Vulkanutbruddenes innvirkning på klima, miljø, og vikingenes samfunn 500-1250 e.Kr. (VIKINGS)

• Fuglestvedt, Herman Fæhn; Zhuo, Zhihong; Toohey, Matthew & Krüger, Kirstin (2024). Volcanic forcing of high-latitude Northern Hemisphere eruptions. npj Climate and Atmospheric Science. ISSN 2397-3722. 7(1), s. 1–12. doi: 10.1038/s41612-023-00539-4.
• Van Dijk, Evelien; Gundersen, Ingar Mørkestøl; de Bode, Anna; Høeg, Helge Irgens; Loftsgarden, Kjetil & Iversen, Frode [Vis alle 9 forfattere av denne artikkelen] (2023). Climate and societal impacts in Scandinavia following the 536 and 540 CE volcanic double event. Climate of the Past. ISSN 1814-9324. 19(2), s. 357–398. doi: 10.5194/cp-19-357-2023. Fulltekst i vitenarkiv Vis sammendrag

  In the Northern Hemisphere, the mid-6th century was one of the coldest periods of the last 2000 years, as indicated by both proxy records and Earth System Model (ESM) simulations. This cold period was initiated by volcanic eruptions in 536 CE and 540 CE. Evidence from historical sources, archaeological findings, and proxy records suggests that the extent and severity of this volcanic induced cooling was spatially heterogeneous and that the effect on society resulted in adaptation and resilience at some locations, whereas social crisis has been indicated at others. Here, we study the effect of the volcanic double event in 536 CE and 540 CE on the climate and society in Scandinavia with a special focus on Southern Norway. Using an ensemble of Max Planck Institute ESM transient simulations for 521–680 CE, the temperature, precipitation and atmospheric circulation patterns are studied. The simulated cooling magnitude is then used as input for the growing degree day (GDD) model set-up for Southern Norway. This GDD model indicates the possible effects on agriculture for three different study areas in Southern Norway, representative of typical meteorological and landscape conditions. Pollen from bogs and archaeological records inside the study area are then analysed at high resolution (1–3 cm sample intervals) to give insights into the validity of the GDD model set-up with regard to the volcanic climate impact on the regional scale, and to link the different types of data sets. After the 536/540 CE double event, a maximum surface air cooling of up to 3.5 °C during the mean growing season is simulated regionally in Southern Norway. With a worst-case scenario cooling of 3 °C, the GDD model indicates crop failures were likely in our northernmost and western study areas, while crops were more likely to mature in the southeastern study area. These results are in agreement with the pollen records from the respective areas. During the sixth century, excavations show an abandonment of farms, severe social impact but also a continuation of occupation or a mix of those. In addition, archaeological findings from one of the excavation sites suggest wetter conditions for the mid-sixth century in Scandinavia, as simulated by individual ensemble members. Finally, we discuss the likely climate and societal impacts of the 536/540 CE volcanic double event by synthesising the new and available data sets for the whole Scandinavia.

• Zhuo, Zhihong; Fuglestvedt, Herman Fæhn; Toohey, Matthey & Krüger, Kirstin (2023). Initial conditions control transport of volcanic volatiles, forcing and impacts. Atmospheric Chemistry and Physics Discussions (ACPD). ISSN 1680-7367. doi: 10.5194/egusphere-2023-2374.
• Plunkett, Gill; Sigl, Michael & et al, . (2022). No evidence for tephra in Greenland from the historic eruption of Vesuvius in 79 CE: implications for geochronology and paleoclimatology. Climate of the Past. ISSN 1814-9324. 18, s. 45–65. doi: 10.5194/cp-18-45-2022. Vis sammendrag

  Volcanic fallout in polar ice sheets provides important opportunities to date and correlate ice-core records as well as to investigate the environmental impacts of eruptions. Only the geochemical characterization of volcanic ash (tephra) embedded in the ice strata can confirm the source of the eruption, however, and is a requisite if historical eruption ages are to be used as valid chronological checks on annual ice layer counting. Here we report the investigation of ash particles in a Greenland ice core that are associated with a volcanic sulfuric acid layer previously attributed to the 79 CE eruption of Vesuvius. Major and trace element composition of the particles indicates that the tephra does not derive from Vesuvius but most likely originates from an unidentified eruption in the Aleutian arc. Using ash dispersal modeling, we find that only an eruption large enough to include stratospheric injection is likely to account for the sizable (24–85 µm) ash particles observed in the Greenland ice at this time. Despite its likely explosivity, this event does not appear to have triggered significant climate perturbations, unlike some other large extratropical eruptions. In light of a recent re-evaluation of the Greenland ice-core chronologies, our findings further challenge the previous assignation of this volcanic event to 79 CE. We highlight the need for the revised Common Era ice-core chronology to be formally accepted by the wider ice-core and climate modeling communities in order to ensure robust age linkages to precisely dated historical and paleoclimate proxy records.

• Bajard, Manon Juliette Andree; Ballo, Eirik Gottschalk; Høeg, Helge Irgens; Bakke, Jostein; Støren, Eivind Wilhelm Nagel & Loftsgarden, Kjetil [Vis alle 11 forfattere av denne artikkelen] (2022). Climate adaptation of pre-Viking societies. Quaternary Science Reviews. ISSN 0277-3791. 278. doi: 10.1016/j.quascirev.2022.107374. Fulltekst i vitenarkiv Vis sammendrag

  Understanding how the Viking societies were impacted by past climate variability and how they adapted to it has hardly been investigated. Here, we have carried out a new multi-proxy investigation of lake sediments, including geochemical and palynological analyses, to reconstruct past changes in temperature and agricultural practices of pre-Viking and Viking societies in Southeastern Norway during the period between 200 and 1300 CE. The periods 200–300 and 800–1300 CE were warmer than the 300–800 CE period, which is known as the “Dark Ages Cold Period”. This cold period was punctuated by century-scale more temperate intervals, which were dominated by the cultivation of cereals and hemp (before 280 CE, 420–480 CE, 580–700 CE, and after 800 CE). In between, cold intervals were dominated by livestock farming. Our results demonstrate that the pre-Viking societies changed their agricultural strategy in response to climate variability during the Late Antiquity.

• Mjærum, Axel; Loftsgarden, Kjetil & Solheim, Steinar (2022). Human-vegetation dynamics in Holocene south-eastern Norway based on radiocarbon dated charcoal from archaeological excavations. The Holocene. ISSN 0959-6836. 32(7), s. 690–702. doi: 10.1177/09596836221088242. Fulltekst i vitenarkiv Vis sammendrag

  Charcoal from archaeological contexts differs from off-site pollen samples as it is mainly a product of intentional human action. As such, analysis of charcoal from excavations is a valuable addition to studies of past vegetation and the interaction between humans and the environment. In this paper, we use a dataset consisting of 6186 dated tree species samples from 1239 archaeological sites as a proxy to explore parts of the Holocene forest development and human-vegetation dynamics in South-Eastern Norway. From the middle of the Late Neolithic (from c. 2000 BC) throughout the Early Iron Age (to c. AD 550) the region’s agriculture is characterized by fields, pastures and fallow. Based on our data, we argue that these practices, combined with forest management, clearly altered the natural distribution of trees and favoured some species of broadleaved trees. The past distribution of hazel (Corylus avellana) is an example of human impact on the vegetation. Today, hazel is not even among the 15 most common tree species, while it is one of the most prevalent species in the archaeological record before AD 550. The data indicate that this species was favoured already by the region’s Mesolithic hunter-fisher-gatherers, and that it was among the species that thrived extremely well in the early farming landscape. Secondly, our analysis also indicates that spruce (Picea abies) first formed large stands in the south-eastern parts of Norway c. 500 BC, centuries earlier than previously assumed. It is argued that this event, and a further westward expansion of spruce, was partly a consequence of a specific historical event – the first millennium BC farming expansion.

