| 1. |
- Moore, Peter L., et al.
(author)
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Effect of a cold margin on ice flow at the terminus of Storglaciären, Sweden : implications for sediment transport
- 2011
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In: Journal of Glaciology. - 0022-1430 .- 1727-5652. ; 57:201, s. 77-87
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Journal article (peer-reviewed)abstract
- The cold-based termini of polythermal glaciers are usually assumed to adhere strongly toan immobile substrate and thereby supply significant resistance to the flow of warm-based ice upglacier.This compressive environment is commonly thought to uplift basal sediment to the surface ofthe glacier by folding and thrust faulting. We present model and field evidence from the terminus ofStorglaci¨aren, Sweden, showing that the cold margin provides limited resistance to flow from up-glacier.Ice temperatures indicate that basal freezing occurs in this zone at 10−1 –10−2 ma−1, but model resultsindicate that basal motion at rates greater than 1ma−1 must, nevertheless, persist there for surface andbasal velocities to be consistent with measurements. Estimated longitudinal compressive stresses of 20–25 kPa within the terminus further indicate that basal resistance offered by the cold-based terminusis small. These results indicate that where polythermal glaciers are underlain by unlithified sediments,ice-flow trajectories and sediment transport pathways may be affected by subglacial topography andhydrology more than by the basal thermal regime
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| 2. |
- Moore, Peter L., et al.
(author)
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Entrainment and emplacement of englacial debris bands near the margin of Storglaciären, Sweden
- 2013
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In: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 42:1, s. 71-83
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Journal article (peer-reviewed)abstract
- Internal structure, stable isotope composition and tritium concentration were measured in and around debrisbearingice at the margin of Storglaciären, where englacial debris bands have previously been inferred to form bythrusting. Two types of debris bands were distinguished: (i) an unsorted diamicton band that is laterally continuousfor more than 200 m, and (ii) well-sorted sand and gravel bands that are lenticular and discontinuous.Above-background tritium levels and enrichment of d18O and dD in ice from the diamicton band indicateentrainment by basal freeze-on since 1952. Isotopic enrichment and tritium-free ice in the sandy debris bands alsoindicate entrainment in freezing water, but prior to 1952. The lenticular cross-section, sorting and stratification ofthe sandy bands suggest that they were deposited englacially. The basally accreted diamicton band has beenelevated tens of metres above the bed and presently overlies the englacially deposited sandy bands, suggesting thatthe stratigraphy has been disrupted. Three interpretations could account for these observations: (i) thrusting offast-moving ice over slow, marginal ice uplifting recently accreted basal ice along the fault; (ii) folding near themargin, elevating young basal ice over older basal and englacial ice; and (iii) debris-band formation by anunknown mechanism and subsequent contamination of ice geochemical properties by meltwater flow throughdebris bands. Although none of these interpretations is consistent with all measurements, folding is mostcompatible with observations and local ice-flow kinematics.
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| 3. |
- Clemenzi, Ilaria, et al.
(author)
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Annual water balance and hydrological trends in the glacierised Tarfala Catchment, Sweden
- 2023
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In: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 626
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Journal article (peer-reviewed)abstract
- Quantifying components of the hydrological cycle in glacierised catchments is important for the assessment of the temporal distribution, quantity and quality of water resources available to downstream regions, especially under a changing climate. However, this assessment requires long time series of observations, which are typically unavailable for remote catchments, such as those in mountainous areas. In this study, we leverage a unique ∼40 year time series of hydrological data recorded in the subarctic glacierised Tarfala catchment (Sweden) to explore temporal trends in the components of the catchment water balance (precipitation, runoff, change in storage, and evaporation), and to assess if water balance residuals are associated with specific hydro-climatic conditions. No significant temporal trends were found in precipitation and storage changes of the glacierised area, but significant increases were found in evaporation and summer discharge (in part attributed to glacier volume losses). The annual water balance could not be perfectly closed, and water losses were on average 112 mm y−1 larger than the water inputs over the study period. Among the water balance components, discharge contributed most to the total water balance uncertainty, and storage surplus due to antecedent meteorological conditions could explain why water losses in specific years exceeded the uncertainty bounds. It is therefore essential to consider legacy effects from previous years when applying water balance calculations in mountainous and/or glacierised catchments.
