| 1. |
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| 2. |
- Buckland, Philip I., 1973-, et al.
(författare)
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The Strategic Environmental Archaeology Database : a resource for international, multiproxy and transdisciplinary studies of environmental and climatic change
- 2015
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Konferensbidrag (refereegranskat)abstract
- Climate and environmental change are global challenges which require global data and infrastructure to investigate. These challenges also require a multi-proxy approach, integrating evidence from Quaternary science and archaeology with information from studies on modern ecology and physical processes among other disciplines. The Strategic Environmental Archaeology Database (SEAD http://www.sead.se) is a Swedish based international research e-infrastructure for storing, managing, analysing and disseminating palaeoenvironmental data from an almost unlimited number of analysis methods. The system currently makes available raw data from over 1500 sites (>5300 datasets) and the analysis of Quaternary fossil insects, plant macrofossils, pollen, geochemistry and sediment physical properties, dendrochronology and wood anatomy, ceramic geochemistry and bones, along with numerous dating methods. This capacity will be expanded in the near future to include isotopes, multi-spectral and archaeo-metalurgical data. SEAD also includes expandable climate and environment calibration datasets, a complete bibliography and extensive metadata and services for linking these data to other resources. All data is available as Open Access through http://qsead.sead.se and downloadable software. SEAD is maintained and managed at the Environmental Archaeology Lab and HUMlab at Umea University, Sweden. Development and data ingestion is progressing in cooperation with The Laboratory for Ceramic Research and the National Laboratory for Wood Anatomy and Dendrochronology at Lund University, Sweden, the Archaeological Research Laboratory, Stockholm University, the Geoarchaeological Laboratory, Swedish National Historical Museums Agency and several international partners and research projects. Current plans include expanding its capacity to serve as a data source for any system and integration with the Swedish National Heritage Board's information systems. SEAD is partnered with the Neotoma palaeoecology database (http://www.neotomadb.org) and a new initiative for building cyberinfrastructure for transdisciplinary research and visualization of the long-term human ecodynamics of the North Atlantic funded by the National Science Foundation (NSF).
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| 3. |
- Barnes, Paul W., et al.
(författare)
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Ozone depletion, ultraviolet radiation, climate change and prospects for a sustainable future
- 2019
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Ingår i: Nature Sustainability. - : Springer Science and Business Media LLC. - 2398-9629. ; 2:7, s. 569-579
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Forskningsöversikt (refereegranskat)abstract
- © 2019, Springer Nature Limited. Changes in stratospheric ozone and climate over the past 40-plus years have altered the solar ultraviolet (UV) radiation conditions at the Earth’s surface. Ozone depletion has also contributed to climate change across the Southern Hemisphere. These changes are interacting in complex ways to affect human health, food and water security, and ecosystem services. Many adverse effects of high UV exposure have been avoided thanks to the Montreal Protocol with its Amendments and Adjustments, which have effectively controlled the production and use of ozone-depleting substances. This international treaty has also played an important role in mitigating climate change. Climate change is modifying UV exposure and affecting how people and ecosystems respond to UV; these effects will become more pronounced in the future. The interactions between stratospheric ozone, climate and UV radiation will therefore shift over time; however, the Montreal Protocol will continue to have far-reaching benefits for human well-being and environmental sustainability.
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| 4. |
- Åkesson, Sofia, et al.
(författare)
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Characterizing natural degradation of tetrachloroethene (PCE) using a multidisciplinary approach
- 2020
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Ingår i: Ambio: a Journal of the Human Environment. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 50, s. 1074-1088
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Tidskriftsartikel (refereegranskat)abstract
- A site in mid-western Sweden contaminated with chlorinated solvents originating from a previous dry cleaning facility, was investigated using conventional groundwater analysis combined with compound-specific isotope data of carbon, microbial DNA analysis, and geoelectrical tomography techniques. We show the value of this multidisciplinary approach, as the different results supported each interpretation, and show where natural degradation occurs at the site. The zone where natural degradation occurred was identified in the transition between two geological units, where the change in hydraulic conductivity may have facilitated biofilm formation and microbial activity. This observation was confirmed by all methods and the examination of the impact of geological conditions on the biotransformation process was facilitated by the unique combination of the applied methods. There is thus significant benefit from deploying an extended array of methods for these investigations, with the potential to reduce costs involved in remediation of contaminated sediment and groundwater.
