Cold season CO<sub>2</sub>emission from Arctic soils

Oechel, Walter C.; Vourlitis, George L.; Hastings, Steven J.

doi:10.1029/96gb03035

Cited by 244 publications

(249 citation statements)

References 18 publications

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“…5b). Highest CO 2 concentrations were present in the soil (up to 5000 µmol mol −1 , data not shown), and these patterns are consistent with an expected source of soils for CO 2 and diffusive and advective mixing of CO 2 produced in snow through the snowpack with the atmosphere Oechel et al, 1997). Analysis of Hg 0 gas / CO 2 ratios showed no statistically significant differences from the top to the bottom of the snowpack, as evidenced from calculated gradients between 0 and 10 cm, 10 and 20 cm, and 20 and 30 cm heights (Fig.…”

Section: Snowpack Diffusivity Of Trace Gasessupporting

confidence: 66%

Mercury in the Arctic tundra snowpack: temporal and spatial concentration patterns and trace gas exchanges

Agnan¹,

Douglas²,

Helmig³

et al. 2018

The Cryosphere

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Abstract. In the Arctic, the snowpack forms the major interface between atmospheric and terrestrial cycling of mercury (Hg), a global pollutant. We investigated Hg dynamics in an interior Arctic tundra snowpack in northern Alaska during two winter seasons. Using a snow tower system to monitor Hg trace gas exchange, we observed consistent concentration declines of gaseous elemental Hg (Hg 0 gas ) from the atmosphere to the snowpack to soils. The snowpack itself was unlikely a direct sink for atmospheric Hg 0 gas . In addition, there was no evidence of photochemical reduction of Hg II to Hg 0 gas in the tundra snowpack, with the exception of short periods during late winter in the uppermost snow layer. The patterns in this interior Arctic snowpack thus differ substantially from observations in Arctic coastal and temperate snowpacks. We consistently measured low concentrations of both total and dissolved Hg in snowpack throughout the two seasons. Chemical tracers showed that Hg was mainly associated with local mineral dust and regional marine sea spray inputs. Mass balance calculations show that the snowpack represents a small reservoir of Hg, resulting in low inputs during snowmelt. Taken together, the results from this study suggest that interior Arctic snowpacks are negligible sources of Hg to the Arctic.

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Section: Snowpack Diffusivity Of Trace Gasessupporting

confidence: 66%

Mercury in the Arctic tundra snowpack: temporal and spatial concentration patterns and trace gas exchanges

Agnan¹,

Douglas²,

Helmig³

et al. 2018

The Cryosphere

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“…This trend is consistent with our minirhizotron observations, but contrasts with the results of a previous study over the same depth interval in acidic tussock tundra (Nadelhoffer et al 2002). There are two key methodological differences between our ingrowth core study and the Nadelhoffer et al demonstrated that nearly all losses of leaf litter mass occur during winter (Hobbie and Chapin 1996) and that winter CO 2 efflux is an important component of the annual C budget (Oechel et al 1997, Fahnestock et al, 1998, 1999, Grogan and Chapin 1999, Jones et al 1999, Welker et al 2000, Schimel et al 2006. It is possible that our ingrowth cores underestimated fine root production, as a result of root litter mass loss over winter.…”

mentioning

confidence: 91%

Climate and species affect fine root production with long-term fertilization in acidic tussock tundra near Toolik Lake, Alaska

et al. 2007

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Long-term fertilization of acidic tussock tundra has led to changes in plant species composition, increases in aboveground production and biomass and substantial losses of soil organic carbon (SOC). Root litter is an important input to SOC pools, though little is known about fine root demography in tussock tundra. In this study, we examined the response of fine root production and live standing fine root biomass to short-and long-term fertilization, as changes in fine root demography may contribute to observed declines in SOC. Live standing fine root biomass increased with long-term fertilization, while fine root production declined, reflecting replacement of the annual fine root system of Eriophorum vaginatum, with the longlived fine roots of Betula nana. Fine root production increased in fertilized plots during an unusually warm growing season, but remained unchanged in control plots, consistent with observations that B. nana shows a positive response to climate warming. Calculations based on a few simple assumptions suggest changes in fine root demography with long-term fertilization and species replacement could account for between 20 and 39% of observed declines in SOC stocks.

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“…The kinetic Q 10 formulation is based on the Arrhenius equation for chemical reaction rates: the higher the temperature, the greater the number of molecules that have energies greater than the minimum activation energy and the faster the rate of microbial decay. Q 10 varies between 1.5 and 3.0 based on incubation studies or analysis of eddy covariance flux data (Oechel et al, 1997;Mast et al, 1998;Hobbie et al, 2000;Mikan et al, 2002). In contrast, Q 10f varies between 164 and 237 based on incubation of frozen soil samples (Mikan et al, 2002).…”

Section: K Schaefer and E Jafarov: A Parameterization Of Respiratiomentioning

confidence: 99%

A parameterization of respiration in frozen soils based on substrate availability

Schaefer

Jafarov

2016

Biogeosciences

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Abstract. Respiration in frozen soils is limited to thawed substrate within the thin water films surrounding soil particles. As temperatures decrease and the films become thinner, the available substrate also decreases, with respiration effectively ceasing at −8 • C. Traditional exponential scaling factors to model this effect do not account for substrate availability and do not work at the century to millennial timescales required to model the fate of the nearly 1100 Gt of carbon in permafrost regions. The exponential scaling factor produces a false, continuous loss of simulated permafrost carbon in the 20th century and biases in estimates of potential emissions as permafrost thaws in the future. Here we describe a new frozen biogeochemistry parameterization that separates the simulated carbon into frozen and thawed pools to represent the effects of substrate availability. We parameterized the liquid water fraction as a function of temperature based on observations and use this to transfer carbon between frozen pools and thawed carbon in the thin water films. The simulated volumetric water content (VWC) as a function of temperature is consistent with observed values and the simulated respiration fluxes as a function of temperature are consistent with results from incubation experiments. The amount of organic matter was the single largest influence on simulated VWC and respiration fluxes. Future versions of the parameterization should account for additional, non-linear effects of substrate diffusion in thin water films on simulated respiration. Controlling respiration in frozen soils based on substrate availability allows us to maintain a realistic permafrost carbon pool by eliminating the continuous loss caused by the original exponential scaling factors. The frozen biogeochemistry parameterization is a useful way to represent the effects of substrate availability on soil respiration in model applications that focus on century to millennial timescales in permafrost regions.

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Cold season CO₂emission from Arctic soils

Cited by 244 publications

References 18 publications

Mercury in the Arctic tundra snowpack: temporal and spatial concentration patterns and trace gas exchanges

Mercury in the Arctic tundra snowpack: temporal and spatial concentration patterns and trace gas exchanges

Climate and species affect fine root production with long-term fertilization in acidic tussock tundra near Toolik Lake, Alaska

A parameterization of respiration in frozen soils based on substrate availability

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Cold season CO2emission from Arctic soils

Cited by 244 publications

References 18 publications

Mercury in the Arctic tundra snowpack: temporal and spatial concentration patterns and trace gas exchanges

Mercury in the Arctic tundra snowpack: temporal and spatial concentration patterns and trace gas exchanges

Climate and species affect fine root production with long-term fertilization in acidic tussock tundra near Toolik Lake, Alaska

A parameterization of respiration in frozen soils based on substrate availability

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Resources

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Cold season CO₂emission from Arctic soils