| 1. |
- Bokhorst, Stef, et al.
(författare)
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Changing Arctic snow cover : A review of recent developments and assessment of future needs for observations, modelling, and impacts
- 2016
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 45:5, s. 516-537
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Forskningsöversikt (refereegranskat)abstract
- Snow is a critically important and rapidly changing feature of the Arctic. However, snow-cover and snowpack conditions change through time pose challenges for measuring and prediction of snow. Plausible scenarios of how Arctic snow cover will respond to changing Arctic climate are important for impact assessments and adaptation strategies. Although much progress has been made in understanding and predicting snow-cover changes and their multiple consequences, many uncertainties remain. In this paper, we review advances in snow monitoring and modelling, and the impact of snow changes on ecosystems and society in Arctic regions. Interdisciplinary activities are required to resolve the current limitations on measuring and modelling snow characteristics through the cold season and at different spatial scales to assure human well-being, economic stability, and improve the ability to predict manage and adapt to natural hazards in the Arctic region.
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| 2. |
- Brown, Ian A., et al.
(författare)
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Spatial and temporal variations in Antarctic snow particle size identified in AMSR-E 89 GHz data
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Here we use in situ observations to identify spatio-temporal variations of snow particle size in 89 GHz AMSR-E passive microwave satellite imagery. We have correlated high temporal resolution data daily AMSR-E with reference to high spatial resolution Envisat ASAR images to a validation dataset of snow particle size acquired during the Japanese Swedish Antarctic Expedition (JASE) 2007/2008. We have found strong correlations between the 89 GHz AMSR-E data and two different size parameters: particle length and estimated Specific Surface Area (SSA). These correlations have been used to model the grain size variations over the entire region of interest. The daily AMSR-E data have been used to study the evolution of the snowpack over time revealing a seasonal metamorphosis of snow particles at the coast that is largely absent on the polar plateau. Furthermore, the AMSR-E data may exhibit effects from the passing of coastal weather systems on 3-6 day cycles. These effects penetrate to the polar plateau and may represent the drainage of cold air from the plateau drawn-down by passing coastal weather systems.
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| 3. |
- Cosgrove, Christopher, et al.
(författare)
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Environmental controls on snow water equivalent in two sub-Arctic mountain catchments
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Spatial variability of seasonal snow depth poses a challenge when estimating snow water equivalent (SWE) from in-situ measurements in mountainous areas. Poor accessibility, complex topographic effects and localized microclimates make extrapolation of in-situ SWE measurements to a basin scale difficult. Remotely-sensed passive microwave SWE products are also inaccurate in complex terrain and/or at the forest-alpine tundra transition zone. To address these caveats, we investigated the relative importance of landscape qualities (altitude, slope, aspect, vegetation) and climate (winter temperatures, precipitation) on SWE distribution in two sub-Arctic mountainous catchments in Hemavan, Sweden, and Wolf Creek, Yukon, Canada. The two catchments are comparable, but have contrasted climate regimes. In-situ SWE measurements were made in March-April 2014 across the forest-tundra ecotone in both catchments. These were supplemented with historical snow-survey data since 2012 in Hemavan, and 1993 in Wolf Creek. Pairwise linear regressions of SWE against different landscape factors indicate that overall, altitude exerts the largest control on SWE at both Hemavan and Wolf Creek, but its effect is lesser within individual vegetation zones. In other respects, the two sites differ. SWE is inversely correlated to surface slope at forested sites in Hemavan (R^2 = 0.57, p = 0.25), but not in Wolf Creek. Slope aspect is positively correlated with SWE at forest-tundra transition sites (R^2 = 0.49, p = 0.12) in Wolf Creek, but not in Hemavan. For alpine tundra sites, slope angle strongly influences SWE in Hemavan (R^2 = 0.58, p = 0.24), but only weakly in Wolf Creek (R^2 = 0.05, p = 0.71). We discuss possible causes of these inter-catchment differences, and also evaluate the effect of inter-annual climate variations on SWE distribution at Wolf Creek using the long-term snow-survey record. Finally, we compare and discuss SWE estimates obtained by three different field measurement methods.
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| 4. |
- Fujita, S., et al.