• Van Dijk, Evelien; Jungclaus, Johann; Lorenz, Stephan; Timmreck, Claudia & Krüger, Kirstin (2022). Was there a volcanic-induced long-lasting cooling over the Northern Hemisphere in the mid-6th-7th century? Climate of the Past. ISSN 1814-9324. 18(7), s. 1601–1623. doi: 10.5194/cp-18-1601-2022. Fulltekst i vitenarkiv
• Abbott, Peter; Plunkett, Gill; et al, . & Sigl, Michael (2021). Cryptotephra from the Icelandic Veiðivötn 1477 CE eruption in a Greenland ice core: confirming the dating of volcanic events in the 1450s CE and assessing the eruption's climatic impact. Climate of the Past. ISSN 1814-9324. 17, s. 565–585. doi: 10.5194/cp-17-565-2021. Vis sammendrag

  Volcanic eruptions are a key source of climatic variability, and reconstructing their past impact can improve our understanding of the operation of the climate system and increase the accuracy of future climate projections. Two annually resolved and independently dated palaeoarchives – tree rings and polar ice cores – can be used in tandem to assess the timing, strength and climatic impact of volcanic eruptions over the past ∼ 2500 years. The quantification of post-volcanic climate responses, however, has at times been hampered by differences between simulated and observed temperature responses that raised questions regarding the robustness of the chronologies of both archives. While many chronological mismatches have been resolved, the precise timing and climatic impact of two major sulfate-emitting volcanic eruptions during the 1450s CE, including the largest atmospheric sulfate-loading event in the last 700 years, have not been constrained. Here we explore this issue through a combination of tephrochronological evidence and high-resolution ice-core chemistry measurements from a Greenland ice core, the TUNU2013 record. We identify tephra from the historically dated 1477 CE eruption of the Icelandic Veiðivötn–Bárðarbunga volcanic system in direct association with a notable sulfate peak in TUNU2013 attributed to this event, confirming that this peak can be used as a reliable and precise time marker. Using seasonal cycles in several chemical elements and 1477 CE as a fixed chronological point shows that ages of 1453 CE and 1458 CE can be attributed, with high precision, to the start of two other notable sulfate peaks. This confirms the accuracy of a recent Greenland ice-core chronology over the middle to late 15th century and corroborates the findings of recent volcanic reconstructions from Greenland and Antarctica. Overall, this implies that large-scale Northern Hemisphere climatic cooling affecting tree-ring growth in 1453 CE was caused by a Northern Hemisphere volcanic eruption in 1452 or early 1453 CE, and then a Southern Hemisphere eruption, previously assumed to have triggered the cooling, occurred later in 1457 or 1458 CE. The direct attribution of the 1477 CE sulfate peak to the eruption of Veiðivötn, one of the most explosive from Iceland in the last 1200 years, also provides the opportunity to assess the eruption's climatic impact. A tree-ring-based reconstruction of Northern Hemisphere summer temperatures shows a cooling in the aftermath of the eruption of −0.35 ∘C relative to a 1961–1990 CE reference period and −0.1 ∘C relative to the 30-year period around the event, as well as a relatively weak and spatially incoherent climatic response in comparison to the less explosive but longer-lasting Icelandic Eldgjá 939 CE and Laki 1783 CE eruptions. In addition, the Veiðivötn 1477 CE eruption occurred around the inception of the Little Ice Age and could be used as a chronostratigraphic marker to constrain the phasing and spatial variability of climate changes over this transition if it can be traced in more regional palaeoclimatic archives.

• ter Schure, Anneke Theresia Maria; Bajard, Manon Juliette Andree; Loftsgarden, Kjetil; Høeg, Helge Irgens; Ballo, Eirik Gottschalk & Bakke, Jostein [Vis alle 12 forfattere av denne artikkelen] (2021). Anthropogenic and environmental drivers of vegetation change in southeastern Norway during the Holocene. Quaternary Science Reviews. ISSN 0277-3791. 270. doi: 10.1016/j.quascirev.2021.107175. Fulltekst i vitenarkiv Vis sammendrag

  Uncovering anthropogenic and environmental drivers behind past biological change requires integrated analyses of long-term records from a diversity of disciplines. We applied an interdisciplinary approach exploring effects of human land-use and environmental changes on vegetation dynamics at Lake Ljøgottjern in southeastern Norway during the Holocene. Combined analysis of pollen and sedimentary ancient DNA (sedaDNA) metabarcoding of the sedimentary sequence of the lake describes the vegetation dynamics at different scales, and establishes a timeline for pastoral farming activities. We integrate this reconstruction with geochemical analysis of the sediments, climate data, archaeological evidence of local human settlement and regional human population dynamics. Our data covering the last 10,000 years reveals consistent vegetation signals from pollen and sedaDNA indicating periods of deforestation connected to cultivation, matching the archaeological evidence. Multivariate analysis integrating the environmental data from geochemical and archaeological reconstructions with the vegetation composition indicates that the vegetation dynamics at Lake Ljøgottjern were primarily related to natural processes from the base of the core (in ca. 8000 BCE, Mesolithic) up to the Early Iron Age (ca. 500 BCE–550 CE), when agricultural activities in the region intensified. The pollen signal reflects the establishment of a Bronze Age (ca. 1800–500 BCE) farm in the area, while subsequent intensification of pollen concentrations of cultivated plants combined with the first sedaDNA signals of cultivation and pastoralism are consistent with evidence of the establishment of farming closer to the lake at around 300 BCE. These signals also correspond to the intensification of agriculture in southeastern Norway in the first centuries of the Early Iron Age. Applying an interdisciplinary approach allows us to reconstruct anthropogenic and environmental dynamics, and untangle effects of human land-use and environmental changes on vegetation dynamics in southeastern Norway during the Holocene.

• Loftsgarden, Kjetil (2019). Ferd og frakt over fjell og vidde. Primitive tider. ISSN 1501-0430. 21, s. 7–23. doi: 10.5617/pt.7555. Fulltekst i vitenarkiv Vis sammendrag

  This study demonstrates how routes over mountain plateaus and passes connected farms, hamlets and regions. The routes enabled wide social and economic networks and were a prerequisite for regional surplus production in the Norwegian inland areas from the Viking Age. Iron, furs, skins and antlers were among the important commodities for farmers in the mountain and valley regions. These resources were exchanged for goods from the coastal areas, and it is likely that the purpose for much of the traffic over the mountains was trade. Medieval law texts and later historical sources indicate that the bulk of the traffic over mountains took place during the summer. The commodities were transported on packhorses or by foot. Using archaeological sites and findings, as well as place-names and historical sources, I have mapped the main mountain trails in South Norway. The historical significance of these communication routes are indicated by large burial sites, some consisting of hundreds of burial mounds, at the foot of several mountain crossings. These sites are testament to the great importance and value of communication and transportation across mountains passes – and its control – well before the extensive regional surplus production from the last half the Viking Age.

