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  • 1. Aamaas, Borgar
    et al.
    Boggild, Carl Egede
    Stordal, Frode
    Berntsen, Terje
    Holmen, Kim
    Ström, Johan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Elemental carbon deposition to Svalbard snow from Norwegian settlements and long-range transport2011In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 63, no 3, 340-351 p.Article in journal (Refereed)
    Abstract [en]

    The impact on snow pack albedo from local elemental carbon (EC) sources in Svalbard has been investigated for the winter of 2008. Highly elevated EC concentrations in the snow are observed around the settlements of Longyearbyen and Svea (locally > 1000 ng g(-1), about 200 times over the background level), while EC concentrations similar to the background level are seen around Ny-Alesund. Near Longyearbyen and Svea, darkened snow influenced by wind transported coal dust from open coal stockpiles is clearly visible from satellite images and by eye at the ground. As a first estimate, the reduction in snow albedo caused by local EC pollution from the Norwegian settlements has been compared to the estimated reduction caused by long-range transported EC for entire Svalbard. The effect of local EC from Longyearbyen, Svea and all Norwegian settlements are estimated to 2.1%, 7.9% and 10% of the total impact of EC, respectively. The EC particles tend to stay on the surface during melting, and elevated EC concentrations due to the spring melt was observed. This accumulation of EC enhances the positive albedo feedbacks. The EC concentrations were observed to be larger in metamorphosed snow than in fresh snow, and especially around ice lenses.

  • 2. Abbasi, Alireza
    et al.
    Geranmayeh, Shokoofeh
    Skripkin, Mikhail Y.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Potassium ion-mediated non-covalent bonded coordination polymers2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 3, 850-859 p.Article in journal (Refereed)
    Abstract [en]

    Crystal structures and vibrational spectra of three related network-forming coordination complexes have been studied. Two novel thermodynamically stable pseudo-polymorphic solvated rhodium chloro compounds, [cis-RhCl4(DMSO-kappa S)(2)K](n), 1, and [cis-RhCl4(DMSO-kappa S)(2)K center dot 3H(2)O](n), 2, and one metastable compound [trans-RhCl4(DMSO-kappa S)(2)K center dot 0.25H(2)O](n), 3, crystallize at ambient temperature in the orthorhombic space group P2(1)2(1)2(1) for 1, and the monoclinic space groups P2(1)/n and P2(1)/c for 2 and 3, respectively. All three structures contain [RhCl4(DMSO-kappa S)(2)]-complexes in which the rhodium(III) ions bind to two dimethyl sulfoxide (DMSO) sulfur atoms and four chloride ions in distorted octahedral coordination geometries. The complexes are connected in networks via potassium ions interacting with the Cl- and the DMSO oxygen atoms. As the sum of Shannon ionic radii of K+ and Cl- exceeds the K-Cl distances in compounds under study, these compounds can be described as Rh-Cl-K coordination polymers with non-covalent bonding, which is not common in these systems, forming 1- and 2-D networks for 1/2 and 3, respectively. The 2-D network with nano-layered sheets for compound 3 was also confirmed by TEM images. Further evaluation of the bonding in the cis- and trans-[RhCl4(DMSO-kappa S)(2)](-) entities was obtained by recording Raman and FT-IR absorption spectra and assigning the vibrational frequencies with the support of force-field calculations. The force field study of complexes reveals the strong domination of trans-effect (DMSO-kappa S > Cl) over the effect of non-covalent bonding in coordination polymeric structures. The comparison of calculated RhCl, RhS and SO stretching force constants showed evidence of K+-ligand interactions whereas direct experimental evidences of K+-Cl- interaction were not obtained because of strong overlap of the corresponding spectral region with that where lattice modes and Rh-ligand bendings appear.

  • 3. Abbasi, Saeed
    et al.
    Jansson, Anders
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Olander, Lars
    Olofsson, Ulf
    Sellgren, Ulf
    A pin-on-disc study of the rate of airborne wear particle emissions from railway braking materials2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 284, 18-29 p.Article in journal (Refereed)
    Abstract [en]

    The current study investigates the characteristics of particles generated from the wear of braking materials, and provides an applicable index for measuring and comparing wear particle emissions. A pin-on-disc tribometer equipped with particle measurement instruments was used. The number concentration, size, morphology, and mass concentration of generated particles were investigated and reported for particles 10 nm-32 mu m in diameter. The particles were also collected on filters and investigated using EDS and SEM. The effects of wear mechanisms on particle morphology and changes in particle concentration are discussed. A new index, the airborne wear particle emission rate (AWPER), is suggested that could be used in legislation to control non-exhaust emissions from transport modes, particularly rail transport.

  • 4.
    Abbasi, Saeed
    et al.
    KTH Royal Inst Technol, Dept Machine Design, Stockholm, Sweden.
    Jansson, Anders
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Sellgren, Ulf
    KTH Royal Inst Technol, Dept Machine Design, Stockholm, Sweden.
    Olofsson, Ulf
    KTH Royal Inst Technol, Dept Machine Design, Stockholm, Sweden.
    Particle Emissions From Rail Traffic: A Literature Review2013In: Critical reviews in environmental science and technology, ISSN 1064-3389, E-ISSN 1547-6537, Vol. 43, no 23, 2511-2544 p.Article, review/survey (Refereed)
    Abstract [en]

    Particle emissions are a drawback of rail transport. This work is a comprehensive presentation of recent research into particle emissions from rail vehicles. Both exhaust and nonexhaust particle emissions are considered when examining particle characteristics such as PM10, and PM2.5 concentration levels, size, morphology, composition, and adverse health effects, current legislation, and available and proposed solutions for reducing such emissions. High concentration levels in enclosed rail traffic environments are reported and some toxic effects of the particles. The authors find that only a few limited studies have examined the adverse health effects of nonexhaust particle emissions and that no relevant legislation exists. Thus further research in this area is warranted.

  • 5. Abbott, Benjamin W.
    et al.
    Jones, Jeremy B.
    Schuur, Edward A. G.
    Chapin, F. Stuart
    Bowden, William B.
    Bret-Harte, M. Syndonia
    Epstein, Howard E.
    Flannigan, Michael D.
    Harms, Tamara K.
    Hollingsworth, Teresa N.
    Mack, Michelle C.
    McGuire, A. David
    Natali, Susan M.
    Rocha, Adrian V.
    Tank, Suzanne E.
    Turetsky, Merritt R.
    Vonk, Jorien E.
    Wickland, Kimberly P.
    Aiken, George R.
    Alexander, Heather D.
    Amon, Rainer M. W.
    Benscoter, Brian W.
    Bergeron, Yves
    Bishop, Kevin
    Blarquez, Olivier
    Bond-Lamberty, Ben
    Breen, Amy L.
    Buffam, Ishi
    Cai, Yihua
    Carcaillet, Christopher
    Carey, Sean K.
    Chen, Jing M.
    Chen, Han Y. H.
    Christensen, Torben R.
    Cooper, Lee W.
    Cornelissen, J. Hans C.
    de Groot, William J.
    DeLuca, Thomas H.
    Dorrepaal, Ellen
    Fetcher, Ned
    Finlay, Jacques C.
    Forbes, Bruce C.
    French, Nancy H. F.
    Gauthier, Sylvie
    Girardin, Martin P.
    Goetz, Scott J.
    Goldammer, Johann G.
    Gough, Laura
    Grogan, Paul
    Guo, Laodong
    Higuera, Philip E.
    Hinzman, Larry
    Hu, Feng Sheng
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jafarov, Elchin E.
    Jandt, Randi
    Johnstone, Jill F.
    Karlsson, Jan
    Kasischke, Eric S.
    Kattner, Gerhard
    Kelly, Ryan
    Keuper, Frida
    Kling, George W.
    Kortelainen, Pirkko
    Kouki, Jari
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Laudon, Hjalmar
    Laurion, Isabelle
    Macdonald, Robie W.
    Mann, Paul J.
    Martikainen, Pertti J.
    McClelland, James W.
    Molau, Ulf
    Oberbauer, Steven F.
    Olefeldt, David
    Pare, David
    Parisien, Marc-Andre
    Payette, Serge
    Peng, Changhui
    Pokrovsky, Oleg S.
    Rastetter, Edward B.
    Raymond, Peter A.
    Raynolds, Martha K.
    Rein, Guillermo
    Reynolds, James F.
    Robards, Martin
    Rogers, Brendan M.
    Schaedel, Christina
    Schaefer, Kevin
    Schmidt, Inger K.
    Shvidenko, Anatoly
    Sky, Jasper
    Spencer, Robert G. M.
    Starr, Gregory
    Striegl, Robert G.
    Teisserenc, Roman
    Tranvik, Lars J.
    Virtanen, Tarmo
    Welker, Jeffrey M.
    Zimov, Sergei
    Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire: an expert assessment2016In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 11, no 3, 034014Article in journal (Refereed)
    Abstract [en]

    As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.

  • 6. Abbott, P. M.
    et al.
    Austin, W. E. N.
    Davies, S. M.
    Pearce, N. J. G.
    Rasmussen, T. L.
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Brendryen, J.
    Re-evaluation and extension of the Marine Isotope Stage 5 tephrostratigraphy of the Faroe Islands region: The cryptotephra record2014In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 409, 153-168 p.Article in journal (Refereed)
    Abstract [en]

    Previous studies of marine sequences from the Faroe Islands region have identified a series of coarse-grained tephra horizons deposited during Marine Isotope Stage (MIS) 5. Here we reassess the MIS 5 tephrostratigraphy of the Faroe Islands region and focus on the cryptotephra deposits preserved within the fine-grained fraction of marine core LINK 16. We also extend the record to encompass the late MIS 6 and early MIS 4 periods. A density separation technique, commonly used for tephra investigations in lacustrine settings but rarely applied to marine sediments, is utilised to explore the fine-grained material and EPMA and LA-ICP-MS are employed to determine the major and trace element composition of individual tephra shards. In total, 3 basaltic and 3 rhyolitic Icelandic cryptotephra deposits with homogeneous geochemical compositions are identified - all of which have the potential to act as isochronous tie-lines. Geochemical results highlight that the Grimsvotn volcanic system of Iceland is the predominant source of the basaltic horizons and the Oraefajokull or Torfajokull systems are the likely sources of the rhyolitic deposits. Three of the horizons have been previously recognised in Faroe Islands region marine sequences, with two of these deposits traceable into a Norwegian Sea sequence. An early MIS 4 rhyolitic horizon is the most widespread deposit as it can be traced into the Norwegian Sea and to the south into a record from the Rockall Trough. Basaltic and rhyolitic horizons deposited during late MIS 6 have not been recognised in other sequences and represent new additions to the regional tephrostratigraphy.

