| 1. |
- Bennike, Ole, et al.
(författare)
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Tristan da Cunha
- 2005
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Ingår i: Naturens Verden. - 0028-0895. ; 88:7/8, s. 10-23
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 2. |
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| 3. |
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| 4. |
- Berggren, Karl-Fredrik, et al.
(författare)
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Nature of streamlines for Berry-type wave functions in open 3D cavities
- 2009
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Ingår i: MATHEMATICAL MODELING OF WAVE PHENOMENA. - : American Institute of Physics (AIP). - 9780735406438 ; , s. 253-259
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Konferensbidrag (refereegranskat)abstract
- We explore preliminary a 3D wave cavity in which the interior complex wave functions are of Berry-type. Streamlines and novel disc-like features are uncovered by means of selective and interactive visualization.
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| 5. |
- Bjork, Anders Anker, et al.
(författare)
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Possible Late Pleistocene volcanic activity on Nightingale Island, South Atlantic Ocean, based on geoelectrical resistivity measurements, sediment corings and (14)C dating
- 2011
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Ingår i: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 133:3-4, s. 141-147
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Tidskriftsartikel (refereegranskat)abstract
- Tristan da Cunha is a volcanic island group situated in the central South Atlantic. The oldest of these islands, Nightingale Island, has an age of about 18Ma. In the interior of the island, there are several wetlands situated in topographic depressions. The ages of these basins have been unknown, and their genesis has been debated. Aiming towards the reconstruction of the geomorphological history of these basins, we conducted geoelectrical resistivity measurements to map the subsurface topography, extracted peat and sediment cores and dated the onset of sedimentation applying the radiocarbon method. The irregular shapes of the basins and the lack of clear erosional features indicate that they are not eruption craters and were not formed by erosion. Instead, we regard them as morphological depressions formed between ridges of trachytic lava flows and domes at a late stage of the formation of the volcanic edifice. The onset of sedimentation within these basins appears to have occurred between 24 and 37 ka with the highest situated wetland yielding the highest ages. These ages are very young compared to the timing of the main phase of the formation of the island, implying volcanic activity on the island during the Late Pleistocene.
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| 6. |
- Björck, Svante, et al.
(författare)
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A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial
- 2019
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 15:6, s. 1939-1958
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Tidskriftsartikel (refereegranskat)abstract
- Changes in the latitudinal position and strength of the Southern Hemisphere westerlies (SHW) are thought to be tightly coupled to important climate processes, such as cross-equatorial heat fluxes, Atlantic Meridional Overturning Circulation (AMOC), the bipolar seesaw, Southern Ocean ventilation and atmospheric CO2 levels. However, many uncertainties regarding magnitude, direction, and causes and effects of past SHW shifts still exist due to lack of suitable sites and scarcity of information on SHW dynamics, especially from the last glacial. Here we present a detailed hydroclimate multiproxy record from a 36.4-18.6 kyr old lake sediment sequence on Nightingale Island (NI). It is strategically located at 37ĝF S in the central South Atlantic (SA) within the SHW belt and situated just north of the marine Subtropical Front (SF). This has enabled us to assess hydroclimate changes and their link to the regional climate development as well as to large-scale climate events in polar ice cores. The NI record exhibits a continuous impact of the SHW, recording shifts in both position and strength, and between 36 and 31 ka the westerlies show high latitudinal and strength-wise variability possibly linked to the bipolar seesaw. This was followed by 4 kyr of slightly falling temperatures, decreasing humidity and fairly southerly westerlies. After 27 ka temperatures decreased 3-4 ĝC, marking the largest hydroclimate change with drier conditions and a variable SHW position. We note that periods with more intense and southerly-positioned SHW seem to be related to periods of increased CO2 outgassing from the ocean, while changes in the cross-equatorial gradient during large northern temperature changes appear as the driving mechanism for the SHW shifts. Together with coeval shifts of the South Pacific westerlies, our results show that most of the Southern Hemisphere experienced simultaneous atmospheric circulation changes during the latter part of the last glacial. Finally we can conclude that multiproxy lake records from oceanic islands have the potential to record atmospheric variability coupled to large-scale climate shifts over vast oceanic areas..
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| 7. |
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| 8. |
- Björck, Svante, et al.
(författare)
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Multi-proxy analyses of a peat bog on Isla de los Estados, easternmost Tierra del Fuego: a unique record of the variable Southern Hemisphere Westerlies since the last deglaciation
- 2012
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 42, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- We have analyzed an almost 14,000 year old peat sequence on the island of Isla de los Estados (55 degrees S. 64 degrees W), east of Tierra del Fuego, in the core of the Southern Hemisphere Westerlies. A multitude of methods have been used: high resolution C-14 dating; detailed lithologic descriptions including humification degree; loss on ignition; magnetic susceptibility; bulk density; pollen and spore analysis and determination of Aeolian sand influx. By combining proxies for wind and precipitation we have been able to reconstruct how the westerlies have varied over time in the Atlantic sector of the Southern Ocean. It shows that this westerly wind belt was most intense at the onset of the record, 13,600-13,200 cal BP, coinciding with the mid to late part of the Antarctic Cold Reversal, followed by a gradual decline. At 12,200 cal BP the westerlies seem to have shifted to a position south of Tierra del Fuego and this phase, the calmest and driest period on the island throughout the sequence, ended at 10,000 cal BP when the westerlies moved equatorward again. Since then the westerlies have been present but with a variable impact on the 55 degrees S latitude of the Atlantic. Mostly conditions have been fairly similar to today, but occasionally with a wider or narrower and/or weaker or stronger wind belt. At 7200 cal BP wind intensity began to increase and between 4500 and 3500 cal BP these southern latitudes experienced a distinct wind and precipitation maximum, both in terms of perseverance and intensity. Our results show a both wide and strong wind belt, with possible niveo-aeolian activity in Tierra del Fuego in winter, and possibly creating milder summers around the Antarctic Peninsula. In the later part of the Holocene, expansion contraction phases of the wind belt, especially in winter, seem to have been a common phenomenon. (C) 2012 Elsevier Ltd. All rights reserved.
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| 9. |
- Brink, Mikael, et al.
(författare)
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Anti-citrullinated protein antibody specificities and pulmonary fibrosis in relation to genetic loci in early rheumatoid arthritis
- 2022
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Ingår i: Rheumatology. - : Oxford University Press. - 1462-0324 .- 1462-0332. ; 61:12, s. 4985-4990
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Tidskriftsartikel (refereegranskat)abstract
- Objectives Pulmonary manifestations in RA are common comorbidities, but the underlying mechanisms are largely unknown. The added value of a multiplex of ACPA and genetic risk markers was evaluated for the development of pulmonary fibrosis (PF) in an inception cohort. Methods A total of 1184 patients with early RA were consecutively included and followed prospectively from the index date until death or 31 December 2016. The presence of 21 ACPA fine specificities was analysed using a custom-made microarray chip (Thermo Fisher Scientific, Uppsala, Sweden). Three SNPs, previously found related to PF were evaluated, rs2609255 (FAM13A), rs111521887 (TOLLIP) and rs35705950 (MUC5B). ACPA and genetic data were available for 841 RA patients, of whom 50 developed radiologically defined PF. Results In unadjusted analyses, 11 ACPA specificities were associated with PF development. In multiple variable analyses, six ACPA specificities were associated with increased risk of PF: vimentin (Vim)60-75, fibrinogen (Fib)beta 62-78 (72), Fib alpha 621-635, Bla26, collagen (C)II359-369 and F4-CIT-R (P < 0.01 to P < 0.05). The number of ACPA specificities was also related to PF development (P < 0.05 crude and adjusted models). In multiple variable models respectively adjusted for each of the SNPs, the number of ACPA specificities (P < 0.05 in all models), anti-Vim60-75 (P < 0.05, in all models), anti-Fib beta 62-78 (72) (P < 0.001 to P < 0.05), anti-CII359-369 (P < 0.05 in all models) and anti-F4-CIT-R AQ4 (P < 0.01 to P < 0.05), anti-Fib alpha 621-635 (P < 0.05 in one) and anti-Bla26 (P < 0.05 in two) were significantly associated with PF development. Conclusion The development of PF in an inception cohort of RA patients was associated with both presence of certain ACPA and the number of ACPA specificities and risk genes.