• Gundersen, Ingar Mørkestøl (2019). The Fimbulwinter theory and the 6th century crisis in the light of Norwegian archaeology: Towards a human-environmental approach. Primitive tider. ISSN 1501-0430. 21, s. 101–119. doi: 10.5617/pt.7538. Fulltekst i vitenarkiv Vis sammendrag

  In this article, I have tried to discuss the Fimbulwinter theory in a research historical perspective, in order to disentangle the premises presented by both advocates and critics alike. By and large, the current debate follows the contours of previous discourses on the 6th century transition, at the risk of entrenching the arguments within two defined and established perspectives: material change as a reflection of crisis, and, secondly, material change as an expression of cultural innovation. Neither of these perspectives is satisfactory, as they both run the risk of downplaying either, in the first case, long-term socio-cultural dynamics or, in the second case, environmental factors. In other words, an environmental perspective is inadequate as an analytical framework, since it is liable to provide simplified and deterministic interpretations of past societal change. The roots of environmental disasters must be studied from a social perspective, in which societal preconditions for vulnerability to hazards are analysed. Consequently, an integrated human-environmental approach must be developed, which takes into consideration the importance of both human and natural systems, and the interaction between them. There is, indeed, no contradiction between the two interpretative frameworks of crisis and a change of practice, as both perspectives are required for an in-depth understanding of the spatial and temporal complexity associated with the transition from the Early to the Late Iron Age. Considerable scientific potential might be obtained by employing a human-environmental approach, in which the 6th century transition is analysed at the interface of human and environmental systems, rather than within an explicit social or climatic interpretative framework.

• Loftsgarden, Kjetil (2019). The prime movers of iron production in the Norwegian Viking and Middle Ages. Fornvännen. ISSN 0015-7813. 2019(2), s. 75–87. Vis sammendrag

  The thousands of iron production sites scattered across the mountain and valley regions of Norway are testament to a massive surplus production from the latter half of the Viking Age throughout the High Middle Ages. Archaeological and historical sources indicate that this production was carried out by singular farms. Still, the amount of iron produced surpassed both local and regional demands and constituted a regional and interregional commodity in the period 950–1300 AD. The point of departure in exploring the organisation of iron production, and the subsequent trade, is the spatial distribution of various types of iron bars. The regional differentiation in iron bars may reflect differences in trade and economic sophistication. The smaller and standardised axe-like bars indicate that the trade in Valdres, Hallingdal, and Østerdalen had a layer of professionalism and a relatively more hierarchical social and economic organisation. In contrast the larger, less standardised split blooms points to Numedal, Telemark, and Setesdal as less economically and socially differentiated, with less professionalism and homogeneity. This study shows how farmers in marginal agricultural areas could provide a surplus of iron and is important in furthering our understanding of the socio-economic development of Scandinavian Viking and Middle Ages. The substantial production of iron in the inland shows a willingness to risk valuable time and resources. The risk lay on the farmers, but so did the possible gains. The extent of the iron production alone suggests that it was a risk worth taking.

• Solheim, Steinar & Iversen, Frode (2019). The mid-6th century crises and their impacts on human activity and settlements in southeastern Norway. I Brady, Niall & Theune, Claudia (Red.), SETTLEMENT CHANGE ACROSS MEDIEVAL EUROPE OLD PARADIGMS AND NEW VISTAS. Sidestone Press. ISSN 978-90-8890-806-4. s. 423–434. Fulltekst i vitenarkiv Vis sammendrag

  AD 536 is a poignant date in European history and marks the advent of a series of documented environmental changes that affected societies across Europe in various ways. Sudden and severe climate deterioration led to vast crop failures and was followed by plague epidemics in the following decades. In this article, we examine the timing of the changes in human activity with a detailed investigation of 855 radiocarbon determinations from Vestfold, Norway. The modelled radiocarbon data show a decrease in activity concurrent with the climatic events and plague epidemics that took place in the mid-6th century, and provide another proxy for the significant changes that occurred during this time. The results may support the idea that fimbulvetr was the start of a long-lasting cooling period combined with severe population declines and a dramatic decrease in cultural activity. In the past and present, the investigated area represents a heartland of rural production and settlements in Scandinavia. The time span of the crises is fundamental to our academic understanding of the character and societal impacts of the crises, and this study examines it more precisely than previous work.

• Toohey, Matthew; Krüger, Kirstin; Schmidt, Hauke; Timmreck, Claudia; Sigl, Michael & Stoffel, Markus [Vis alle 7 forfattere av denne artikkelen] (2019). Disproportionately strong climate forcing from extratropical explosive volcanic eruptions. Nature Geoscience. ISSN 1752-0894. 12, s. 100–107. doi: 10.1038/s41561-018-0286-2. Vis sammendrag

  Extratropical volcanic eruptions are commonly thought to be less effective at driving large-scale surface cooling than tropical eruptions. However, recent minor extratropical eruptions have produced a measurable climate impact, and proxy records suggest that the most extreme Northern Hemisphere cold period of the Common Era was initiated by an extratropical eruption in 536 ce. Using ice-core-derived volcanic stratospheric sulfur injections and Northern Hemisphere summer temperature reconstructions from tree rings, we show here that in proportion to their estimated stratospheric sulfur injection, extratropical explosive eruptions since 750 ce have produced stronger hemispheric cooling than tropical eruptions. Stratospheric aerosol simulations demonstrate that for eruptions with a sulfur injection magnitude and height equal to that of the 1991 Mount Pinatubo eruption, extratropical eruptions produce time-integrated radiative forcing anomalies over the Northern Hemisphere extratropics up to 80% greater than tropical eruptions, as decreases in aerosol lifetime are overwhelmed by the enhanced radiative impact associated with the relative confinement of aerosol to a single hemisphere. The model results are consistent with the temperature reconstructions, and elucidate how the radiative forcing produced by extratropical eruptions is strongly dependent on the eruption season and sulfur injection height within the stratosphere.

Se alle arbeider i Cristin

• Krüger, Kirstin (2023). Volcanic eruptions and viking society. [Internett]. https://www.sigma2.no/volcanic-eruptions-and-viking-society. Vis sammendrag

  How did volcanic eruptions and their climate impact shape the early history and society of Scandinavia? .... Article is to be read at this link: https://www.sigma2.no/volcanic-eruptions-and-viking-society

• Zhuo, Zhihong; Fuglestvedt, Herman Fæhn; Toohey, Matthew; Mills, Michael J & Krüger, Kirstin (2022). Impacts of tropical versus extratropical volcanic eruptions co-injecting sulphur and halogen to the stratosphere.
• Zhuo, Zhihong; Fuglestvedt, Herman Fæhn & Krüger, Kirstin (2022). Impacts of tropical versus extratropical volcanic eruptions co-injecting sulfur and halogen to the stratosphere.
• Tjoflot, Gunn Kristin (2022). The Vikings-project; UiO selected for an Inter Circle U. Prize 2022. Vis sammendrag

  The Circle U: ICUP Evaluation Panel has selected the "VIKINGS: Volcanic Eruptions and Their Impacts on Climate, Environment and Viking Society from 500 to 1250 Common Era" research project as one of the three Circle U. ICUP 2022 award recipients!

• Tjoflot, Gunn Kristin (2022). The Vikings project in brief: New YouTube film. Vis sammendrag

  The interdisciplinary research team behind the Vikings project, represented by Manon Bajard and Ingar M. Gundersen are announced as winners of the first 'Inter Circle U. Prize. See this new film which give an presentation of the project.

• Tjoflot, Gunn Kristin (2022). Kirstin Krüger presents the Vikings-project and results; streamed lecture on YouTube. Vis sammendrag

  The GeoWednesday seminar entitled 'VIKINGS - Volcanic Eruptions and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE', was presented by Kirstin Krüger for a full audience in The Science Library@UiO, 16. March 2022. She presented exciting multidisciplinary results, and a tree core sample found in the Raknehaugen burial mound showing bad years of growth around the volcanic winter year 536.

