| 1. |
- Aldahan, Ala, et al.
(författare)
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Atmospheric impact on beryllium isotopes as solar activity proxy
- 2008
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 35:L21812
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Tidskriftsartikel (refereegranskat)abstract
- Reconstructing solar activity variability beyond the time scale of actual measurements provides invaluable data for modeling of past and future climate change. The 10 Be isotope has been a primary proxy archive of past solar activity and cosmic ray intensity, particularly for the last millennium. There is, however, a lack of direct high-resolution atmospheric time series on 10 Be that enable estimating atmospheric modulation on the production signal. Here we report quasi-weekly data on 10 Be and 7 Be isotopes covering the periods 1983-2000 and 1975-2006 respectively, that show, for the first time, coherent variations reflecting both atmospheric and production effects. Our data indicate intrusion of stratosphere/upper troposphere air masses that can modulate the isotopes production signal, and may induce relative peaks in the natural 10 Be archives (i.e., ice and sediment). The atmospheric impact on the Be-isotopes can disturb the production signals and consequently the estimate of past solar activity magnitude. Citation: Aldahan, A., J. Hedfors, G. Possnert, A. Kulan, A.-M. Berggren, and C. Soderstrom (2008), Atmospheric impact on beryllium isotopes as solar activity proxy, Geophys. Res. Lett., 35, L21812, doi: 10.1029/2008GL035189.
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| 2. |
- Goransson, Gunnel, et al.
(författare)
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Assessing the Risk of Contaminant Dispersion From Fibrous Sediments of Industrial Origin
- 2021
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Ingår i: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Unregulated discharges of wastewater from pulp and paper factories resulted in the formation of relatively thick organic (cellulose) rich sediments in shallow waters along the Swedish coast. These deposits are known as fiberbanks and are contaminated by persistent organic pollutants (POPs), metals and methylmercury, which can be dispersed by diffusion and advective processes coupled to propeller wash, high river discharges, strong wind waves and submarine landslides. Based on a case study of polychlorinated biphenyls (PCBs), one group of prevalent POPs in the fiberbanks, we present a probabilistic approach to estimate the potential risk of dispersion of fiberbank contaminants. The approach allows for estimation of the dispersal pathways that dominates the risk within a given time and provides more insight about the significance of various dispersion processes. We show that it is highly likely that chemical diffusion and advection triggered by ship-induced resuspension will disperse PCBs (sum of seven congeners; sigma 7PCB) above a threshold level for environmental impact, while the likelihood of river and wind-wave generated resuspension dispersion pathways are lower (similar to 20%, respectively). We further show that there is approximately 5% likelihood that a submarine landslide will disperse sigma 7PCB above the threshold level. The study implies that the governing parameters for risk assessment specifically should include reliable data on contaminant concentration, water depth above the fiberbank, estimation of concerned fiberbank areas, time duration of erosive fluid flows and measured diffusion. The approach provides insight into the importance of various dispersion processes. We suggest that it can be applied to support risk assessment, especially when there are limited available data and/or knowledge about the system under study.
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| 3. |
- Göransson, Gunnel, et al.
(författare)
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Opportunities for planned retreat and flexible land use in Sweden : Local, regional and national governance perspectives
- 2023
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Ingår i: Climate Risk Management. - : Elsevier. - 2212-0963. ; 41
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Tidskriftsartikel (refereegranskat)abstract
- As the sea level rises and the frequency of intense rains increase, so does the need for climate adaptation. Planning for a successive development of society away from current and future flood prone areas to give room for water is not seen as an alternative in Sweden today, although it could be a strategy that creates long-term security. In this study, we investigated Swedish public authorities' perceptions of planned retreat and flexible land use. This was done through an online survey and interviews directed to officials directly involved in climate adaptation work, at municipalities, County Administration Boards (CABs), Regions, national authorities (NAs), and industry organizations (IOs). The responses were analyzed through the lens of a windows of opportunity approach. The study indicates that the extent to which climate scenarios are used and how far into the future the planning horizon extends in the practical work, varies between governance level which also have impact on the perspectives on planned retreat. The openness for planned retreat and flexible strategies seemed to differ slightly between governance levels in an ascending scale from regions, IOs / NAs, municipalities, to CABs. The survey has generated insights from a large number of respondents at different governance levels sharing their perceptions of retreat and adaptation in Sweden as a main contribution of this work.Difficulties to deal with uncertainties in climate scenarios and considering long-term perspectives were identified as some reasons that close the window for planned retreat. Enabling a flexible use of the land that will gradually become more exposed to flooding and sea level rise could be an intermediate step towards retreat. This would be a way to reframe a closed window of opportunity and begin the process of turning it into something transformative. It could be where the short- and long-term planning meet and a way to reframe our way of thinking about how we live and reside in dynamic waterfront areas, and perhaps lead to a more transformative, safe, and sustainable society for future generations.