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| 10. |
- Charrieau, Laurie M., et al.
(författare)
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Decalcification and survival of benthic foraminifera under the combined impacts of varying pH and salinity
- 2018
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Ingår i: Marine Environmental Research. - : Elsevier BV. - 0141-1136. ; 138, s. 36-45
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Tidskriftsartikel (refereegranskat)abstract
- Coastal areas display natural large environmental variability such as frequent changes in salinity, pH, and carbonate chemistry. Anthropogenic impacts – especially ocean acidification – increase this variability, which may affect the living conditions of coastal species, particularly, calcifiers. We performed culture experiments on living benthic foraminifera to study the combined effects of lowered pH and salinity on the calcification abilities and survival of the coastal, calcitic species Ammonia sp. and Elphidium crispum. We found that in open ocean conditions (salinity ∼35) and lower pH than usual values for these species, the specimens displayed resistance to shell (test) dissolution for a longer time than in brackish conditions (salinity ∼5 to 20). However, the response was species specific as Ammonia sp. specimens survived longer than E. crispum specimens when placed in the same conditions of salinity and pH. Living, decalcified juveniles of Ammonia sp. were observed and we show that desalination is one cause for the decalcification. Finally, we highlight the ability of foraminifera to survive under Ωcalc < 1, and that high salinity and [Ca2+] as building blocks are crucial for the foraminiferal calcification process.
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| 11. |
- Charrieau, Laurie M., et al.
(författare)
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The effects of multiple stressors on the distribution of coastal benthic foraminifera: A case study from the Skagerrak-Baltic Sea region
- 2018
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Ingår i: Marine Micropaleontology. - : Elsevier BV. - 0377-8398. ; 139, s. 42-56
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Tidskriftsartikel (refereegranskat)abstract
- Coastal ecosystems are subjected to both large natural variability and increasing anthropogenic impact on environmental parameters such as changes in salinity, temperature, and pH. This study documents the distribution of living benthic foraminifera under the influence of multiple environmental stressors in the Skagerrak-Baltic Sea region. Sediment core tops were studied at five sites along a transect from the Skagerrak to the Baltic Sea, with strong environmental gradients, especially in terms of salinity, pH, calcium carbonate saturation and dissolved oxygen concentration in the bottom water and pore water. We found that living foraminiferal densities and species richness were higher at the Skagerrak station, where the general living conditions were relatively beneficial for Foraminifera, with higher salinity and Ωcalc in the water column and higher pH and oxygen concentration in the bottom and pore water. The most common species reported at each station reflect the differences in the environmental conditions between the stations. The dominant species were Cassidulina laevigata and Hyalinea balthica in the Skagerrak, Stainforthia fusiformis, Nonionella aff. stella and Nonionoides turgida in the Kattegat and N. aff. stella and Nonionellina labradorica in the Öresund. The most adverse conditions, such as low salinity, low Ωcalc, low dissolved oxygen concentrations and low pH, were noted at the Baltic Sea stations, where the calcareous tests of the dominant living taxa Ammonia spp. and Elphidium spp. were partially to completely dissolved, probably due to a combination of different stressors affecting the required energy for biomineralization. Even though Foraminifera are able to live in extremely varying environmental conditions, the present results suggest that the benthic coastal ecosystems in the studied region, which are apparently affected by an increase in the range of environmental variability, will probably be even more influenced by a future increase in anthropogenic impacts, including coastal ocean acidification and deoxygenation.
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| 12. |
- Charrieau, Laurie, et al.
(författare)
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Rapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entrance
- 2019
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189 .- 1726-4170. ; 16, s. 3835-3852
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Tidskriftsartikel (refereegranskat)abstract
- The Öresund (the Sound), which is a part of the Danish straits, is linking the marine North Sea and the brackish Baltic Sea. It is a transition zone where ecosystems are subjected to large gradients in terms of salinity, temperature, carbonate chemistry, and dissolved oxygen concentration. In addition to the highly variable environmental conditions, the area is responding to anthropogenic disturbances in e.g. nutrient loading, temperature, and pH. We have reconstructed environmental changes in the Öresund during the last c. 200 years, and especially dissolved oxygen concentration, salinity, organic matter content, and pollution levels, using benthic foraminifera and sediment geochemistry. Five zones with characteristic foraminiferal assemblages were identified, each reflecting the environmental conditions for respective period. The largest changes occurred ~ 1950, when the foraminiferal assemblage shifted from a low diversity fauna, dominated by the species Stainforthia fusiformis to higher diversity and abundance, and dominance of the Elphidium group. Concurrently, the grain-size distribution shifted from clayey – to more sandy sediment. To explore the causes for the environmental changes, we used time-series of reconstructed wind conditions coupled with large-scale climate variations as recorded by the NAO index, as well as the ECOSMO II model of currents in the Öresund area. The results indicate increased changes in the water circulation towards stronger currents in the area since the 1950's. The foraminiferal fauna responded quickly (< 10 years) to the environmental changes. Notably, when the wind conditions, and thereby the current system, returned in the 1980's to the previous pattern, the foraminiferal species assemblage did not rebound, but the foraminiferal faunas rather displayed a new equilibrium state.
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| 13. |
- Chen, Peng, et al.
(författare)
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Relationship between precipitation and Be-10 and impacts on soil dynamics
- 2020
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Ingår i: Catena (Cremlingen. Print). - : Elsevier BV. - 0341-8162 .- 1872-6887. ; 195
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Tidskriftsartikel (refereegranskat)abstract
- Meteoric beryllium-10 (Be-10) is commonly used as a proxy of landscape dynamics (erosion and sedimentation rates) and soil development. Soil represents the first-stage reservoir of meteoric Be-10, and variability in the concentration of the isotope in soils may be affected by soil properties and atmospheric deposition. Although many investigations have targeted this issue, there are still problems in estimating the atmospheric input of the isotope in different soil environments. Here, we used Be-10 data measured in soils distributed across China to explore the potential influence of meteorological and pedological conditions on the isotope concentration and related applications. In addition, to determine the mechanisms controlling Be-10 concentrations in topsoil on a regional scale, the soil samples were sub-divided into 18 different catchments according to fluvial systems. The results indicated that there were significant negative correlations between precipitation and the soil Be-10 concentration in high-precipitation regions (> 1200 mm.y(-1)) and significant positive correlations for soils in low precipitation regions (< 1200 mm.y(-1)). The data also revealed that precipitation is the most important variable controlling the Be-10 concentration in soils of China when compared with the effects of soil properties such as grain size, mineralogy, pH, and cation exchange capacity. Land use and soil erosion may have limited impacts on the distribution of Be-10 in soils.
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| 14. |
- Eckdahl, Johan A., et al.
(författare)
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Mineral soils are an important intermediate storage pool of black carbon in fennoscandian boreal forests
- 2022
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Ingår i: Global Biogeochemical Cycles. - : John Wiley & Sons. - 0886-6236 .- 1944-9224. ; 36:11
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Tidskriftsartikel (refereegranskat)abstract
- Approximately 40% of earth's carbon (C) stored in land vegetation and soil is within the boreal region. This large C pool is subjected to substantial removals and transformations during periodic wildfire. Fire-altered C, commonly known as pyrogenic carbon (PyC), plays a significant role in forest ecosystem functioning and composes a considerable fraction of C transport to limnic and oceanic sediments. While PyC stores are beginning to be quantified globally, knowledge is lacking regarding the drivers of their production and transport across ecosystems. This study used the chemo-thermal oxidation at 375°C (CTO-375) method to isolate a particularly refractory subset of PyC compounds, here called black carbon (BC), finding an average increase of 11.6 g BC m−2 at 1 year postfire in 50 separate wildfires occurring in Sweden during 2018. These increases could not be linked to proposed drivers, however BC storage in 50 additional nearby unburnt soils related strongly to soil mass while its proportion of the larger C pool related negatively to soil C:N. Fire approximately doubled BC stocks in the mineral layer but had no significant effect on BC in the organic layer where it was likely produced. Suppressed decomposition rates and low heating during fire in mineral subsoil relative to upper layers suggests potential removals of the doubled mineral layer BC are more likely transported out of the soil system than degraded in situ. Therefore, mineral soils are suggested to be an important storage pool for BC that can buffer short-term (production in fire) and long-term (cross-ecosystem transport) BC cycling.