• Loftsgarden, Kjetil (2022). The wonderful 7th century.
• Boessenkool, Sanne (2022). Unearthing past ecologies and societies using sedimentary ancient DNA.
• Fuglestvedt, Herman Fæhn (2022). High-Latitude Explosive Volcanic Eruptions and Their Sensitivity to Source Parameters.
• Fuglestvedt, Herman Fæhn (2022). Arctic Polar Vortex Controls Aerosol Evolution After High-Latitude Volcanic Eruptions.
• Zhuo, Zhihong; Fuglestvedt, Herman Fæhn; Toohey, Matthew & Krüger, Kirstin (2022). Impacts of tropical versus extratropical volcanic eruptions with sulphur and halogen injections to the stratosphere.
• Gundersen, Ingar Mørkestøl (2022). Iron Age Vulnerability. An analytical approach to the Fimbulwinter hypothesis.
• Ballo, Eirik Gottschalk (2022). Lipid biomarkers in Lake Sagtjernet, Norway.
• Ballo, Eirik Gottschalk; Bajard, Manon Juliette Andree; Bakke, Jostein; Støren, Eivind Wilhelm Nagel; D'Andrea, William J. & Høeg, Helge Irgens (2022). Lake Sagtjernet hydrogen isotopes and pollen .
• Gabriel, Imogen & Sigl, Michael (2022). Deciphering the sources and climate impact potential of pre-historic volcanic eruptions from Iceland using the Greenland ice cores: a case study from the 8th century.
• Sigl, Michael; Gabriel, Imogen & Krüger, Kirstin (2022). Timing of Holocene volcanic eruptions and their radiative aerosol forcing.
• Gabriel, Imogen & Sigl, Michael (2022). Insight into volcano-climate impacts between 750 and 770 CE using the Greenland ice core records.
• Krüger, Kirstin (2022). VIKINGS - Volcanic Eruptions and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE. [Internett]. YouTube. Vis sammendrag

  Welcome to the Geo-Wednesday in March! This month Kirstin Krüger, Professor at Meteorology and Oceanography, will give a talk about VIKINGS. VIKINGS is a multi-disciplinary project that aims to understand the role of volcanic eruptions and climate change in shaping the early history of Scandinavia. The period 500-1250 Common Era is characterized by societal unrest, Viking expansion, emerging kingship - and large volcanic eruptions evidenced by geochemical markers in natural archives. The climate variations in Europe, and especially in Scandinavia during this period, are however poorly resolved even on a timescale of centuries. Moreover, available dating of archeological findings from the time period have hardly been interpreted within a framework of climatic and environmental change. The VIKINGS project seeks to unravel the climate of this intriguing historic period and to address the role of volcanic eruptions impacting environmental and societal changes with a special focus on Southern Norway. Kirstin Krüger is a Professor in Meteorology at the UiO Department of Geosciences and the leader of the VIKINGS project – a Norwegian TOPPFORSK project. Her research focuses on stratospheric dynamics and the role of transport from climate relevant gases from the surface to the middle atmosphere. In the past 15 years, she has worked on large explosive volcanic eruptions and their impacts on climate, environment and society during present day and paleo time scales.

• Hutchinson, William & Sigl, Michael (2022). Timing and climate impact of Iceland’s largest basaltic eruptions: new insights from ice core archives.
• Bajard, Manon Juliette Andree (2022). Agricultural and climatic contexts associated to the Fimbulwinter in the area of Gardermoen: when pre-Viking societies adapted to the climate.
• Krüger, Kirstin; Fuglestvedt, Herman Fæhn; Van Dijk, Evelien; Zhuo, Zhihong; Sigl, Michael & Toohey, Matthew (2022). Modelling volcanic climate and environmental impacts and their signals in ice cores.
• Krüger, Kirstin; Fuglestvedt, Herman Fæhn; Zhuo, Zhihong; Mills, Mike & Sigl, Michael (2022). Volcanic sulfate deposition to Greenland and Antarctica: A modeling sensitivity study with CESM(WACCM). Vis sammendrag

  Reconstructions of the atmospheric sulfate aerosol burdens resulting from past volcanic eruptions are based on ice core-derived estimates of volcanic sulfate deposition and the assumption that the two quantities are directly proportional. Toohey et al (2013) modelled that the Antarctic and Greenland volcanic sulfate deposition is nonlinear for very large sulfur rich tropical eruptions (Tambora magnitude and larger), with significantly less sulfate deposition to Antarctica than to Greenland using the MAECHAM5-HAM aerosol-climate model. Here we test the relationship for simulations of explosive tropical and extratropical Northern Hemisphere volcanic eruptions by co-injecting sulfur and halogens into the stratosphere with the CESM2(WACCM) model including aerosol, chemistry, climate, and earth system processes. We consider different eruption parameters varying composition, latitude, season, injection height and magnitude. We run the model injecting 17 Tg and 200 Tg of SO2, together with scaled halogens, at 24 km altitude 15° N and 64° N during January and July pre industrial 1850 conditions. We will analyse the modelled sulphate deposition signals over Greenland and Antarctica and compare them to the volcanic ice core records of known eruptions of comparable strength during the Common Era and the Holocene. The analysis will focus on the deposition fluxes and their Greenland/Antarctica efficiencies in relation to the eruption parameters, sulphate aerosol transport, and the atmospheric circulation and deposition. With the help of the model data we will learn more about the volcanic sources to the sink processes, which will be helpful to better interpret volcanic signals in bipolar ice core records.

• Krüger, Kirstin (2022). VIKINGS: Volcanic Eruptions and their Impacts on Climate, Environment, and Viking Society in 500-1250 Common Era. Vis sammendrag

  Welcome to the Geo-Wednesday in March! This month Kirstin Krüger, Professor at Meteorology and Oceanography, will give a talk about VIKINGS. VIKINGS is a multi-disciplinary project that aims to understand the role of volcanic eruptions and climate change in shaping the early history of Scandinavia. The period 500-1250 Common Era is characterized by societal unrest, Viking expansion, emerging kingship - and large volcanic eruptions evidenced by geochemical markers in natural archives. The climate variations in Europe, and especially in Scandinavia during this period, are however poorly resolved even on a timescale of centuries. Moreover, available dating of archeological findings from the time period have hardly been interpreted within a framework of climatic and environmental change. The VIKINGS project seeks to unravel the climate of this intriguing historic period and to address the role of volcanic eruptions impacting environmental and societal changes with a special focus on Southern Norway. Kirstin Krüger is a Professor in Meteorology at the UiO Department of Geosciences and the leader of the VIKINGS project – a Norwegian TOPPFORSK project. Her research focuses on stratospheric dynamics and the role of transport from climate relevant gases from the surface to the middle atmosphere. In the past 15 years, she has worked on large explosive volcanic eruptions and their impacts on climate, environment and society during present day and paleo time scales.

• Tjoflot, Gunn Kristin (2021). Food Security Lessons from the Vikings. Vis sammendrag

  Farming practices of the Vikings and their ancestors could provide inspiration for resilient food systems today. A new study from the VIKINGS project, GEO, UiO exploring how Scandinavian societies adapted their agricultural activities in a period of European history marked by stark climate fluctuations.