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| 4. |
- Hedfors, Jim, et al.
(författare)
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Clouds and Be-7: Perusing connections between cosmic rays and climate
- 2006
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 111:D2, s. D02208-
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Tidskriftsartikel (refereegranskat)abstract
- [1] Time series data on Be-7, precipitation, temperature, and satellite imagery of cloud cover over Scandinavia, together with cosmic ray and sunspot activity, were used to elucidate the relationship between cosmic rays and clouds, and ultimately climate change. The results indicate a coherent negative correlation between total cloud cover and Be-7 on intraseasonal, seasonal, and decadal scales. Although the reasons behind this correlation are unclear, a full-scale implication of this feature is in the possible use of Be-7 and Be-10 records for proxy paleo-reconstruction of total cloud cover. This is a strongly needed, but generally difficult to quantify parameter in climate models.
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| 5. |
- Hedfors, Jim, et al.
(författare)
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Clouds and beryllium-7
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 268:7-8, s. 1129-1134
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Tidskriftsartikel (refereegranskat)abstract
- We present a 10-year record of 10 different cloud cover types at three different locations in Scandinavia together with Be-7 surface concentration data. The aim is to estimate the degree of correlation, if any, between various cloud types at different latitudes and measured Be-7 concentrations. The study matches weekly Be-7 data to cloud raster data from high resolution multispectral satellite sensors recorded on a monthly basis between 1991 and 2001. The results are presented as a Be-7 correlation coefficient and show a consistent pattern with small variations across the latitudes and rather large variations between the different cloud classes. The strongest coherence is inverse and associated with Be-7 and high-level clouds (cumulonimbus and nimbostratus), generally, at low latitudes while mid-level clouds (altocumulus, altostratus and cumulus congestus) show little (insignificant) correlation. Despite variable correlation trends, merging of the two data sets has proven valuable in order to understand aerosols-Be-7 (and likely Be-10) correlation to different cloud types.
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| 6. |
- Hedfors, Jim, 1971-
(författare)
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Force Budget Analysis of Glacier Flow : Ice Dynamical Studies on Storglaciären, Sweden, and Ice Flow Investigations of Outlet Glaciers in Dronning Maud Land, Antarctica
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis contributes to the understanding of glacier response to climate change by ice dynamical studies on Storglaciären, Sweden, and Bonnevie-Svendsenbreen, Kibergbreen and Plogbreen in Dronning Maud Land, Antarctica. Ice surface velocities, ice geometry and temperature information is fed through a force budget model to calculate ice mass outflux of these glacial systems via three-dimensional stress distributions for a flux-gate. Field data were collected through repeated DGPS and GPR observations on Storglaciären between July 2000 to September 2001 and on Kibergbreen and Plobreen during the SWEDARP 2002/03 expedition to Antarctica. The work was strongly supported by remotely-sensed information.The results from Storglaciären show a strength in the force budget model to discern both spatial and temporal variability in ice dynamical patterns. It highlights the influence of seasonality and bedrock topography upon glacier flow. A modeling experiment on Bonnevie-Svendsenbreen suggested that ice temperature increases substantially under conditions of high stress (≥0.4 MPa) due to strain-heating. This provides a positive feedback loop, increasing ice deformation, as long as it overcomes the advection of cool ice from the surface. These results explain, to some extent, the mechanism behind fast flowing ice streams. Mass flux caclulations from Bonnevie-Svendsenbreen suggest that the outflux given from force budget calculations can be used as a gauge for influx assuming steady state conditions. Plogbreen receives an influx of 0.48±0.1 km3 a-1 and expedites a discharge volume of 0.55±0.05 km3 a-1. This indicative negative mass balance is explained by a falling trend in upstream accumulation and the recent rise in global sea level, as it is likely to induce glacier acceleration due to a reduction in resistive forces at the site of the gate. This result is comparable with other Antarctic studies reporting negative mass balances, e.g. from WAIS, as caused by changes in the global atmospheric circulation pattern.