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| 15. |
- Gedeborg, Rolf, et al.
(författare)
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Federated analyses of multiple data sources in drug safety studies
- 2023
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Ingår i: Pharmacoepidemiology and Drug Safety. - : John Wiley & Sons. - 1053-8569 .- 1099-1557. ; 32:3, s. 279-286
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Forskningsöversikt (refereegranskat)abstract
- PurposeStudies of rare side effects of new drugs with limited exposure may require pooling of multiple data sources. Federated Analyses (FA) allow real-time, interactive, centralized statistical processing of individual-level data from different data sets without transfer of sensitive personal data.MethodsWe review IT-architecture, legal considerations, and statistical methods in FA, based on a Swedish Medical Products Agency methodological development project.ResultsIn a review of all post-authorisation safety studies assessed by the EMA during 2019, 74% (20/27 studies) reported issues with lack of precision in spite of mean study periods of 9.3 years. FA could potentially improve precision in such studies. Depending on the statistical model, the federated approach can generate identical results to a standard analysis. FA may be particularly attractive for repeated collaborative projects where data is regularly updated. There are also important limitations. Detailed agreements between involved parties are strongly recommended to anticipate potential issues and conflicts, document a shared understanding of the project, and fully comply with legal obligations regarding ethics and data protection. FA do not remove the data harmonisation step, which remains essential and often cumbersome. Reliable support for technical integration with the local server architecture and security solutions is required. Common statistical methods are available, but adaptations may be required.ConclusionsFederated Analyses require competent and active involvement of all collaborating parties but have the potential to facilitate collaboration across institutional and national borders and improve the precision of postmarketing drug safety studies.
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| 16. |
- Herlevi, Heidi, et al.
(författare)
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Environmental abundances of the non-native round goby Neogobius melanostomus influence feeding of native fish predators
- 2023
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Ingår i: Journal of Fish Biology. - : Wiley-Blackwell. - 0022-1112 .- 1095-8649. ; 102:6, s. 1340-1357
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Tidskriftsartikel (refereegranskat)abstract
- The authors assessed the importance of the round goby Neogobius melanostomus as prey for three native predatory fish species, Atlantic cod Gadus morhua, European perch Perca fluviatilis and northern pike Esox lucius, in a northern and southern area of the Baltic Proper, using a combination of visual analysis and DNA metabarcoding of predator stomach contents. To explore the influence of environmental abundances of N. melanostomus on predation, they related the occurrence of N. melanostomus in predator diets to its abundance in survey fishing. Gadus morhua and E. lucius in the southern area showed the highest tendency to feed on N. melanostomus when it was abundant, as N. melanostomus occurred in up to 100% of stomachs and constituted up to 88% of the total diet volume proportion. The diet contribution of N. melanostomus was associated with N. melanostomus abundances for G. morhua and E. lucius, and when N. melanostomus was abundant, these predators exhibited lower prey richness and a higher degree of piscivory. G. morhua and P. fluviatilis also fed less on crustacean prey when N. melanostomus was abundant. The high importance of N. melanostomus in diets of native fish predators may modify indirect interactions between N. melanostomus and native prey species in invaded coastal communities.
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| 17. |
- Holmgren, Sofia, et al.
(författare)
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Holocene environmental changes on Nightingale Island, South Atlantic, based on diatom floristic changes in an infilled pond
- 2013
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 378, s. 45-51
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Tidskriftsartikel (refereegranskat)abstract
- A Holocene diatom stratigraphy of 2nd Pond, a small, filled pond on Nightingale Island (37 degrees 25 S, 12 degrees 29 W) was analyzed and interpreted to infer paleolimnological changes on Tristan da Cunha, South Atlantic. The diatom assemblage of 2nd Pond has the character of an acidic, oligotrophic wetland and the diatom record suggests that 2nd Pond most likely has been a bog/wetland throughout most of the Holocene. The-flora is largely dominated by Pinnularia viridis, a species typically found in peat bogs. The flora also includes benthic and epiphytic Gomphonema sp, Achnanthes saxonica, Frustulia cf. rhomboides, Staurosira venter as well as Pinnularia cf. divergens var. decrescens and Eunotia paludosa var. paludosa. Peaks of aerophytic diatom (i.e. mostly Diadesmis spp. and Luticola spp.) abundances and concentrations correspond to increased magnetic susceptibility and slightly higher C/N ratios and are interpreted to be the result of increased catchment erosion due to precipitation and following increased in-wash of terrestrial diatoms. The diatom record suggests dry conditions in the early Holocene, followed by recurrent periods of increased precipitation in the region at 8600-5600 cal a BP and at 2200-1700 cal a BP. The main causes for these hydrological changes are probably changes in intensity and/or position of the Southern hemisphere west wind belt. (C) 2013 Elsevier B.V. All rights reserved.
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| 18. |
- Holmgren, Sofia, et al.
(författare)
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Late Holocene environmental history on Tristan da Cunha, South Atlantic, based on diatom floristic changes and geochemistry in sediments of a volcanic crater lake
- 2012
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Ingår i: Journal of Paleolimnology. - : Springer Science and Business Media LLC. - 0921-2728 .- 1573-0417. ; 47:2, s. 221-232
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Tidskriftsartikel (refereegranskat)abstract
- A late Holocene diatom stratigraphy of Bottom Pond (37050S, 12 70W) was studied and interpreted to infer paleolimnological and climate changes on Tristan da Cunha, South Atlantic. The diatom flora of Bottom Pond is dominated by meroplanktonic Aulacoseira alpigena and A. distans and a benthic/epiphytic flora including Achnanthes spp., Naviculadicta spp., Eunotia taxa and Frustulia rhomboides. The flora also includes an important terrestrial and aerophytic component, consisting of several Diadesmis spp., Navicula lapidosa, Nitzschia terrestris and some Pinnularia spp., at times dominating the flora. Peaks of high terrestrial diatom abundances and low abundances and concentrations of Aulacoseira spp., correspond to periods of increased magnetic susceptibility and are interpreted to be the result of increased catchment erosion and/or precipitation leading to enhanced in-wash of species living in the soils around the lake. The diatom record of Bottom Pond most likely registers both local responses to increased erosion in the catchment as well as climatic change of a more regional character. Comparisons with the geochemical record in 2nd Pond on Nightingale Island show a correspondence between the two data sets at 2,000–1,750 cal yrs BP, most likely evidence of increased precipitation in the Tristan da Cunha region. The Tristan da Cunha archipelago is situated at the northern limit of the Southern hemisphere west wind belt and stronger and/ or a northward shift of the westerlies, are probably the main causes of the precipitation changes.
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| 19. |
- Hygge, Staffan, 1944-, et al.
(författare)
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Acoustical conditions in the classroom I : Speech intelligibility and recall of spoken material heard at different signal-to-noise ratios.
- 2013
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Ingår i: 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life. ; , s. 4957-4964
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Konferensbidrag (refereegranskat)abstract
- This study explored speech intelligibility and free recall of word lists heard under different signal-to-noise (S/N) ratios. Pre-experimental measures of working memory capacity (WMC) were taken to explore individual susceptibility to the disruptive effects of noise. The thirty-five participants first completed a WMC-operation span task in quiet and later listened to spoken word lists containing 11 one-syllable phonetically balanced words presented at four different S/N ratios (+12, +9, +6, and +3). Participants repeated (shadowed) each word aloud immediately after its presentation and performed a free recall task of the words after the end of the list. The speech intelligibility function decreased linearly with increasing S/N levels for both the high-WMC and low-WMC groups. Recall and memory of the words decreased with increasing S/N levels only for the low-WMC group. Recall and memory for the high-WMC individuals was not affected by increased S/N levels. Our results suggest that impoverished acoustical conditions impair speech intelligibility and memory, but also that a high WMC may counteract some of the negative effects of speech noise.