(författare)
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Spatial and temporal variability of snow accumulation rate on the East Antarctic ice divide between Dome Fuji and EPICA DML
- 2011
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Ingår i: The Cryosphere. - : Copernicus GmbH. - 1994-0416 .- 1994-0424. ; 5:4, s. 1057-1081
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Tidskriftsartikel (refereegranskat)abstract
- To better understand the spatio-temporal variability of the glaciological environment in Dronning Maud Land (DML), East Antarctica, a 2800-km-long Japanese-Swedish traverse was carried out. The route includes ice divides between two ice-coring sites at Dome Fuji and EPICA DML. We determined the surface mass balance (SMB) averaged over various time scales in the late Holocene based on studies of snow pits and firn cores, in addition to radar data. We find that the large-scale distribution of the SMB depends on the surface elevation and continentality, and that the SMB differs between the windward and leeward sides of ice divides for strong-wind events. We suggest that the SMB is highly influenced by interactions between the large-scale surface topography of ice divides and the wind field of strong-wind events that are often associated with high-precipitation events. Local variations in the SMB are governed by the local surface topography, which is influenced by the bedrock topography. In the eastern part of DML, the accumulation rate in the second half of the 20th century is found to be higher by similar to 15% than averages over longer periods of 722 a or 7.9 ka before AD 2008. A similar increasing trend has been reported for many inland plateau sites in Antarctica with the exception of several sites on the leeward side of the ice divides.
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| 5. |
- Ingvander, Susanne, 1979-, et al.
(författare)
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Comparison between digital and manual methods of snow grain size determination
- 2012
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Ingår i: Hydrology Research. - : IWA Publishing. - 0029-1277 .- 2224-7955. ; 43:3, s. 192-202
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Tidskriftsartikel (refereegranskat)abstract
- Maintaining long time series of observations of the Cryosphere is a key issue in climate research. Long observational time series involve problems due to change in methodology or observers. In order to extend time series and introduce new methods, careful comparisons must be made to ensure homogeneity in the observational data. We have compared an established method for snow grain-size observations used by the Abisko Scientific Research Station (ASRS) in northern Sweden, based on visual interpretation, with a newly developed method for Digital Snow Particle Properties (DSPP) analysis. Transition from subjective visual method into digital reproducible analysis creates less subjective and more comparable results. The ASRS method generates size classifications excluding quantitative analysis size ranges. By determining the sizes of the classified snow using the DSPP-method, actual size ranges for classified snow can be established. By performing a digital analysis of the reference samples and the snow samples classified, we can compare the ASRS classification system to existing official classification systems. The results indicate underestimation of the visual particle size in comparison to the reference samples. Our results show how to quantify the historical data set, which enables us to perform quantitative analysis on the historical data set.
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| 6. |
- Ingvander, Susanne, et al.
(författare)
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Comparison of digital and manual methods of snow particle size estimation
- 2012
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Ingår i: Hydrology Research. - : IWA Publishing. - 0029-1277 .- 2224-7955. ; 43:3, s. 192-202
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Tidskriftsartikel (refereegranskat)abstract
- Maintaining long time series of observations of the Cryosphere is a key issue in climate research. Long observational time series involve problems due to change in methodology or observers. In order to extend time series and introduce new methods, careful comparisons must be made to ensure homogeneity in the observational data. We have compared an established method for snow grain-size observations used by the Abisko Scientific Research Station (ASRS) in northern Sweden, based on visual interpretation, with a newly developed method for Digital Snow Particle Properties (DSPP) analysis. Transition from subjective visual method into digital reproducible analysis creates less subjective and more comparable results. The ASRS method generates size classifications excluding quantitative analysis size ranges. By determining the sizes of the classified snow using the DSPP method, actual size ranges for classified snow can be established. By performing a digital analysis of the reference samples and the snow samples classified, we can compare the ASRS classification system to existing official classification systems. The results indicate underestimation of the visual particle size in comparison to the reference samples. Our results show how to quantify the historical data set, which enables us to perform quantitative analysis on the historical data set.
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| 7. |
- Ingvander, Susanne, et al.
(författare)
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In situ sampled snow particle sizes of the East Antarctic ice sheet and their relation to physical and remotely sensed snow surface parameters
- 2013
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Ingår i: Annals of Glaciology. - 0260-3055 .- 1727-5644. ; 54:62, s. 166-174
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of snow properties across Antarctica is important in estimating how climate could potentially influence the mass balance of the Antarctic ice sheet. However, measuring these variables has proven to be challenging because appropriate techniques have not yet been developed and extensive datasets of field estimates are lacking. The goal of this study was to estimate the relationship between field-observed snow particle-size parameters from across the East Antarctic ice sheet and a suite of spatial datasets (i.e. topography, remote-sensing data) using a principal component analysis (PCA). Five snow particle-size parameters were correlated to spatial datasets of the following five groups: (1) relief properties such as elevation and slope; (2) remote-sensing data from Moderate Resolution Imaging Spectroradiometer (MODIS) and synthetic aperture radar (SAR) sensors; (3) spatially interpolated data (i.e. 10 m maps of temperature and approximate snow accumulation in kg m(-2) a(-1)); (4) field-retrieved data on surface roughness; and (5) in situ elevation and distance from the coast. The results show that the relief parameter slope correlated best with the snow particle length and area (r=0.76, r=0.80). Further, the PCA indicated that the different remote-sensing parameters correlated differently with the size parameters and that the most common parameter in visual analysis, particle length (grain diameter), is not always the optimal parameter to characterize the snow particle size as, for example, area correlates better to slope and aspect than length.