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| 5. |
- Bobrowski, Nicole, et al.
(författare)
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Multi-component gas emission measurements of the active lava lake of Nyiragongo, DR Congo
- 2017
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Ingår i: Journal of African Earth Sciences. - : Elsevier BV. - 1879-1956 .- 1464-343X. ; 134, s. 856-865
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Tidskriftsartikel (refereegranskat)abstract
- Between 2007 and 2011 four measurement campaigns (June 2007, July 2010, June 2011, and December 2011) were carried out at the crater rim of Nyiragongo volcano, DR Congo. Nyiragongo is one of the most active volcanoes in Africa. The ground-based remote sensing technique Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), which uses scattered sunlight, the in-situ Multi-Component Gas Analyzer System (Multi-GAS) and alkaline impregnated filter were simultaneously applied during all field trips. The bromine monoxide to sulfur dioxide (BrO/SO2) and carbon dioxide to sulfur dioxide (CO2/SO2) molar ratios were determined, among other ratios. During the different field trips variations of the level of the lava lake up to several tens of meters were observed during intervals of the order of minutes up to days and also between the years. The measured gas ratios presented covariations with the lava lake level changes. BrO/SO2 ratios and CO2/SO2 ratios showed similar behavior. Annual CO2/SO2 and BrO/SO2 average values are generally positively correlated. In June 2011 increased BrO/SO2 as well as increased CO2/SO2 ratios have been observed before a sudden decrease of the lava lake. Overall the Cl/S ratio, determined by filter-pack sampling, shows an increasing trend with time, which is accompanied by a decreasing sulfur dioxide flux, the later measured nearly continuously by automated MAX-DOAS instruments since 2004. Mean gas emission fluxes of CO2, Cl and ‘minimum-BrO’ fluxes are calculated using their ratio to SO2. The first two show an increase with time, in contrast to the SO2 fluxes. A simple conceptual model is proposed which can explain in particular the June 2011 data, but as well our entire data set. The proposed model takes up the idea of convective magma cells inside the conduit and the possible temporary interruption of part of the cycling. We propose than two alternatives to explain the observed gas emission variation: 1. It is assumed that the diffuse and fumarolic degassing could have significant influence on measured gas composition. The measured gas composition might rather represent a gas mixture of plume, diffuse and fumarolic degassing than only representing the volcanic plume. 2. It is proposed that the interruption of the convection has taken place in the upper part of the conduit and deep degassing of CO2 and bromine initially continues while mixing already with gas emissions from an ageing source, which is characterized by an already diminishing sulfur content. These complex process but as well as the gas mixing of different sources, could explain general features of our dataset, but can unfortunately neither be confirmed nor disproven by the data available today.
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| 6. |
- Aldenhoff, Wiebke, 1985, et al.
(författare)
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Comparison of ice/water classification in Fram Strait from C- and L-band SAR imagery
- 2018
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Ingår i: Annals of Glaciology. - : Cambridge University Press (CUP). - 0260-3055 .- 1727-5644. ; 59:76pt2, s. 112-123
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Tidskriftsartikel (refereegranskat)abstract
- In this paper an algorithm for ice/water classification of C- and L-band dual polarization synthetic aperture radar data is presented. A comparison of the two different frequencies is made in order to investigate the potential to improve classification results with multi-frequency data. The algorithm is based on backscatter intensities in co- and cross-polarization and autocorrelation as a texture feature. The mapping between image features and ice/water classification is made with a neural network. Accurate ice/water maps for both frequencies are produced by the algorithm and the results of two frequencies generally agree very well. Differences are found in the marginal ice zone, where the time difference between acquisitions causes motion of the ice pack. C-band reliably reproduces the outline of the ice edge, while L-band has its strengths for thin ice/calm water areas within the icepack. The classification shows good agreement with ice/water maps derived from met.no ice-charts and radiometer data from AMSR-2. Variations are found in the marginal ice zone where the generalization of the ice charts and lower accuracy of ice concentration from radiometer data introduce deviations. Usage of high-resolution dual frequency data could be beneficial for improving ice cover information for navigation and modelling.
