| 1. |
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| 2. |
- Barbieri, Maurizio, et al.
(författare)
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Changes in groundwater trace element concentrations before seismic and volcanic activities in Iceland during 2010-2018
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 793
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Tidskriftsartikel (refereegranskat)abstract
- We analysed temporal variations of trace element concentrations in groundwater from a 101 m-deep borehole (HA01) in northern Iceland during 2010–2018 and compared them with seismic and volcanic events that occurred in the same period to identify potential hydrogeochemical precursors. An increase of B, Al, V, Li and Mo concentrations started from eight months to one month before the 2014 Bárðarbunga eruption (~115 km from HA01), a major rifting event in central Iceland, while Ga and V concentrations began to increase one day and one month after the onset of the event, respectively. We also found that concentrations of some trace elements (Li, B, Ga, Mo, Sr, Rb and Fe) significantly increased before an Mw 5.0 earthquake that occurred ~80 km from the borehole in 2018. However, other notable hydrogeochemical changes were detected during the monitoring period without apparent correlation with the seismic and volcanic events in the region. This study shows that the systematic long-term hydrogeochemical monitoring in seismic and volcanic areas is critical to advance the science of seismic and eruptive precursors. Furthermore, the use of statistical tools, such as Principal Component Analysis (PCA) and Change Point (CP) detection can help identify the most useful chemical elements and validate the trend variability of those elements in the time series, reducing arbitrary choices of pre-seismic and pre-volcanic hydrogeochemical anomalies as potential precursors.
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| 3. |
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| 4. |
- Boschetti, Tiziano, et al.
(författare)
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Geothermometry and water-rock interaction modelling at Hafralækur : Possible implications of temperature and CO2 on hydrogeochemical changes previously linked to earthquakes in northern Iceland
- 2022
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Ingår i: Geothermics. - : Elsevier BV. - 0375-6505 .- 1879-3576. ; 105
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Tidskriftsartikel (refereegranskat)abstract
- The low enthalpy (T < 150 °C) groundwater in the HA01 borehole at Hafralækur has a long time series (2008–2018) of chemical and isotopic data. In the previous studies, the variations in chemical and isotope parameters were statistically related to seismic activity. However, the possible effect of temperature has not yet been evaluated. To fill this gap, the results obtained from the classical geothermometric equations (silica solid phases, Na/K, Na-K-Ca) were compared. However, considering that the use of classical geothermometry using the Na/K ratio or silica solid phases solubility is limited by the presence of clay minerals and alkaline conditions (i.e., the presence of pH-dependant silicate anions), new equilibria reactions between labradorite, zeolites (analcime, stilbite) and the activity of the dissolved species in the fluid are presented to overcome this problem. In addition, kinetic reaction path models are presented to trace the possible role of both temperature and CO2 during the most evident chemical variations during earthquakes.
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| 5. |
- Fru, Ernest Chi, et al.
(författare)
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Transient fertilization of a post-Sturtian Snowball ocean margin with dissolved phosphate by clay minerals
- 2023
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Ingår i: Nature Communications. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Marine sedimentary rocks deposited across the Neoproterozoic Cryogenian Snowball interval, similar to 720-635 million years ago, suggest that post-Snowball fertilization of shallow continental margin seawater with phosphorus accelerated marine primary productivity, ocean-atmosphere oxygenation, and ultimately the rise of animals. However, the mechanisms that sourced and delivered bioavailable phosphate from land to the ocean are not fully understood. Here we demonstrate a causal relationship between clay mineral production by the melting Sturtian Snowball ice sheets and a short-lived increase in seawater phosphate bioavailability by at least 20-fold and oxygenation of an immediate post-Sturtian Snowball ocean margin. Bulk primary sediment inputs and inferred dissolved seawater phosphate dynamics point to a relatively low marine phosphate inventory that limited marine primary productivity and seawater oxygenation before the Sturtian glaciation, and again in the later stages of the succeeding interglacial greenhouse interval.
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| 6. |
- Gerhardt, Karin, et al.
(författare)
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Nog nu, politiker – ta klimatkrisen på allvar : 1 944 svenska forskare och anställda i forskarvärlden: Vad är det ni inte förstår?