  • 7. Abbott, Peter M.
    et al.
    Davies, Siwan M.
    Steffensen, Jorgen Peder
    Pearce, Nicholas J. G.
    Bigler, Matthias
    Johnsen, Sigfus J.
    Seierstad, Inger K.
    Svensson, Anders
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    A detailed framework of Marine Isotope Stages 4 and 5 volcanic events recorded in two Greenland ice-cores2012In: Quaternary Science Reviews, ISSN 0277-3791, Vol. 36, 59-77 p.Article in journal (Refereed)
    Abstract [en]

    Sulphate records from Greenland ice-cores indicate that Marine Isotope Stages 4 and 5 were charactensed by a higher incidence of large volcanic eruptions than other periods during the last glacial period, however, few investigations have focused on tephra deposits associated with these volcanic eruptions and the nature and origin of the events. Here we present a detailed tephrochronological framework of the products of 15 volcanic events spanning this interval: the majority of which have been preserved as cryptotephra horizons within the Greenland records. The major element compositions of individual glass shards within these horizons indicate that 13 of the eruptions originated from Iceland and 6 of these events can be correlated to the specific volcanic systems of Katla, Grimsvotn, Grimsvotn-Kverkfjoll and either Reykjanes or Veidivotn-Bardarbunga. For the remaining Icelandic horizons a source from either the rift zone or a flank zone can be suggested based on rock suite affinities. Two horizons have been correlated to a source from the Jan Mayen volcanic system which represents the first discovery of material from this system within any Greenland ice-cores. The robust geochemical characterisations, independent ages for these horizons (derived from the GICCO5 ice-core chronology) and stratigraphic positions relative to the Dansgaard-Oeschger climate events recorded in the Greenland ice-cores represent a critical framework that provides new information on the frequency and nature of volcanic events occurring in the North Atlantic region during MIS 4 and 5. This framework can now be utilised in the assessment of the differential timing and rate of response to the millennial-scale climatic events that characterised this period, through the use of the tephra horizons as time-synchronous tie-lines to other palaeoclimatic sequences.

  • 8. Abdelkader, M.
    et al.
    Metzger, S.
    Mamouri, R. E.
    Astitha, M.
    Barrie, Leonard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Levin, Z.
    Lelieveld, J.
    Dust-air pollution dynamics over the eastern Mediterranean2015In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, no 16, 9173-9189 p.Article in journal (Refereed)
    Abstract [en]

    Interactions of desert dust and air pollution over the eastern Mediterranean (EM) have been studied, focusing on two distinct dust transport events on 22 and 28 September 2011. The atmospheric chemistry-climate model EMAC has been used at about 50 km grid spacing, applying an on-line dust emission scheme and calcium as a proxy for dust reactivity. EMAC includes a detailed tropospheric chemistry mechanism, aerosol microphysics and thermodynamics schemes to describe dust aging. The model is evaluated using ground-based observations for aerosol concentrations and aerosol optical depth (AOD) as well as satellite observations. Simulation results and back trajectory analysis show that the development of synoptic disturbances over the EM can enhance dust transport from the Sahara and Arabian deserts in frontal systems that also carry air pollution to the EM. The frontal systems are associated with precipitation that controls the dust removal. Our results show the importance of chemical aging of dust, which increases particle size, dust deposition and scavenging efficiency during transport, overall reducing the lifetime relative to non-aged dust particles. The relatively long travel periods of Saharan dust result in more sustained aging compared to Arabian dust. Sensitivity simulations indicate 3 times more dust deposition of aged relative to pristine dust, which significantly decreases the dust lifetime and loading.

  • 9. Abdelkader, Mohamed
    et al.
    Metzger, Swen
    Steil, Benedikt
    Klingmüller, Klaus
    Tost, Holger
    Pozzer, Andrea
    Stenchikov, Georgiy
    Barrie, Leonard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lelieveld, Jos
    Sensitivity of transatlantic dust transport to chemical aging and related atmospheric processes2017In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 6, 3799-3821 p.Article in journal (Refereed)
    Abstract [en]

    We present a sensitivity study on transatlantic dust transport, a process which has many implications for the atmosphere, the ocean and the climate. We investigate the impact of key processes that control the dust outflow, i.e., the emission flux, convection schemes and the chemical aging of mineral dust, by using the EMAC model following Abdelkader et al. (2015). To characterize the dust outflow over the Atlantic Ocean, we distinguish two geographic zones: (i) dust interactions within the Intertropical Convergence Zone (ITCZ), or the dust-ITCZ interaction zone (DIZ), and (ii) the adjacent dust transport over the Atlantic Ocean (DTA) zone. In the latter zone, the dust loading shows a steep and linear gradient westward over the Atlantic Ocean since particle sedimentation is the dominant removal process, whereas in the DIZ zone aerosol-cloud interactions, wet deposition and scavenging processes determine the extent of the dust outflow. Generally, the EMAC simulated dust compares well with CALIPSO observations; however, our reference model configuration tends to overestimate the dust extinction at a lower elevation and underestimates it at a higher elevation. The aerosol optical depth (AOD) over the Caribbean responds to the dust emission flux only when the emitted dust mass is significantly increased over the source region in Africa by a factor of 10. These findings point to the dominant role of dust removal (especially wet deposition) in transatlantic dust transport. Experiments with different convection schemes have indeed revealed that the transatlantic dust transport is more sensitive to the convection scheme than to the dust emission flux parameterization. To study the impact of dust chemical aging, we focus on a major dust outflow in July 2009. We use the calcium cation as a proxy for the overall chemical reactive dust fraction and consider the uptake of major inorganic acids (i.e., H2SO4, HNO3 and HCl) and their anions, i.e., sulfate (SO42-), bisulfate (HSO4-), nitrate (NO 3) and chloride (Cl), on the surface of mineral particles. The subsequent neutralization reactions with the calcium cation form various salt compounds that cause the uptake of water vapor from the atmosphere, i.e., through the chemical aging of dust particles leading to an increase of 0.15 in the AOD under subsaturated conditions (July 2009 monthly mean). As a result of the radiative feedback on surface winds, dust emissions increased regionally. On the other hand, the aged dust particles, compared to the non-aged particles, are more efficiently removed by both wet and dry deposition due to the increased hygroscopicity and particle size (mainly due to water uptake). The enhanced removal of aged particles decreases the dust burden and lifetime, which indirectly reduces the dust AOD by 0.05 (monthly mean). Both processes can be significant (major dust outflow, July 2009), but the net effect depends on the region and level of dust chemical aging.

  • 10. Abel, Sebastian
    et al.
    Nybom, Inna
    Maenpaa, Kimmo
    Hale, Sarah E.
    Cornelissen, Gerard
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Norwegian Geotechnical Institute, Norway; Norwegian University of Life Sciences, Norway.
    Akkanen, Jarkko
    Mixing and capping techniques for activated carbon based sediment remediation Efficiency and adverse effects for Lumbriculus variegatus2017In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 114, 104-112 p.Article in journal (Refereed)
    Abstract [en]

    Activated carbon (AC) has been proven to be highly effective for the in-situ remediation of sediments contaminated with a wide range of hydrophobic organic contaminants (HOCs). However, adverse biological effects, especially to benthic organisms, can accompany this promising remediation potential. In this study, we compare both the remediation potential and the biological effects of several AC materials for two application methods: mixing with sediment (MIX) at doses of 0.1 and 1.0% based on sediment dw and thin layer capping (TLC) with 0.6 and 1.2 kg AC/m(2). Significant dose dependent reductions in PCB bioaccumulation in Lumbriculus variegatus of 35-93% in MIX treatments were observed. Contaminant uptake in TLC treatments was reduced by up to 78% and differences between the two applied doses were small. Correspondingly, significant adverse effects were observed for L. variegatus whenever AC was present in the sediment. The lowest application dose of 0.1% AC in the MIX system reduced L variegatus growth, and 1.0% AC led to a net loss of organism biomass. All TLC treatments let to a loss of biomass in the test organism. Furthermore, mortality was observed with 1.2 kg ACim(2) doses of pure AC for the TLC treatment. The addition of clay (Kaolinite) to the TLC treatments prevented mortality, but did not decrease the loss in biomass. While TLC treatments pose a less laborious alternative for AC amendments in the field, the results of this study show that it has lower remediation potential and could be more harmful to the benthic fauna.

  • 11. Abernethy, K. E.
    et al.
    Bodin, Örjan
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Olsson, Per
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Hilly, Z.
    Schwarz, A.
    Two steps forward, two steps back: The role of innovation in transforming towards community-based marine resource management in Solomon Islands2014In: Global Environmental Change, ISSN 0959-3780, E-ISSN 1872-9495, Vol. 28, 309-321 p.Article in journal (Refereed)
    Abstract [en]

    In many coastal nations, community-based arrangements for marine resource management (CBRM) are promoted by government, advocated for by non-government actors, and are seen by both as one of the most promising options to achieve sustainable use and secure inshore fisheries and aquatic resources. Although there is an abundant literature on what makes CBRM effective, is it less clear how CBRM is introduced or develops as an idea in a community, and the process of how the idea leads to the adoption of a new resource management approach with supporting institutions. Here we aim to address this gap by applying an explicit process-based approach drawing on innovation history methodology by mapping and analysing the initiation and emergence of CBRM in five fishing-dependent communities in Solomon Islands. We use insights from the literatures on diffusion of innovation and transformability to define phases of the process and help guide the inductive analysis of qualitative data. We show the CBRM institutionalisation processes were non-linear, required specific strategies to move from one phase to the next, and key elements facilitated or hindered movement. Building active support for CBRM within communities depended on the types of events that happened at the beginning of the process and actions taken to sustain this. Matching CBRM to known resource management ideas or other social problems in the community, developing legitimate institutions and decision-making processes, strong continual interactions between key actors and the rest of the community (not necessarily NGO actors), and community members witnessing benefits of CBRM, all contributed to the emergence and diffusion of CBRM in the communities, and helped to overcome barriers to transformative change.

