| 1. |
- Kylander, Malin E., 1977-, et al.
(författare)
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Storm chasing : Tracking Holocene storminess in southern Sweden using mineral proxies from inland and coastal peat bogs
- 2023
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 299, s. 107854-
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Tidskriftsartikel (refereegranskat)abstract
- Severe extratropical winter storms are a recurrent feature of the European climate and cause widespread socioeconomic losses. Due to insufficient long-term data, it remains unclear whether storminess has shown a notable response to changes in external forcing over the past millennia, which impacts our ability to project future storminess in a changing climate. Reconstructing past storm variability is essential to improving our understanding of storms on these longer, missing timescales. Peat sequences from coastal ombrotrophic bogs are increasingly used for this purpose, where greater quantities of coarser grained beach sand are deposited by strong winds during storm events. Moving inland however, storm intensity decreases, as does sand availability, muting potential paleostorm signals in bogs. We circumvent these issues by taking the innovative approach of using mid-infrared (MIR) spectral data, supported by elemental information, from the inorganic fraction of Store Mosse Dune South (SMDS), a 5000-year-old sequence from a large peatland located in southern Sweden. We infer past changes in mineral composition and thereby, the grain size of the deposited material. The record is dominated by quartz, whose coarse nature was confirmed through analyses of potential local source sediments. This was supported by further mineralogical and elemental proxies of atmospheric input. Comparison of SMDS with within-bog and regionally relevant records showed that there is a difference in proxy and site response to what should be similar timing in shifts in storminess over the-100 km transect considered. We suggest the construction of regional storm stacks, built here by applying changepoint modelling to four transect sites jointly. This modelling approach has the effect of reinforcing signals in common while reducing the influence of random noise. The resulting Southern Sweden-Storm Stack dates stormier periods to 4495-4290, 3880-3790, 2885-2855, 2300-2005, 1175-1065 and 715-425 cal yr BP. By comparing with a newly constructed Western Scotland-Storm Stack and proximal dune records, we argue that regional storm stacks allow us to better compare past storminess over wider areas, gauge storm track movements and by extension, increase our understanding of the drivers of storminess on centennial to millennial timescales.
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| 2. |
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| 3. |
- Mustafa, Mudassir Imran, 1978-
(författare)
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Sustaining the Usefulness of eHealth Research Software : Lessons Learned in Action Design Research
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Research software is vital to advancement in the sciences, engineering, humanities, and all other fields. Scientific research is dependent on the quality of and accessibility to research software. Research software is often developed hastily to solve one-off problems, leading to flimsy code that is not sustainable or usable beyond the lifetime of a given research project and is difficult for researchers, outside of the original context, to use, reuse or extend. It is critical to address the many challenges related to the development, deployment, and maintenance of research software. Therefore, there is a growing concern in the scientific community regarding designing sustainable research software. The academic research context refers to the environment or community concerned with scientific research, sponsored by research grants and public funding. Despite the increasing dependence on research software, software development practices in academia lag far behind those in the commercial sector.Health care relies on a very complex information technology architecture with many different IT components and also has a highly complex governance structure alongside the very rapid technology development. Additionally, there are ever-increasing demands and needs from health care users for more flexibility, more functionality and making the care transparent and patient-centred. Taken together, this poses significant challenges for eHealth and Information Systems researchers, as each artefact, depending on the context, has different quality characteristics to operationalise the requirements under consideration.The research objective is to explore what Information Systems researchers and practitioners need to be aware of for sustaining the usefulness of eHealth research software, in the academic research context. This longitudinal action design research (ADR) project, with its three cases, was conducted in an eHealth research project over a period of six years. Contributions from this research include the identification of quality characteristics and their enactment in the actual organisational settings, as well as empirically grounded design principles and a typology for sustaining the usefulness of eHealth research software, based on a formalisation of learning in the three ADR cases. This dissertation also contributes to the method space with the introduction of the augmented action design research (AADR) method, an extension of ADR, on how to conduct multiple ADR projects that build towards an overarching knowledge aim.Practice contributions are the design and development of internet-based eHealth research software to offer patients psychological treatment and support for issues resulting from physical illnesses, while also providing a chance for researchers to study the effectiveness of the aid provided. The dissertation also contributed in a broader sense to the research software development practice, as the findings extend to research areas in which research software is needed to read and interpret research data, and where software must continue to function so that it allows continued access and use of research data.