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| 20. |
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| 21. |
- Jaakkola, Erica, et al.
(författare)
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Spruce bark beetles (Ips typographus) cause up to 700 times higher bark BVOC emission rates compared to healthy Norway spruce (Picea abies)
- 2023
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 20:4, s. 803-826
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Tidskriftsartikel (refereegranskat)abstract
- Biogenic volatile organic compound (BVOC) emissions from trees subjected to biotic stress are higher compared to healthy trees, and they may also have a different compound composition. This in turn affects atmospheric chemistry and can lead to either positive or negative feedback to the climate. Climate change favors the abundance of the European spruce bark beetle (Ips typographus) which attacks the bark of Norway spruce (Picea abies) trees, causing induced BVOC emissions from the trees as a response to the insect stress. Here, results are reported from a study analyzing the difference in emission rates between healthy and bark-beetle-infested Norway spruce trees, changes in emission rates over time since the infestation started, and differences in emission rates from bark-beetle-drilled entry and exit holes.Bark chamber measurements on both healthy and infested trees were performed during the summer of 2019 at Hyltemossa and Norunda research stations in Sweden. The measurements showed that induced BVOC emissions following the bark beetle infestation were dominated by entry hole emissions in the early growing season and exit hole emissions in the later season. The results showed a significant difference in emission rates between healthy and infested trees during both seasons. The seasonal average standardized BVOC emission rate of healthy trees was 32 ± 52 µg m−2 h−1 (mean ± standard deviation), while the average standardized BVOC emission rates of infested trees were 6700 ± 6900 and 2000 ± 1300 µg m−2 h−1 during the early and late season respectively. BVOC emission rates were highest at the start of the infestation and decreased exponentially with time, showing induced emission rates for up to 1 year after which the emission rates were similar to those from healthy bark. Constitutive needle emission rates from healthy trees were found to be 11 times higher than bark emissions from healthy trees. However, when Norway spruce trees were infested, the bark emission rates were instead 6 to 20 times higher than the needle emissions, causing substantial increases in the total tree BVOC emission rate. This could lead to high impacts on atmospheric processes, specifically the formation of secondary organic aerosols, which have a higher yield from some monoterpene compounds, which increased from infested trees.
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| 22. |
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| 23. |
- Lindvall, Hanna, et al.
(författare)
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A Holocene peat record in the central South Atlantic: an archive of precipitation changes
- 2011
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Ingår i: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 133:3-4, s. 195-206
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Tidskriftsartikel (refereegranskat)abstract
- Peat deposits from the littoral part of the wetland 2nd Pond on Nightingale Island in the central South Atlantic have been analysed to investigate the Holocene climate development on the island and to test a hypothesis about regionally persistent humidity variations. A variety of proxies were analysed - total carbon and nitrogen, biogenic silica, diatoms, amount of organic matter, macrofossils and magnetic susceptibility - and together with the lithology they are interpreted as a record reflecting changes in humidity/precipitation. Early Holocene (10,000-8500 cal. BP) was possibly significantly drier than today, probably caused by a southerly displacement of the Southern Hemisphere Westerlies (SHW) during the Antarctic climate optimum. From 8500 cal. BP and onwards, the climate became generally more humid and surface run-off increased due to higher precipitation, possibly as an effect of increased influence from the SHW as it moved north. During this generally humid period, our data disclose a distinct pattern of recurrent centennial- to millennial-long events of increased precipitation and the results corroborate the only other study in the region with a similar humidity record. The events might represent large-scale climate oscillations in the Southern Hemisphere, such as latitudinal shifts of the SHW, but may also be related to changes in sea surface temperatures.
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| 24. |
- Ljung, Karl, et al.
(författare)
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A lacustrine record of the Pleistocene-Holocene boundary in southernmost Greenland
- 2004
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Ingår i: GFF. - 2000-0863. ; 126, s. 273-278
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Tidskriftsartikel (refereegranskat)abstract
- A sediment core from a lake in the Kap Farvel area on South Greenland was analysed with respect to pollen and microfossil content, loss-on-ignition, magnetic susceptibility and radiocarbon age. The aim was to reconstruct the limnic arid terrestrial changes taking place at the Pleistocene-Holocene boundary. Organic sedimentation started between 12 200 and 12 800 cal yr B.P. Break-up of sea-ice around Kap Farvel, as indicated by the appearance of marine dinoflagellates (Hystrix), took place some hundred years after the transition into Preboreal. The pollen analysis indicates that the area was barren during the Younger Dryas and that the Holocene vegetation establishment was slightly delayed.
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| 25. |
- Ljung, Karl, et al.
(författare)
-
A pollen record of the last 450 years from a lowland peat bog on Tristan da Cunha, South Atlantic, implying early anthropogenic influence
- 2011
-
Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 26:7, s. 688-693
-
Tidskriftsartikel (refereegranskat)abstract
- A pollen diagram from a small peat bog on the island of Tristan da Cunha in the central South Atlantic (37 degrees 05'S, 12 degrees 17'W) is presented. The pollen diagram contains data from both introduced and native plant taxa. The earliest pollen grains from introduced Plantago lanceolata are dated to around AD 1570, and probably represent unintentional introductions of weeds by the earliest Portuguese explorers visiting the islands. After AD 1600, a greater abundance of pollen from introduced plants and declining tree pollen values indicate opening of the lowland vegetation and more intense land use, probably attributable to the effect of seasonal seal and whale hunters. After AD 1800, evidence of increased erosion and more intense land use are inferred from the pollen diagram, reflecting permanent settlement. Copyright (C) 2011 John Wiley & Sons, Ltd.
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| 26. |
- Ljung, Karl
(författare)
-
Holocene climate and environmental dynamics on the Tristan da Cunha island group, South Atlantic
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It has been shown that the present interglacial has been climatically dynamic with both rapid and severe climatic fluctuations. The spatial and temporal differences of these changes are however not fully resolved. The aim of this thesis is to present a detail high resolution record of past climate changes from the central South Atlantic. Peat and lacustrine sediment sequences were retrieved from the Tristan da Cunha island group in the central South Atlantic. These sequences were analysed with a multiproxy approach including pollen analysis, measurements of total carbon, nitrogen and sulphur, mineral magnetic measurements and detailed radiocarbon dating. In addition tree-ring widths from two trees are presented. The oldest sediment sequence extends back to 10 700 cal. yrs BP and the analyses show that the climate varied considerably during this time. Peat was accumulating from 10 700 cal. yrs BP to around 8600 cal. yrs BP when it was replaced by gyttja deposition. This change implies a substantial increase in effective humidity probably by precipitation. The cause of this change was probably a northward shift of the Southern Hemisphere westerlies, related to a large scale reorganization of the circulation system. This was probably caused by cooling of the Southern Ocean and the Atlantic sector of Antarctica, which caused expansion of sea ice and northward movement of the westerlies. Several periods with increased catchment erosion and further increased precipitation follow this transition. These periods were probably caused by increased air humidity as a response to higher sea surface temperatures. In the North Atlantic conditions were cool with increased deposition of ice rafted debris. Probably, these changes was caused by weaker meridional overturning circulation and less northward transport of warm shallow water in the Atlantic, which caused higher sea surface temperatures in the central South Atlantic and cooler conditions in the North Atlantic. One period of increased precipitation and sea surface temperature is contemporaneous with the 8.2 ka event in the Greenland ice cores and is probably the South Atlantic response to the weaker circulation induced by freshwater forcing in the North Atlantic. Tristan da Cunha was discovered in 1506 AD by Portuguese explorers and their arrival is clearly seen in the pollen diagram. The introduced species Plantago lanceolata appears around 1550 AD. The seal hunting and establishment of the permanent settlement caused introduction of more species and clearing of the lowland forest.
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| 27. |
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| 28. |
- Ljung, Karin, et al.
