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Sökning: WFRF:(Kattner Gerhard)

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  • 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.
  • Ericson, Ylva, et al. (författare)
  • Increasing carbon inventory of the intermediate layers of the Arctic Ocean
  • 2014
  • Ingår i: Journal of Geophysical Research - Oceans. - 0148-0227 .- 2156-2202. ; 119:4, s. 2312-2326
  • Tidskriftsartikel (refereegranskat)abstract
    • Concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA), nutrients, and oxygen in subsurface waters of the central Arctic Ocean have been investigated for conceivable time trends over the last two decades. Data from six cruises (1991–2011) that cover the Nansen, Amundsen, and Makarov Basins were included in this analysis. In waters deeper than 2000 m, no statistically significant trend could be observed for DIC, TA, phosphate, or nitrate, but a small rate of increase in apparent oxygen utilization (AOU) was noticeable. For the individual stations, differences in concentration of each property were computed between the mean concentrations in the Arctic Atlantic Water (AAW) or the upper Polar Deep Water (uPDW), i.e., between about 150 and 1400 m depth, and in the deep water (assumed invariable over time). In these shallower water layers, we observe significant above-zero time trends for DIC, in the range of 0.6–0.9 μmol kg−1 yr−1 (for AAW) and 0.4–0.6 µmol kg−1 yr−1 (for uPDW). No time trend in nutrients could be observed, indicating no change in the rate of organic matter mineralization within this depth range. Consequently, the buildup of DIC is attributed to increasing concentrations of anthropogenic carbon in the waters flowing into these depth layers of the Arctic Ocean. The resulting rate of increase of the column inventory of anthropogenic CO2 is estimated to be between 0.6 and 0.9 mol C m−2 yr−1, with distinct differences between basins.
  • Ulfsbo, Adam, 1985, et al. (författare)
  • Late summer net community production in the central Arctic Ocean using multiple approaches
  • 2014
  • Ingår i: Global Biogeochemical Cycles. - 0886-6236. ; 28:10, s. 1129-1148
  • Tidskriftsartikel (refereegranskat)abstract
    • Large-scale patterns of net community production (NCP) were estimated during the late summer cruise ARK-XXVI/3 (TransArc, August/September 2011) to the central Arctic Ocean. Several approaches were used based on the following: (i) continuous measurements of surface water oxygen to argon ratios (O2/Ar), (ii) underway measurements of surface partial pressure of carbon dioxide (pCO2), (iii) discrete samples of dissolved inorganic carbon, and (iv) dissolved inorganic nitrogen and phosphate. The NCP estimates agreed well within the uncertainties associated with each approach. The highest late summer NCP (up to 6 mol C m−2) was observed in the marginal sea ice zone region. Low values (<1 mol C m−2) were found in the sea ice-covered deep basins with a strong spatial variability. Lowest values were found in the Amundsen Basin and moderate values in the Nansen and Makarov Basins with slightly higher estimates over the Mendeleev Ridge. Our findings support a coupling of NCP to sea ice coverage and nutrient supply and thus stress a potential change in spatial and temporal distribution of NCP in a future Arctic Ocean. To follow the evolution of NCP in space and time, it is suggested to apply one or several of these approaches in shipboard investigations with a time interval of 3 to 5 years.
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