- 2022
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Ingår i: Aftonbladet. - 1103-9000. ; :2022-08-25
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- DEBATT. Som forskare och medborgare är vi arga och förtvivlade över den senaste tidens utveckling. Vi ser hur en majoritet av våra politiska partier överger klimatpolitiken och i stället föreslår eller genomför politik som går stick i stäv med Parisavtalet och Sveriges klimat- och miljömål.Våra politiker måste ta krisen på allvar och leda omställningen till ett framtida samhälle inom planetens gränser. Forskningen visar att en sådan framtid är möjlig. Det skriver 1 944 forskare och anställda från 45 svenska lärosäten och forskningsinstitut.
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| 7. |
- Kylander, Malin E., et al.
(författare)
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It's in your glass : a history of sea level and storminess from the Laphroaig bog, Islay (southwestern Scotland)
- 2020
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 49:1, s. 152-167
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Tidskriftsartikel (refereegranskat)abstract
- Severe winter windstorms have become an increasingly common occurrence over recent decades in northwestern Europe. Although there exists considerable uncertainty, storminess is projected to increase in the future. On centennial to millennial time scales in particular, the mechanisms forcing storminess remain unsettled. We contribute to available palaeostorm records by reconstructing changes over the last 6670 years using a coastal peat sequence retrieved from the ombrotrophic Laphroaig bog on Islay, southwestern Scotland. We use a combination of ash content, grain size and elemental chemistry to identify periods of greater storminess, which are dated to 6605, 6290-6225, 5315-5085, 4505, 3900-3635, 3310-3130, 2920-2380, 2275-2190, 2005-1860, 1305-1090, 805-435 and 275 cal. a BP. Storm signals in the first half of the record up to similar to 3000 cal. a BP are mainly apparent in the grain-size changes. Samples from this time period also have a different elemental signature than those later in the record. We speculate that this is due to receding sea levels and the consequent establishment of a new sand source in the form of dunes, which are still present today. The most significant events and strongest winds are found during the Iron Ages Cold Epoch (2645 cal. a BP), the transition into, and in the middle of, the Roman Ages Warm Period (2235 and 1965 cal. a BP) and early in the Little Ice Age (545 cal. a BP). The Laphroaig record generally agrees with regionally relevant peat palaeostorm records from Wales and the Outer Hebrides, although the relative importance of the different storm periods is not the same. In general, stormier periods are coeval with cold periods in the region as evidenced by parallels with increased ice-rafted debris in the North Atlantic, highlighting that sea-ice conditions could impact future storminess and storm track position.
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| 8. |
- Nicholas, Kimberly, et al.
(författare)
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Analys av sju riksdagspartiers klimatpolitik utförd av klimat- och omställningsforskare : Sveriges klimatpolitik inför riksdagsvalet 2022 enligt Researchers’ Desk
- 2022
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Rapport (populärvet., debatt m.m.)abstract
- ● Syftet med denna rapport är att ge forskares analys av riksdagspartiernas klimatpolitik inför valet 2022.● Alla som har bidragit till denna rapport är klimat- eller omställningsforskare och medlemmar i Researchers’ Desk1.● Researchers’ Desk är en oberoende, ideell organisation, med över 80 ledande forskare i Sverige, som arbetar med olika aspekter av klimatförändringarna.● Alla de åtta politiska partierna tillfrågades om att besvara en enkät med frågor om sina klimatmål och sin politik. Moderaterna avböjde att delta i undersökningen. De övriga sju partierna svarade med varierande grad av utförlighet.● Författarna av denna rapport har använt partiernas svar som underlag för sin kvalitativa analys och bedömning.● Vår granskning har fokuserat på förslagens ambitionsnivå, potential, realism och problem i relation till befintlig forskning.● Tidigare publicerat genom detta projekt:○ Mål för territoriella utsläpp, av Alasdair Skelton, Paul Glantz, och KimberlyNicholas○ Mål för LULUCF-sektorn, av Erik Pihl, Åsa Kasimir, och Peter Roberntz
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| 9. |
- Niemi, Maria, et al.