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| 4. |
- Ryberg, Eleonor E., et al.
(författare)
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Postglacial peatland vegetation succession in Store Mosse bog, south-central Sweden : An exploration of factors driving species change
- 2022
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 51:3, s. 651-666
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Tidskriftsartikel (refereegranskat)abstract
- Boreal peatlands are facing significant changes in response to a warming climate. Sphagnum mosses are key species in these ecosystems and contribute substantially to carbon sequestration. Understanding the factors driving vegetation changes on longer time scales is therefore of high importance, yet challenging since species changes are typically affected by a range of internal and external processes acting simultaneously within the system. This study presents a high-resolution macrofossil analysis of a peat core from Store Mosse bog (south-central Sweden), dating back to nearly 10 000 cal. a BP. The aim is to identify factors driving species changes on multidecadal to millennial timescales considering internal autogenic, internal biotic and external allogenic processes. A set of independent proxy data was used as a comparison framework to estimate changes in the bog and regional effective humidity, nutrient input and cold periods. We found that Store Mosse largely follows the expected successional pathway for a boreal peatland (i.e. lake -> fen -> bog). However, the system has also been affected by other interlinked factors. Of interest, we note that external nutrient input (originating from dust deposition and climate processes) has had a negative effect on Sphagnum while favouring vascular plants, and increased fire activity (driven by allogenic and autogenic factors) typically caused post-fire, floristic wet shifts. These effects interactively caused a floristic reversal and near disappearance of a once-established Sphagnum community, during which climate acted as an indirect driver. Overall, this study highlights that the factors driving vegetation change within the peatland are multiple and complex. Consideration of the role of interlinked factors on Sphagnum is crucial for an improved understanding of the drivers of species change on short- and long-term scales.
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| 5. |
- Sjöström, Jenny K., 1978-, et al.
(författare)
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Complex evolution of Holocene hydroclimate, fire and vegetation revealed by molecular, minerogenic and biogenic proxies, Marais Geluk wetland, eastern Free State, South Africa
- 2023
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Ingår i: Quaternary Science Reviews. - 0277-3791 .- 1873-457X. ; 314
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Tidskriftsartikel (refereegranskat)abstract
- The Holocene climate history of Southern Africa remains inconclusive despite the increasing number of proxy records from the region. This might be related to the diversity of proxy records, how the proxies are interpreted, or that proxies may respond to more than one forcing (e.g. hydroclimate, fire, temperature.). Here, a 175-cm peat sequence from Free State, South Africa (28°17′53″S, 29°25′10.9″E), was analyzed using a comprehensive set of novel and conventional proxies, including isotopic (δ13C), elemental (CS-XRF), mineral (pXRD), molecular (FTIR-ATR and pyrolysis-GC-MS), grain size (Malvern 3000) and GSSC phytolith composition. The chronology was constructed through AMS radiocarbon dating (n = 7). The early Holocene (10,380–7000 cal yr BP) was characterized by an initial wet phase, followed by relative dryness, at least seasonally, evidenced by slow accumulation rates, low organic content and dominance of terrestrial vegetation in the organic matter matrix. From 7000 cal yr BP, decreasing temperatures, as evidenced in regional climate reconstructions, were associated at Marias Geluk with higher biogenic silica and organic matter content and an increase of moisture-adapted grasses, indicating increasingly mesic conditions. This trend was amplified after 6000 cal yr BP, co-occurring with a southward displacement of the ITCZ. Complex proxy dynamics were observed between 4300 and 2180 cal yr BP, with bulk organic proxies indicating a drier environment (lower carbon content, slow accumulation rates, enriched δ13C values) but the phytolith record pointing towards relatively mesic conditions. The period was also associated with increased fire frequency, that also reached the local wetland. We suggest that the period was associated with seasonally mesic conditions together with increased fire incidence, which affected some of the organic proxies. Increased fire activity was also recorded in the region, while the hydroclimatic indications differed. The last 2000 years, during which human activity is known to have increased in the region, was characterized by lower fire incidence and variable, but relatively moist, conditions. The hydroclimatic inferences for the last 2000 years are in line with previous studies from the region, but additional studies are needed to decipher if the decline in fire incidence was associated to climate forcings, human activities, or a combination of both. The multiproxy approach applied here - in particular the inclusion of FTIR-ATR and pyrolysis GC-MS - revealed a complex interplay between vegetation dynamics, hydrology and paleofire variability. This study confirms that relatively small Holocene temperature variations (compared to northern higher latitudes) were associated with major hydrological variability at Marais Geluk, and reinforces concerns from earlier studies that the hydroclimate of the region is vulnerable to climate change. The result s also show that the southward displacement of the ITCZ, and associated tropical air masses, likely had significant effects on regional hydrology and fire incidence.
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| 6. |
- Sjöström, Jenny K., 1978-, et al.
(författare)
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Late Holocene peat paleodust deposition in south-western Sweden : exploring geochemical properties, local mineral sources and regional aeolian activity
- 2022
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Ingår i: Chemical Geology. - : Elsevier. - 0009-2541 .- 1872-6836. ; 602
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric mineral dust not only interacts with the climate system by scattering incoming solar radiation and affecting atmospheric photochemistry, but also contributes critical nutrients to marine and terrestrial ecosystems. In a high-resolution analysis of paleodust deposition, peat development and soil dust sources, we assess the interplay between dust deposition and bog development of the Davidsmosse bog in south-western Sweden. Analyses of the 5400-year record (458 cm) included radiocarbon dating, bulk density, ash content, chemical and mineralogical composition and carbon stable isotopes, subsequently explored using principal component analysis. Fourteen dust events (DEs) were recorded (cal BP) in the peat sequence: 3580–3490; 3280; 3140; 3010–2840; 2740; 2610; 2480; 2340; 2240–2130; 1690; 1240; 960, 890–760, and 620–360. The majority of the DEs were coupled to increases in peat accumulation rates and increased nutrient content (N, P and K) suggesting that the DEs contributed with nutrients to the bog ecosystem, promoting increased accumulation. We also analyzed the chemical and mineral composition of potential mineral source deposits (separated into 6 grain-size fractions) from sites within a 4 km radius as well as aeolian dunes closer to the coast (25 km). The composition deposited on the present-day bog surface indicates that the bulk of the contemporary minerals have a local origin (<1.5 km), but the DEs may be of a more distant origin. The results also indicate that quartz and plagioclase feldspar content consistently increase with increasing grain-size, both in the source samples as well as in the peat sequence, and that the Si/Al ratio can be used to infer grain size changes in the peat. Two longer phases saw numerous DEs, between 2800 and 2130 cal BP and a stepwise increase from 960 towards 360 cal BP. The episodic character of the events, together with the inferred coarse grain size, suggest that the particles were deposited by (winter) storms. Future studies should include grain size analysis as well as a more in-depth comparison with regional paleo dust and storm records to increase knowledge on both transport processes (creep, saltation, suspension) and the climate processes driving late Holocene dust and storm events in Scandinavia.