(författare)
-
Human Fetal Cardiac Mesenchymal Stromal Cells Differentiate In Vivo into Endothelial Cells and Contribute to Vasculogenesis in Immunocompetent Mice
- 2019
-
Ingår i: Stem Cells and Development. - : MARY ANN LIEBERT, INC. - 1547-3287 .- 1557-8534. ; 28:5, s. 310-318
-
Tidskriftsartikel (refereegranskat)abstract
- Mesenchymal stromal cells (MSCs) have shown great potential as a treatment for systemic inflammatory diseases, but their local regenerative properties are highly tissue- and site specific. Previous studies have demonstrated that adult human MSCs respond to inflammatory cytokines through the release of paracrine factors that stimulate angiogenesis, but they do not themselves differentiate into vascular structures in vivo. In this study, we used human fetal cardiac MSCs (hfcMSCs) harvested during the first trimester of heart development and injected them into the subcutaneous tissue of normal immunocompetent mice treated with short-term costimulation blockade for tolerance induction. When hfcMSCs were transplanted subcutaneously together with Matrigel matrix, they contributed to vasculogenesis through differentiation into endothelial cells and generation of the basal membrane protein Laminin 4. These characteristics of hfcMSCs are similar to the mesodermal progenitors giving rise to the developing heart and they may be useful for treatment of ischemic injuries.
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| 29. |
- Ljung, Karl, et al.
(författare)
-
Late Holocene multi-proxy records of environmental change on the South Atlantic island Tristan da Cunha
- 2006
-
Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 241:3-4, s. 539-560
-
Tidskriftsartikel (refereegranskat)abstract
- Sediment stratigraphies from three sites, one lake, one overgrown lake, and an exposed section, on the island Tristan da Cunha in the temperate South Atlantic were analysed by means of pollen analysis, total carbon, nitrogen and sulphur content determination, magnetic susceptibility measurements and detailed radiocarbon dating. The aim of these studies was to reconstruct the late Holocene vegetation and climatic variations. The oldest sediment sequence extends back to 2300 cal. years BP. The vegetation was relatively stable up to the arrival of humans in the 17th century. The appearance of the introduced taxon Rumex acetosa/acetosella at c. 300 cal. years BP and a subsequent decline in forest cover on the lowland plain provide evidence of substantial human influence on the vegetation well before the establishment of the first permanent settlement in the 19th century. Before the first anthropogenic influence centennial-scale fluctuations in the proxy records are interpreted as reflections of local hydrological changes, probably caused by variations in precipitation. As inferred mainly from changing proportions of pollen derived from telmatic and terrestrial taxa and corresponding changes in the deposition of mineral matter by fluvial erosion, lake levels were low between c. 1450 and 1050 cal. years BP, and high between c. 1050 and 300 cal. years BP. These variations coincide with known climatic changes in Southern Africa and in the North Atlantic, suggesting that the inferred hydrological changes on Tristan da Cunha were related to large-scale variations in the general oceanic and atmospheric circulation in the Atlantic region.
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| 30. |
- Ljung, Karl, et al.
(författare)
-
Naturvetarnas arbetsliv - resultat, utvärdering och slutsatser från alumnenkät 2019
- 2021
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- För att öka kunskapen om var studenter med examen i naturvetenskap frånLunds universitet får jobb och hur användbara deras utbildningar är i arbetslivethar vi genomfört en alumnenkät. Alumnenkäten har fokus på interaktionenmellan utbildning och arbetsliv och rör arbete i nära tid efter studierna. Enkätenskickades ut till kandidatalumnerna som tagit ut examen mellan september2017 och september 2018, det vill säga ett till två år efter examen, och tillmasteralumner som tagit ut examen mellan september 2016 och september2017, det vill säga två till tre år efter examen.Resultaten ger information om alumnernas sysselsättning och beskrivernaturvetarnas arbetsmarknad. Det går att identifiera tre övergripande verksamhetsområdensom beskriver naturvetarnas arbetsmarknad; ”Natur, miljöoch klimat”, ”Life science” och ”It, data och teknik”. Från undersökningengår att utläsa skillnader på arbetsmarknaden för kandidatalumner och förmasteralumner. Resultaten visar också könsfördelning och lönebild för olikadelar av naturvetarnas arbetsmarknad. Betydelsen av generella kompetenserframkommer tydligt i resultaten.Undersökningens fokus ligger på användbarheten av utbildningarna i arbetslivetoch kopplingen mellan utbildning och arbetsliv. Vi hoppas att resultatenfrån enkäten leder till större kunskap om övergången från studier till arbete,och att utbildningarnas arbete med att förbereda studenterna för arbetsmarknadenutvecklas.
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| 31. |
- Ljung, Karl, et al.
(författare)
-
Organic Carbon Burial in Constructed Ponds in Southern Sweden
- 2023
-
Ingår i: Earth Science, Systems and Society. - : Frontiers Media SA. - 2634-730X. ; 3, s. 1-13
-
Tidskriftsartikel (refereegranskat)abstract
- Small ponds constructed for nutrient retention, biodiversity conservation or recreation also store large amounts of carbon. The potential role of small ponds for carbon storage and greenhouse gas emissions have been highlighted both in the scientific literature and in management plans. The role of small ponds in the global carbon budget is likely significant, but the potential has not been fully explored. Here we present measurements of yearly sedimentary carbon accumulation and carbon stocks in six small, constructed and restored ponds in southern Sweden. The ponds were constructed or restored during the last 20 years primarily for nutrient retention. The sediment cores span the time from the construction of the ponds until today. The ponds had high carbon accumulation, with mean total carbon stocks in the top 6 cm of sediment of 836 g C m−2 and a yearly mean C accumulation rate of 152 g C m−2 yr−1. The total amount of restored wetlands within the restoration program studied here has a total area of 480 ha, and upscaling the carbon stocks to the whole area of restored ponds and wetlands gave a total carbon stock of 4.013 × 106 kg C in the top 6 cm of the sediments. If considering the potential increase of CO2 and CH4 from the ponds it is likely that the constructed ponds studied here are net carbon sources. We compared our results with published measurements of CO2 and CH4 emissions from small ponds in Sweden. This shows that the CO2 equivalent emissions could be between 1.8 and 37.5 times higher than the sedimentary carbon accumulation. Our data indicate that small constructed ponds are potential net carbon sources. Therefore, we suggest that using small, constructed, or restored ponds as carbon mitigation strategy must be done with caution, and the potential for increased methane emissions must be considered.
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| 32. |
- Ljung, Karl, et al.
(författare)
-
Recent Increased Loading of Carbonaceous Pollution from Biomass Burning in the Baltic Sea
- 2022
-
Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7, s. 35102-35108
-
Tidskriftsartikel (refereegranskat)abstract
- Black carbon (BC), spheroidal carbonaceous particles (SCP), and polycyclic aromatic hydrocarbons (PAH) are carbonaceous pollutants affecting the climate, environment, and human health. International regulations limit their emissions, and the present emissions are followed by monitoring programs. However, the monitoring programs have limited spatio-temporal coverage and only span the last decades. We can extend the knowledge of historical emission rates by measuring pollution levels in radiometrically dated marine and lacustrine sediment sequences. Here we present measurements of BC, SCP, and PAH from a sediment sequence sampled in the Öresund strait, between Denmark and Sweden and dated back to CE 1850. Our data show a massive increase in the burial rates of all measured pollutants starting in the 1940s. The pollution deposition peaked in the 1970-1980s and declined through the 1990s. However, the declining trend was reversed in the 2000s. Source appointment of PAHs shows a relatively higher contribution of emissions from wood-burning since CE 2000. This coincides with a change towards the increased use of biomass for both municipal and regional energy production in Scandinavia. Our results demonstrate that changes in energy production have caused changes in the delivery of carbonaceous pollution to marine environments. The increase in particle emissions from wood burning is potentially posing a future environmental and health risk.
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| 33. |
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| 34. |
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| 35. |
- Ljung, Karl, et al.