  • 12. Abunge, Caroline
    et al.
    Coulthard, Sarah
    Daw, Tim M.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Connecting Marine Ecosystem Services to Human Well-being: Insights from Participatory Well-being Assessment in Kenya2013In: Ambio, ISSN 0044-7447, Vol. 42, no 8, 1010-1021 p.Article in journal (Refereed)
    Abstract [en]

    The linkage between ecosystems and human well-being is a focus of the conceptualization of ecosystem services as promoted by the Millennium Ecosystem Assessment. However, the actual nature of connections between ecosystems and the well-being of individuals remains complex and poorly understood. We conducted a series of qualitative focus groups with five different stakeholder groups connected to a small-scale Kenyan coastal fishery to understand (1) how well-being is understood within the community, and what is important for well-being, (2) how people's well-being has been affected by changes over the recent past, and (3) people's hopes and aspirations for their future fishery. Our results show that people conceive well-being in a diversity of ways, but that these can clearly map onto the MA framework. In particular, our research unpacks the freedoms and choices element of the framework and argues for greater recognition of these aspects of well-being in fisheries management in Kenya through, for example, more participatory governance processes.

  • 13. Achtert, P.
    et al.
    Brooks, I. M.
    Brooks, B. J.
    Moat, B. I.
    Prytherch, J.
    Persson, P. O. G.
    Tjernström, Michael
    Stockholm University, Faculty of Science, Department of Meteorology .
    Measurement of wind profiles by motion-stabilised ship-borne Doppler lidar2015In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 8, no 11, 4993-5007 p.Article in journal (Refereed)
    Abstract [en]

    Three months of Doppler lidar wind measurements were obtained during the Arctic Cloud Summer Experiment on the icebreakerOden during the summer of 2014. Such ship-borne Doppler measurements require active stabilisation to remove the effects of ship motion. We demonstrate that the combination of a commercial Doppler lidar with a custom-made motion-stabilisation platform enables the retrieval of wind profiles in the Arctic atmospheric boundary layer during both cruising and ice-breaking with statistical uncertainties comparable to land-based measurements. This held true particularly within the atmospheric boundary layer even though the overall aerosol load was very low. Motion stabilisation was successful for high wind speeds in open water and the resulting wave conditions. It allows for the retrieval of vertical winds with a random error below 0.2 m s−1. The comparison of lidar-measured wind and radio soundings gives a mean bias of 0.3 m s−1 (2°) and a mean standard deviation of 1.1 m s−1 (12°) for wind speed (wind direction). The agreement for wind direction degrades with height. The combination of a motion-stabilised platform with a low-maintenance autonomous Doppler lidar has the potential to enable continuous long-term high-resolution ship-based wind profile measurements over the oceans.

  • 14.
    Achtert, Peggy
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Birmili, W.
    Nowak, A.
    Wehner, B.
    Wiedensohler, A.
    Takegawa, N.
    Kondo, Y.
    Miyazaki, Y.
    Hu, M.
    Zhu, T.
    Hygroscopic growth of tropospheric particle number size distributions over the North China Plain2009In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 114, D00G07- p.Article in journal (Refereed)
    Abstract [en]

    The hygroscopic growth of atmospheric submicrometer particle size distributions (diameter D-p ranging from 22 to 900 nm) was studied at a rural/suburban site in the North China Plain within the framework of the international Campaigns of Air Quality Research in Beijing and Surrounding Region 2006 (CAREBeijing-2006) research project. The goal was to characterize the regional aerosol in the polluted northeastern plain in China. Size descriptive hygroscopic growth factors (DHGFs) were determined as a function of relative humidity (RH) by relating the particle number size distribution at a dry condition ( 100 nm), the DHGF are substantially higher than in the Aitken particle mode (D-p < 100 nm) as a result of different chemical composition. The size-dependent behavior of the DHGF highlights the relevance of particulate sulfate production over the North China Plain, accomplished by secondary formation from the gas phase and, potentially, liquid phase processes in convective clouds. Furthermore, all results concerning the DHGF show a significant dependency on meteorological air masses. The hygroscopic growth of accumulation mode particles correlates significantly with the PM1-mass fraction of sulfate ions determined by chemical analysis. Finally, this investigation provides a parameterization of the hygroscopic growth of 250-nm particles, which might be useful when predicting visibility and radiative forcing and performing atmospheric aerosol model validations.

  • 15.
    Achtert, Peggy
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Karlsson Andersson, M.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khosrawi, Farahnaz
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    On the linkage between tropospheric and Polar Stratospheric clouds in the Arctic as observed by space-borne lidar2012In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, no 8, 3791-3798 p.Article in journal (Refereed)
    Abstract [en]

    The type of Polar stratospheric clouds (PSCs) as well as their temporal and spatial extent are important for the occurrence of heterogeneous reactions in the polar stratosphere. The formation of PSCs depends strongly on temperature. However, the mechanisms of the formation of solid PSCs are still poorly understood. Recent satellite studies of Antarctic PSCs have shown that their formation can be associated with deep-tropospheric clouds which have the ability to cool the lower stratosphere radiatively and/or adiabatically. In the present study, lidar measurements aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite were used to investigate whether the formation of Arctic PSCs can be associated with deep-tropospheric clouds as well. Deep-tropospheric cloud systems have a vertical extent of more than 6.5 km with a cloud top height above 7 km altitude. PSCs observed by CALIPSO during the Arctic winter 2007/2008 were classified according to their type (STS, NAT, or ice) and to the kind of underlying tropospheric clouds. Our analysis reveals that 172 out of 211 observed PSCs occurred in connection with tropospheric clouds. 72% of these 172 observed PSCs occurred above deep-tropospheric clouds. We also find that the type of PSC seems to be connected to the characteristics of the underlying tropospheric cloud system. During the Arctic winter 2007/2008 PSCs consisting of ice were mainly observed in connection with deep-tropospheric cloud systems while no ice PSC was detected above cirrus. Furthermore, we find no correlation between the occurrence of PSCs and the top temperature of tropospheric clouds. Thus, our findings suggest that Arctic PSC formation is connected to adiabatice cooling, i.e. dynamic effects rather than radiative cooling.

  • 16.
    Achtert, Peggy
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khosrawi, Farahnaz
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Pure rotational-Raman channels of the Esrange lidar for temperature and particle extinction measurements in the troposphere and lower stratosphere2013In: Atmospheric Measurement Techniques, ISSN 1867-8548, Vol. 6, no 1, 91-98 p.Article in journal (Refereed)
    Abstract [en]

    The Department of Meteorology at Stockholm University operates the Esrange Rayleigh/Raman lidar at Esrange(68° N, 21° E) near the Swedish city of Kiruna. This paper describes the design and first measurements of the newpure rotational-Raman channel of the Esrange lidar. The Esrange lidar uses a pulsed Nd:YAG solid-state laser operating at 532 nm as light source with a repetition rate of 20 Hz and a pulse energy of 350 mJ. The minimum vertical resolution is 150m and the integration time for one profile is 5000 shots. The newly implemented channel allows for measurements of atmospheric temperature at altitudes below 35 km and is currently optimized for temperature measurements between 180 and 200 K. This corresponds to conditions in the lower Arctic stratosphere during winter. In addition to the temperature measurements, the aerosol extinction coefficientand the aerosol backscatter coefficient at 532 nm can be measured in dependently. Our filter-based design minimizes the systematic error in the obtained temperature profile to less than 0.51 K. By combining rotational-Raman measurements (5–35 km height) and the integration technique (30–80 kmheight), the Esrange lidar is now capable of measuring atmospheric temperature profiles from the upper troposphere up to the mesosphere. With the improved setup, the system can be used to validate current lidar-based polar stratospheric cloud classification schemes. The new capability of the instrument measuring temperature and aerosol extinction furthermore enables studies of the thermal structure and variability of the upper troposphere/lower stratosphere. Although several lidars are operated at polar latitudes, there are few instruments that are capable of measuring temperature profiles in the troposphere, stratosphere, and mesosphere, as well as aerosols extinction in the troposphere and lower stratospherewith daylight capability.

  • 17.
    Achtert, Peggy
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khosrawi, Farahnaz
    Stockholm University, Faculty of Science, Department of Meteorology .
    Blum, U.
    Fricke, K. H.
    Investigation of polar stratospheric clouds in January 2008 by means of ground-based and spaceborne lidar measurements and microphysical box model simulations2011In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116, D07201- p.Article in journal (Refereed)
    Abstract [en]

    Polar stratospheric clouds (PSCs) play a key role in heterogeneous chemistry and ozone depletion in the lower stratosphere. The type of PSC as well as their temporal and spatial extent are important for the occurrence of heterogeneous reactions and, thus, ozone depletion. In this study a combination of ground-based and spaceborne lidar measurements were used together with microphysical box model simulations along back trajectories to investigate the formation and alteration of Arctic PSCs. The measurements were made by the Rayleigh/Mie/Raman lidar system at Esrange and by the Cloud-Aerosol Lidar with Orthogonal Polarization aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite. Between 20 and 23 January 2008 PSCs composed of liquid particles were observed by CALIPSO between Greenland and the western side of the Scandinavian Mountains. Between 21 and 23 January 2008 the Esrange lidar observed a PSC composed of distinct layers of liquid and solid particles on the eastern side of the mountain range. Microphysical box model simulations along air parcel back trajectories indicate that liquid particles had formed at least 40 h before the observation at Esrange. Furthermore, the model indicates a high HNO(3) uptake into the liquid layer between 10 and 20 h before the observation. The PSC was formed when the air mass was over Greenland. On two occasions during these 20 h, CALIPSO observed PSCs when its measurement tracks crossed the air parcel back trajectory ending at the location of the Esrange lidar. Backscatter ratios calculated from the output of the box model simulation indicate good agreement with the values observed with the Esrange lidar and by CALIPSO. The box model simulations along the back trajectories from Esrange to the CALIPSO ground track and beyond provide us with the unique opportunity to relate ground-based and spaceborne lidar measurements that were not performed at the same spatial location and time. Furthermore, possible differences in the observations from ground and space can be traced to temporal and/or geographically induced changes in particle microphysics within the measured PSCs.