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| 7. |
- Weis, Franz A., et al.
(författare)
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Magmatic water contents determined through clinopyroxene : Examples from the Western Canary Islands, Spain
- 2015
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Ingår i: Geochemistry Geophysics Geosystems. - 1525-2027. ; 16:7, s. 2127-2146
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Tidskriftsartikel (refereegranskat)abstract
- Water is a key parameter in magma genesis, magma evolution, and resulting eruption styles, because it controls the density, the viscosity, as well as the melting and crystallization behavior of a melt. The parental water content of a magma is usually measured through melt inclusions in minerals such as olivine, a method which may be hampered, however, by the lack of melt inclusions suitable for analysis, or postentrapment changes in their water content. An alternative way to reconstruct the water content of a magma is to use nominally anhydrous minerals (NAMs), such as pyroxene, which take up low concentrations of hydrogen as a function of the magma's water content. During magma degassing and eruption, however, NAMs may dehydrate. We therefore tested a method to reconstruct the water contents of dehydrated clinopyroxene phenocrysts from the Western Canary islands (n=28) through rehydration experiments followed by infrared and Mossbauer spectroscopy. Employing currently available crystal/melt partitioning data, the results of the experiments were used to calculate parental water contents of 0.710.07 to 1.490.15 wt % H2O for Western Canary magmas during clinopyroxene crystallization at upper mantle conditions. This H2O range is in agreement with calculated water contents using plagioclase-liquid-hygrometry, and with previously published data for mafic lavas from the Canary Islands and comparable ocean island systems elsewhere. Utilizing NAMs in combination with hydrogen treatment can therefore serve as a proxy for pre-eruptive H2O contents, which we anticipate becoming a useful method applicable to mafic rocks where pyroxene is the main phenocryst phase.
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| 8. |
- Arellano, Santiago, 1981
(författare)
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Studies of Volcanic Plumes with Remote Spectroscopic Sensing Techniques -DOAS and FTIR measurements on volcanoes of the Network for Observation of Volcanic and Atmospheric Change-
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Volcanism is a rich geodynamical process, closely linked to the origin and ongoing evolution of the lithosphere, atmosphere, hydrosphere and biosphere. Humans have benefited from the resources provided by volcanoes but also been threatened by the dangers of volcanic eruptions, which accurate prediction remains elusive. This is partly due to the inherent complexity of volcanic systems and partly because of the difficulty of conducting key observations to characterize them. In particular, since the segregation and escape of magmatic volatiles are essential mechanisms behind volcanic eruptions, monitoring the intensity and composition of the resulting emissions in the atmosphere is essential to characterize the state of volcanic activity; however, their direct measurement is not always feasible.Remote spectroscopic sensing, whereby gas species can be quantified by their spectral signatures in electromagnetic radiation gathered at a prudent distance from the plume, offers the possibility to conduct reliable and sustainable monitoring of volcanic emissions. To expand the remote sensing capabilities of volcanological observatories the Network for Observation of Volcanic and Atmospheric Change (NOVAC) was established in 2005. The central theme of this thesis is the acquisition, analysis and interpretation of measurements of volcanic gas emissions on volcanoes of NOVAC. Measurements of the mass flow rate of SO2 and the molar ratios of SO2 against BrO and HCl were obtained by scanning-Differential Optical Absorption Spectroscopy (DOAS) of scattered solar ultraviolet radiation and by Fourier-Transform Spectroscopy (FTIR) of direct solar infrared radiation. The uncertainty of the measurements is characterized and methods for combining observations from different sensors implemented. Statistical and physical models of degassing are proposed for selected volcanoes of the network. The resulting time-series of emission on 16 volcanoes is one of the more detailed compilations of volcanic degassing in the last decade, particularly from passive emissions which are difficult to detect from satellite platforms. This work aims at advancing our knowledge of volcanic eruptions for a better mitigation of their risks.
