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Sökning: WFRF:(Harms Tamara K.)

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1.
  • Abbott, Benjamin W., et al. (författare)
  • Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment
  • 2016
  • Ingår i: Environmental Research Letters. - : IOP Publishing: Open Access Journals / IOP Publishing. - 1748-9326 .- 1748-9326. ; 11:3
  • Tidskriftsartikel (refereegranskat)abstract
    • 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, wildfire, and hydrologic carbon flux 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 identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, 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.
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2.
  • Rocher-Ros, Gerard, et al. (författare)
  • Metabolism overrides photo-oxidation in CO2 dynamics of Arctic permafrost streams
  • 2020
  • Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590.
  • Tidskriftsartikel (refereegranskat)abstract
    • Global warming is enhancing the mobilization of organic carbon (C) from Arctic soils into streams, where it can be mineralized to CO2 and released to the atmosphere. Abiotic photo‐oxidation might drive C mineralization, but this process has not been quantitatively integrated with biological processes that also influence CO2 dynamics in aquatic ecosystems. We measured CO2 concentrations and the isotopic composition of dissolved inorganic C (δ13CDIC) at diel resolution in two Arctic streams, and coupled this with whole‐system metabolism estimates to assess the effect of biotic and abiotic processes on stream C dynamics. CO2 concentrations consistently decreased from night to day, a pattern counter to the hypothesis that photo‐oxidation is the dominant source of CO2. Instead, the observed decrease in CO2 during daytime was explained by photosynthetic rates, which were strongly correlated with diurnal changes in δ13CDIC values. However, on days when modeled photosynthetic rates were near zero, there was still a significant diel change in δ13CDIC values, suggesting that metabolic estimates are partly masked by O2 consumption from photo‐oxidation. Our results suggest that 6–12 mmol CO2‐C m−2 d−1 may be generated from photo‐oxidation, a range that corresponds well to previous laboratory measurements. Moreover, ecosystem respiration rates were 10 times greater than published photo‐oxidation rates for these Arctic streams, and accounted for 33–80% of total CO2 evasion. Our results suggest that metabolic activity is the dominant process for CO2 production in Arctic streams. Thus, future aquatic CO2 emissions may depend on how biotic processes respond to the ongoing environmental change.
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3.
  • Rocher-Ros, Gerard, et al. (författare)
  • Metabolism overrides photo-oxidation inCO(2)dynamics of Arctic permafrost streams
  • 2020
  • Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590.
  • Tidskriftsartikel (refereegranskat)abstract
    • Global warming is enhancing the mobilization of organic carbon (C) from Arctic soils into streams, where it can be mineralized to CO(2)and released to the atmosphere. Abiotic photo-oxidation might drive C mineralization, but this process has not been quantitatively integrated with biological processes that also influence CO(2)dynamics in aquatic ecosystems. We measured CO(2)concentrations and the isotopic composition of dissolved inorganic C (delta C-13(DIC)) at diel resolution in two Arctic streams, and coupled this with whole-system metabolism estimates to assess the effect of biotic and abiotic processes on stream C dynamics. CO(2)concentrations consistently decreased from night to day, a pattern counter to the hypothesis that photo-oxidation is the dominant source of CO2. Instead, the observed decrease in CO(2)during daytime was explained by photosynthetic rates, which were strongly correlated with diurnal changes in delta(13)C(DIC)values. However, on days when modeled photosynthetic rates were near zero, there was still a significant diel change in delta(13)C(DIC)values, suggesting that metabolic estimates are partly masked by O(2)consumption from photo-oxidation. Our results suggest that 6-12 mmol CO2-C m(-2)d(-1)may be generated from photo-oxidation, a range that corresponds well to previous laboratory measurements. Moreover, ecosystem respiration rates were 10 times greater than published photo-oxidation rates for these Arctic streams, and accounted for 33-80% of total CO(2)evasion. Our results suggest that metabolic activity is the dominant process for CO(2)production in Arctic streams. Thus, future aquatic CO(2)emissions may depend on how biotic processes respond to the ongoing environmental change.
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