| 1. |
- Björck, Svante, et al.
(author)
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A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial
- 2019
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In: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 15:6, s. 1939-1958
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Journal article (peer-reviewed)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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| 3. |
- Enkirch, Theresa, et al.
(author)
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Hepatitis A outbreak linked to imported frozen strawberries by sequencing, Sweden and Austria, June to September 2018
- 2018
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In: Eurosurveillance. - : European Centre for Disease Prevention and Control. - 1025-496X .- 1560-7917. ; 23:41
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Journal article (peer-reviewed)abstract
- Between June-September 2018, 20 hepatitis A cases were notified in six counties in Sweden. Combined epidemiological and microbiological investigations identified imported frozen strawberries produced in Poland as the source of the outbreak. Sequence analysis confirmed the outbreak strain IB in the strawberries with 100 % identity and the respective batch was withdrawn. Sharing the sequence information internationally led to the identification of 14 additional cases in Austria, linked to strawberries from the same producer.
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| 4. |
- Hammarlund, Dan, et al.
(author)
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Palaeolimnological and sedimentary responses to Holocene forest retreat in the Scandes Mountains, west-central Sweden
- 2004
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In: Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 14:6, s. 862-876
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Journal article (peer-reviewed)abstract
- A suite of analyses was performed on sediments accumulated during the last 10 700 years in Lake Spaime, a small, hydrologically open water body in the modern alpine tundra zone of the Scandes Mountains, west-central Sweden. The study aimed to evaluate (1) the nature of climate changes that forced the late-Holocene lowering of altitudinal tree limit in the region, the timing of which is known from prior studies based on radiocarbon dating of subfossil wood, and (2) the impact of these vegetational changes on an aquatic ecosystem. Arboreal pollen and plant macrofossil data confirm the persistence of trees in the lake catchment at least from c. 9700 cal. BP until c. 3700 cal. BP. Although growing-season temperature is commonly believed to be the dominant factor driving boreal forest tree-limit variations in the region, a chironomid-based reconstruction of mean July air temperature suggests that local deforestation during the late Holocene was not accompanied by a significant cooling. The tree-limit retreat was more likely caused by increasing effective moisture and declining length of the growing season. The ecohydrological response of Lake Spaime to this combination of climate and vegetational changes included a decline in primary productivity, as indicated by an abrupt decrease in sediment organic matter content, while associated increases in organic delta(13)C, delta(15)N and C/N point to diminished fluxes and altered balance of catchment-derived nutrients following deforestation. The decline in aquatic productivity is also marked by a distinct change in the mineral magnetic properties, from a high magnetic concentration assemblage dominated by fine-grained magnetite of biogenic origin to one dominated by background levels of coarse-grained detrital magnetite.
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| 6. |
- Hansson, Anton, et al.
(author)
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Shoreline displacement and human resource utilization in the southern Baltic Basin coastal zone during the early Holocene: New insights from a submerged Mesolithic landscape in south-eastern Sweden
- 2018
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In: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 28:5, s. 721-737
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Journal article (peer-reviewed)abstract
- Along parts of the Hanö Bay coast in south-eastern Sweden, remains of a submerged landscape can be found down to depths of almost 25 m b.s.l. The coastal landscape was formed during two periods of lowered water levels in the Baltic Basin: the Yoldia Sea and the Initial Littorina Sea stages. In order to reconstruct the local environment and shoreline displacement during the Yoldia Sea and Ancylus Lake stages, sediment sequences were obtained at 4.5, 17.5 and 18.7 m b.s.l. Detailed bathymetric mapping was based on multi-beam echo-sounding while surveillance and sampling of tree remains and archaeological findings were performed through diving. The Yoldia Sea low-stand reached its minimum level at 24–25 m b.s.l. just before 10,800 cal. BP. During the subsequent Ancylus transgression, a slow-flowing river passed through the area, accumulating thick deposits of fine-grained organic sediments in lagoonal basins. The river was surrounded by open woodland dominated by pine. Based on successive flooding of rooted tree stumps, the transgression rate was estimated at 4 cm·yr−1, until the Ancylus high-stand was reached at 5 m b.s.l. at 10,400–10,300 cal. BP. Findings of worked aurochs and beaver bones provide evidence of human presence in the landscape and show the importance of terrestrial resources for their subsistence. These integrated palaeoecological and archaeological investigations demonstrate the importance of submerged landscapes with well-preserved sediment, wood and bone material for our understanding of southern Baltic coastal landscapes and their inhabitants during the Early Mesolithic.
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| 9. |
- Holmgren, Sofia, et al.
(author)
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Cytokine mRNA expression in bronchoalveolar lavage cells during Dictyocaulus viviparus infection in calves
- 2014
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In: Parasite Immunology. - : Wiley. - 0141-9838 .- 1365-3024. ; 36, s. 78-86
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Journal article (peer-reviewed)abstract
- The purpose of this study was to monitor local cytokine responses to Dictyocaulus viviparus in calves during primary infection and re-infection. Bronchoalveolar lavage fluid (BALF) was collected weekly from experimentally infected calves and interleukin-2 (IL-2), IL-4, IL-5, IL-10 and IFN- mRNA expression was quantified in BALF cells. The major finding was a prominent transient increase in IL-4 mRNA expression, compared with that of uninfected calves, observed in BALF cells collected 2-3weeks post-primary D.viviparus infection. At 2weeks post-infection, macroscopic worms were also first observed in BALF. Calves re-infected after 10weeks were partially immune which was evident at slaughter 5weeks post-infection as a lower worm burden than in previously naive calves infected at the same time. IL-4 mRNA expression in BALF cells 2weeks post-re-infection was increased compared with that of uninfected animals but not as high as that of primarily infected calves. BALF cell expression of the other cytokines tested for was not as clearly effected by the D.viviparus infection. It seems likely that the strong IL-4 response observed during primary infection reflects an innate response to the worms that may initiate an ensuing Th2 response, which confers protective immunity.
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| 10. |
- Holmgren, Sofia, et al.
(author)
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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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In: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 378, s. 45-51
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Journal article (peer-reviewed)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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