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Träfflista för sökning "WFRF:(Hansen Steen H.) "

Search: WFRF:(Hansen Steen H.)

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  • Dahl-Jensen, D., et al. (author)
  • Eemian interglacial reconstructed from a Greenland folded ice core
  • 2013
  • In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 493:7433, s. 489-494
  • Journal article (peer-reviewed)abstract
    • Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 +/- 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 +/- 250 metres, reaching surface elevations 122,000 years ago of 130 +/- 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.
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  • Patel, Riyaz S., et al. (author)
  • Subsequent Event Risk in Individuals With Established Coronary Heart Disease : Design and Rationale of the GENIUS-CHD Consortium
  • 2019
  • In: Circulation. - 2574-8300. ; 12:4
  • Journal article (peer-reviewed)abstract
    • BACKGROUND: The Genetics of Subsequent Coronary Heart Disease (GENIUS-CHD) consortium was established to facilitate discovery and validation of genetic variants and biomarkers for risk of subsequent CHD events, in individuals with established CHD.METHODS: The consortium currently includes 57 studies from 18 countries, recruiting 185 614 participants with either acute coronary syndrome, stable CHD, or a mixture of both at baseline. All studies collected biological samples and followed-up study participants prospectively for subsequent events.RESULTS: Enrollment into the individual studies took place between 1985 to present day with a duration of follow-up ranging from 9 months to 15 years. Within each study, participants with CHD are predominantly of self-reported European descent (38%-100%), mostly male (44%-91%) with mean ages at recruitment ranging from 40 to 75 years. Initial feasibility analyses, using a federated analysis approach, yielded expected associations between age (hazard ratio, 1.15; 95% CI, 1.14-1.16) per 5-year increase, male sex (hazard ratio, 1.17; 95% CI, 1.13-1.21) and smoking (hazard ratio, 1.43; 95% CI, 1.35-1.51) with risk of subsequent CHD death or myocardial infarction and differing associations with other individual and composite cardiovascular endpoints.CONCLUSIONS: GENIUS-CHD is a global collaboration seeking to elucidate genetic and nongenetic determinants of subsequent event risk in individuals with established CHD, to improve residual risk prediction and identify novel drug targets for secondary prevention. Initial analyses demonstrate the feasibility and reliability of a federated analysis approach. The consortium now plans to initiate and test novel hypotheses as well as supporting replication and validation analyses for other investigators.
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  • Kvile, KØ, et al. (author)
  • Kelp Forest Distribution in the Nordic Region.
  • 2022
  • In: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 9
  • Journal article (peer-reviewed)abstract
    • Kelp forests are productive coastal ecosystems that provide a range of ecosystem services. Mapping the distribution and area occupied by kelp forests is a critical step to identify their ecosystem functions and services, including their role in the carbon cycle, and to detect changes in their distribution. We compiled quantitative data of the dominant genera Laminaria and Saccharina across the Nordic region, allowing us to separate kelp forests (areas with dense or moderately dense kelp coverage) from occurrences of single or few individuals. By fitting boosted regression trees to the compiled data, we modelled and predicted the distribution of kelp forests across the Nordic region. Despite the large scale of the analyses, the models captured well the kelps’ environmental affinities and predicted the presence of kelp forests with high accuracy. Dense kelp forests are found along the rocky shores of all the Nordic countries, except in the brackish Baltic Sea, with largest areas in Norway, Greenland and Iceland. The results of this study set the scene for future studies on the importance of kelp forests in the Nordic region, including their contribution to the marine carbon budget.
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  • Elberling, Bo, et al. (author)
  • Soil and Plant Community Characteristics and Dynamics at Zackenberg
  • 2008
  • In: High-arctic ecosystem dynamics in a changing climate - Ten years of monitoring and research at Zackenberg Research Station, Northeast Greenland (Advances in Ecological Research). - 0065-2504. - 9780123736659 ; 40, s. 223-248
  • Book chapter (other academic/artistic)abstract
    • Arctic soils hold large amounts of nutrients in the weatherable minerals and the soil organic matter, which slowly decompose. The decomposition processes release nutrients to the plant-available nutrient pool as well as greenhouse gases to the atmosphere. Changes in climatic conditions, for example, changes in the distribution of snow, water balance and the length of the growing season, are likely to affect the complex interactions between plants, abiotic and biotic soil processes as well as the composition of soil micro- and macro-fauna and thereby the overall decomposition rates. These interactions, in turn, will influence soil-plant functioning and vegetation composition in the short as well as in the long term. In this chapter, we report on soils and. plant communities and their distribution patterns in the valley Zackenbergdalen and focus on the detailed investigations within five dominating plant communities. These five communities are located along an ecological gradient in the landscape and are closely related to differences in water availability. They are therefore indirectly formed as a result of the distribution of landforms, redistribution of snow and drainage conditions. Each of the plant communities is closely related to specific nutrient levels and degree of soil development including soil element accumulation and translocation, for example, organic carbon. Results presented here show that different parts of the landscape have responded quite differently to the same overall climate changes the last 10 years and thus, most likely in the future too. Fens represent the wettest sites holding large reactive buried carbon stocks. A warmer climate will cause a permafrost degradation, which most likely will result in anoxic decomposition and increasing methane emissions. However, the net gas emissions at fen sites are sensitive to long-term changes in the water table level. Indeed, increasing maximum active layer depth at fen sites has been recorded together with a decreasing water level at Zackenberg. This is in line with the first signs of increasing extension of grasslands at the expense of fens. In contrast, the most exposed and dry areas have less soil carbon, and decomposition processes are periodically water limited. Here, an increase in air temperatures may increase active layer depth more than at fen sites, but water availability will be critical in determining nutrient cycling and plant production. Field manipulation experiments of increasing temperature, water supply and nutrient addition show that soil-plant interactions are sensitive to these variables. However, additional plant-specific investigations are needed before net effects of climate changes on different landscape and plant communities can be integrated in a landscape context and used to assess the net ecosystem effect of future climate scenarios.
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