheric CO2 and CH4 concentrations. The reduction of uncertainties can be accomplished through (1) the strategic placement of more CO2 and CH4 monitoring stations to reduce uncertainties in inversions, (2) improved observation networks of ground-based measurements of CO2 and CH4 exchange to understand exchange in response to disturbance and across gradients of hydrological variability, and (3) the effective transfer of information from enhanced observation networks into Process-based models to improve the simulation of CO2 and CH4 exchange from arctic tundra to the atmosphere.

Guido Waldhoff - One of the best experts on this subject based on the ideXlab platform.

  • RegionalIZATION OF AGRICULTURAL MANAGEMENT BY USING THE MULTI-DATA APPROACH (MDA)
    ISPRS - International Archives of the Photogrammetry Remote Sensing and Spatial Information Sciences, 2012
    Co-Authors: Georg Bareth, Guido Waldhoff
    Abstract:

    Regional Process-based (agro-)ecosystem modelling depends mainly on data availability of land use, weather, soil, and agricultural management. While land use, weather, and soil data are available from official sources or can be captured with monitoring systems, management data are usually derived from official statistics for administrative units. For numerous spatial modeling approaches, these data are not satisfying. Especially for Process-based agro-ecosystem modeling on Regional scales, spatially disaggregated and land use dependent information on agricultural management is a must. Information about date of sowing, dates of fertilization, dates of weeding etc. are required as input parameters by such models. These models consider nitrogen (N)- and carbon (C)-matter fluxes but essential amounts of N-/C-input and N-/C-output are determined by crop management. Therefore, in this contribution a RS- and GIS-based approach for Regional generation of management data is introduced. The approach is based on the Multi-data Approach (MDA) for enhanced land use/land cover mapping. The MDA is a combined RS and GIS approach. The retrieved information from multitemporal and multisensoral remote sensing analysis is integrated into official land use data to enhance both the information level of existing land use data and the quality of the land use classification. The workflow of the MDA to generate enhanced land use and land cover data consists basically of two components: (a) the methods and data of the remote sensing analysis and (b) the methods and data of the GIS analysis. The MDA results in disaggregated land use data which can be used to link crop management information about the major crops and especially crop rotations like date of sowing, fertilization, irrigation, harvest etc. to the derived land use classes. Consequently, depending on the land use, a distinct management is given in a spatial context on Regional scale. In this contribution, three case studies of different regions in Germany will be presented: (i) the dairy farm region "Wurttembergisches Allgau", (ii) the arable land region "Kraichgau", and (iii) the diverse Rur-Watershed in Western Germany. For each of the study regions, a different MDA-based approach for Regionalizing agricultural management is applied and will be discussed.

  • RegionalIZATION OF AGRICULTURAL MANAGEMENT BY USING THE MULTI-DATA APPROACH (MDA)
    ISPRS - International Archives of the Photogrammetry Remote Sensing and Spatial Information Sciences, 2012
    Co-Authors: Georg Bareth, Guido Waldhoff
    Abstract:

    Regional Process-based (agro-)ecosystem modelling depends mainly on data availability of land use, weather, soil, and agricultural management. While land use, weather, and soil data are available from official sources or can be captured with monitoring systems, management data are usually derived from official statistics for administrative units. For numerous spatial modeling approaches, these data are not satisfying. Especially for Process-based agro-ecosystem modeling on Regional scales, spatially disaggregated and land use dependent information on agricultural management is a must. Information about date of sowing, dates of fertilization, dates of weeding etc. are required as input parameters by such models. These models consider nitrogen (N)- and carbon (C)-matter fluxes but essential amounts of N-/C-input and N-/C-output are determined by crop management. Therefore, in this contribution a RS- and GIS-based approach for Regional generation of management data is introduced. The approach is based on the Multi-data Approach (MDA) for enhanced land use/land cover mapping. The MDA is a combined RS and GIS approach. The retrieved information from multitemporal and multisensoral remote sensing analysis is integrated into official land use data to enhance both the information level of existing land use data and the quality of the land use classification. The workflow of the MDA to generate enhanced land use and land cover data consists basically of two components: (a) the methods and data of the remote sensing analysis and (b) the methods and data of the GIS analysis. The MDA results in disaggregated land use data which can be used to link crop management information about the major crops and especially crop rotations like date of sowing, fertilization, irrigation, harvest etc. to the derived land use classes. Consequently, depending on the land use, a distinct management is given in a spatial context on Regional scale. In this contribution, three case studies of different regions in Germany will be presented: (i) the dairy farm region "Wurttembergisches Allgau", (ii) the arable land region "Kraichgau", and (iii) the diverse Rur-Watershed in Western Germany. For each of the study regions, a different MDA-based approach for Regionalizing agricultural management is applied and will be discussed.