  • 18.
    Achtert, Peggy
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Tesche, Matthias
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Assessing lidar-based classification schemes for polar stratospheric clouds based on 16 years of measurements at Esrange, Sweden2014In: Journal of Geophysical Research: Atmospheres, ISSN 2169-8996, Vol. 119, no 3, 1386-1405 p.Article in journal (Refereed)
    Abstract [en]

    Lidar measurements of polar stratospheric clouds (PSCs) are commonly analyzed in classification schemes that apply the backscatter ratio and the particle depolarization ratio. This similarity of input data suggests comparable results of different classification schemes—despite measurements being performed with a variety of mostly custom-made instruments. Based on a time series of 16 years of lidar measurements at Esrange (68°N, 21°E), Sweden, we show that PSC classification differs substantially depending on the applied scheme. The discrepancies result from varying threshold values of lidar-derived parameters used to define certain PSC types. The resulting inconsistencies could impact the understanding of long-term PSC observations documented in the literature. We identify two out of seven considered classification schemes that are most likely to give reliable results and should be used in future lidar-based studies. Using polarized backscatter ratios gives the advantage of increased contrast for observations of weakly backscattering and weakly depolarizing particles. Improved confidence in PSC classification can be achieved by a more comprehensive consideration of the effect of measurement uncertainties. The particle depolarization ratio is the key to a reliable identification of different PSC types. Hence, detailed information on the calibration of the polarization-sensitive measurement channels should be provided to assess the findings of a study. Presently, most PSC measurements with lidar are performed at 532 nm only. The information from additional polarization-sensitive measurements in the near infrared could lead to an improved PSC classification. Coincident lidar-based temperature measurements at PSC level might provide useful information for an assessment of PSC classification.

  • 19.
    Acosta Navarro, Juan C.
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ekman, Annica M. L.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Pausata, Francesco S. R.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Lewinschal, Anna
    Stockholm University, Faculty of Science, Department of Meteorology .
    Varma, Vidya
    Seland, Øyvind
    Gauss, Michael
    Iversen, Trond
    Kirkevåg, Alf
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Hansson, Hans Christen
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Future response of temperature and precipitation to reduced aerosol emissions as compared with increased greenhouse gas concentrations2017In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 30, no 3, 939-954 p.Article in journal (Refereed)
    Abstract [en]

    Experiments with a climate model (NorESM1) were performed to isolate the effects of aerosol particles and greenhouse gases on surface temperature and precipitation in simulations of future climate. The simulations show that by 2025-2049, a reduction of aerosol emissions from fossil fuels following a maximum technically feasible reduction (MFR) scenario could lead to a global and Arctic warming of 0.26 K and 0.84 K, respectively; as compared with a simulation with fixed aerosol emissions at the level of 2005. If fossil fuel emissions of aerosols follow a current legislation emissions (CLE) scenario, the NorESM1 model simulations yield a non-significant change in global and Arctic average surface temperature as compared with aerosol emissions fixed at year 2005. The corresponding greenhouse gas effect following the RCP4.5 emission scenario leads to a global and Arctic warming of 0.35 K and 0.94 K, respectively.

    The model yields a marked annual average northward shift in the inter-tropical convergence zone with decreasing aerosol emissions and subsequent warming of the northern hemisphere. The shift is most pronounced in the MFR scenario but also visible in the CLE scenario. The modeled temperature response to a change in greenhouse gas concentrations is relatively symmetric between the hemispheres and there is no marked shift in the annual average position of the inter-tropical convergence zone. The strong reduction in aerosol emissions in MFR also leads to a net southward cross-hemispheric energy transport anomaly both in the atmosphere and ocean, and enhanced monsoon circulation in Southeast and East Asia causing an increase in precipitation over a large part of this region.

  • 20.
    Acosta Navarro, Juan Camilo
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Anthropogenic influence on climate through changes in aerosol emissions from air pollution and land use change2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Particulate matter suspended in air (i.e. aerosol particles) exerts a substantial influence on the climate of our planet and is responsible for causing severe public health problems in many regions across the globe. Human activities have altered the natural and anthropogenic emissions of aerosol particles through direct emissions or indirectly by modifying natural sources. The climate effects of the latter have been largely overlooked. Humans have dramatically altered the land surface of the planet causing changes in natural aerosol emissions from vegetated areas. Regulation on anthropogenic and natural aerosol emissions have the potential to affect the climate on regional to global scales. Furthermore, the regional climate effects of aerosol particles could potentially be very different than the ones caused by other climate forcers (e.g. well mixed greenhouse gases). The main objective of this work was to investigate the climatic effects of land use and air pollution via aerosol changes.

    Using numerical model simulations it was found that land use changes in the past millennium have likely caused a positive radiative forcing via aerosol climate interactions. The forcing is an order of magnitude smaller and has an opposite sign than the radiative forcing caused by direct aerosol emissions changes from other human activities. The results also indicate that future reductions of fossil fuel aerosols via air quality regulations may lead to an additional warming of the planet by mid-21st century and could also cause an important Arctic amplification of the warming. In addition, the mean position of the intertropical convergence zone and the Asian monsoon appear to be sensitive to aerosol emission reductions from air quality regulations. For these reasons, climate mitigation policies should take into consideration aerosol air pollution, which has not received sufficient attention in the past.

  • 21.
    Acosta Navarro, Juan Camilo
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Historical anthropogenic radiative forcing of changes in biogenic secondary organic aerosol2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Human activities have lead to changes in the energy balance of the Earth and the global climate. Changes in atmospheric aerosols are the second largest contributor to climate change after greenhouse gases since 1750 A.D. Land-use practices and other environmental drivers have caused changes in the emission of biogenic volatile organic compounds (BVOCs) and secondary organic aerosol (SOA) well before 1750 A.D, possibly causing climate effects through aerosol-radiation and aerosol-cloud interactions. Two numerical emission models LPJ-GUESS and MEGAN were used to quantify the changes in aerosol forming BVOC emissions in the past millennium. A chemical transport model of the atmosphere (GEOS-Chem-TOMAS) was driven with those BVOC emissions to quantify the effects on radiation caused by millennial changes in SOA.

    The specific objectives of this licentiate thesis are: 1) to understand what drove the changes in aerosol-forming BVOC emissions (i.e. isoprene, monoterpenes and sesquiterpenes) and to quantify these changes; 2) to calculate for the first time the combined historical aerosol direct and aerosol-cloud albedo effects on radiation from changing BVOC emissions through SOA formation; 3) to investigate how important the biological climate feedback associated to BVOC emissions and SOA formation is from a global climate perspective.

    We find that global isoprene emissions decreased after 1800 A.D. by about 12% - 15%. This decrease was dominated by losses of natural vegetation, whereas monoterpene and sesquiterpene emissions increased by about 2% - 10%, driven mostly by rising surface air temperatures. From 1000 A.D. to 1800 A.D, isoprene, monoterpene and sesquiterpene emissions decline by 3% - 8% driven by both, natural vegetation losses, and the moderate global cooling between the medieval climate anomaly and the little ice age. The millennial reduction in BVOC emissions lead to a 0.5% to 2% reduction in climatically relevant aerosol particles (> 80 nm) and cause a direct radiative forcing between +0.02 W/m² and +0.07 W/m², and an indirect radiative forcing between -0.02 W/m² and +0.02 W/m². The suggested biological climate feedback seems to be too small to have observable consequences on the global climate in the recent past.

  • 22.
    Acosta Navarro, Juan Camilo
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Smolander, S.
    Struthers, H.
    Zorita, E.
    Ekman, Annica M. L.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Kaplan, J. O.
    Guenther, A.
    Arneth, A.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Global emissions of terpenoid VOCs from terrestrial vegetation in the last millennium2014In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 119, no 11, 6867-6885 p.Article in journal (Refereed)
    Abstract [en]

    We investigated the millennial variability (1000 A.D.-2000 A.D.) of global biogenic volatile organic compound (BVOC) emissions by using two independent numerical models: The Model of Emissions of Gases and Aerosols from Nature (MEGAN), for isoprene, monoterpene, and sesquiterpene, and Lund-Potsdam-Jena-General Ecosystem Simulator (LPJ-GUESS), for isoprene and monoterpenes. We found the millennial trends of global isoprene emissions to be mostly affected by land cover and atmospheric carbon dioxide changes, whereas monoterpene and sesquiterpene emission trends were dominated by temperature change. Isoprene emissions declined substantially in regions with large and rapid land cover change. In addition, isoprene emission sensitivity to drought proved to have significant short-term global effects. By the end of the past millennium MEGAN isoprene emissions were 634 TgC yr-1 (13% and 19% less than during 1750-1850 and 1000-1200, respectively), and LPJ-GUESS emissions were 323 TgC yr-1(15% and 20% less than during 1750-1850 and 1000-1200, respectively). Monoterpene emissions were 89 TgC yr-1(10% and 6% higher than during 1750-1850 and 1000-1200, respectively) in MEGAN, and 24 TgC yr-1 (2% higher and 5% less than during 1750-1850 and 1000-1200, respectively) in LPJ-GUESS. MEGAN sesquiterpene emissions were 36 TgC yr-1(10% and 4% higher than during 1750-1850 and 1000-1200, respectively). Although both models capture similar emission trends, the magnitude of the emissions are different. This highlights the importance of building better constraints on VOC emissions from terrestrial vegetation.