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| 8. |
- Ingvander, Susanne, 1979-, et al.
(författare)
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Method study : Grain size sampling and digital object oriented image analysis for explanation of snow grain size, shape and distribution
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Ingår i: Journal of Glaciology. - 0022-1430 .- 1727-5652.
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a digital image processing method for snow particle size and shape analysis suitable for quick and reliable analysis in the eld. Snow particle size is an important parameter strongly aecting snow cover albedo from seasonally snow covered areas and ice sheets. It is also important in remote sensing analysis because it influences the reflectance and scattering properties of the snow. Alternatively traditional methods based on visual inspection of samples can be used but they do not yield quantitative data. Our method provides an additional alternative to both simpler and more complex methods by providinga tool that limits the subjective eect of the visual analysis and provides a quantitativeparticle size distribution. The method involves image analysis software and field efficient instrumentation in order to develop a complete process-chain easily implemented under field conditions. The results from the analysis are a two dimensional analysis of particle size, shape and distributions for each sample. The developed method improves snow particle analysis being quantitative, reproducible and applicable for dierent types of eld sites.
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| 9. |
- Ingvander, Susanne, et al.
(författare)
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Particle Size Sampling and Object-Oriented Image Analysis for Field Investigations of Snow Particle Size, Shape, and Distribution
- 2013
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Ingår i: Arctic, Antarctic and Alpine research. - : Informa UK Limited. - 1523-0430 .- 1938-4246. ; 45:3, s. 330-341
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Tidskriftsartikel (refereegranskat)abstract
- Snow particle size is an important parameter strongly affecting snow cover broadband albedo from seasonally snow covered areas and ice sheets. It is also important in remote sensing analyses because it influences the reflectance and scattering properties of the snow. We have developed a digital image processing method for the capture and analysis of data of snow particle size and shape. The method is suitable for quick and reliable data capture in the field. Traditional methods based on visual inspection of samples have been used but do not yield quantitative data. Our method provides an alternative to both simpler and more complex methods by providing a tool that limits the subjective effect of the visual analysis and provides a quantitative particle size distribution. The method involves image analysis software and field efficient instrumentation in order to develop a complete process-chain easily implemented under field conditions. The output from the analysis is a two-dimensional analysis of particle size, shape, and distributions for each sample. The results of the segmentation process were validated against manual delineation of snow particles. The developed method improves snow particle analysis because it is quantitative, reproducible, and applicable for different types of field sites.
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| 10. |
- Ingvander, Susanne, 1979-, et al.
(författare)
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Regional and local Snow Grain Size variations in Dronning Maud Land, Antarctica and analysis of various distribution scales
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Understanding spatial snow particle size variations are key to help interpretation of remotely sensed data of snow cover. In the case of Antarctica, remote sensing is the only viable option to estimate the surface mass balance of the ice sheet on continental scale. We have investigated snow particle size variability along a transect from the coast onto the polar plateau in Dronning Maud Land, Antarctica, to better understand the spatial and temporal variations in surface snow properties. Two daily samples were collected during a 55 day traverse to capture the regional variability. Local variability was assessed by sampling in grids at selected locations and the particle size and shape distributions for each site was analysed through digital image analysis, which has the benefit of yielding large quantities of reproducible quantitative data without the need for advanced laboratory analysis. The results provide an understanding of the complexity of snow particle size variability at different scales and show a variability range from 0.18–3.31 mm depending on the sample type (surface, grid or pit). We can verify relationships between grain size and both elevation and distance to the coast (moisture source) but have also identified regional seasonal changes, particularly on the lower elevations of the polar plateau. Our data provide possibilities to quantitatively assess the optical properties of the surface snow for remote sensing. The details of the spatial and temporal variations observed in our data provides a basis for further studies of the complex and coupled processes affecting snow particle size and the interpretation of remote sensing of snow covered areas.
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