(författare)
-
The last termination in the central South Atlantic
- 2015
-
Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 123, s. 193-214
-
Tidskriftsartikel (refereegranskat)abstract
- Lake sediments and peat deposits from two basins on Nightingale Island (37 degrees S), in the Tristan da Cunha archipelago, South Atlantic, have been analyzed. The studies were focused on the time period 16.2-10.0 cal ka BP, determined by 36 C-14 dates from the two sequences. A wide variety of proxies were used, including pollen and diatom analyzes, biogenic silica content, C and N analyzes, stable isotopes (C-13 and N-15), elemental concentrations and magnetic susceptibility measurements, to detect environmental changes that can be related to shifts of the circulation belts of the Southern Ocean. In addition, climate model simulations were carried out. We find that the sediments are underlain by a >2 cal ka BP long hiatus, possibly representing a dried-out lake bed. The climate simulations corroborate that the area might have been exposed to arid conditions as a consequence of the Heinrich I event in the north and a southward displacement of the ITCZ. The development on the island after 16.2 cal ka BP is determined by the position of the Subtropical Front (STF) and the Southern Hemisphere Westerlies (SHW). The period 16.2-14.75 cal ka BP was characterized by varying influence from SHW and with STF situated south of Tristan da Cunha, ending with a humidity peak and cooler conditions. The stable conditions 14.7-14.1 cal ka BP with cool and fairly arid conditions imply that STF and SHW were both north of the islands during the first part of the Antarctic Cold Reversal. The most unstable period, 14.1-12.7 cal ka BP, indicates incessant latitudinal shifts of the zonal circulation, perhaps related to climate variability in the Northern Hemisphere and bipolar seesaw mechanisms as the strength of the Atlantic Meridional Overturning Circulation (AMOC) varied. At 12.7 cal ka BP the Holocene warming began with a gradually drier and warmer climate as a result of a dampened AMOC during the Younger Dryas cooling in the north with ITCZ, STF and SHW being displaced southwards. Peak warming seems to have occurred in the earliest part of the Holocene, but this period was also characterized by humidity shifts, possibly an effect of retraction and expansion phases of SHW during AMOC variations in the north. (C) 2015 Elsevier Ltd. All rights reserved.
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| 36. |
- Ljung, Karl, et al.
(författare)
-
Variable Be-10 fluxes in lacustrine sediments from Tristan da Cunha, South Atlantic: a solar record?
- 2007
-
Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 26:7-8, s. 829-835
-
Tidskriftsartikel (refereegranskat)abstract
- A 650-yr-long sediment sequence from a crater lake on Tristan da Cunha, South Atlantic, was analysed for its Be-10 content. Based on C-14 dating, and sedimentary, geochemical, magnetic and palynological records, the period between 900 and 1450 AD appears to have been unusually stable in terms of sedimentation and vegetation and therefore this period was chosen for analysis of the Be-10 content. During this period of highly organic sedimentation and closed vegetation, the pattern of Be-10 flux variations follows the Be-10 fluctuations from the GRIP ice core and estimated C-14 production rates well. However, before and after this stable period, variable sedimentation rates have to be accounted for to obtain results that are comparable to the established Be-10/C-14 records. Our data show not only the possibility of obtaining detailed enough Be-10 flux data from sedimentary sequences to reconstruct past solar forcing but also how sensitive this type of record is to sedimentary and environmental changes. If suitable archives can be found, they have the potential to improve reconstructions of solar activity far back in time. (c) 2007 Elsevier Ltd. All rights reserved.
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| 37. |
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| 38. |
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| 39. |
- Ludvigsson, Jonas F., et al.
(författare)
-
Registers of the Swedish total population and their use in medical research
- 2016
-
Ingår i: European Journal of Epidemiology. - Stockholm : Springer Science and Business Media LLC. - 0393-2990 .- 1573-7284. ; 31:2, s. 125-136
-
Tidskriftsartikel (refereegranskat)abstract
- The primary aim of the Swedish national population registration system is to obtain data that (1) reflect the composition, relationship and identities of the Swedish population and (2) can be used as the basis for correct decisions and measures by government and other regulatory authorities. For this purpose, Sweden has established two population registers: (1) The Population Register, maintained by the Swedish National Tax Agency ("Folkbokforingsregistret"); and (2) The Total Population Register (TPR) maintained by the government agency Statistics Sweden ("Registret over totalbefolkningen"). The registers contain data on life events including birth, death, name change, marital status, family relationships and migration within Sweden as well as to and from other countries. Updates are transmitted daily from the Tax Agency to the TPR. In this paper we describe the two population registers and analyse their strengths and weaknesses. Virtually 100 % of births and deaths, 95 % of immigrations and 91 % of emigrations are reported to the Population Registers within 30 days and with a higher proportion over time. The over-coverage of the TPR, which is primarily due to underreported emigration data, has been estimated at up to 0.5 % of the Swedish population. Through the personal identity number, assigned to all residents staying at least 1 year in Sweden, data from the TPR can be used for medical research purposes, including family design studies since each individual can be linked to his or her parents, siblings and offspring. The TPR also allows for identification of general population controls, participants in cohort studies, as well as calculation of follow-up time.
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| 40. |
- Lundqvist, Jennie Mari, et al.
(författare)
-
A Phenomenographic Analysis Of Students’ Experience Of Geological Time
- 2021
-
Ingår i: Journal of Astronomy & Earth Sciences Education (JAESE). - : Clute Institute. - 2374-6254 .- 2374-6246. ; 8:1, s. 1-26
-
Tidskriftsartikel (refereegranskat)abstract
- Geological time is by many geoscience instructors considered a threshold concept for geoscience students, being acentral concept for how we experience geosceince phenomena that takes place on a spatio-temporal scale rangingfrom micro (e.g. cloud formation) to macro (e.g. plate tectonics). If one wishes to understand geoscience phenomenathat goes beyond human perception, one must move from the concrete toward the abstract—from experiencing aphenomenon with one’s senses toward an experience of the phenomenon that is based on an mind construct; we referto such competency as disciplinary spatio-temporal competency (DSTC). The purpose of this study is to gain anunderstanding of how first-year students in a geoscience program in Sweden experience and represent thephenomenon of geological time, i.e. to capture their DSTC. Analyazing data from three semi-structured groupinterviews using a phenomenographic approach revealed how the students express geological time through theirlanguage, their gestures, and their visualizations. From the result in this study, including four qualitatively differentthemes, or categories of description, it is possible to conclude that the students' way of expressing geological timegive rise to exciting interpretations and we believe that these expressions can provide information also about howstudents experience (and learn about) geological time. We report that through students’ illustrations and discussions,students experience geological time as something more than a static one-dimensional straight line. The data analysisshows that students connect geological time with spatio-temporal aspects from various geosientific phenomena, oneexample of such an dynamic description of geological time is “One simply fills it with more information” indicatingthat the students experience geological time as two-dimensional (space and time).
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| 41. |
- Lygnerud, Kristina, et al.
(författare)
-
Handbook for increased recovery of urban excess heat
- 2022
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this book is to consolidate information from low temperature waste heat recovery demonstration sites. Apart from technical validation, the ReUseHeat project has generated knowledge about the urban waste heat potential in Europe, main stakeholders and different business aspects. Five stakeholder groups are targeted. These are urban waste heat owners, District Heating (DH) companies, policy makers, investors and customers. In the first chapter of the book, the concept of urban waste heat is introduced and the urban waste heat potential in Europe is presented. Thereafter (chapter two), information on business aspects is provided (stakeholders, value chain, risks, contracts and business model characteristics). Chapter three showcases the demonstrator concepts (waste heat recovery from data centre, hospital, metro and awareness creation about urban waste heat recovery) and performance data. Throughout the writing of the handbook, it was identified that it is important to compare the cost of different heating alternatives, to facilitate customer decision making. Therefore, a model was derived to compare costs of heating alternatives. It is presented in chapter four. Urban waste heat recovery is news. It is therefore important that stakeholders are made aware of the possibility to use the locally available heat and to start collaborating in new ways. To ensure as much stakeholder engagement as possible, the writing process of this book encompassed a six-month stakeholder involvement process. The stakeholder input is presented in chapter five. In chapter six, thoughts on the future development of district energy, policy implications and major learnings from the project are presented. This book was written within the ReUseHeat project. The work on the book was initiated after the first out of five years of activity to ensure that the consortium would be engaged in its development and to capture the knowledge generated on an ongoing basis. The final version of the book was ready and placed on the ReUseHeat webpage in September 2022. The project webpage remains in operation until 2024. The book not only exists in digital format. 600 copies were also printed and distributed to relevant stakeholders. All partners of the consortium have contributed to the writing of the book.