  • 23.
    Acosta Navarro, Juan Camilo
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Varma, Vidya
    Stockholm University, Faculty of Science, Department of Meteorology .
    Riipinen, Irina
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Seland, O.
    Kirkevag, A.
    Struthers, Hamish
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Linköping University, Sweden.
    Iversen, T.
    Hansson, Hans-Christen
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ekman, Annica M. L.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Amplification of Arctic warming by past air pollution reductions in Europe2016In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 9, no 4, 277-+ p.Article in journal (Refereed)
    Abstract [en]

    The Arctic region is warming considerably faster than the rest of the globe(1), with important consequences for the ecosystems(2) and human exploration of the region(3). However, the reasons behind this Arctic amplification are not entirely clear(4). As a result of measures to enhance air quality, anthropogenic emissions of particulate matter and its precursors have drastically decreased in parts of the Northern Hemisphere over the past three decades(5). Here we present simulations with an Earth system model with comprehensive aerosol physics and chemistry that show that the sulfate aerosol reductions in Europe since 1980 can potentially explain a significant fraction of Arctic warming over that period. Specifically, the Arctic region receives an additional 0.3Wm(-2) of energy, and warms by 0.5 degrees C on annual average in simulations with declining European sulfur emissions in line with historical observations, compared with a model simulation with fixed European emissions at 1980 levels. Arctic warming is amplified mainly in fall and winter, but the warming is initiated in summer by an increase in incoming solar radiation as well as an enhanced poleward oceanic and atmospheric heat transport. The simulated summertime energy surplus reduces sea-ice cover, which leads to a transfer of heat from the Arctic Ocean to the atmosphere. We conclude that air quality regulations in the Northern Hemisphere, the ocean and atmospheric circulation, and Arctic climate are inherently linked.

  • 24.
    Acton, Gary
    et al.
    University of California, Davis.
    et al., incl. Jan Backman,
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Magnetostratigraphic and Cyclostratigraphic Records from Eocene-Miocene Sediments Cored in the Paleoequatorial Pacific: Initial Results from IODP Expedition 3202009Conference paper (Other academic)
    Abstract [en]

    Sediments from the paleoequatorial Pacific record the paleomagnetic field with high-fidelity and contain cyclic variations in chemical and physical properties that can be astronomically tuned, as has been shown from past Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) cruises, e.g., Legs 85, 138, 198, and 199. In an effort to fill gaps from past coring and to construct complete stratigraphic sections spanning the Cenozoic, Integrated Ocean Drilling Program (IODP) Expeditions 320 and 321 cored sediments along a Pacific Equatorial Age Transect (PEAT) earlier this year. A total of 23 holes at 8 Sites (Sites U1331 through U1338) were cored, recovering 6,141 m of sediment (Preliminary Reports are available at http://iodp.tamu.edu/publications/PR.html). Initial paleomagnetic results from Expedition 320 include measurements at 56,222 intervals along ~2000 split-core sections, as well as detailed progressive alternating field (AF) and thermal demagnetization of over 400 discrete samples (7 cm3 cubes). The cleaned paleomagnetic data were characterized by shallow inclinations, consistent with the sites being near the paleoequator, and by 180° alternations in declination downhole, reflecting magnetic polarity zones. The resulting magnetostratigraphies, which are used to develop initial age models for the drill sites, yield 803 dates ranging from 51.743 Ma (the base of Chron 23n.2n at Site 1331) to the present (Chron C1n; 0 to 0.783 Ma at Site U1335). In addition, 83 short polarity intervals were observed that might correspond to cryptochrons or geomagnetic excursions. We will discuss initial efforts to further resolve the PEAT magnetostratigraphies and to integrate them with bio-, chemo-, and cyclo- stratigraphies from the equatorial Pacific and elsewhere in order to improve and extend astronomical calibration of the geologic timescale.

  • 25. Adler, Carolina E.
    et al.
    Aldunce, Paulina
    Indvik, Katherine
    Alegria, Denis
    Borquez, Roxana
    Galaz, Victor
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Resilience2016In: Research Handbook on Climate Governance / [ed] Karin Bäckstrand, Eva Lövbrand, Northampton, MA: Edward Elgar Publishing, 2016, 491-502 p.Chapter in book (Refereed)
    Abstract [en]

    Despite receiving relatively little traction in climate change discussions among scholars and policymakers in the early 1990s, the term ‘climate resilience’ is now moving rapidly into prominent policy arenas and academic fora. However, how useful is the term in enabling normative aspirations to reduce net losses to climate change impacts? In this chapter, we first take stock of this seemingly rapid rise in the use of the term by presenting an overview of the progress and ongoing discussions on ‘climate resilience.’ This chapter illustrates these trends based on evidence of the terms’ growth and evolution over the years in two realms: within academia and in public policy. In both cases, we find an increasing trend in the way ‘climate resilience’ is conceptualized and used in academia and in public policy, yet these trends present different challenges and consequences for each case. Taking a problem-oriented approach, we conclude that despite the term’s popularity and growth, a critical review of its measurable effectiveness and pragmatic utility is still needed. Evaluating the terms utility in application is particularly important in light of recent conceptualizations of the climate resilience imperative as ‘transformation’ in a changing climate. We recommend some possible avenues for further research to address this deficit.

  • 26.
    Adler, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Studier av geomorfologi på Mani, Peloponnesos, Grekland2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The Mani peninsula in the south of Peloponnesos, Greece, is situated only 50 km from the subduction zone of the Hellenic arc. The active, tectonic processes taking place influence the geomorphology of the area. Through the use of remote sensing, analysis of a Digital Terrain Model and a five-day fieldwork study, certain areas of the southern peninsula’s geomorphology were examined for this project including recent processes that create landforms to date. Among those, chemical weathering and tectonics dominate. Also relict landforms were studied to get a greater understanding of the area. Fieldwork resulted in the discovery of two fields of rocks in one of the capes, which most likely were created before the cape underwent uplift to its current level. Also, a conglomerate superimposition of limestone in one of the bays showed indication that great mass movements took place when the surface was lower than today. A pediment is located on the west side of the Sagia Mountain. The asymmetry is probably due to a combination of tectonics and sea level changes.

  • 27. Adler, Ruth E.
    et al.
    Polyak, Leonid
    Ortiz, Joseph D.
    Kaufman, Darrell S.
    Channell, James E. T.
    Xuan, Chuang
    Grottoli, Andrea G.
    Sellen, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Crawford, Kevin A.
    Sediment record from the western Arctic Ocean with an improved Late Quaternary age resolution: HOTRAX core HLY0503-8JPC, Mendeleev Ridge2009In: Global and Planetary Change, ISSN 0921-8181, Vol. 68, no 02-jan, 18-29 p.Article in journal (Refereed)
    Abstract [en]

    Sediment core HLY0503-8JPC raised by the HOTRAX'05 expedition from the Mendeleev Ridge was analyzed for multiple lithological, paleontological. and stable-isotopic proxies to reconstruct paleoceanographic conditions in the western Arctic Ocean during the Late Quaternary. The core, extensively sampled in the upper 5 m, reveals pronounced changes in sedimentary environments during the ca. 250 kyr interval encompassing Marine Isotopic Stages (MIS) 1 to 7. An estimated average resolution of 500 yr/sample, at least for the last glacial cycle including the last interglacial, provides more detail than seen in other sedimentary records from the western Arctic Ocean. The age control is provided by C-14 and amino acid racemization measurements on planktonic foraminifers and correlations with the stratigraphy developed for the central Lomonosov Ridge and with glacial events at the Eurasian Arctic margin. Cyclic variations in lithology combined with foraminiferal abundance and stable-isotopic composition indicate profound changes in hydrographic and depositional environments between interglacial-type and glacial-type periods apparently reflecting a combination of 100-kyr and precessional time scales. This periodicity is complicated by abrupt iceberg- and/or meltwater-discharge events with variable (Laurentide vs. Eurasian) provenance. The proxy record from the interval identified as the last interglacial (MIS 5e), which may aid in understanding the future state of the Arctic Ocean, indicates low ice conditions and possibly enhanced stratification of the water column.

  • 28.
    Adolfsson-Erici, Margaretha
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Fish bile in environmental analysis2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This work explores the usefulness of fish bile analysis in combination with biomarkers for identifying and evaluating new environmental contaminants in the aquatic environment. It illustrates how bile analysis can be used together with biomarkers to assess the causes of estrogenic effects, to identify chemicals in the aquatic environment that are taken up by fish, and to monitor environmental exposure.

    In a first application, fish exposed to sewage treatment plant effluent were studied. Elevated levels of vitellogenin in the exposed fish demonstrated that estrogenic effects occurred. Several estrogen disrupting substances were identified in the fish bile, and analysis of water samples confirmed that these substances were present in the effluent. The synthetic estrogen 17a-ethinylestradiol, which is known to be present in sewage treatment plant effluent, was shown for the first time to be taken up by fish. Considering the reported potencies of the detected substances, it was concluded that 17a-ethinylestradiol was the major contributor to the estrogenic effects.

    Chemical analysis of bile was used to identify rubber additives that were released from tires immersed in water. The bile of rainbow trout held in the water contained high levels of metabolites of PAHs and aromatic nitrogen compounds. Several biomarkers were also measured in the exposed fish, and EROD induction and oxidative stress were observed. Based on the bile analysis observations together with knowledge of toxicological mechanisms, it was postulated that the EROD induction was due to the PAHs, while aromatic nitrogen compounds caused the oxidative stress.

    Resin acids in fish bile proved to be a good indicator of exposure in a chronic long-term study of rainbow trout exposed to effluent from a total chlorine free (TCF) pulp mill. Elevated levels of GST (gluthatione-S-transferase) and GR (gluthatione reductase) activity, and the presence of DNA adducts after a two month recovery period, indicated that compounds in the pulp mill effluents have persistent effects. In addition to characterising the exposure of the fish to the effluent, the analysis of the resin acids in the bile provided evidence of accidents in the pulp mill that the existing process monitoring system had not detected.

    Resin acids in bile were also found to be a valuable indicator of exposure to pulp mill effluents for eelpout living in the Baltic Sea. A correlation between resin acid levels in bile and skewed sex ratios provided an important link in the chain of evidence that substances in the pulp mill effluents cause male bias of the eelpout embryos.