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| 7. |
- Sjöström, Jenny, 1978-
(författare)
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Mid-Holocene mineral dust deposition in raised bogs in southern Sweden : Processes and links
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atmospheric mineral dust is a key component of the climate system, which affects insolation, brings nutrients to marine and terrestrial ecosystems, and acts as a cloud condensation nuclei. To reconstruct past patterns in terrestrial dust deposition natural archives may be utilized, such as loess, dunes, lakes, and peat bogs. Bogs became an established dust archive in the early 2000s, and the number of studies has since increased. However, most studies use single records to represent dust deposition, meaning that we have limited understanding of regional paleodust dynamics or about the representativeness of single bog records. This thesis aims to address these uncertainties by comparing paleodust deposition between bogs located on a 65 km transect. The thesis includes a methodological development for organic matter removal from peat samples for XRD mineral analysis (Paper I) and two peat paleodust reconstruction studies (Paper II, III). The first paleodust reconstruction from Draftinge Mosse (mosse translates to bog in English), Småland, showed that four dust events (DE) were recorded during the ombrotrophic stage (Paper II). These results were compared to a previously conducted study on Store Mosse, 20 km northeast of Draftinge Mosse, which showed similar patterns in DE and peat accumulation rate (PAR), indicating that the events were at least regional in character. However, the magnitude of the DE differed, which was related to differences in the sizes of the two bogs. The second paleodust reconstruction, from (Davidsmosse) located c. 25 km from the west coast, recorded many more DE (14) compared to the more inland sites (Paper III). Two longer periods saw numerous DE, dominated by coarse particles: between 2800 and 2130 cal BP, and from 1000 towards 490 cal BP. These two periods occurred during regionally cold periods. Human activities also intensified during the latter period, possibly amplifying the DE. Most of these episodic events were not recorded at the inland sites, and the Davidsmosse record seemed to be more in line with previously constructed coastal paleostorm records. That the bog located closer to the coast recorded many more events compared to the inland sites suggests that the location of a bog will influence the aeolian events recorded. However, the DE observed at the inland sites were also recorded at Davidsmosse, indicating that the inland events might represent winds that were sustained over longer distance, or alternatively, that regionally dry conditions prevailed during these periods. The paleostorm records from south-western Sweden, including the new results from Davidsmosse presented here, suggest that storm intensities have varied during the last 3000 years, with increased storminess frequency coupled to colder episodes related to extended sea ice and a southward shift of storm tracks. When comparing DE and PAR at both sites studied here, a recurring pattern of increased accumulation rates were observed during a majority of DE, supporting the suggestion of previous studies that dust deposition may affect peat growth, and thus also peat carbon sequestration.Combining elemental data with XRD mineral analysis enabled anchoring of elemental inferences with mineral observations, allowed identification of authigenic minerals, and aided in source tracing. Despite the fact that local factors affect mineral deposition and PAR, this work has outlined some of the possible mechanisms behind these observations (e.g. distance to the coast, or bog size difference) which may be important for future peat paleodust studies to consider. For example, future studies should include grain size analysis (down-core, as well as across a bog surface); pollen analysis to further elaborate on human activities and vegetation cover; and further investigate differences in mass accumulation rates between bogs.
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| 8. |
- Sjöström, Jenny, 1978-, et al.
(författare)
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Mid-Holocene reconstruction of peat paleodust deposition and accumulation rates in southern Sweden during the last 5400 years : processes and links
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We present a peat paleodust and accumulation rates study from Davidsmosse, Halland region, south-west Sweden. The 458 cm peat sequence was studied for peat composition, bulk density, elemental composition and ash content. The results were quantitatively assessed using principal component analysis and related to calendar ages by radiocarbon dating. Local soil and sediments samples from the surrounding area (within 4 km radius) as well as aeolian dunes located closer to the coast (25 km) were analysed for elemental concentrations and mineral content. These results were compared to the minerals on the current bog surface and their similarity suggests that the deposited minerals have a local origin. From the peat paleodust reconstruction fourteen dust events (DE) were recorded (cal BP): 3580–3490; 3280; 3140; 3010–2840; 2740; 2610; 2480; 2340; 2240–2130; 2050; 1890; 1690; 1240; and 960–490. A majority of these events were coupled to increases in peat accumulation rates (13 of 14), indicating a relationship between these two processes. Davidsmosse recorded two longer phases that saw numerous DE with larger inferred grain size between 2800 and 2130 cal BP and a stepwise increase from 1000 towards 490 cal BP. These phases overlap in time with increased storm activity recorded in previous studies, both in nearby bog records as well as from dune records in Denmark, and a coastal bog in Scotland, suggesting storminess as a driver of DE signals at Davidsmosse. These stormier periods are related to colder periods, coupled to extended sea ice south of Iceland and a southward shift in storm tracks. Comparison with peat paleodust records further inland did not register these events, indicating that the location of the bog will affect which type of DE that will be recorded. Those DE found at both coastal and inland sites may represent periods with particularly strong winds, or alternatively, regionally dry phases. Further studies are required to untangle which of these processes are responsible for this pattern, for example by conducting grain size analysis on an event recorded at all three bogs, coupled with high resolution dating.