(författare)
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Lockdown Measures Which Reduced Greenhouse Gas Emissions With Little Negative Impact on Quality of Life
- 2021
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Ingår i: Earth's Future. - 2328-4277. ; 9:5
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Tidskriftsartikel (refereegranskat)abstract
- Lockdown measures in response to the new Covid-19 virus have caused the largest ever fall of annual greenhouse gas emissions. A key question that we attempt to answer in this study is which, if any, of these measures can be productively encouraged post-lockdown in efforts to sustain at least part of this reduction in emissions. Sweden is uniquely suited for our study because the voluntary nature of lockdown in Sweden allowed us to assess the level of compliance to recommendations and its effects on greenhouse gas emissions. First, we assessed the change of perceived quality of life (QOL) among 746 individuals from Stockholm region due to adhering to lockdown measures. Second, we calculated the associated change of annual per capita greenhouse emissions. We found that avoiding travel for work, avoiding purchasing, and avoiding restaurants had the least negative effect on QOL, and at the same time the largest positive effect on carbon dioxide equivalent (CO(2)e) emission reductions. We conclude that these are potential leverage points for stimulating behavioral change that has a positive climatic impact.
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| 10. |
- Nosenzo, Francesco, 1993-
(författare)
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Chemical and isotopic records of polycyclic histories in a subducted continental crust (Dora-Maira Massif, Western Alps)
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- At convergent plate margin, part of the continental crust can be subducted and exhumed. During continental subduction a pre-existing crust is reworked. Remnants of an older orogen are recycled and subjected to (ultra)-high-pressure metamorphism. During subduction, polycyclic rocks undertake a second metamorphic cycle, whereas monocyclic rocks are metamorphosed for the first time. In reworked rocks the pre-subduction record is overprinted and partially or completely lost. Despite this difficulty, reconstructing the pre-subduction history of the recycled crust is crucial, because pre-subduction characters (such as H2O content) can strongly influence how rocks respond to reworking during subduction.The Dora-Maira Massif is worldwide renowned as a (ultra)-high-pressure continental terrane. However, its northern part remained essentially unexplored in recent times. In this thesis work the northern Dora-Maira Massif is used as a case study to investigate recycling of continental crust. The aim is to constrain what type of crust is subducted and exhumed and to unravel the role of fluids during subduction of polycyclic material. Field work, petrology, thermodynamic modelling and geochronology are integrated.New field and geochronological evidence indicate that the northern Dora-Maira Massif displays an internal architecture more complex than what previously thought. It is subdivided in several tectonic units likewise the southern Dora-Maira Massif. Chemical and isotopic records of the reworked rocks reveal a pre-Alpine history spanning from the Lower Palaeozoic to the Mesozoic. A polycyclic basement preserves relicts of a pre-Alpine Barrovian metamorphism connected with the Variscan orogenesis. The absence of granulite-facies partially molten pre-Alpine rocks indicates that only the upper crust was reworked in the Dora-Maira Massif.Thermodynamic modelling indicates that polycyclic micaschists were rehydrated between the Variscan and the Alpine peak metamorphism. Polycyclic garnet texture and chemistry and metamorphic zircon record a main episode of fluid infiltration at the end of the Variscan cycle and not during the Alpine cycle. Pre-Alpine re-hydration of the upper crust allowed high-pressure re-equilibration during subduction.
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| 11. |
- Ring, Uwe, et al.
(författare)
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Forced Return Flow Deep in the Subduction Channel, Syros, Greece
- 2020
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Ingår i: Tectonics. - 0278-7407 .- 1944-9194. ; 39:1
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of a detailed structural study in the Cycladic Blueschist Unit at Fabrika on Syros Island, Greece, and discuss their significance for tectonic processes at the subduction interface. Some samples record top-to-the-west shear reflecting prograde (burial), peak high-pressure (HP) and initial decompression (exhumation) conditions. Other nearby samples record top-to-the-east shear during HP metamorphism and exhumation. Some rocks re-equilibrated at greenschist-facies conditions and record top-to-the-west shear. Greenschist-facies top-to-the-west shear is also found at the base of non-HP upper units above the Fabrika HP sequence. We interpret the HP structures to reflect forced return flow and incipient formation of an extrusion wedge in the subduction channel. The HP top-to-the-west structures resulted from thrusting along the base of the wedge and started to form during burial before the rocks reached their deepest point. The HP top-to-the-east structures reflect deformation near the top of the developing extrusion wedge. After considerable exhumation during ongoing subduction, out-of-sequence, top-to-the-west thrusts emplaced the non-HP upper units above the exhuming extrusion wedge 10 Myr after the wedge initially formed. Our work suggests that the HP rocks were considerably exhumed during sustained lithospheric shortening in the subduction channel by forced return flow. Because return flow is controlled by the velocity of the subducting slab, it may explain why HP rocks can be exhumed at subduction rates. On the regional scale we find that four distinct HP belts were sequentially accreted and exhumed between 50 and 20 Ma suggesting continuous subduction-channel return flow in the Hellenic subduction zone.