    A particularly good example of the potential of bile analysis was the identification of a previously unknown environmental contaminant. A large peak was observed in the bile extracts of fish that had been exposed to sewage treatment plant effluent. This peak was identified as triclosan, which demonstrated its presence in sewage treatment plant effluent. Other work went on to show that it is a common contaminant of the aquatic environment. The ability of fish to concentrate contaminant metabolites in bile to levels very much higher than in the environment, and the comparatively low levels of analytic interferences, make bile a particularly attractive matrix to search for new, unknown organic pollutants

  • 29.
    Adolfsson-Erici, Margaretha
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Åkerman, Gun
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Jahnke, Annika
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Mayer, Philipp
    McLachlan, Michael S.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    A flow-through passive dosing system for continuously supplying aqueous solutions of hydrophobic chemicals to bioconcentration and aquatic toxicity tests2012In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 86, no 6, 593-599 p.Article in journal (Refereed)
    Abstract [en]

    A continuous supply of water with defined stable concentrations of hydrophobic chemicals is a requirement in a range of laboratory tests such as the OECD 305 protocol for determining the bioconcentration factor in fish. Satisfying this requirement continues to be a challenge, particularly for hydrophobic chemicals. Here we present a novel solution based on equilibrium passive dosing. It employs a commercially available unit consisting of similar to 16000 polydimethylsiloxane (PDMS) tubes connected to two manifolds. The chemicals are loaded into the unit by repeatedly perfusing it with a methanol solution of the substances that is progressively diluted with water. Thereafter the unit is perfused with water and the chemicals partition from the unit into the water. The system was tested with nine chemicals with logK(ow) ranging from 4.1 to 6.3. The aqueous concentrations generated were shown to be largely independent of the water flow rate, and the unit to unit reproducibility was within a factor of similar to 2. In continuous flow experiments the aqueous concentrations of most of the study chemicals remained constant over 8 d. A model was assembled that allows prediction of the operating characteristics of the system from the logKow or PDMS/water partition coefficient of the chemical. The system is a simple, safe, predictable and flexible tool that generates stable aqueous concentrations of hydrophobic chemicals.

  • 30.
    Adolfsson-Erici, Margaretha
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Åkerman, Gun
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    McLachlan, Michael S.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Internal Benchmarking Improves Precision and Reduces Animal Requirements for Determination of Fish Bioconcentration Factors2012In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 46, no 15, 8205-8211 p.Article in journal (Refereed)
    Abstract [en]

    The enactment of new chemical regulations has generated a large need for the measurement of the fish bioconcentration factor (BCF). Past experience shows that the BCF determination lacks precision, requires large numbers of fish, and is costly. A new protocol was tested that shortens the experiment from up to 12 weeks for existing protocols to 2 weeks and reduces the number of fish by a factor of 5, while introducing internal benchmarking for the BCF determination. Rainbow trout were simultaneously exposed to 11 chemicals. The BCFs were quantified using one of the test chemicals, musk xylene, as a benchmark. These were compared with BCFs measured in a parallel experiment based on the OECD 305 guideline. The agreement was <20% for five chemicals and between 20%-25% for two further, while two chemicals lay outside the BCF operating window of the experiment and one was lost due to analytical difficulties. This agreement is better than that observed in a BCF Gold Standard Database. Internal benchmarking allows the improvement of the precision of BCF determination in parallel to large reduction in costs and fish requirements.

  • 31.
    Adolfsson-Erici, Margaretha
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Åkerman, Gun
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    McLachlan, Michael S.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    In-vivo passive sampling to measure elimination kinetics in bioaccumulation tests2012In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 88, no 1, 62-68 p.Article in journal (Refereed)
    Abstract [en]

    The application of in-tissue passive sampling to quantify chemical kinetics in fish bioconcentration experiments was investigated. A passive sampler consisting of an acupuncture needle covered with a PDMS tube was developed together with a method for its deployment in rainbow trout. The time to steady state for chemical uptake into the passive sampler was >1 d, so it was employed as a kinetically limited sampler with a deployment time of 2 h. The passive sampler was employed in parallel with the established whole tissue extraction method to study the elimination kinetics of 10 diverse chemicals in rainbow trout. 4-n-nonylphenol and 2,4,6-tri-tert-butylphenol were close to or below the limit of quantification in the sampler. For chlorpyrifos, musk xylene, hexachlorobenzene, 2,5-dichlorobiphenyl and p,p'-DDT. the elimination rate constants determined with the passive sampler method and the established method agreed within 18%. Poorer agreement (35%) was observed for 2,3,4-trichloroanisole and p-diisopropylbenzene because fewer data were obtained with the passive sampling method due to its lower sensitivity. The work shows that in-tissue passive sampling can be employed to measure contaminant elimination kinetics in fish. This opens up the possibility of studying contaminant kinetics in individual fish, thereby reducing the fish requirements and analytical costs for the determination of bioconcentration factors.

  • 32.
    Adolfsson-Erici, Margaretha
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Åkerman, Gun
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    McLachlan, Michael S.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Measuring bioconcentration factors in fish using exposure to multiple chemicals and internal benchmarking to correct for growth dilution2012In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 31, no 8, 1853-1860 p.Article in journal (Refereed)
    Abstract [en]

    Modern chemical legislation requires measuring the bioconcentration factor (BCF) of large numbers of chemicals in fish. The BCF must be corrected for growth dilution, because fish growth rates vary between laboratories. Two hypotheses were tested: (1) that BCFs of multiple chemicals can be measured simultaneously in one experiment, and (2) that internal benchmarking using a conservative test substance in the chemical mixture can be used to correct for growth dilution. Bioconcentration experiments were conducted following major elements of the OECD 305 guideline. Fish were simultaneously exposed to 11 chemicals selected to cover a range of BCFs and susceptibility to biotransformation. A method was developed to calculate the growth-corrected elimination rate constant from the concentration ratio of the analyte and a benchmarking chemical for which growth dilution dominated other elimination mechanisms. This method was applied to the experimental data using hexachlorobenzene as the benchmarking chemical. The growth dilution correction lowered the apparent elimination rate constants by between 5% and a factor of four for eight chemicals, while for two chemicals the growth-corrected elimination rate constant was not significantly different from zero. The benchmarking method reduced the uncertainty in the elimination rate constant compared to the existing method for growth dilution correction. The BCFs from exposing fish to 10 chemicals at once were consistent with BCF values from single-chemical exposures from the literature, supporting hypothesis 1. Environ. Toxicol. Chem. 2012; 31: 18531860. (c) 2012 SETAC

  • 33.
    Aeppli, Christoph
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bastviken, David
    Andersson, Per
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Chlorine Isotope Effects and Composition of Naturally Produced Organochlorines from Chloroperoxidases, Flavin-Dependent Halogenases, and in Forest Soil2013In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, no 13, 6864-6871 p.Article in journal (Refereed)
    Abstract [en]

    The use of stable chlorine isotopic signatures (delta Cl-37) of organochlorine compounds has been suggested as a tool to determine both their origins and transformations in the environment. Here we investigated the delta Cl-37 fractionation of two important pathways for enzymatic natural halogenation: chlorination by chloroperoxidase (CPO) and flavin-dependent halogenases (FDH). Phenolic products of CPO were highly Cl-37 depleted (delta Cl-37 = -12.6 +/- 0.9 parts per thousand); significantly more depleted than all known industrially produced organochlorine compounds (delta Cl-37 = -7 to +6 parts per thousand). In contrast, four FDH products did not exhibit any observable isotopic shifts (delta Cl-37 = -0.3 +/- 0.6 parts per thousand). We attributed the different isotopic effect to the distinctly different chlorination mechanisms employed by the two enzymes. Furthermore, the delta Cl-37 in bulk organochlorines extracted from boreal forest soils were only slightly depleted in Cl-37 relative to inorganic Cl. In contrast to previous suggestions that CPO plays a key role in production of soil organochlorines, this observation points to the additional involvement of either other chlorination pathways, or that dechlorination of naturally produced organochlorines can neutralize delta Cl-37 shifts caused by CPO chlorination. Overall, this study demonstrates that chlorine isotopic signatures are highly useful to understand sources and cycling of organochlorines in nature. Furthermore, this study presents delta Cl-37 values of FDH products as well of bulk organochlorines extracted from pristine forest soil for the first time.

  • 34.
    Aeppli, Christoph
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Tysklind, Mats
    Holmstrand, Henry
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Use of Cl and C Isotopic Fractionation to Identify Degradation and Sources of Polychlorinated Phenols: Mechanistic Study and Field Application2013In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, no 2, 790-797 p.Article in journal (Refereed)
    Abstract [en]

    The widespread use of chlorinated phenols (CPs) as a wood preservative has led to numerous contaminated sawmill sites. However, it remains challenging to assess the extent of in situ degradation of CPs. We evaluated the use of compound-specific chlorine and carbon isotope analysis (Cl- and C-CSLA) to assess CP biotransformation. In a laboratory system, we measured isotopic fractionation during oxidative 2,4,6-trichlorophenol dechlorination by representative soil enzymes (C. fumago chloroperoxidase, horseradish peroxidase, and laccase from T. versicolor). Using a mathematical model, the validity of the Rayleigh approach to evaluate apparent kinetic isotope effects (AKIE) was confirmed. A small but significant Cl-AKIE of 1.0022 +/- 0.0006 was observed for all three enzymes, consistent with a reaction pathway via a cationic radical species. For carbon, a slight inverse isotope effect was observed (C-AKIE = 0.9945 +/- 0.0019). This fractionation behavior is clearly distinguishable from reported reductive dechlorination mechanisms. Based on these results we then assessed degradation and apportioned different types of technical CP mixtures used at two former sawmill sites. To our knowledge, this is the first study that makes use of two-element CSIA to study sources and transformation of CPs in the environment.