• Gabriel, Imogen & Sigl, Michael (2021). Unlocking the secrets of past Icelandic volcanism with tephra.
• Gabriel, Imogen & Sigl, Michael (2021). Tephra in the Greenland Ice cores: Insights into Icelandic volcano-climate impacts.
• Sigl, Michael (2021). Volcanism & Climate during the past 2,500 years; Joint seminar in atmospheric, ocean and climate science.
• Zhuo, Zhihong; Fuglestvedt, Herman; Toohey, Matthew; Mills, Michael J. & Krüger, Kirstin (2021). Model comparison of volcanic aerosol forcing and climate impact of tropical and extratropical eruptions.
• Van Dijk, Evelien; Gundersen, Ingar Mørkestøl; Loftsgarden, Kjetil; Ballo, Eirik Gottschalk; Krüger, Kirstin & Iversen, Frode (2021). Can we link volcanic impacts on the climate to a change in society?
• Van Dijk, Evelien; Gundersen, Ingar Mørkestøl; Loftsgarden, Kjetil; Krüger, Kirstin & Iversen, Frode (2021). Can we link volcanic impacts on the climate to a change in society in Norway?
• Ballo, Eirik Gottschalk; Bajard, Manon Juliette Andree; Bakke, Jostein & Støren, Eivind Wilhelm Nagel (2021). Using CT scans to count varves: Application to Lake Sagtjernet.
• Bajard, Manon Juliette Andree & Dacey, James (2021). Food Security Lessons from the Vikings. [Tidsskrift]. EOS Science News by AGU. Vis sammendrag

  Scandinavian societies of the first millennium adapted their farming practices to volcano-driven climate changes.

• Zhuo, Zhihong; Fuglestvedt, Herman Fæhn; Toohey, Matthew; Mills, Michael J. & Krüger, Kirstin (2021). Model comparison of stratospheric aerosol forcing of tropical and extratropi-cal volcanic eruptions. Vis sammendrag

  Major volcanic eruptions, as one of the natural forcing, increase sulfate aerosols in the stratosphere. The stratospheric aerosol forcing differs from tropical and extratropical eruptions, and depends on the eruption season and height, and volcanic volatile injections. In order to study different aerosol forcing and their impact, we perform simulations based on the fully coupled Community Earth System Model version 2 (CESM2) with the Whole Atmosphere Community Climate Model version 6 (WACCM6) with prognostic stratospheric aerosol and chemistry. Explosive eruptions at 14.6 N and 63.6 N in January and July injecting 17 Tg and 200 Tg SO2 at 24 km with and without halogens are simulated, in line with Central American Volcanic Arc and Icelandic volcanic eruptions. Simulated changes in the stratospheric sulfate and halogen burdens, and impacts on aerosol optical depth and ozone are analyzed.

• Zhuo, Zhihong; Fuglestvedt, Herman Fæhn; Toohey, Matthew; Mills, Michael J. & Krüger, Kirstin (2021). Model comparison of aerosol forcing and impactof tropicaland extratropical eruptions.
• Bajard, Manon Juliette Andree (2021). PC1. Improving food security: new techniques. [Internett]. Press conference/EGU General Assembly 2021. Vis sammendrag

  "In 2019, nearly 750 million people were exposed to severe levels of food insecurity. Conservative estimates indicate that more than 3 billion people can’t afford healthy diets, and that the social costs of greenhouse gas emissions associated with current food-consumption patterns will top $1.7 trillion per year within the next decade. This press conference will introduce journalists to some of the latest geoscience research being conducted to help improve global food security, including two types of forecasting that support early warnings in Africa. Additional research strives to improve agricultural management strategies with respect to greenhouse gas emissions and to balance food and water security in cities. Lastly, we will hear how one group of scientists is researching how pre-Viking and Viking societies adapted their agricultural practices to a changing climate to glean fresh insights into how we can improve our future food security." (EGU: 2021)

• Sigl, Michael; Krüger, Kirstin & Et al, More authors (2021). Insights on the timing, global sulfate lifecycle an􀀀 climate impact of Earth's largest (pre-) historic volcanic eruptions. EGU General Assembly. EGU21-946. doi: 10.5194/egusphere-egu21-946,%202021. Vis sammendrag

  Extratropical volcanic eruptions are commonly thought to be less effective at driving large-scale surface cooling than tropical eruptions, and only the latter are commonly thought to be able to distribute sulfate globally. Here, we test both of these assumptions using a network of ice cores from the polar regions of Antarctica and Greenland covering the past 15’000 years and climate-aerosol modeling. We employ state-of-the-art analyses of trace elements, cryptoptephra and sulphur isotopes (Burke et al., 2019) to gain new insights into the timing of past eruptions, their stratospheric sulphur mass injections and subsequent sulphate aerosol lifecycle. We use this information to estimate the climate impact potential due to negative radiative forcing caused by Earth’s largest volcanic eruptions since the last Glacial. Our analysis encompasses over 1’000 eruptions and include the caldera-forming eruptions of Okmok II (Alaska, 43 BCE, VEI=6, 53°N; McConnell et al., 2020), Aniakchak II (Alaska, 1600s BCE, VEI=6, 57°N), Crater Lake (Mazama, Oregon, 5600s BCE, VEI=7, 43°N) and Laacher See (Germany, c. 13 ka BP, VEI=6, 50°N). We use our reconstructed radiative forcing and the coupled earth system models MPI-ESM1.2 and CESM (version 1.2.2) to analyze the climatic impact caused by these eruptions and compare the simulated temperature response with temperature reconstructions based on ultra-long tree-ring chronologies. Finally, based on these comparisons, we propose a number of stratigraphic age tie-points to anchor ice-core chronologies from Greenland (GICC05) and Antarctica (WD2014) to the absolute dated tree-ring chronology. We thereby aim to improve proxy synchronization throughout the Holocene -- a prerequisite for detection and attribution studies -- and invite the paleo-climate community to update climate proxy records based on ice cores to the latest chronologies. The European Research Council Grant 820047 under the European Union’s Horizon 2020 research and innovation program funded the research project THERA - Timing of Holocene Volcanic eruptions and their radiative aerosol forcing.

• Van Dijk, Evelien & Krüger, Kirstin (2021). Impact of large volcanic eruptions on the 6th-7th century climate.
• Van Dijk, Evelien & Krüger, Kirstin (2021). Large volcanic eruptions as a natural hazard: The impact of the 536/540 CE double event on the atmospheric circulation, surface climate, vegetation and society in Scandinavia.
• Bajard, Manon Julietto Andree; Ballo, Eirik Magnus Gottschalk; Høeg, Helge I.; Bakke, Jostein; Støren, Eivind N. & Loftsgarden, Kjetil [Vis alle 11 forfattere av denne artikkelen] (2021). Instability or adaptation of the pre-Viking society to the climate variability of the Late Antiquity? Vis sammendrag

  Understanding how agricultural societies were impacted and adapted to past climate variations is critical to adapt to contemporary climate change and guaranty the food security. However, linking climate and change in the behaviour of a population are difficult to evidence. Here, we studied the climate variations of the period between 200 and 1300 CE and its impact on the pre-Viking and Viking societies in south Norway. We used a retrospective approach combining a multi-proxy analysis of lake sediments, including geochemical and palynological analyses, to reconstruct past changes in temperature and agricultural practices during the period 200-1300 CE. We associated variations in Ca/Ti ratio as a result of change in lake productivity with the temperature. The periods 200-300 and 800-1300 CE were warmer than the period between 300 and 800 CE, which is known as the “Dark Ages Cold Period” in the Northern Hemisphere. During this colder period, phases dominated by grazing activities (280-420 CE, 480-580 CE, 700-780 CE) alternated with phases dominated by the cultivation of cereals and hemp (before 280 CE, 420-480 CE, 580-700 CE, and after 800 CE). The alternation of these phases is synchronous of temperature changes. Cold periods are associated to livestock farming, and warmer periods to crop farming. This result suggests that when temperature no longer allowed crop farming, the food production specialized in animal breeding. The development of activities reached a maximum between 400 and 550 CE and a minimum between 680 and 800 CE, in agreement with archaeological findings. The Viking Age (800-1000 CE) started with an increase in temperature and corresponds to the warmest period between 200 and 1300 CE, allowing a larger development of the agriculture practices and society. Our results prove that the pre-Viking society adapted their agricultural practices to the climate variability of the Late Antiquity and that the Vikings expanded with climate warming.

