| 11. |
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| 12. |
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| 13. |
- Abbott, Benjamin W., et al.
(författare)
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Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment
- 2016
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 11:3
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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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| 14. |
- Amvrosiadi, Nino, et al.
(författare)
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Soil moisture storage estimation based on steady vertical fluxes under equilibrium
- 2017
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Ingår i: Journal of Hydrology. - : Elsevier B.V.. - 0022-1694 .- 1879-2707. ; 553, s. 798-804
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Tidskriftsartikel (refereegranskat)abstract
- Soil moisture is an important variable for hillslope and catchment hydrology. There are various computational methods to estimate soil moisture and their complexity varies greatly: from one box with vertically constant volumetric soil water content to fully saturated-unsaturated coupled physically-based models. Different complexity levels are applicable depending on the simulation scale, computational time limitations, input data and knowledge about the parameters. The Vertical Equilibrium Model (VEM) is a simple approach to estimate the catchment-wide soil water storage at a daily time-scale on the basis of water table level observations, soil properties and an assumption of hydrological equilibrium without vertical fluxes above the water table. In this study VEM was extended by considering vertical fluxes, which allows conditions with evaporation and infiltration to be represented. The aim was to test the hypothesis that the simulated volumetric soil water content significantly depends on vertical fluxes. The water content difference between the no-flux, equilibrium approach and the new constant-flux approach greatly depended on the soil textural class, ranging between ∼1% for silty clay and ∼44% for sand at an evapotranspiration rate of 5 mm·d−1. The two approaches gave a mean volumetric soil water content difference of ∼1 mm for two case studies (sandy loam and organic rich soils). The results showed that for many soil types the differences in estimated storage between the no-flux and the constant flux approaches were relatively small.
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| 15. |
- Amvrosiadi, Nino
(författare)
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The value of experimental data and modelling for exploration of hydrological functioning: The case of a till hillslope
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Successfully modeling one system response (e.g. hydrograph or solute transport) sometimes gives the false sense of well-characterizing the modeled system. This is partly because of the well-known equifinality issue; during the calibration process multiple parameter combinations can produce similarly good results. One step forward towards a better-defined system is using measured (at relevant scale) values for the model parameters, as well as using multiple conditions to constrain the model.But when not enough, or relevant, field measurements are available, virtual experiments (VE’s) can be used as a supplementary method to model calibration. The advantage of VE’s over model calibration is that they can also be used to explore assumptions both on the system hydrological processes, and on the model structure.One goal of this study was to utilize both field measurements and models for better characterization of the S-transect hillslope, located in Västrabäcken catchment, Northern Sweden. This included (a) characteristics in space: system vertical boundaries, hydraulic parameters, pore water velocity distribution, spatial correlation of flowpaths, soil water retention properties; (b) characteristic of system’s dynamic behavior: storage – discharge relationship, transit time distribution, turnover time; and (c) outputs’ sensitivity to external forcing, and to small scale structure assumptions. The second goal was to comment on the value of field measurements and virtual experiments for extracting information about the studied system.An intensely monitored study hillslope was chosen for this work. Although the hillslope has already been the subject of multiple field and modelling studies, there are still open questions regarding the characteristics listed above. The models used were the Vertical Equilibrium Model (VEM), and the Multiple Interacting Pathways (MIPs) model.It was found that the hillslope was well connected; from the near-stream areas up to the water divide the storage – discharge relationship could be described as an exponential function. Also, the dynamic storage (which controls the hydrograph dynamics) was much smaller comparing to the total hillslope storage. The unsaturated soil storage was found to be more sensitive to water table positions than vertical flux magnitude. The dynamic condition of external forcing (precipitation and evapotranspiration) affected the transit time distribution (TTD) shape. And, opposite to expectations, TTD was not sensitive to micro-scale structural assumptions tested here.
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| 16. |
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| 17. |
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| 18. |
- Amvrosiadi, Nino, et al.
(författare)
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Water storage dynamics in a till hillslope : the foundation for modeling flows and turnover times
- 2017
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Ingår i: Hydrological Processes. - : John Wiley and Sons Ltd. - 0885-6087 .- 1099-1085. ; 31:1, s. 4-14
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Tidskriftsartikel (refereegranskat)abstract
- Studies on hydrology, biogeochemistry, or mineral weathering often rely on assumptions about flow paths, water storage dynamics, and transit times. Testing these assumptions requires detailed hydrometric data that are usually unavailable at the catchment scale. Hillslope studies provide an alternative for obtaining a better understanding, but even on such well-defined and delimited scales, it is rare to have a comprehensive set of hydrometric observations from the water divide down to the stream that can constrain efforts to quantify water storage, movement, and turnover time. Here, we quantified water storage with daily resolution in a hillslope during the course of almost an entire year using hydrological measurements at the study site and an extended version of the vertical equilibrium model. We used an exponential function to simulate the relationship between hillslope discharge and water table; this was used to derive transmissivity profiles along the hillslope and map mean pore water velocities in the saturated zone. Based on the transmissivity profiles, the soil layer transmitting 99% of lateral flow to the stream had a depth that ranged from 8.9 m at the water divide to under 1 m closer to the stream. During the study period, the total storage of this layer varied from 1189 to 1485 mm, resulting in a turnover time of 2172 days. From the pore water velocities, we mapped the time it would take a water particle situated at any point of the saturated zone anywhere along the hillslope to exit as runoff. Our calculations point to the strengths as well as limitations of simple hydrometric data for inferring hydrological properties and water travel times in the subsurface.
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| 19. |
- Bishop, Kevin, et al.
(författare)
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A primer for hydrology : the beguiling simplicity of Water's journey from rain to stream at 30 Preface
- 2015
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 29:16, s. 3443-3446
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Water's journey from rain to stream by Harald Grip and Allan Rodhe (1985, in Swedish: Vattnets vag fran regn till back) was one of the first textbooks to present groundwater contributions as a major feature of runoff generation, with implications for water quality and management. Three decades later, we have the privilege of presenting a special issue of Hydrological Processes, Runoff Generation in a Nordic Light: 30Years with Water's Journey from Rain to Stream' that seeks to introduce the book to a larger audience and continue the journey of ideas that the authors set in motion with their book.
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| 20. |
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