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33
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Introduction
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January 2001 - present
Publications
Publications (33)
This study investigates solar variability between 650 CE and 1900 based on new and published ¹⁴C records with a time resolution of two years or higher. The new high-resolution ¹⁴C data presented here are derived from Danish oak and span the period 1058–1250 CE. We determine the durations of past solar minima and periods with moderate solar activity...
It is often argued that the repetitive removal of branches to improve the quantity and the quality of wood, i.e. woodland management, has been practiced in Europe from the Mesolithic and/or Neolithic onwards. The Neolithic pile dwelling of Alvastra in Sweden has been mentioned in textbooks as a classical example of this practice. The conclusion abo...
Although variations in building activity are a useful indicator of societal well-being and demographic development, historical datasets for larger regions and longer periods are still rare. Here, we present 54,045 annually precise dendrochronological felling dates from historical construction timber from across most of Europe between 1250 and 1699...
Viking Age ring fortresses were some of the largest construction projects in Danish prehistory. In this article we reconstruct the amount of turf and timber used in the construction of the Borgring ring fortress and estimate the resource area needed to supply the building materials. Using REVEALS pollen data modelling, we quantify the regional oak...
We present a new biennial record of radiocarbon ( ¹⁴ C) measured in Danish oak. The new record covers the years 1251–1378 CE, thereby spanning the Grand Solar Minimum known as the Wolf Minimum. Two oak samples from every other year were measured at the AMS facility at Aarhus University (Denmark), resulting in an average precision of 1.4‰ for the re...
Single-year measurements of radiocarbon ( ¹⁴ C) in tree rings have led to the discovery of rapid cosmic-ray events as well as longer lasting anomalies, which have given new insights into the Sun’s behavior in the past. Here, we present two new single-year ¹⁴ C records based on Danish oak that span the periods AD 692–790 and 966–1057, respectively,...
It is often presumed that woodland management, i.e. pollarding and coppicing, was practised in prehistory, but the precise beginning and the details of such practices in the past are unknown. This is because, in contrast to historical times, from which written and iconographic sources are available, prehistoric archaeological sites rarely yield dir...
Alvastra, a Neolithic wetland site in Sweden, is sometimes presented as an example of a site where people practiced coppicing in the Neolithic. On which evidence is this hypothesis based, and what do the wood data tell when we look at these from a new perspective?
Hvor gammelt er det? Det er normalt det første spørgsmål der stilles i forbindelse med en bygnings-arkæologisk undersøgelse. Det var nu ikke det spørgsmål, der blev stillet, da det blev besluttet at gennemføre dendrokronologiske undersøgelser (årringsdateringer) i gamle huse i Hidra. Ifølge traditionen er flere huse flyttet til herredet fra for eks...
Several aspects concerning the origin and nature of grand solar minima remain unclear, and more high‐resolution ¹⁰Be and ¹⁴C records are needed to improve our understanding of these phenomena. Here, we report 137 new high‐precision, annually resolved radiocarbon concentrations based on oak from the Danish dendrochronology. The new record covers a p...
Using a combination of microscopic examination and electronic scanning and printing, we analyzed the impacts of early spring snow cover extent and temperature during the growing season on the annual radial growth in arctic willow (Salix arctica Pallas) in the Zackenberg valley, High Arctic Northeast Greenland. So far, only little dendroclimatologic...
Wood used in construction and boat building, in domestic productions or as a fuel resource in for medieval North European societies.
Svalbard is a Norwegian archipelago in the Arctic Ocean. It has a rich cultural heritage, and visitors will find traces of human activity everywhere. There is little soil, so even the oldest traces are exposed. Cultural remains are found in coastal areas all around the archipelago. The artifacts in Svalbard are vulnerable treasures preserved well i...
Arctic terrestrial ecosystems are heterogeneous because of the strong influences of microtopography, soil moisture and snow accumulation on vegetation distribution. The interaction between local biotic and abiotic factors and global climate patterns will influence species responses to climate change. Salix arctica (Arctic willow) is a structuring s...
Climate model projections suggest widespread drying in the Mediterranean Basin and wetting in Fennoscandia in the coming decades largely as a consequence of greenhouse gas forcing of climate. To place these and other “Old World” climate projections into historical perspective based on more complete estimates of natural hydroclimatic variability, we...
Dendrochronological and wood anatomical examination of finds from historical shipwrecks etc. found on the shores of Svalbard, now kept in the Svalbard Museum in Longyearbyen -
Material from wooden shipwrecks and other objects
Rapid climate warming in the tundra biome has been linked to increasing shrub dominance. Shrub expansion can modify climate by altering surface albedo, energy and water balance, and permafrost yet the drivers of shrub growth remain poorly understood. Dendroecological data consisting of multi-decadal time series of annual shrub growth provide an und...
Wood anatomical research done on samples submitted autumn 2014 by Snorre Haukalid, Sysselmannen på Svalbard.
Dendroclimatological reconstructions may be influenced by intraspecific variation in radial growth caused by plant gender and ecotypic differentiation. We examined the growth response of the High Arctic Salix arctica to interannual variation in snow precipitation in Zackenberg, NE Greenland. Tree ring examinations revealed a consistent response of...
Part of a large male woolly mammoth (Mammuthus primigenius) was preserved in permafrost in northern Yakutia. It was radiocarbon dated to ca. 18,500 14C yr BP (ca. 22,500 cal yr BP). Dung from the lower intestine was subjected to a multiproxy array of microscopic, chemical, and molecular techniques to reconstruct the diet, the season of death, and t...
In this study, we investigated whether dendrochronology can be used to determine the felling dates and origin of the trees that were used as wooden pile foundations under historic buildings. Dating and dendroprovenancing of the timber was possible for eight out of nine buildings. This is due mainly to the availability of newly constructed tree-ring...
Using a combination of microscopic examination and electronic scanning and printing, we analyzed the impacts of early spring snow cover extent and temperature during the growing season on the annual radial growth in arctic willow (Salix arctica Pallas) in the Zackenberg valley, High Arctic Northeast Greenland. So far, only little dendroclimatologic...
Part of a large male woolly mammoth (Mammuthus primigenius) was preserved in permafrost in northern Yakutia. It was radiocarbon dated to ca. 18,500 14 C yr BP (ca. 22,500 cal yr BP). Dung from the lower intestine was subjected to a multiproxy array of microscopic, chemical, and molecular techniques to reconstruct the diet, the season of death, and...
Projects
Projects (4)
High energy cosmic rays of galactic and solar origin, natural radioactivity, lighting in thunderstorms and electrified shower clouds, produce ion clusters and charge the whole atmosphere causing a ubiquitous potential difference between the ionosphere and the surface. This Global Electric Circuit (GEC) allows the flow of charges to the surface in the fair-weather (undisturbed) regions of the globe. Theory indicates that atmospheric charging has the potential to influence layered clouds but little is known about the climatic relevance of charge-cloud interactions, because a) experimental evidence is very limited and b) climate models do not include yet relevant parameterizations.
This project aims to narrow the knowledge gap in charge-cloud processes. This is accomplished by collecting and analyzing a unique set of observations at the most ideal location, the Villum Research Station (VRS). Observational results will ultimately improve the parameterization and refine the modeling of GEC-related processes. The project brings together expertise in space-climate and climate modelling (Physics, Astronomy and Geoscience, Uni. Aarhus), aerosol and clouds theory and measurements at VRS (Env. Science, Uni. Aarhus), atmospheric electricity measurements and instrumentation (NOA) to assess the climatic relevance of GEC through influencing layered clouds.