  • 35.
    Afrifa, Yamoah Kweku Kyei
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Reconstruction of the Southeast Asian hydro-climate using biomarkers and their hydrogen isotopic composition2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Southeast Asia is characterized by a monsoonal climate, with distinct wet and dry seasons. This has great impact on societies, agriculture and infrastructures. Despite the critical importance to understand the mechanisms that influence the variability of the Asian Monsoon, there is scarcity of both historical and paleoclimate proxy data from Southeast Asia. For this reason, two lakes from Thailand, Lake Pa Kho (LPK) and Lake Nong Thale Pron (NTP), which are located in the northeastern and southern part of Thailand, respectively, were cored. The region also offers the opportunity to study the potential influence of climate on the Angkor civilization. Overall, this project seeks to improve our understanding of the mechanisms that contribute to Asian monsoon variability and how the variability influenced Angkor Civilization. Here I present results on a 2000-years sediment record from LPK. The most important part of the work presented here consists of compound-specific hydrogen isotope ratios (δD), which are used to infer past changes in the hydrological cycle of Southeast Asia. This approach is based on the premise that δD of lipid biomarkers from plants, algae and microorganisms deposited in sediments reflects the δD of their source water, which in turn is influenced by local hydrology. A rapid increase in precipitation is inferred from ca. 700 to ca. 850 AD, after a long dry phase. The inferred shift to wet conditions likely contributed to the rise of the Angkor Civilization, by boosting agriculture. However, gradual drying occurred at around 900 AD until the 19th century. This long-term decline in precipitation, favoring ever more frequent occurrences of severe droughts, likely also contributed to the demise and fall of the Angkor, around 1400 AD. Comparison with other hydroclimate proxy records revealed that wet conditions in tropical SE Asia corresponded to a dry Western Pacific, wet conditions in the East Pacific, and vice versa - a pattern that can be explained by opposing centers of convection and subsidence. Moreover, our tropical record also appears to be anti-correlated with the subtropical East Asian Monsoon, possibly caused by rainout effects along moisture trajectories. These long-term rainfall shifts closely match patterns observed during periods of strong El Niño, and suggests a central role for Pacific Walker circulation as a driver of centennial-scale hydroclimatic change. Besides these results from LPK oriented towards reconstructing hydroclimate, I also present some initial results concerning the evolution of the plant community of LPK, based on compound specific 13C analysis, as well as first biomarker results from NTP.

  • 36. Agarwal, Sahil
    et al.
    Wettlaufer, John S.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Yale University, USA; University of Oxford, United Kingdom.
    The Statistical Properties of Sea Ice Velocity Fields2017In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 30, no 13, 4873-4881 p.Article in journal (Refereed)
    Abstract [en]

    By arguing that the surface pressure field over the Arctic Ocean can be treated as an isotropic, stationary, homogeneous, Gaussian random field, Thorndike estimated a number of covariance functions from two years of data (1979 and 1980). Given the active interest in changes of general circulation quantities and indices in the polar regions during the recent few decades, the spatial correlations in sea ice velocity fields are of particular interest. It is thus natural to ask, How persistent are these correlations?'' To this end, a multifractal stochastic treatment is developed to analyze observed Arctic sea ice velocity fields from satellites and buoys for the period 1978-2015. Since it was previously found that the Arctic equivalent ice extent (EIE) has a white noise structure on annual to biannual time scales, the connection between EIE and ice motion is assessed. The long-term stationarity of the spatial correlation structure of the velocity fields and the robustness of their white noise structure on multiple time scales is demonstrated; these factors (i) combine to explain the white noise characteristics of the EIE on annual to biannual time scales and (ii) explain why the fluctuations in the ice velocity are proportional to fluctuations in the geostrophic winds on time scales of days to months. Moreover, it is shown that the statistical structure of these two quantities is commensurate from days to years, which may be related to the increasing prevalence of free drift in the ice pack.

  • 37.
    Aggemyr, Elsa
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Landscape structure and land use history influence changes in island plant composition after 100 years2012In: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 39, no 9, 1645-1656 p.Article in journal (Refereed)
    Abstract [en]

    Aim We investigated how current and historical land use and landscape structure affect species richness and the processes of extinction, immigration and species turnover. Location The northern part of the Stockholm archipelago, Baltic Sea, Sweden. We resurveyed 27 islands ranging from 0.3 to 33 ha in area. Methods We compared current plant survey data, cadastral maps and aerial photographs with records obtained from a survey in 1908, using databases and a digital elevation model to examine changes in plant community dynamics in space and time. We examined the effects of local and landscape structure and land use changes on plant species dynamics by using stepwise regression in relation to eight local and three landscape variables. The eight local variables were area, relative age, shape, soil heterogeneity, bedrock ratio, number of houses, forest cover change, and grazing 100 years ago. The three landscape variables were distance to mainland, distance to closest island with a farm 100 years ago, and structural connectivity. Hanskis connectivity measure was modified to incorporate both connectivity and fragmentation. Results The investigated islands have undergone drastic changes, with increasing forest cover, habitation, and abandonment of grassland management. Although the total species richness increased by 31% and mean island area by 23%, we found no significant increase in species richness per unit area. Local variables explain past species richness (100 years ago), whereas both local and landscape variables explain current species richness, extinctions, immigrations and species turnover. Grazing that occurred 100 years ago still influences species richness, even though grazing management was abandoned several decades ago. The evidence clearly shows an increase in nitrophilous plant species, particularly among immigrant species. Main conclusions This study highlights the importance of including land use history when interpreting current patterns of species richness. Furthermore, local environment and landscape patterns affect important ecological processes such as immigration, extinction and species turnover, and hence should be included when assessing the impact of habitat fragmentation and land use change. We suggest that our modified structural connectivity measure can be applied to other types of landscapes to investigate the effects of fragmentation and habitat loss.

  • 38.
    Aggemyr, Elsa
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Plant species richness and composition, changes over a 100 year period in the Swedish archipelago - a landscape study2010In: The Future of Biodiversity: Genes, Species, Ecosystems: 40th Anniversary Conference / [ed] Volkmar Wolters, Janine Groh, Franziska Peter, Rainer Waldhardt, Giessen: Justus Liebig University Giessen , 2010, 118-118 p.Conference paper (Refereed)
  • 39. Agnini, C
    et al.
    Fornaciari, E
    Rio, D
    Tateo, F
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Giusberti, L
    Responses of calcareous nannofossil assemblages, mineralogy and geochemistry to the environmental pertubartions across the Paleocene/Eocene boundary in the Venetian Pre-Alps2007In: Marine micropaleontology, Vol. 63Article in journal (Refereed)
  • 40.
    Agnini, Claudia
    et al.
    University of Padova.
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    An early Eocene carbon cycle perturbation at ~52.5 Ma from the southern Alps: Chronology and biotic response2009In: Paleoceanography, ISSN 0883-8305, Vol. 24, no PA2209, 1-14 p.Article in journal (Refereed)
  • 41.
    Agnini, Claudia
    et al.
    University of Padova.
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    It Paleognee inferiore in facies pelagica ne Venetor nord-orientalie2009In: Rendiconto online Soc. Geol. It, Vol. 4, 5-12 p.Article in journal (Refereed)
  • 42. Agnini, Claudia
    et al.
    Fornaciari, Eliana
    Raffi, Isabella
    Catanzariti, Rita
    Paelike, Heiko
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Rio, Domenico
    Biozonation and biochronology of Paleogene calcareous nannofossils from low and middle latitudes2014In: Newsletters on stratigraphy, ISSN 0078-0421, Vol. 47, no 2, 131-181 p.Article in journal (Refereed)
    Abstract [en]

    Calcareous nannofossils have provided a powerful biostratigraphic tool since the 1950's and 1960's, when several milestone papers began to highlight their potential use in dating Cenozoic sediments and rocks. Here, we present a new calcareous nannofossil biozonation for the Paleogene Period, which is based on biostratigraphic data collected during the past 30 years. Semi-quantitative counting methods applied on DSDP/ODP drill sites and marine on-land sections have been used to demonstrate the details of the abundance patterns of each biostratigraphically useful calcareous nannofossil taxon. This new biozonation still partly relies on older biozonations and thus represents an integration between those classical biohorizons that proved reliable and new biohorizons proposed as substitutes for bioevents considered problematic. Thirty-eight new Paleogene biozones are proposed using a new code system: 11 Paleocene biozones (CNP1-CNP11), 21 Eocene biozones (CNE1-CNE21) and 6 Oligocene biozones (CNO1-CNO6). The new scheme uses a limited number of biohorizons, one for each biozone boundary, which guarantees more stability although with a coarser resolution. A series of additional biohorizons are included in almost every biozone. This new Paleogene biozonation has an average duration of 1.1 Myr per biozone, ranging from 0.9 Myr in the Paleocene, to 1.0 Myr in the Eocene, and 1.8 Myr in the Oligocene. Age estimates provided for calcareous nannofossil biohorizons are calculated using both magnetostratigraphic and astronomically tuned cyclostratigraphic data.

  • 43. Agnini, Claudia
    et al.
    Fornaciari, Eliana
    Rio, Domenico
    Tateo, Fabio
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Responses of calcareous nannofossil assemblages, mineralogy, and geochemistry to the environmental perturbations across the Paleocene/Eocene boundary in the Venetian Pre-Alps2007In: Marine Micropaleontology, Vol. 63, 19-38 p.Article in journal (Refereed)
  • 44. Agnini, Claudia
    et al.
    Spofforth, David J. A.
    Dickens, Gerald R.
    Rio, Domenico
    Pälike, Heiko
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Backman, Jan
    Muttoni, Giovanni
    Dallanave, Edoardo
    Stable isotope and calcareous nannofossil assemblage record of the late Paleocene and early Eocene (Cicogna section)2016In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 12, no 4, 883-909 p.Article in journal (Refereed)
    Abstract [en]

    We present records of stable carbon and oxygen isotopes, CaCO3 content, and changes in calcareous nannofossil assemblages across an 81 m thick section of upper Paleocene lower Eocene marine sedimentary rocks now exposed along the Cicogna Stream in northeast Italy. The studied stratigraphic section represents sediment accumulation in a bathyal hemipelagic setting from approximately 57.5 to 52.2 Ma, a multi-million-year time interval characterized by perturbations in the global carbon cycle and changes in calcareous nannofossil assemblages. The bulk carbonate delta C-13 profile for the Cicogna section, once placed on a common timescale, resembles that at several other locations across the world, and includes both a long-term drop in delta C-13 and multiple short-term carbon isotope excursions (CIEs). This precise correlation of widely separated delta C-13 records in marine sequences results from temporal changes in the carbon composition of the exogenic carbon cycle. However, diagenesis has likely modified the delta C-13 record at Cicogna, an interpretation supported by variations in bulk carbonate 8180, which do not conform to expectations for a primary signal. The record of CaCO3 content reflects a combination of carbonate dilution and dissolution, as also inferred at other sites. Our detailed documentation and statistical analysis of calcareous nannofossil assemblages show major differences before, during and after the Paleocene Eocene Thermal Maximum. Other CIEs in our lower Paleogene section do not exhibit such a distinctive change; instead, these events are sometimes characterized by variations restricted to a limited number of taxa and transient shifts in the relative abundance of primary assemblage components. Both long-lasting and short-lived modifications to calcareous nannofossil assemblages preferentially affected nannoliths or holococcoliths such as Discoaster,, Fasciculithus, Rhomboaster/Tribrachiatus, Sphenolithus and Zygrhablithus, which underwent distinct variations in abundance as well as permanent evolutionary changes in terms of appearances and disappearances. By contrast, placoliths such as Coccolithus and Tow eius, which represent the main component of the assemblages, were characterized by a gradual decline in abundance over time. Comparisons of detailed nannofossil assemblage records at the Cicogna section and at ODP Site 1262 support the idea that variations in the relative and absolute abundances, even some minor changes, were globally synchronous. An obvious link is through climate forcing and carbon cycling, although the linkages between variations in calcareous nannoplankton, changes in delta C-13 records and oceanography will need additional work.

