| 1. |
- Björkman, Mats P., 1978, et al.
(author)
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A comparison of annual and seasonal carbon dioxide effluxes between sub-Arctic Sweden and High-Arctic Svalbard
- 2010
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In: Polar Research. - : Norwegian Polar Institute. - 1751-8369. ; 29:1, s. 75-84
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Journal article (peer-reviewed)abstract
- Recent climate change predictions suggest altered patterns of winter precipitation across the Arctic. It has been suggested that the presence, timing and amount of snow all affect microbial activity, thus influencing CO2 production in soil. In this study annual and seasonal emissions of CO2 were estimated in High-Arctic Adventdalen, Svalbard, and sub-Arctic Latnjajaure, Sweden, using a new trace gas-based method to track real time diffusion rates through the snow. Summer measurements from snow-free soils were made using a chamber-based method. Measurements were obtained at different snow regimes in order to evaluate the effect of snow depth on winter CO2 effluxes. Total annual emissions of CO2 from the sub-Arctic site (0.662–1.487 kg CO2 m-2 yr-1) were found to be more than double the emissions from the High-Arctic site (0.369–0.591 kg CO2 m-2 yr-1). There were no significant differences in winter effluxes between snow regimes or vegetation types, indicating that spatial variability in winter soil CO2 effluxes are not directly linked to snow cover thickness or soil temperatures. Total winter emissions (0.004–0.248 kg CO2 m-2) were found to be in the lower range of those previously described in the literature. Winter emissions varied in their contribution to total annual production between 1 and 18%. Artificial snow drifts shortened the snow-free period by two weeks and decreased annual CO2 emission by up to 20%. This study suggests that future shifts in vegetation zones may increase soil respiration from Arctic tundra regions.
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| 2. |
- Björkman, Mats P., 1978, et al.
(author)
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Winter carbon dioxide effluxes from Arctic ecosystems - A presentation of a novel trace gas method and comparison with previously used methodologies
- 2009
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In: Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract A54D-03..
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Conference paper (peer-reviewed)abstract
- Winter CO2 efflux from subnivean environments is an important component of annual C budgets in arctic ecosystems and consequently makes prediction and estimations of winter processes as well as incorporations of these processes into existing models important. Several methods have been used for estimating winter CO2 production, by using different snow pack assumptions. Here, measurements from three commonly used methods and one novel trace gas method used during the winter 2007-2008 are compared and discussed: (1) measurements with chamber on snow surface, Fsnow, (2) chamber measurements directly on the soil, Fsoil, after snow removal, (3) diffusion measurements, F2-point, within the snow pack, and (4) a novel trace gas technique, FSF6, with multiple gas sampling within the snow pack. According to measurements in shallow and deep snow cover in High-arctic Svalbard and Sub-arctic Sweden total winter emissions from the trace gas technique, 0.004-0.248 kg CO2 m-2, were found to be in the lower range of those previously described in the literature, however, results from all four methods differ by up to two orders of magnitude. Highest mean winter CO2 effluxes were observed using Fsoil, 7.7-216.8 mg CO2 m-2 h-1, and lowest values using FSF6, 0.8-12.6 mg CO2 m-2 h-1. Fsnow and F2-point were both within the lower range, 2.1-15.1 mg CO2 m-2 h-1 and 6.8-11.2 mg CO2 m-2 h-1, respectively. Differences are considered a result of contrasting methods but also that the assumptions within the methods are not equivalent when quantifying CO2 production and effluxes to the atmosphere. As snow can act as a barrier for CO2, Fsoil is assumed to measure soil production whereas FSF6, Fsnow and F2-point are considered better approaches for quantifying exchange processes between the soil, snow, and the atmosphere. This study indicates that estimation of winter CO2 emissions might vary more due to the method used than due to the actual variation in soil CO2 production or release. This is of major concern, especially when CO2 efflux data is used in climate models or in carbon budget calculations and highlights the need for further development and validation of techniques.
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| 3. |
- Björkman, Mats P., 1978, et al.
(author)
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Winter carbon dioxide effluxes from Arctic ecosystems: An overview and comparison of methodologies
- 2010
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In: Global Biogeochemical Cycles. ; 24, s. GB3010-
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Journal article (peer-reviewed)abstract
- The winter CO2 efflux from subnivean environments is an important component of annual C budgets in arctic ecosystems and consequently makes prediction and estimations of winter processes as well as incorporations of these processes into existing models important. Several methods have been used for estimating winter CO2 effluxes, involving different assumptions about the snow pack, all aiming to quantify CO2 production. Here, four different methods are compared and discussed: (1) measurements with a chamber on the snow surface, Fsnow; (2) chamber measurements directly on the soil, Fsoil, after snow removal; (3) diffusion measurements, F2-point, within the snow pack; and (4) a trace gas technique, FSF6, with multiple gas sampling within the snow pack. According to measurements collected from shallow and deep snow cover in High-Arctic Svalbard and Sub-Arctic Sweden during the winter of 2007-2008, the four methods differ by up to two orders of magnitude in their estimates of total winter emissions. The highest mean winter CO2 effluxes, 7.7-216.8 mg CO2 m-2 h-1, were observed using Fsoil and lowest values, 0.8-12.6 mg CO2 m-2 h-1, using FSF6. The Fsnow and F2-point methods were both within the lower range, 2.1-15.1 mg CO2 m-2 h-1 and 6.8-11.2 mg CO2 m-2 h-1, respectively. These differences are considered to be a result of contrasting methods, but also because the assumptions within the methods are not the same when quantifying CO2 production and effluxes to the atmosphere. Since snow can act as a barrier to CO2, Fsoil is assumed to measure soil production, whereas FSF6, Fsnow and F2-point are considered better approaches for quantifying exchange processes between the soil, snow, and the atmosphere. This study indicates that estimates of winter CO2 emissions may vary more as a result of the method used than due to the actual variation in soil CO2 production or release. This is a major concern, especially when CO2 efflux data are used in climate models or in carbon budget calculations, thus highlighting the need for further development and validation of accurate and appropriate techniques.
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| 4. |
- Björkman, Mats P., 1978, et al.
(author)
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Winter fluxes of carbon dioxide – a comparison of current methodology
- 2008
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In: The 15th ITEX workshop, Reykjavik, Iceland, 9–12 October 2008..
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Conference paper (other academic/artistic)abstract
- During winter as much as 47 % of the land mass of the northern hemisphere may experience the insulating effect of a snow-cover, during which vast areas have a longer snow-covered period than growing season. The snow cover allows soil microbial activities to continue during winter with a production of CO2 as a result. Estimations of winter fluxes are difficult since snow is a highly complex media, with large uncertainties as a result. Using a newly developed trace gas diffusion technique this project aims to improve winter flux estimations and to minimise the uncertainties given by the snow-cover itself. Current methodology for winter CO2 emissions will be presented and evaluated together with a discussion on measurement standardization.
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