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| 4. |
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| 5. |
- Gusmeroli, Alessio, et al.
(author)
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Vertical distribution of water within the polythermal Storglaciären, Sweden
- 2010
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In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 115:F4, s. F04002-
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Journal article (peer-reviewed)abstract
- Knowledge of water content and its distribution in polythermal glaciers is required to model their flow and thermal state. However, observ of water content variations with depth in polythermal glaciers are scarce. Water content can be estimated from radio wave speed because they depend on one another. We obtained continuous profiles of radio wave speed variations with depth from zero-offset radar profiles collected in boreholes approximately 80 m deep in the upper ablation area of Storglaciaren, northern Sweden. These profiles show that the microcrystalline water system in the temperate ice is relatively homogeneous. The overall hydrothermal structure at this location is composed of a 20 m thick upper layer of cold, water-free ice, underlain by a temperate ice layer whose average water content is 0.6% +/- 0.3%. These results are corroborated by surface radar and thermistor measurements, which show that the depth of the cold temperate transition is 21 m and the calculated water content at that transition is 0.6% +/- 0.1%. These findings imply that the whole temperate ice layer is from 3 to 4 times softer than the cold ice and, consequently, that realistic ice flow models of polythermal glaciers should include the effect of water content on viscosity.
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| 6. |
- Hedfors, Jim, et al.
(author)
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Investigating the ratio of basal drag and driving stress in relation to bedrock topography during a melt season on Storglaciären, Sweden, using force budget analysis
- 2003
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In: Annals of Glaciology. - : International Glaciological Society. - 0260-3055 .- 1727-5644. ; 37:1, s. 263-268
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Journal article (peer-reviewed)abstract
- We apply the force-budget technique using the isothermal block-flow model, on Storglacia« ren, Sweden, to investigate the ratio between basal drag and driving stress in relation to a bedrock ridge in the bed topography during a peak melt season. The input data consist of glacier surface velocities collected using differential global positioning system surveying of a stake net and geometry fromprevious radar soundings and digitized ice surface maps. The study focuses on the effects of transverse bedrock ridges upon basal stress conditions.The pattern of the calculated ratio of basal drag and driving stress shows a rhythmical position of relatively high and lowbasal drags onthe stoss and lee sides, respectively, of the bedrock thresholds. One of the zones of low basal drag corresponds to the location where the highest basal sliding rate has been measured previously by borehode deformation studies. This zone also aligns with the area where the drainage system is suggested to change from englacial to subglacial.
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| 7. |
- Hooke, Roger LeB., et al.
(author)
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Intra-seasonal changes in deformation profiles revealed by borehole studies, Storglaciären, Sweden.
- 1992
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In: Journal of Glaciology. - 0022-1430 .- 1727-5652. ; 38:130, s. 348-358
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Journal article (peer-reviewed)abstract
- In 1985, 1987 and 1988, we measured deformation of bore holes in the ablation zone of Storglaciaren. A different hole was used each year. Deformation profiles were determined for four consecutive time periods between mid-July and early September. All three holes were in an area where the glacier lies in an overdeepened part of the bed, up-glacier from a riegel. The first hole was approximately on the glacier center line while the others were midway between the center line and one or the other margin. Despite large standard errors, variations in the deformation profiles during the melt season are broadly consistent with other data. We thus believe that they are real, and that they reflect changes in the stress field resulting from changes in drag at the bed. A decrease in drag early in the melt season, coupled with convergence of the bed contours towards the riegel, is believed to be responsible for a previously documented increase in vertical velocity just upglacier from the riegal at this time of year. Also noteworthy, but perhaps problematical, was an abrupt transverse shear of",! m at a depth of ",25 m near the center of the glacier inJuly 1985. The shear took place in the zone in which cold ice near the surface gives way to temperate ice deeper in the glacier.