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| 42. |
- Möller, Per, et al.
(författare)
-
Deglaciation history and subsequent lake dynamics in the Siljan region, south-central Sweden, based on new LiDAR evidence and sediment records
- 2022
-
Ingår i: Earth Surface Processes and Landforms. - : Wiley. - 0197-9337 .- 1096-9837. ; 47, s. 3515-3545
-
Tidskriftsartikel (refereegranskat)abstract
- The Siljan region hosts Europe´s largest impact structure. The high-relief landscape, with a central granite dome bordered by lake basins, contains an array of glacial and shore-level landforms. We investigated its deglaciation history by mapping and analysing landforms on high resolution LiDAR-based Digital Surface Models coupled with well-dated sediment successions from peat and lake sediment cores. The granite dome and bordering areas are characterized by streamlined terrain and ribbed moraine with a streamlined overprint. These suggest an ice-flow direction from NNW with wet-based thermal conditions prior to deglaciation. During its retreat, the ice sheet was split into thinner plateau ice and thicker basin ice. Sets of low-gradient glaciofluvial erosion channels suggest intense ice-lateral meltwater drainage across gradually ice-freed slopes, while 'down-the-slope' erosion channels and eskers show meltwater drainage from stagnated plateau ice. Thick basin ice receded with a subaqueous margin across the deep Siljan–Orsasjön Basin c. 10,700–10,500 cal. BP. During ice recession the ingression of the Baltic Ancylus Lake led to diachronous formation of highest shoreline marks, from c. 207 m in the south to c. 220 m a.s.l. in the north. Differential uplift resulted in shallowing of the water body, which led to the isolation of the Siljan–Orsasjön Basin from the Baltic Basin at c. 9800 cal. BP. The post-isolation water body – the ‘Ancient Lake Siljan' – was drained through the ancient Åkerö Channel with a water level at 168–169 m a.s.l. during c. 1000 years. A later rerouting of the outlet to the present course was initiated at c. 8800 cal. BP, which led to a lake-level lowering of 6–7 m to today’s level of Lake Siljan (c. 162 m a.s.l.). This study shows the strength of an integrated methodological approach for deciphering the evolution of a complex landscape, combining highly resolved geomorphological analysis with well-dated sediment successions.
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| 43. |
- Möller, Per, et al.
(författare)
-
Deglaciation history and subsequent lake dynamics in the Siljan region, south-central Sweden - LiDAR evidence and sediment records
- 2024
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Siljan region hosts Europe´s largest impact structure. The high-relief landscape, with a central granite dome bordered by lake basins, contains an array of glacial and shore-level landforms. We investigated its deglaciation history by mapping and analysing landforms on high resolution LiDAR-based Digital Surface Models coupled with well-dated sediment successions from peat and lake sediment cores. The granite dome and bordering areas are characterized by streamlined terrain and ribbed moraine with a streamlined overprint. These suggest an ice-flow direction from NNW with wet-based thermal conditions prior to deglaciation. During its retreat, the ice sheet was split into thinner plateau ice and thicker basin ice. Sets of low-gradient glaciofluvial erosion channels suggest intense ice-lateral meltwater drainage across gradually ice-freed slopes, while 'down-the-slope' erosion channels and eskers show meltwater drainage from stagnated plateau ice. Thick basin ice receded with a subaqueous margin across the deep Siljan–Orsasjön Basin c. 10,700–10,500 cal. BP. During ice recession the ingression of the Baltic Ancylus Lake led to diachronous formation of highest shoreline marks, from 207 m in the south to 220 m a.s.l. in the north. Differential uplift resulted in shallowing of the water body, which led to the isolation of the Siljan¬–Orsasjön Basin from the Baltic Basin at c. 9800 cal. BP. The post-isolation water body – the ‘Ancient Lake Siljan' – was drained through the ancient Åkerö Channel with a water level at 168–169 m a.s.l. during c. 1000 years. A later rerouting of the outlet to the present course was initiated at c. 8800 cal. BP, which led to a lake-level lowering of 6–7 m to today’s level of Lake Siljan (162 m a.s.l.). This study shows the strength of an integrated methodological approach for deciphering the evolution of a complex landscape, combining highly resolved geomorphological analysis with well-dated sediment successions.
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| 44. |
- Möller, Per, et al.
(författare)
-
Severnaya Zemlya, Arctic Russia: a nucleation area for Kara Sea ice sheets during the Middle to Late Quaternary
- 2006
-
Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 25:21-22, s. 2894-2936
-
Tidskriftsartikel (refereegranskat)abstract
- Quaternary glacial stratigraphy and relative sea-level changes reveal at least four expansions of the Kara Sea ice sheet over the Severnaya Zemlya Archipelago at 79 degrees N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from raised-beach sequences that occur at altitudes up to 140 m a.s.l. Chronologic control is provided by AMS C-14, electron-spin resonance, green-stimulated luminescence, and aspartic-acid geochronology. Major glaciations followed by deglaciation and marine inundation occurred during MIS 10-9, MIS 8-7, MIS 6-5e and MIS 5d-3. The MIS 6-5e event, associated with the high marine limit, implies ice-sheet thickness of > 2000m only 200km from the deep Arctic Ocean, consistent with published evidence of ice grounding at similar to 1000m water depth in the central Arctic Ocean. Till fabrics and glacial tectonics record repeated expansions of local ice caps exclusively, suggesting wet-based ice cap advance followed by cold-based regional ice-sheet expansion. Local ice caps over highland sites along the perimeter of the shallow Kara Sea, including the Byrranga Mountains, appear to have repeatedly fostered initiation of a large Kara Sea ice sheet, with exception of the Last Glacial Maximum (MIS 2), when Kara Sea ice did not impact Severnaya Zemlya and barely graced northernmost Taymyr Peninsula.
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| 45. |
- Nogué, Sandra, et al.
(författare)
-
The human dimension of biodiversity changes on islands
- 2021
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 372:6541, s. 488-491
-
Tidskriftsartikel (refereegranskat)abstract
- Islands are among the last regions on Earth settled and transformed by human activities, and they provide replicated model systems for analysis of how people affect ecological functions. By analyzing 27 representative fossil pollen sequences encompassing the past 5000 years from islands globally, we quantified the rates of vegetation compositional change before and after human arrival. After human arrival, rates of turnover accelerate by a median factor of 11, with faster rates on islands colonized in the past 1500 years than for those colonized earlier. This global anthropogenic acceleration in turnover suggests that islands are on trajectories of continuing change. Strategies for biodiversity conservation and ecosystem restoration must acknowledge the long duration of human impacts and the degree to which ecological changes today differ from prehuman dynamics.
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| 46. |
- Rohozin, Yevhenii, et al.