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| 12. |
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| 13. |
- Skelton, Alasdair, et al.
(författare)
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Skewness of Temperature Data Implies an Abrupt Change in the Climate System Between 1985 and 1991
- 2020
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 47:23
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Tidskriftsartikel (refereegranskat)abstract
- Instrumental records of mean annual temperature extend back to the seventeenth and eighteenth centuries at multiple sites in Europe. For such long time series, we expect and find that histograms of mean annual temperature data become skewed toward higher temperatures with time because of global warming. However, we also find that skewness changed abruptly and started increasing between 1985 and 1991 (95% confidence) at 17 sites. We argue that this finding may imply an abrupt change in the climate system affecting Europe which probably occurred at this time. We investigate possible causes and find Arctic sea ice loss, potentially linked to reduced sulfate aerosol emissions and coupled to temperature by an albedo feedback mechanism, a likely candidate. This is based on good correlations of sea ice extent and sulfate aerosol emissions with skewness of mean annual temperature data.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Tollefsen, Elin, 1960-
(författare)
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Experimental, petrological and geochemical investigations of ikaite (CaCO3·6H2O) formation in marine environments
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbonates are a group of minerals that play an essential role in several processes on planet Earth, for example in the global carbon cycle and as a product of biomineralisation. Calcite (CaCO3) is by far the most common mineral in the carbonate group, and the stable form of carbonate at Earth surface conditions. However, calcite growth is often kinetically limited and polymorphs of calcite or hydrous calcium carbonates will form instead under certain circumstances. In this thesis, I investigate a hydrous form of calcium carbonate, ikaite (CaCO3 · 6H2O), which occasionally forms under conditions where normally calcite formation would be expected.Ikaite is metastable at surface conditions and has only been observed in nature at temperatures below 7°C. In Ikka Fjord, southwest Greenland, several hundred ikaite columns occur at the bottom of the fjord. Previous studies in Ikka Fjord have shown that ikaite columns are forming above submarine springs that are extremely sodium carbonate rich (pH ~10.5). An association with the surrounding igneous rocks, which comprise nepheline syenite and carbonatite, has been suggested. In the first part of this thesis, I investigate this association. A petrographic study of rocks samples from the igneous complex showed that the combined alteration of the minerals siderite and nepheline could explain the composition of the submarine spring water, and thereby the unique formation of ikaite columns at this site.It is from the mixture of sodium carbonate spring water and seawater that ikaite precipitates in Ikka Fjord, despite the fact that all other calcium carbonates are supersaturated in this mixture. Why ikaite precipitates and not the other forms of calcium carbonate was investigated by a series of experiments in the second and third parts of this thesis. Previous studies have suggested that ikaite was favoured by the low temperature in the fjord (<7°C) and the presence of phosphate (95- 263 μmol/kg) in the submarine spring water, which is known to inhibit calcite growth even at only trace concentrations. In the second part of this thesis, we simulated Ikka Fjord conditions in laboratory and showed that ikaite precipitation is not controlled by the presence of phosphate in the mixture. Instead, after a second series of experiments I found that it is the presence Mg in seawater that inhibits calcite growth and therefore favour ikaite precipitation.Ikaite is metastable and at temperatures above 7°C the mineral will transform or decompose to calcite and water. The transformation can occur pseudomorphically and pseudomorphs after ikaite have been found worldwide in the sediment record. Pseudomorphs after authigenic ikaite in sediments are named glendonite, and because of the narrow temperature range of ikaite observations in nature, glendonite has been used as a paleotemperature indicator. In the fourth part of this thesis, I explore the temperature range of ikaite nucleation by a series of experiments and found that ikaite nucleation can occur up to at least 35°C. This challenges the use of glendonite as a paleotemperature indicator.