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| 8. |
- Jansson, Peter, 1960-
(author)
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Ice sheet hydrology from observations
- 2010
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Reports (other academic/artistic)abstract
- This report summarizes our understanding of ice sheet hydrology as reported on observations from Antarctica and Greenland. Much of our general understanding of ice sheet hydrological processes are based on work performed on valley glaciers. Since processes do not differ in function but perhaps in magnitude, the understanding gained from smaller glaciers work applies to ice sheets. Hence, this report does not deal with such basic processes. Glacier hydrological investigations on ice sheets have been few but are perhaps accelerating in numbers with the increased focus on both Greenland and Antarctica from the scientific community in the light of effects from climate change. The process oriented studies carried out over the past 50 years or so have not generally been much applied to ice sheets and observations on the morphology of ice sheet and valley glacier hydrological systems have not been connected although most glacier hydrologists would not consider such parallels a stretch of their imagination. Much of the new studies on ice sheet hydrology, thus far, fits in two categories. One concerns verification of well-documented processes but on an ice sheet scale; the other concerns ice sheet specific features. These categories constitute the basis for this report.
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| 9. |
- Jansson, Peter, 1960-, et al.
(author)
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Spatial and temporal variations in glacier hydrology on Storglaciären, Sweden
- 2009
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Reports (other academic/artistic)abstract
- The purpose of this report is to summarize the experimental work on glacier hydrology and basal hydraulic conditions performed on Storglaciären, northern Sweden, during the years 2003–2005. The aim of the project has been to provide a framework of real conditions within which to interpret theory and extrapolate conditions beneath a future ice sheet over Fennoscandia. Surface fed subglacial hydrological systems are extremely dynamic because the input rates of rain and temperature-contolled surface melt fluctuate and the geometry of flow paths is constantly changing due to ice deformation which tends to close the flow paths. The hydrological system of a glacier is unique since water is flowing through conduits made of its solid phase (ice). A possible analogy is lava flowing through rock of the same composition. Hence understanding the expected dynamic range of the glacier hydrological system is best studied by in situ measurements. The processes studied on Storglaciären can be expected to apply to ice sheet scale, albeit on different spatial scales. Since Storglaciären is a polythermal glacier with a large fraction of ice below freezing and at the melting point and with a surface-fed hydrological system of conduits and tunnels, results apply to the margins (ablation zone) of the past Fennoscandian Ice Sheet, at least along its southern margin. In this report we discuss the measurements made to assess the subglacial conditions that provide an analogue for conditions under the Fennoscandian Ice Sheet. We have also included a large quantity of unpublished data from Storglaciären from different research projects conducted since 1990. Together these data provide a good picture of the temporal and spatial water pressure conditions in and under Storglaciären. The report is the first comprehensive analysis of these subglacial water pressure records.
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| 10. |
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| 11. |
- Jaquet, Olivier, et al.
(author)
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Groundwater flow modelling under ice sheet conditions : Scoping calculations
- 2010
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Reports (other academic/artistic)abstract
- SKB, POSIVA (Finland) and NWMO (Canada) have established in 2009 the GAP project (Greenland Analogue Project). These organisations want to improve current understanding of continental ice sheet and permafrost effects on groundwater flow and water chemistry in crystalline rocks at depths of a potential repository. The idea is to apply the Greenland ice sheet as an analogue to future glaciations in Fennoscandia and Canada. The GAP project will enable to perform geological and geophysical investigations, measurements of glacial hydrology and hydrogeology as well as geochemical analyses in relation to current ice sheet conditions in Greenland.
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| 12. |
- Karlsson, Dennis, et al.