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| 9. |
- Löfgren, Johan, 1983, et al.
(författare)
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Sea level measurements using multi-frequency GPS and GLONASS observations
- 2014
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Ingår i: Eurasip Journal on Advances in Signal Processing. - : Springer Science and Business Media LLC. - 1687-6172 .- 1687-6180. ; 2014:1
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Tidskriftsartikel (refereegranskat)abstract
- Global Positioning System (GPS) tide gauges have been realized in different configurations, e.g., with one zenith-looking antenna, using the multipath interference pattern for signal-to-noise ratio (SNR) analysis, or with one zenith- and one nadir-looking antenna, analyzing the difference in phase delay, to estimate the sea level height. In this study, for the first time, we use a true Global Navigation Satellite System (GNSS) tide gauge, installed at the Onsala Space Observatory. This GNSS tide gauge is recording both GPS and Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) signals and makes it possible to use both the one- and two-antenna analysis approach. Both the SNR analysis and the phase delay analysis were evaluated using dual-frequency GPS and GLONASS signals, i.e., frequencies in the L-band, during a 1-month-long campaign. The GNSS-derived sea level results were compared to independent sea level observations from a co-located pressure tide gauge and show a high correlation for both systems and frequency bands, with correlation coefficients of 0.86 to 0.97. The phase delay results show a better agreement with the tide gauge sea level than the SNR results with root-mean-square differences of 3.5 cm (GPS L1 and L2) and 3.3/3.2 cm (GLONASS L1/L2 bands) compared to 4.0/9.0 cm (GPS L1/L2 ) and 4.7/8.9 cm (GLONASS L1/L2 bands). GPS and GLONASS show similar performance in the comparison, and the results show that for the phase delay analysis, it is possible to use both frequencies, whereas for the SNR analysis, the L2 band should be avoided if other signals are available. Note that standard geodetic receivers using code-based tracking, i.e., tracking the un-encrypted C/A-code on L1 and using the manufacturers’ proprietary tracking method for L2 , were used. Signals with the new C/A-code on L2 , the so-called L2C, were not tracked.Using wind speed as an indicator for sea surface roughness, we find that the SNR analysis performs better in rough sea surface conditions than the phase delay analysis. The SNR analysis is possible even during the highest wind speed observed during this campaign (17.5 m/s), while the phase delay analysis becomes difficult for wind speeds above 6 m/s.
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| 10. |
- Hobiger, Thomas, 1978, et al.
(författare)
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Software-Defined Radio Direct Correlation GNSS Reflectometry by Means of GLONASS
- 2016
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Ingår i: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. - 2151-1535 .- 1939-1404. ; 9:10, s. 4834-4842
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Tidskriftsartikel (refereegranskat)abstract
- Ground-based GNSS reflectometry (GNSS-R)systems can be realized by different means. The concept ofcorrelation between direct and reflected GNSS signals is basicallypossible with all GNSS systems. However, using signals fromthe Russian GLONASS system simplifies the signal processingso that software-defined radio (SDR) components can be usedat replace expensive hardware solutions. This paper discusseshow such a solution, called GLONASS-R, can be realized usingentirely off-the-shelf components. Field tests with such a systemdemonstrate the capability to monitor sea surface heights with aprecision of 3 cm or better even with a sampling rate of 1.5 Hz.The flexibility of a SDR and the simple concept of GLONASS-Rallow build such a system with low costs and adapt it to the needsof any ground-based GNSS-R problem.
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