• ter Schure, Anneke; Bajard, Manon Julietto Andree; Loftsgarden, Kjetil; Høeg, Helge Irgens; Ballo, Eirik Magnus Gottschalk & Bakke, Jostein [Vis alle 12 forfattere av denne artikkelen] (2021). Disentangling anthropogenic and environmental drivers of biological change in southeastern Norway during the Holocene.
• ter Schure, Anneke; Bajard, Manon Julietto Andree; Loftsgarden, Kjetil; Høeg, Helge Irgens; Ballo, Eirik Magnus Gottschalk & Bakke, Jostein [Vis alle 12 forfattere av denne artikkelen] (2021). Anthropogenic and environmental drivers of biological change in southeastern Norway during the Holocene.
• Fuglestvedt, Herman; Krüger, Kirstin; Zhuo, Zhihong; Sigl, Michael; Toohey, Matthew & Mills, Michael J. (2021). Modelling high-latitude explosive eruptions and their atmospheric and environmental impacts .
• Fuglestvedt, Herman Fæhn; Zhuo, Zhihong; Mills, Michael J. & Krüger, Kirstin (2021). Modelling the atmospheric impacts of high-latitude explosive volcanic eruptions.
• Fuglestvedt, Herman Fæhn; Zhuo, Zhihong; Michael, Mills & Krüger, Kirstin (2021). Modelling the atmospheric impacts of high-latitude explosive volcanic eruptions.
• Zhuo, Zhihong; Fuglestvedt, Herman Fæhn & Krüger, Kirstin (2021). Impacts of tropical versus extratropical volcanic eruptions (including volcanic sulphur and halogen injections).
• Tjoflot, Gunn Kristin (2020). Finner tegn på at fimbulvinteren har skjedd. Vis sammendrag

  Ifølge norrøn mytologi skulle fimbulvinteren bli etterfulgt av ragnarok. Klimaforskerne har nå påvist en kuldeperiode i jernalderen, trolig på grunn av to store vulkanutslipp i 536 og 540. Forskerne tilknyttet Vikings-prosjektet/UiO ser nå etter samenhenger, og hvordan kuldeperioden påvirket befolkningen i Skandinavia.

• Van Dijk, Evelien & Krüger, Kirstin (2020). Was there a volcanic induced long lasting cooling in the mid 6th-7th century?
• Smedsrud, Morten Skipenes & Loftsgarden, Kjetil (2020). Finner tegn til ekte fimbulvinter. [Tidsskrift]. Apollon.
• Bajard, Manon Julietto Andree (2020). The hidden face of lakes: how natural archives bring us back to the Viking Age and beyond. Vis sammendrag

  Since 10,000 years, lakes have continuously accumulated sediments. These sediments contain particles of soil, plant, pollen and DNA from the surrounding environment, brought by rivers, runoff and the wind. They allow us to reconstruct the past evolution of the landscapes, the vegetation and agricultural practices, but also climate changes. By studying and dating cores of lake sediments in Norway, we can reconstruct the history of the environment throughout the last 10 000 years and explore the Viking Age.

• Bajard, Manon Julietto Andree; Ballo, Eirik Magnus Gottschalk; Støren, Eivind Wilhelm Nagel; Bakke, Jostein; Høeg, Helge Irgens & Loftsgarden, Kjetil [Vis alle 9 forfattere av denne artikkelen] (2020). Record of climate and environmental changes in a dead-ice lake close to Gardermoen told by a 10 000 years old freshwater fish and a Viking King. Vis sammendrag

  We studied a six-meter long sediment sequence retrieved from the kettle lake Ljøgottjern, close to Oslo-Gardermoen Airport, to reconstruct environmental and climate changes during the last millennia. The lake is 18 m depth and located at 185 m a.s.l., under the maximum postglacial sea level. The largest burial mound of Northern Europe was built in the mid-6th century on the shore of this lake allegedly for King Rakni and makes this place ideal to study human-environment interactions in a paleo-perspective approach. Using a multi-proxy sedimentological analysis of this record, including 14C dating, paleo-secular variations, XRF and CT scans, and pollen, this study highlights different climate patterns throughout the Holocene. At the bottom of the core, a carbonated sandy-clayey layer with centimetric twigs overlays an organic rich black peaty-type layer, suggesting a continental environment. On top of that, a disturbed clay layer containing fish bones from a freshwater Carpinidae species was found. The fish could have been buried by the massive (70 cm) sandy carbonated deposit covering it. A sharp transition separates a clay cap on top of the deposit and the start of a finely laminated lacustrine sedimentation dated 9.3 ka cal. BP. The massive deposit could be associated to the outburst flood from the glacial lake Nedre Glomsjø dated 10-10.4 ka cal BP (Longva, 1984; Høgaas and Longva, 2016). A major change in the sedimentation occurred around 8 ka cal. BP, with darker sediments and a lower sedimentation rate. This change could be related to a warming climate and stabilization of the catchment by soil and forest development around the lake in the mid-Holocene. The sedimentation rate increased again between 2000 and 3000 years cal. BP as a result of the development of first human activities and major change in the vegetation (Høeg, 1997). We reconstructed temperature changes during the first millennia and compared it to societal dynamics. The period between 300 and 800 years cal. CE is colder than the period 800-1300 years cal. CE. After 1600 years cal. CE, an increase in erosion could be associated to the extension of the population and agriculture in Scandinavia and revealed a chronicle of the major floods in this area. The presence of freshwater fish older than 9,3 ka attests of their early and natural colonization of Scandinavian lakes. The comparison of this record with archaeological data will allow us to discuss socio-environmental dynamics following the deglaciation in the area. References: Smith, A.A. 2010. CO2 stor¬age. Journal of Sciences 32, 10-20. Høeg, H.I., 1997. Pollenanalytiske undersøkelser på Øvre Romerike : Ullensaker og Nannestad, Akershus fylke : Gardermoprosjektet, Varia (Universitetets oldsaksamling : trykt utg.). Universitetets oldsaksamling, Oslo. Høgaas, F., Longva, O., 2016. Mega deposits and erosive features related to the glacial lake Nedre Glomsjø outburst flood, southeastern Norway. Quat. Sci. Rev. 151, 273–291. https://doi.org/10.1016/j.quascirev.2016.09.015 Longva, O., 1984. Romeriksmjelen danna ved ein storflaum på Austlandet for vel 9000 år siden. Norges geologiske undersøkelse, Årsmelding 1984 8–11.

• Bajard, Manon Julietto Andree; Ballo, Eirik Magnus Gottschalk; Støren, Eivind Wilhelm Nagel; Bakke, Jostein; Høeg, Helge Irgens & Loftsgarden, Kjetil [Vis alle 8 forfattere av denne artikkelen] (2020). Volcanic Eruptions and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE .
• Bajard, Manon Julietto Andree; Ballo, Eirik Magnus Gottschalk; Støren, Eivind Wilhelm Nagel; Bakke, Jostein; Høeg, Helge Irgens & Loftsgarden, Kjetil [Vis alle 9 forfattere av denne artikkelen] (2020). Tracing socio-environmental dynamics and climate changes in the period 300-1300 CE in Scandinavia from lake sediments. Vis sammendrag

  Understanding large volcanic eruptions impacts on environments and societies is necessary to consider future climate and socio-environmental interactions. Lake sediments can record these dynamics on a continuous long time scale and include at the same time footprints from volcanic eruptions, climate changes and human activities. We analysed the sediments of Lake Ljøgottjern, located southeastern Norway. The largest burial mound of Northern Europe was built in the mid-6th century on the shore of this lake and makes this place an ideal site to study human-environmental interactions throughout the last millennia. Using a multi-proxy analysis of this sedimentary record, including 14C dating, geochemistry, as well as palynological data, we reconstructed temperature and socio-environmental changes in this area between 300 and 1300 CE (Common Era). We associated changes in Ca/Ti ratio with changes in temperature. The period between 300 and 800 CE was colder than the periods 200-300 and 800-1300 CE. Five abrupt cooling events seem to be linked to weakened positive NAO (North Atlantic Oscillation) phases, and two of them can also be linked to the two largest volcanic events of the period (i.e. the 536/540 CE double event, and 1257 CE eruption of Samalas). Palynological data indicate a decrease of the human activities and reforestation of the area in the 6th century. This abandonment is consistent with archaeological findings and could be related to the 536/540 cooling event. Very little activities are then recorded between 700 and 850 CE. Agricultural activities start again strongly in the Viking age with increase in temperature.