(author)
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Additive manufacturing of the ferritic stainless steel SS441
- 2020
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In: Additive Manufacturing. - AMSTERDAM, NETHERLANDS : Elsevier BV. - 2214-8604 .- 2214-7810. ; 36
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Journal article (peer-reviewed)abstract
- In this study, the ferritic stainless steel SS441 was produced with excellent mechanical properties using laser powder bed fusion (L-PBF) compared to samples produced by conventional casting and hot-rolling. In addition, thermodynamic calculations were utilized to study the phase stability at elevated temperatures and to understand the solidification behavior. The hot-rolled sample showed a grain size up to several hundred mu m with additional precipitates of TiN and Nb(C,N). In contrast, the as-built L-PBF samples displayed a grain size in the mu m range. Spherical precipitates with a size of around 50 nm could be observed and were attributed to a corundum phase from the thermodynamic calculations. The printed material shows superior mechanical properties, with more than 30 times higher impact energy compared to the hot-rolled alloy (217 +/- 5 J vs. 7 +/- 0.5 J). Furthermore, the properties are anisotropic for the L-PBF produced alloy, with the highest tensile strength vertical to the build direction. The superior mechanical properties of the L-PBF produced sample can be attributed to a smaller grain size, giving a higher strength according to the Hall-Petch relationship. The anisotropy of the material can be eliminated by heat treatments at 900 degrees C followed by water quenching, but the absolute strength decreases slightly due to formation of intermetallic phases such as Nb(C,N) and the Fe2Nb Laves phase. The results clearly illustrates that L-PBF provides a promising manufacturing mute for enhanced strength of ferritic stainless steels.
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| 13. |
- Karlsson, Dennis, et al.
(author)
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Structure and phase transformations in gas atomized AlCoCrFeNi high entropy alloy powders
- 2022
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In: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 893
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Journal article (peer-reviewed)abstract
- In this study, the crystal structure and phase stability of gas atomized equiatomic AlCoCrFeNi powder was investigated. This alloy is usually described as a high entropy alloy forming a solid solution phase stabilized by a high mixing entropy. However, thermodynamic calculations show that the high entropy phase is stable only at very high temperatures close to the melting point and that a mixture of several phases are the most stable state at lower temperatures. This suggest that kinetic effects may influence the phase composition of atomized powder. The unique features of X-ray diffraction, neutron diffraction as well as transmission electron microscopy were used to study the atomic structure of the atomized powder in detail. The results show that the powder crystallises in an ordered B2 (CsCl-type) structure with a preferred site occupation of Al and Fe on the (1/2 1/2 1/2) position and Co and Ni on the (0 0 0) position. During heat-treatment of the powder, the B2 phase decomposes into fcc and sigma phases and the final phase composition is highly dependent on the heating rate. The effect of heat-treatment on the atomized powder was also investigated and revealed a significant phase transformation with e.g. the formation of sigma phase preferably at the surface of the powder particles. The phase content was also dependent on the size fraction of the powder particles. Sintering of green bodies made with different heat cycles showed that the phase composition of the starting material had a significant impact on the final phase composition and microstructure of the sintered components. The results illustrate the importance of well-defined powder materials for powder consolidation, especially additive manufacturing (binder jetting) of high entropy alloys.
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| 14. |
- Koblet, Thomas, et al.