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| 7. |
- Hedfors, Jim, et al.
(författare)
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Ice flux of Plogbreen, a small ice stream in Dronning Maud Land, Antarctica
- 2004
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Ingår i: Annals of Glaciology. - : International Glaciological Society. - 0260-3055 .- 1727-5644. ; 39:1, s. 409-416
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Tidskriftsartikel (refereegranskat)abstract
- As part of a long-term mass-balance program run by SWEDARP since 1988, a detailed study on Plogbreen, Dronning Maud Land, Antarctica, was undertaken during the austral summer of 2003 to investigate the long-term mass balance. We compare ice outflux, out, through a cross-sectional gate with ice influx, in, from the upstream catchment area. The in is based on calculations of snow accumulation upstream of the gate using data available from published ice-core records. The out is based on Glen's flow law aided by thermodynamic modeling and force-budget calculations. Input data from the field consist of measurements of ice surface velocity and ice geometry. The ice surface velocity was measured using repeated differential global positioning system surveying of 40 stakes over a period of 25 days. The ice geometry was determined by 174 km of ground-penetrating radar profiling using ground-based 8 MHz dipole antennas. This study presents the collected velocity and geometry data as well as the calculated ice flux of Plogbreen. The results show a negatively balanced system within the uncertainty limits; out = 0.55 ± 0.05 km3 a−1 and in = 0.4 ± 0.1 km3 a−1. We speculate that the negative balance can be explained by recent eustatic increase reducing resistive stresses and inducing accelerated flow.
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| 8. |
- Hedfors, Jim, et al.
(författare)
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Investigating the ratio of basal drag and driving stress in relation to bedrock topography during a melt season on Storglaciären, Sweden, using force budget analysis
- 2003
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Ingår i: Annals of Glaciology. - : International Glaciological Society. - 0260-3055 .- 1727-5644. ; 37:1, s. 263-268
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Tidskriftsartikel (refereegranskat)abstract
- We apply the force-budget technique using the isothermal block-flow model, on Storglacia« ren, Sweden, to investigate the ratio between basal drag and driving stress in relation to a bedrock ridge in the bed topography during a peak melt season. The input data consist of glacier surface velocities collected using differential global positioning system surveying of a stake net and geometry fromprevious radar soundings and digitized ice surface maps. The study focuses on the effects of transverse bedrock ridges upon basal stress conditions.The pattern of the calculated ratio of basal drag and driving stress shows a rhythmical position of relatively high and lowbasal drags onthe stoss and lee sides, respectively, of the bedrock thresholds. One of the zones of low basal drag corresponds to the location where the highest basal sliding rate has been measured previously by borehode deformation studies. This zone also aligns with the area where the drainage system is suggested to change from englacial to subglacial.
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| 9. |
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| 10. |
- Hou, Xiaolin, et al.
(författare)
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Speciation of I-129 and I-127 in seawater and implications for sources and transport pathways in the North Sea
- 2007
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 41:17, s. 5993-5999
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Tidskriftsartikel (refereegranskat)abstract
- Surface seawater samples collected from the North Sea and English Channel were analyzed for total 129I and 127I, as well as for iodide and iodate. Relatively high 129I concentrations (2−3 × 1011 atoms/L) were observed in the northern part of the English Channel and in the southeastern North Sea. The atomic ratio of 129I/127I decreases from the eastern (1.0−1.9 × 10-6) to the western (4−6 × 10-8) parts of the North Sea and from the northeastern (1.5 × 10-6) to southwestern (1−5 × 10-8) parts of the English Channel. The ratios of iodide to iodate are 0.1−0.5 and 0.5−1.6 for 127I and 129I, respectively, in open seawaters, whereas these ratios range from 0.6 to 1.3 and 0.8 to 2.2, respectively, in coastal waters. The results suggest that (1) imprints of the La Hague facility dominates the 129I distribution in the surface water of the North Sea, (2) reduction of iodate to iodide is relatively fast during the transport to the European continental coast, (3) oxidation of newly produced 129I- to 129IO3- is insignificant during water exchange between the coastal area and open sea, (4) reduction of iodate and oxidation of iodide in the open sea seems to be a slow process.
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