• Krüger, Kirstin (2020). Volcanic Eruptins and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE . Vis sammendrag

  This multi-disciplinary project aims to understand the role of volcanic eruptions and climate change in shaping the early history of Europe. The period 500-1250 CE is characterized by natural disasters, societal unrest, Viking expansion, emerging kingship – and large volcanic eruptions evidenced by geochemical markers in natural archives. Contemporary reports of a mysterious cloud which dimmed the light of the sun for at least a year were written at the dawn of the Middle Ages which marked the beginning of an unusual cold period in the mid of the 6th century due to the double volcanic eruption event in 536/540 CE. The social structure of Scandinavian society was radically changed between 500 and 750 CE. Population levels were reduced by plague and agriculture had to be adapted to a colder climate. Tree ring and climate model data from Scandinavia identify a prolonged period of cooling which may have lasted over a century. Following is a period of volcanic activity which was thought to be more quiescent in a global sense and is marked by the onset of the medieval warm period (c. 950 -1250 CE). However, volcanic eruptions in Iceland were frequently active during 700 to 1100 CE and must have had severe impacts on climate, environment and society in Northern Europe, which is not supported by available records. This presentation aims to shed more light into the background of this early Common Era period based on revised volcanic forcing, complex earth system climate model, proxy, and archaeology data.

• Loftsgarden, Kjetil (2020). I vikingtida stod innlandet for ein enorm jernproduksjon. Forskning.no. ISSN 1891-635X. Vis sammendrag

  Til tross for at jernframstillinga var spreidd på tusenvis av jernframstillingsstader, organisert og driven av spesialiserte bønder, vart det framstilt enorme mengder jern i det norske innlandet.

• Loftsgarden, Kjetil (2020). Ferd og frakt over fjell og vidde. Forskning.no. ISSN 1891-635X.
• Loftsgarden, Kjetil (2020). The population of Western Scandinavia 400–1000 AD.
• Loftsgarden, Kjetil (2020). How many Vikings were there? The population of Western Scandinavia 400–1000.
• Van Dijk, Evelien Jacoba Cornelia & Krüger, Kirstin (2020). Impact of the 536/540 CE double volcanic eruption event on the 6th-7th century climate using model and proxy data.
• Van Dijk, Evelien Jacoba Cornelia & Krüger, Kirstin (2020). Impact of the 536/540 CE double eruption event on the 6th -7th century climate using model and proxy data.
• Van Dijk, Evelien Jacoba Cornelia & Krüger, Kirstin (2020). The impact of the 536/540 CE double volcanic eruption event on the climate.
• Fuglestvedt, Herman & Kirstin, Krüger (2020). Modelling the Atmospheric Forcing of High-Latitude Volcanic Eruptions.
• Loftsgarden, Kjetil (2019). Skeid.
• Ballo, Eirik Magnus Gottschalk; Bajard, Manon Julietto Andree; Bakke, Jostein & Støren, Eivind Wilhelm Nagel (2019). Reconstructing climate and socio-environmental changes using lake sediments .
• Van Dijk, Evelien Jacoba Cornelia (2019). The impact of the double volcanic eruption event 536/540 CE on the climate.
• Ballo, Eirik Magnus Gottschalk; Bajard, Manon Julietto Andree; Bakke, Jostein & Støren, Eivind Wilhelm Nagel (2019). Reconstructing climate and socio-environmental changes using lake sediments .
• Ballo, Eirik Magnus Gottschalk; Bajard, Manon Julietto Andree; Bakke, Jostein & Støren, Eivind Wilhelm Nagel (2019). Reconstructing climate and socio-environmental changes using lake sediments .
• Loftsgarden, Kjetil (2019). The demography of the Viking Age or: How I Learned to Stop Worrying and Love Big Data.
• Loftsgarden, Kjetil (2019). Store og små vestnorske marknadsplassar.
• Loftsgarden, Kjetil (2019). It's Iron ore it's nothing!
• Loftsgarden, Kjetil (2019). Hestekamp og handel i vikingtid og middelalder’.
• Loftsgarden, Kjetil (2019). Mass production and marketplaces from the late Viking Age.
• Loftsgarden, Kjetil (2019). The production of iron at seasonal settlements in the Norwegian mountains.
• Loftsgarden, Kjetil (2019). VIKINGS project.
• Loftsgarden, Kjetil (2019). Vikingar og vulkaner. Klima og samfunnsutvikling 536–1250.
• Ballo, Eirik Magnus Gottschalk; Bajard, Manon Julietto Andree; Støren, Eivind Wilhelm Nagel; Bakke, Jostein & Svensen, Henrik (2019). High-resolution lacustrine records of environmental changes in Scandinavia: a focus on the Migration period and Viking age.
• Ballo, Eirik Magnus Gottschalk; Bajard, Manon Julietto Andree; Støren, Eivind Wilhelm Nagel; Bakke, Jostein & Svensen, Henrik (2019). High-resolution lacustrine records of environmental changes in Scandinavia: a focus on the Migration period and Viking age.
• Ballo, Eirik Magnus Gottschalk; Bajard, Manon Julietto Andree; Støren, Eivind Wilhelm Nagel; Bakke, Jostein & Svensen, Henrik (2019). High-resolution lacustrine records of environmental changes in Scandinavia: a focus on the Migration period and the Viking age.
• Bostic, Joshua Neilson; Hagopian, William Martin; Svensen, Henrik & Jahren, Anne Hope (2019). Predicting seasonal climate using intra-ring stable isotope analysis. Vis sammendrag

  By emitting stratospheric sulphur aerosol clouds that dim the light-energy received from the sun, large-scale volcanic eruptions may cause acute changes in global climate that impact both natural ecosystems and human societies. One example is the 536 Event, a prolonged period of darkness and cooling across the northern hemisphere caused by two separate volcanic eruptions in 536 and 540 CE. Recent mean annual temperature (MAT) and mean annual precipitation (MAP) reconstructions suggest that the decade following the 536 event was one of the coldest and wettest of the past two millennia. This cold period likely contributed to the cultural upheavals that occurred in Scandinavia during the 6th century by reducing the geographic range suitable for cereal grain production. However, while annually-resolved MAT and MAP reconstructions are useful for identifying climatic perturbations, they provide limited insight into the effects of such climate anomalies on regional agricultural productivity due to their limited ability to differentiate summer and winter climatic conditions. To accurately estimate the number of days suitable for growing crops, or Growing Degree Days (GDD), seasonal resolution must be achieved by determining the ratio of summer to winter temperature and precipitation. To reconstruct growing season temperature and precipitation across southern Scandinavia in the decade following the 536 event (535-545 CE), we will combine prior reconstructions of annual mean data with novel analyses of summer/winter temperature and precipitation ratios derived from intra-ring carbon and oxygen stable isotope analysis of Picea abies collected from Raknehaugen, a burial mound in southern Norway constructed in 551 CE. These growing season temperature and precipitation estimates will be combined with other geo-climatic data (latitude, altitude etc.) for regional GDD reconstruction to ultimately determine changes in the geographic range suitable for crop production in Southern Norway following the 536/540 double event. Here, we 1.) Provide a conceptual outline of the project’s expected outcomes and 2.) Demonstrate the ability of intra-ring stable isotope analysis to detect short-term seasonal climatic perturbations in Scandinavia by reconstructing the European summer drought of 1959 from estimates of summer/winter temperature and precipitation ratios derived from stable isotope patterns in Picea abies samples from two locations in southern Norway.