(author)
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Reanalysis of multi-temporal aerial images of Storglaciären, Sweden (1959–99) – Part 1: Determination of length, area, and volume changes
- 2010
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In: The Cryosphere. - Göttingen : Copernicus. - 1994-0416 .- 1994-0424. ; 4, s. 333-343
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Journal article (peer-reviewed)abstract
- Storglaciären, located in the Kebnekaise massif in northern Sweden, has a long history of glaciological research. Early photo documentations date back to the late 19th century. Measurements of front position variations and distributed mass balance have been carried out since 1910 and 1945/46, respectively. In addition to these in-situ measurements, aerial photographs have been taken at decadal intervals since the beginning of the mass balance monitoring program and were used to produce topographic glacier maps. Inaccuracies in the maps were a challenge to early attempts to derive glacier volume changes and resulted in major differences when compared to the direct glaciological mass balances. In this study, we reanalyzed dia-positives of the original aerial photographs of 1959, -69, -80, -90 and -99 based on consistent photogrammetric processing. From ther esulting digital elevation models and orthophotos, changes in length, area, and volume of Storglaciären were computed between the survey years, including an assessment of related errors. Between 1959 and 1999, Storglaciären lost an ice volume of 19×106 m3, which corresponds to a cumulative ice thickness loss of 5.69 m and a mean annual loss of 0.14 m. This ice loss resulted largely from a strong volume loss during the period 1959–80 and was partly compensated during the period 1980–99. As a consequence, the glacier shows a strong retreat in the 1960s, a slowing in the 1970s, and pseudo-stationary conditions in the 1980s and 1990s.
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| 15. |
- Strang, Susann, 1953, et al.
(author)
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Palliative care in COPD-web survey in Sweden highlights the current situation for a vulnerable group of patients.
- 2013
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In: Upsala journal of medical sciences. - : Uppsala Medical Society. - 2000-1967 .- 0300-9734. ; 118:3, s. 181-6
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Journal article (peer-reviewed)abstract
- Abstract Background. Chronic obstructive pulmonary disease (COPD) is a common cause of death. Despite the heavy symptom burden in late stages, these patients are relatively seldom referred to specialist palliative care. Methods. A web-based survey concerning medical and organizational aspects of palliative care in COPD was distributed to respiratory physicians in Sweden. There were 93 respondents included in the study. Results. Palliative care issues were regularly discussed with the patients according to a third of the respondents. About half of the respondents worked in settings where established routines for co-operation with palliative units were available at least to some extent. Less than half of the respondents (39%) were aware of current plans to develop palliative care, either as a co-operative effort or within the facility. Palliative care is focused on physical, psychological, social, and existential dimensions, and the proportions of respondents providing support within these dimensions, 'always' or 'often', were 83%, 36%, 32%, and 11%, respectively. Thus, to treat the physical dimensions was perceived as much more obvious than to address the other dimensions. Conclusions. The survey indicates that the priorities and resources for palliative care in COPD are insufficient in Sweden. The data, despite limitations, reveal a lack of established team-work with specialized palliative care units and actual plans for such co-operation.
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| 16. |
- Watts, Hannah, et al.
(author)
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An Assessment of Geophysical Survey Techniques for Characterising the Subsurface Around Glacier Margins, and Recommendations for Future Applications
- 2022
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In: Frontiers in Earth Science. - : Frontiers Media SA. - 2296-6463. ; 10
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Journal article (peer-reviewed)abstract
- Geophysical surveys provide an efficient and non-invasive means of studying subsurface conditions in numerous sedimentary settings. In this study, we explore the application of three geophysical methods to a proglacial environment, namely ground penetrating radar (GPR), seismic refraction and multi-channel analysis of surface waves (MASW). We apply these geophysical methods to three glacial landforms with contrasting morphologies and sedimentary characteristics, and we use the various responses to assess the applicability and limitations of each method for these proglacial targets. Our analysis shows that GPR and seismic (refraction and MASW) techniques can provide spatially extensive information on the internal architecture and composition of moraines, but careful survey designs are required to optimise data quality in these geologically complex environments. Based on our findings, we define a number of recommendations and a potential workflow to guide future geophysical investigations in analogous settings. We recommend the initial use of GPR in future studies of proglacial environments to inform (a) seismic survey design and (b) the selection of seismic interpretation techniques. We show the benefits of using multiple GPR antenna frequencies (e.g., 25 and 100 MHz) to provide decimetre scale imaging in the near surface (e.g., < 15 m) while also enabling signal penetration to targets at up to ∼40 m depth (e.g., bedrock). This strategy helps to circumvent changes in radar signal penetration resulting from variations in substrate conductivity or abundant scatterers. Our study also demonstrates the importance of combining multiple geophysical methods together with ground-truthing through sedimentological observations to reduce ambiguity in interpretations. Implementing our recommendations will improve geophysical survey practice in the field of glacial geology and allow geophysical methods to play an increasing role in the interpretation of glacial landforms and sediments.