  • 45. Ahlgren, Joakim
    et al.
    Grimvall, Anders
    Omstedt, Anders
    Rolff, Carl
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Swedish Institute for the Marine Environment, Sweden.
    Wikner, Johan
    Temperature, DOC level and basin interactions explain the declining oxygen concentrations in the Bothnian Sea2017In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 170, 22-30 p.Article in journal (Refereed)
    Abstract [en]

    Hypoxia and oxygen deficient zones are expanding worldwide. To properly manage this deterioration of the marine environment, it is important to identify the causes of oxygen declines and the influence of anthropogenic activities. Here, we provide a study aiming to explain the declining oxygen levels in the deep waters of the Bothnian Sea over the past 20 years by investigating data from environmental monitoring programmes. The observed decline in oxygen concentrations in deep waters was found to be primarily a consequence of water temperature increase and partly caused by an increase in dissolved organic carbon (DOC) in the seawater (R-Adj(2). = 0.83) as well as inflow from the adjacent sea basin. As none of the tested eutrophication-related predictors were significant according to a stepwise multiple regression, a regional increase in nutrient inputs to the area is unlikely to explain a significant portion of the oxygen decline. Based on the findings of this study, preventing the development of anoxia in the deep water of the Bothnian Sea is dependent on the large-scale measures taken to reduce climate change. In addition, the reduction of the nutrient load to the Baltic Proper is required to counteract the development of hypoxic and phosphate-rich water in the Baltic Proper, which can form deep water in the Bothnian Sea. The relative importance of these sources to oxygen consumption is difficult to determine from the available data, but the results clearly demonstrate the importance of climate related factors such as temperature, DOC and inflow from adjacent basins for the oxygen status of the sea.

  • 46.
    Ahlgren, Sara
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Changes in size distribution of lakes in the Nadym catchment, northern Russia2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Because of climate change and resource development there is an ongoing increase in the attention directed towards high latitude areas. Over the last years, warming in the Arctic has accelerated quickly. The warming climate can possibly lead to thawing of ground ice, which in turn leads to alterations of the cryosphere. This can have a huge influence on the terrestrial hydrology of the Arctic and, more specifically, on the presence and distribution of lakes in arctic regions since both are coupled to subsurface ice. In this thesis data from remote sensing were used to look at the change in the size distribution of lakes for the Nadym catchment in northern Russia. The aim was to find out if there has been an increase or decrease in the number of lakes in the area over the past years. Results suggest that there were 229 lakes less (representing a 4% decrease) in 2007–2009 compared to 1987, indicating that lakes are slowly disappearing. Also, the total lake surface area decreased with 5%. Almost half of the lakes that disappeared (49%) can be found among the smallest lakes ranging between 10–20 ha. In the entire catchment this size class was also found to be the class with by far the highest number of lakes.

  • 47. Ahlkrona, J.
    et al.
    Kirchner, Nina
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lotstedt, P.
    Accuracy of the zeroth- and second-order shallow-ice approximation - numerical and theoretical results2013In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 6, no 6, 2135-2152 p.Article in journal (Refereed)
    Abstract [en]

    In ice sheet modelling, the shallow-ice approximation (SIA) and second-order shallow-ice approximation (SOSIA) schemes are approaches to approximate the solution of the full Stokes equations governing ice sheet dynamics. This is done by writing the solution to the full Stokes equations as an asymptotic expansion in the aspect ratio epsilon, i.e. the quotient between a characteristic height and a characteristic length of the ice sheet. SIA retains the zeroth-order terms and SOSIA the zeroth-, first-, and second-order terms in the expansion. Here, we evaluate the order of accuracy of SIA and SOSIA by numerically solving a two-dimensional model problem for different values of epsilon, and comparing the solutions with afinite element solution to the full Stokes equations obtained from Elmer/Ice. The SIA and SOSIA solutions are also derived analytically for the model problem. For decreasing epsilon, the computed errors in SIA and SOSIA decrease, but not always in the expected way. Moreover, they depend critically on a parameter introduced to avoid singularities in Glen's flow law in the ice model. This is because the assumptions behind the SIA and SOSIA neglect a thick, high-viscosity boundary layer near the ice surface. The sensitivity to the parameter is explained by the analytical solutions. As a verification of the comparison technique, the SIA and SOSIA solutions for a fluid with Newtonian rheology are compared to the solutions by Elmer/Ice, with results agreeing very well with theory.

  • 48. Ahlkrona, Josefin
    et al.
    Kirchner, Nina
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lötstedt, Per
    A numerical study of scaling relations for non-Newtonian thin film flows with applications in ice sheet modelling2013In: Quarterly Journal of Mechanics and Applied Mathematics, ISSN 0033-5614, E-ISSN 1464-3855, Vol. 66, no 4, 417-435 p.Article in journal (Refereed)
    Abstract [en]

    This article treats the viscous, non-Newtonian thin-film flow of ice sheets, governed by the Stokes equations, and the modelling of ice sheets with asymptotic expansion of the analytical solutions in terms of the aspect ratio, which is a small parameter measuring the shallowness of an ice sheet. An asymptotic expansion requires scalings of the field variables with the aspect ratio. There are several, conflicting, scalings in the literature used both for deriving simplified models and for analysis. We use numerical solutions of the Stokes equations for varying aspect ratios in order to compute scaling relations. Our numerically obtained results are compared with three known theoretical scaling relations: the classical scalings behind the Shallow Ice Approximation, the scalings originally used to derive the so-called Blatter-Pattyn equations, and a non-uniform scaling which takes into account a high viscosity boundary layer close to the ice surface. We find that the latter of these theories is the most appropriate one since there is indeed a boundary layer close to the ice surface where scaling relations are different than further down in the ice. This boundary layer is thicker than anticipated and there is no distinct border with the inner layer for aspect ratios appropriate for ice sheets. This makes direct application of solutions obtained by matched asymptotic expansion problematic.

  • 49. Ahlkrona, Josefin
    et al.
    Lötstedt, Per
    Kirchner, Nina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Zwinger, Thomas
    Dynamically coupling the non-linear Stokes equations with the shallow ice approximation in glaciology: Description and first applications of the ISCAL method2016In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 308, 1-19 p.Article in journal (Refereed)
    Abstract [en]

    We propose and implement a new method, called the Ice Sheet Coupled Approximation Levels (ISCAL) method, for simulation of ice sheet flow in large domains during long time-intervals. The method couples the full Stokes (FS) equations with the Shallow Ice Approximation (SIA). The part of the domain where SIA is applied is determined automatically and dynamically based on estimates of the modeling error. For a three dimensional model problem, ISCAL computes the solution substantially faster with a low reduction in accuracy compared to a monolithic FS. Furthermore, ISCAL is shown to be able to detect rapid dynamic changes in the flow. Three different error estimations are applied and compared. Finally, ISCAL is applied to the Greenland Ice Sheet on a quasi-uniform grid, proving ISCAL to be a potential valuable tool for the ice sheet modeling community.

  • 50.
    Ahlm, Lars
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Julin, Jan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Fountoukis, C.
    Pandis, S. N.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Particle number concentrations over Europe in 2030: the role of emissions and new particle formation2013In: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, E-ISSN 1680-7375, Vol. 13, no 20, 10271-10283 p.Article in journal (Refereed)
    Abstract [en]

    The aerosol particle number concentration is a key parameter when estimating impacts of aerosol particles on climate and human health. We use a three-dimensional chemical transport model with detailed microphysics, PMCAMx-UF, to simulate particle number concentrations over Europe in the year 2030, by applying emission scenarios for trace gases and primary aerosols. The scenarios are based on expected changes in anthropogenic emissions of sulfur dioxide, ammonia, nitrogen oxides, and primary aerosol particles with a diameter less than 2.5 mu m (PM2.5) focusing on a photochemically active period, and the implications for other seasons are discussed. For the baseline scenario, which represents a best estimate of the evolution of anthropogenic emissions in Europe, PMCAMx-UF predicts that the total particle number concentration (N-tot) will decrease by 30-70% between 2008 and 2030. The number concentration of particles larger than 100 nm (N-100), a proxy for cloud condensation nuclei (CCN) concentration, is predicted to decrease by 40-70% during the same period. The predicted decrease in N-tot is mainly a result of reduced new particle formation due to the expected reduction in SO2 emissions, whereas the predicted decrease in N-100 is a result of both decreasing condensational growth and reduced primary aerosol emissions. For larger emission reductions, PMCAMx-UF predicts reductions of 60-80% in both N-tot and N-100 over Europe. Sensitivity tests reveal that a reduction in SO2 emissions is far more efficient than any other emission reduction investigated, in reducing N-tot. For N-100, emission reductions of both SO2 and PM2.5 contribute significantly to the reduced concentration, even though SO2 plays the dominant role once more. The impact of SO2 for both new particle formation and growth over Europe may be expected to be somewhat higher during the simulated period with high photochemical activity than during times of the year with less incoming solar radiation. The predicted reductions in both N-tot and N-100 between 2008 and 2030 in this study will likely reduce both the aerosol direct and indirect effects, and limit the damaging effects of aerosol particles on human health in Europe

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