• Bajard, Manon Julietto Andree; Eirik, Ballo; Jostein, Bakke; Eivind, Støren; Helge, Høeg & Frode, Iversen [Vis alle 8 forfattere av denne artikkelen] (2019). Socio-environmental dynamics and volcanic eruptions in the 500-1250 CE period in Scandinavia: new sight in Lake Ljøgottjern sediment sequence. Vis sammendrag

  Large volcanic eruptions are the major drivers of climate variability in the pre-industrial era of the last two millennia. Understanding their impacts on societies is necessary to consider future climate and socio-environmental interactions. Lake sediments can record these dynamics on a continuous time scale and include at the same time footprints from volcanic eruptions, climate changes and human activities associated to vegetation changes. Lake Ljøgottjern is located in southeastern Norway and is of glacial origin. The lake is 14 m depth, groundwater-fed and provide a sediment sequence covering the last 8000 years. The largest burial mound of Norway was built in the mid-6th century on the shore of this lake for King Rakni and makes this place an ideal site to study human-environmental interactions throughout the last millennia, confronting them to archaeological evidences. Using a high-resolution multi-proxy analysis of this record, including 14C dating, sedimentological and both mineral and organic geochemical analyses as well as palynological data, this study will allow reconstructing climate and socio-environmental changes in this area, with a focus on the 500-1250 CE (Common Era) period. A previous palynological study evidenced the first openings of the environment linked to the development of agriculture between 3000 and 3500 yrs cal. BP. This change in land use was associated with changes in the geochemistry of the sediment. Maximum anthropogenic impacts were recorded in ca. 600 CE, when the mound was raised, and in the Little Ice Age, between the 13th and 17th centuries. The pollen diagram of Lake Ljøgottjern presents also three substantial decreases in charcoal particles between 500 and 1250 CE. An updated and high resolution dating of the new sequence will allow to associate or not these changes in fire regimes to major volcanic events (i.e., 536-540 unknown, 939 Eldgjà and 1257 Samalas). The comparison of this record with other environmental archives from Norway, as well as climate reconstructions from ice cores and tree rings will allow us to discuss resilience times and adaptation of the Viking society in a changing Scandinavian environment.

• Bajard, Manon Julietto Andree; Eirik, Ballo; Jostein, Bakke; Eivind, Støren; Helge, Høeg & Frode, Iversen [Vis alle 8 forfattere av denne artikkelen] (2019). Socio-environmental dynamics and volcanic eruptions in the 500-1250 CE period in Scandinavia: new sight in Lake Ljøgottjern sediment sequence. Vis sammendrag

  Large volcanic eruptions are the major drivers of climate variability in the pre-industrial era of the last two millennia. Understanding their impacts on societies is necessary to consider future climate and socio-environmental interactions. Lake sediments can record these dynamics on a continuous time scale and include at the same time footprints from volcanic eruptions, climate changes and human activities associated to vegetation changes. Lake Ljøgottjern is located in southeastern Norway and is of glacial origin. The lake is 18 m depth, groundwater-fed and provide a sediment sequence covering the last 8000 years. The largest burial mound of Norway was built in the mid-6th century on the shore of this lake for King Rakni and makes this place an ideal site to study human-environmental interactions throughout the last millennia, confronting them to archaeological evidences. Using a high-resolution multi-proxy analysis of this record, including 14C dating, sedimentological and both mineral and organic geochemical analyses as well as palynological data, this study will allow reconstructing climate and socio-environmental changes in this area, with a focus on the 500-1250 CE (Common Era) period. A previous palynological study evidenced the first openings of the environment linked to the development of agriculture between 3000 and 3500 yrs cal. BP. This change in land use was associated with changes in the geochemistry of the sediment. Maximum anthropogenic impacts were recorded in ca. 600 CE, when the mound was raised, and in the Little Ice Age, between the 13th and 17th centuries. The pollen diagram of Lake Ljøgottjern presents also three substantial decreases in charcoal particles between 500 and 1250 CE. An updated and high resolution dating of the new sequence will allow to associate or not these changes in fire regimes to major volcanic events (i.e., 536-540 unknown, 939 Eldgjà and 1257 Samalas). The comparison of this record with other environmental archives from Norway, as well as climate reconstructions from ice cores and tree rings will allow us to discuss resilience times and adaptation of the Viking society in a changing Scandinavian environment.

• Bajard, Manon Julietto Andree & Eirik, Ballo (2019). First insight in Norwegian sedimentary archives .
• Krüger, Kirstin & Bajard, Manon Julietto Andree (2019). Volcanic Eruptions and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE . Vis sammendrag

  VIKINGS(NFR) TACCO(Notur/NorStore)

• Ballo, Eirik Magnus Gottschalk; Bajard, Manon Julietto Andree; Støren, Eivind Wilhelm Nagel; Bakke, Jostein & Svensen, Henrik (2019). High-resolution lacustrine records of environmental changes in Scandinavia: a focus on the Migration period and Viking age.
• Krüger, Kirstin (2019). Working Group Overview. Vis sammendrag

  VIKINGS/NFR TACCO INES KeyCLIM

• Krüger, Kirstin (2019). Volcanic Eruptions and their Impacts on Climate, Environment, and Viking Society in 500-1250 CE .
• Gundersen, Ingar Mørkestøl (2021). Iron Age Vulnerability. The Fimbulwinter hypothesis and the archaeology of the inlands of eastern Norway. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  A growing body of climate data points towards a significant climate cooling in the northern hemisphere during the 6th century AD. Linked to multiple explosive volcanic eruptions between AD 536-547, the cooling event is the coldest that has been documented for the last 2000 years and seems to have persisted, to varying degrees, well into the latter half of the 6th century. Several researchers have claimed that the 6th-century cooling must have resulted in extensive crop failure throughout Scandinavia, followed by famine, plagues, and social unrest. One hypothesis suggests that the population of the Scandinavian Peninsula may have been halved as a result. The combination of prolonged cooling and presumed crop failure is often compared to Norse myths about the Fimbulwinter, but critics argue that the Fimbulwinter hypothesis is rife with the uncritical use of climate data, a lack of source criticism and deterministic conclusions. In many ways, the ongoing discourse follows in line with previous discourses in archaeology, revolving around an artificial dichotomy between crisis and continuity. In this thesis, I examine the climatic and archaeological premises for the Fimbulwinter hypothesis and discuss it against developing theoretical frameworks within the environmental humanities. By using vulnerability and resilience as analytical tools, the subsistence and settlement patterns of selected landscapes are analysed against the possibility of crop failure and famine, with emphasis on the Gudbrandsdalen valley and the Lake Mjøsa region in the inlands of eastern Norway. I conclude that climate cooling had the potential to critically impact some areas, while others were seemingly less affected. These results suggest significant regional diversity in the consequences and adaptations in relation to the 6th-century cooling event. The hypothesis of a halving of the population is up for revision, but the crisis narrative still cannot be fully discounted.

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