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| 17. |
- Watts, Hannah, 1994-
(author)
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Exploring beneath the surface of glacial landscapes : Implementing and improving geophysical investigations in glaciated environments
- 2024
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Doctoral thesis (other academic/artistic)abstract
- The warming climate is having profound impacts on glacier dynamics and extents. To improve our predictions of future ice mass changes, we require an enhanced understanding of both past and present glacial processes. The physical properties and structure of glacial sediments and landforms aid reconstructions of past environments and ice dynamics on numerous scales. Traditionally, these factors have been studied using glacial geological techniques such as sedimentary logging. While this provides valuable in situ data, there are numerous limitations, namely the limited availability and spatial extent of exposures. In recent decades, near-surface geophysical techniques have gained in popularity within the fields of glaciology, geomorphology, and sedimentology. Geophysics offers a non-invasive means of obtaining spatially extensive data on substrate properties and architecture, however issues such as signal scattering and interpretation ambiguity in complex glaciated environments restrict its application.This thesis exemplifies how near-surface geophysical techniques can aid glacial landscape interpretations focusing on ground-penetrating radar, seismic refraction, and multi-channel analysis of surface waves. It explores the current limitations of the methods and outlines solutions to improve their applicability, in terms of geophysical campaign success, as well as uncertainty estimation and visualisation. The reliability of geophysical interpretations can be improved by including direct substrate observations in campaigns. Here, the benefits of performing detailed sediment logging alongside geophysical surveys are exemplified, together with descriptions and explanations of associated method adaptations.Through a combination of method updates and applied studies, this thesis highlights the great potential for geophysical techniques in improving our understanding of glacial processes and outlines potential avenues for further work in this area.
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| 18. |
- Zemp, Michael, et al.
(author)
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Reanalysis of multi-temporal aerial images of Storglaciären, Sweden (1959-1999) – Part 2: Comparison of glaciological and volumetric mass balances
- 2010
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In: The Cryosphere. - Göttingen : Copernicus. - 1994-0424. ; 4, s. 345-357
-
Journal article (peer-reviewed)abstract
- Seasonal glaciological mass balances have been measured on Storglaciären without interruption since 1945/46. In addition, aerial surveys have been carried out on a decadal basis since the beginning of the observation program. Early studies had used the resulting aerial photographs to produce topographic glacier maps with which the in-situ observations could be verified. However, these maps as well as the derived volume changes are subject to errors which resulted in major differences between the derived volumetric and the glaciological mass balance. As a consequence,the original photographs were re-processed using uniform photogrammetric methods, which resulted in new volumetric mass balances for 1959–69, 1969–80, 1980–90, and 1990–99. We compared these new volumetric mass balances with mass balances obtained by standard glaciological methods including an uncertainty assessment considering all related previous studies. The absolute differences between volumetric and the glaciological mass balances are 0.8 m w.e. for theperiod of 1959–69 and 0.3 m w.e. or less for the other survey periods. These deviations are slightly reduced when considering corrections for systematic uncertainties due to differences in survey dates, reference areas, and internal ablation, whereas internal accumulation systematically increases the mismatch. However, the mean annual differences between glaciological and volumetric mass balance are less than the uncertainty of the in-situ stake reading and stochastic error bars of both data series overlap. Hence, no adjustment of the glaciological data series to the volumetric one is required.
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| 19. |
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