(författare)
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Palaeoenvironmental changes in eastern Crimea over the last 7600 years inferred from a multi-proxy study of a sediment archive from Lake Chokrak
- 2024
-
Ingår i: Holocene. - 0959-6836. ; 34:2, s. 175-188
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Tidskriftsartikel (refereegranskat)abstract
- The study presents a multi-proxy archive from hypersaline coastal Lake Chokrak in eastern Crimea, a steppe region which is particularly susceptible to moisture fluctuations. XRF, organic carbon and nitrogen, and palynological analyses are used to reconstruct the evolution of the lake and landscape development around it and to provide information about the driving forces behind those changes, such as climate and human impact. The findings show that the basin was an open marine bay between 7640 and 5500 cal. yr BP. After 5500 cal. yr BP, the low rates of sea-level rise led to gradual infilling of the basin. The prevalence of mesic herb-grass steppe around the site, as well as the expansion of broad-leaved trees in the Crimean mountains, indicate relatively warm and humid climate conditions during the Mid-Holocene. Elemental proxies and marine NPPs point to a transition to lagoonal conditions from 4270 cal. yr BP. The progressive shallowing of the basin was accompanied by the spread of more xeric Artemisia-grass steppe, which suggests a shift to arid conditions. The occurrence of cereal pollen from 3660 cal. yr BP may indicate the first signs of cultivation in the study area. The active build-up of a sand barrier from 3000 cal. yr BP led to a gradual separation of the basin from the sea. By 900 cal. yr BP, the fully-formed sand barrier resulted in a transformation of the lagoon into a hypersaline lake. The closing of the lagoon was accompanied by an expansion of halophytic communities around the site. Human-induced vegetation changes became more pronounced with the development of agrarian and pastoral activities around the site from ca. 750 cal. yr BP.
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| 47. |
- Snowball, Ian, et al.
(författare)
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Radiocarbon wiggle matching of Swedish lake varves reveals asynchronous climate changes around the 8.2 kyr cold event
- 2010
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Ingår i: Boreas. - : Wiley. - 1502-3885 .- 0300-9483. ; 39:4, s. 720-733
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Tidskriftsartikel (refereegranskat)abstract
- A series of nine radiocarbon measurements obtained at increments of 50 years was used to wiggle match varved sediments in Lake Kalksjon (west central Sweden) to the calendar year time scale provided by the tree-ring-derived radiocarbon calibration curve. The anchor point for a series of 400 varves known to span the '8.2 kyr cold event' was derived from a combination of correlation analysis, Monte Carlo statistics and Bayesian age modelling. The GRIP and NorthGRIP ice-cores were matched to the same absolute time scale by comparing Be-10 data and tree-ring Delta C-14. The radiocarbon-based wiggle match, organic carbon measurements, mineral magnetic parameters and XRF data reconstruct a distinct period of enhanced erosion in Kalksjon's catchment between 8066+/-25 and 7920+/-25 cal. yr BP. Prior to human impact, the increased erosion in the boreal environment is assigned to increased winter precipitation in the form of snow, which caused spring meltwater discharge to intensify. Our results suggest that the abrupt onset of increased winter precipitation in west central Sweden started at least 50 years after the onset of the '8.2 kyr cold event' as defined by oxygen isotope data from Greenland. The study highlights the value of synchronized time scales in the reconstruction of abrupt climate changes based on proxy data.
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| 48. |
- Sparrenbom, Charlotte, et al.
(författare)
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Holocene relative sea-level changes in the inner Bredefjord area, southern Greenland
- 2013
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 69, s. 107-124
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present new relative sea-level data from southern Greenland, a key area for understanding the Greenland Ice Sheet (GIS) response to climate change. Within fourteen lakes and marine lagoons from the inner part of Bredefjord (Nordre Sermilik) in southern Greenland, isolations revealed by stratigraphic and palaeoecological analyses are dated and relative sea levels reconstructed. Due to coastal emergence caused by the GIS retreat within the area, the relative sea-level fell rapidly in the early Holocene between at least c. 9600 and c. 7300 cal. yrs BP attaining a rate of 2 cm per year between 9600 and 8000 cal. yrs BP. Spatial variability in relative sea-level changes is show for southern Greenland from a comparison with the Nanortalik and the Qagortoq areas. The regression occurred about 2000 years later in the inner Bredefjord area, compared to the Nanortalik area, and about 1000 years later compared to the Qaqortoq area. This is a consequence of earlier deglaciation in areas located at the outer coast. Between c. 8000 cal. yrs BP and the present day, relative sea level was lower than today. The lowest relative sea level in the Inner Bredefjord area of between -5.4 and -15 m a.h.a.t. (above highest astronomical tide) was reached between 7000 and 1000 cal. yrs BP. The neoglacial readvance together with the collapse of the Laurentide peripheral bulge is probably responsible for the transgression in the Inner Bredefjord area, as has been indicated from the nearby sites Qagortoq and Nanortalik. Our relative sea-level reconstructions showing spatial variability within southern Greenland have implications for Glacial Isostatic Adjustment (GIA) modelling and the understanding of the GIS ice sheet dynamics. The early Holocene regression is consistent with the recession of the southern sector of the GIS from the shelf edge at c. 22 000 cal. yrs BP, reaching inland of the present day outer coast by c. 12 000 cal. yrs BP, and its present margin by c. 10 500 cal. yrs BP. (c) 2013 Elsevier Ltd. All rights reserved.
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| 49. |
- Unkel, Ingmar, et al.
(författare)
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Records of environmental changes during the Holocene from Isla de los Estados (54.4 degrees S), southeastern Tierra del Fuego
- 2010
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 74:3-4, s. 99-113
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Tidskriftsartikel (refereegranskat)abstract
- Southernmost Patagonia, located at the relatively narrow passage between Antarctica and South America, is a highly sensitive region for recording meridional and zonal changes in the pattern of oceanic and atmospheric circulation. The island of Isla de los Estados, situated at 54.5 degrees S, 64 degrees W, east of Argentinean Tierra del Fuego, provides an exceptional possibility, to investigate terrestrial records of atmospheric conditions in an oceanic setting during the last deglaciation and the Holocene. Here we present geochemical and diatom analyses from 10600 to c. 1500 cal BP of one sequence (LGB) with peat, lake sediments and lagoon deposits at the northern coast of the island, and a lake sediment sequence (CAS) 3 km further inland. The data comprise TC, TN, loss on ignition analyses and continuous XRF scanning as well as age-depth modeling based on AMS-C-14 dating on both cores. Diatom analysis of the CAS record complements the geochemical proxies. During the Holocene, our two sites have been impacted by two different forcings: changes in the regional climate regime largely influenced by the varying strength and position of the Southern Hemisphere Westerlies (SHW), while relative sea-level changes affected the deposits of the coastal site. In concert with the onset of the Antarctic thermal optimum, our data suggest fairly warm conditions and the establishment of denser peat and forest vegetation on the island c. 10600 cal BP. Between 8500 and 4500 cal BP geochemistry and diatoms from the CAS record indicate stronger Westerlies at this latitude, which means higher wind speed or higher storm frequency and more precipitation, resulting in more pronounced surface run-off. After 4500 cal BP, the geochemical proxies and large changes in diatom assemblages indicate a decrease in precipitation, weaker winds and possibly cooler conditions, probably as an effect of weaker SHW and/or a latitudinal shift. The depositional environment of CAS changed from gyttja to peat around 1000 cal BP. At LGB, the onset of gyttja sedimentation around 7900 cal BP shows that the former wet land with peat accumulation had become a lake with a fairly rapid sedimentation. The chemical data from LGB imply a gradually increasing marine influence, probably as an effect of both rising sea level and increased impact of storms and maximum high tides. After a marine high-stand during the mid-Holocene, the LGB site returned into a peat bog again around 3400 cal BP. Our data suggest that since then relative sea level first dropped back below present sea level followed by a rise to present day sea level. (C) 2010 Elsevier B.V. All rights reserved.
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| 50. |
- Walentowitz, Anna, et al.
(författare)
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Long-term trajectories of non-native vegetation on islands globally
- 2023
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 26:5, s. 729-741
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Tidskriftsartikel (refereegranskat)abstract
- Human-mediated changes in island vegetation are, among others, largely caused by the introduction and establishment of non-native species. However, data on past changes in non-native plant species abundance that predate historical documentation and censuses are scarce. Islands are among the few places where we can track human arrival in natural systems allowing us to reveal changes in vegetation dynamics with the arrival of non-native species. We matched fossil pollen data with botanical status information (native, non-native), and quantified the timing, trajectories and magnitude of non-native plant vegetational change on 29 islands over the past 5000 years. We recorded a proportional increase in pollen of non-native plant taxa within the last 1000 years. Individual island trajectories are context-dependent and linked to island settlement histories. Our data show that non-native plant introductions have a longer and more dynamic history than is generally recognized, with critical implications for biodiversity baselines and invasion biology.
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