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| 9. |
- Sjöström, Jenny, 1978-
(författare)
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Procedure for organic matter removal from peat samples for XRD mineral analysis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Ombrotrophic peatlands are recognised archives of atmospheric mineral dust deposition, where mainly elemental data has been used to infer past net dust deposition rates, sources, grain size and mineralogy of the deposited dust. Although geochemical analysis can be data–rich, there are some inherent limitations. X–ray diffraction (XRD) directly determines the mineralogy of environmental samples but few studies have applied this method to peat samples and a well–developed protocol for extracting the inorganic fraction of highly organic samples (>95 %) is lacking. We tested and compared different levels of pre–treatment: no pre–treatment, thermal combustion (300, 350, 400, 450 and 500°C) and chemical oxidation (H2O2 and Na2S2O8) using a homogenized high organic content (>98 %) composite peat sample. Subsequently, minerals were identified by XRD. The results show that combustion is preferred to chemical oxidation because it most efficiently removes organic matter (OM), an important pre–requisite in order to identify mineral phases by XRD analysis of a mixed sample matrix, and phase transitions that may occur can be anticipated when temperature is the only factor to take into consideration. Combustion at 500°C is the most efficient temperature for OM removal whereas combustion at lower temperatures left significant OM residues.
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| 10. |
- Sjöström, Jenny, 1978-
(författare)
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Reconstruction of Holocene atmospheric mineral dust deposition from raised peat bogs in south–central Sweden
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atmospheric mineral dust plays a dynamic role in the climate system acting both as a forcing and a feedback mechanism. To date, the majority of paleodust studies have been conducted on marine sediments or polar ice cores, while terrestrial deposition has been less studied. As such, it is important to produce new terrestrial Holocene paleo–dust records and fill existing regional gaps. Ombrotrophic (atmospherically–fed) peat bogs can be used to reconstruct dust deposition through elemental chemistry analysis. Multi–elemental data sets are commonly used infer net dust deposition rates, source changes, grain size, and mineral composition. Mineralogical identification of dust particles is particularly important because it allows both provenance tracing and increased understanding in climate and ecosystem feedbacks. Establishing mineralogy from elemental data of mixed mineral matrixes can however be challenging. X–ray diffraction analysis (XRD) is a standard technique for mineral identification which ideally requires removal of organic matter (OM). Therefore, a test procedure was undertaken where common OM removal methods were evaluated on bulk peat samples was therefore undertaken. The results showed that combustion at 500°C was most efficient in removing OM, while leaving the majority of minerals intact, but not all. In this Licenciate thesis, early result of a paleodust study from Draftinge Mosse, southern Sweden, are also outlined. Here, the method development mentioned above was applied, enabling a combination of elemental data with mineralogy. Future work includes minor and trace element analysis by ICP–AES and ICP–MS, evaluation of the reproducibility of single core reconstructions, tests of some of the methodological assumptions used in previous paleodust studies, source tracing and paleodust reconstruction from a second site (Gällsered Mosse).
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