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| 18. |
- Tollefsen, Elin, et al.
(författare)
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Ikaite nucleation at 35°C challenges the use of glendonite as a paleotemperature indicator
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Glendonites have been found worldwide in marine sediments from the Neoproterozoic Era to the Quaternary Period. The precursor of glendonite, ikaite (CaCO3 · 6H2O), is metastable and has only been observed in nature at temperatures <7 °C. Therefore, glendonites in the sedimentary record are commonly used as paleotemperature indicators. However, several laboratory experiments have shown that the mineral can nucleate at temperatures>7 °C. Here we investigate the nucleation range for ikaite as a function of temperature and pH. We found that ikaite precipitated at temperatures of at least 35 °C at pH 9.3 −10.3 from a mixture of natural seawater and sodium carbonate rich solution. At pH 9.3, we observed pseudomorphic replacement of ikaite by porous calcite during the duration of the experiment (c. 5 hours). These results imply that ikaite can form at relatively high temperatures but will then be rapidly replaced by a calcite pseudomorph. This finding challenges the use of glendonites as paleotemperature indicators.
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| 19. |
- Tollefsen, Elin, et al.
(författare)
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Ikaite nucleation at 35 degrees C challenges the use of glendonite as a paleotemperature indicator
- 2020
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Glendonites have been found worldwide in marine sediments from the Neoproterozoic Era to the Quaternary Period. The precursor of glendonite, ikaite (CaCO3 . 6H(2)O), is metastable and has only been observed in nature at temperatures <7 degrees C. Therefore, glendonites in the sedimentary record are commonly used as paleotemperature indicators. However, several laboratory experiments have shown that the mineral can nucleate at temperatures>7 degrees C. Here we investigate the nucleation range for ikaite as a function of temperature and pH. We found that ikaite precipitated at temperatures of at least 35 degrees C at pH 9.3 -10.3 from a mixture of natural seawater and sodium carbonate rich solution. At pH 9.3, we observed pseudomorphic replacement of ikaite by porous calcite during the duration of the experiment (c. 5hours). These results imply that ikaite can form at relatively high temperatures but will then be rapidly replaced by a calcite pseudomorph. This finding challenges the use of glendonites as paleotemperature indicators.
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| 20. |
- Villa, Igor M., et al.
(författare)
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Petrochronology of polygenetic white micas (Naxos, Greece)
- 2023
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Ingår i: Journal of Metamorphic Geology. - : Wiley. - 0263-4929 .- 1525-1314. ; 41:3, s. 401-423
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Tidskriftsartikel (refereegranskat)abstract
- Naxos in the Greek Cyclades preserves a type example of polymetamorphism. The southern and northern parts of the island record different Tertiary P–T histories between Eocene and Miocene times, including a blueschist facies event, one or more amphibolite/greenschist facies overprint(s) and contact metamorphism. Age attributions for these events are inconsistent in the literature. Here, we propose a new approach that combines electron probe microanalyzer (EPMA) characterization of the white mica (WM) with 39Ar-40Ar–Rb-Sr multichronometry. Textural–petrographic–compositional observations reveal that the polygenetic WM consists of five different generations: pre-Eocene relicts, paragonite, high-Si phengite, low-Si phengite and muscovite. EPMA mapping of four WM samples, previously analysed by Rb-Sr, reveals major element compositions heterogeneous down to the μm scale. Each WM consists of chemically distinct generations, documenting submicron-scale retrogression of high-pressure (HP) phengite grains to muscovite. Four WM samples from a N-S traverse across the island were analysed by 39Ar-40Ar stepheating, comparing coarse and fine sieve size fractions to obtain overdetermined K-Ar systematics. Fine sieve fractions are richer in Cl than coarse ones. Linear arrays in Cl/K-age isotope correlation diagrams show two predominant WM generations (one Cl-poor at ca. 38 Ma and one Cl-rich at <20 Ma). A lower-grade sample from southern Naxos was less pervasively recrystallized, provides older ages and preserves at least three WM generations, including a relict WM with a pre-Palaeocene K-Ar age, consistent with the high Ar retentivity of WM in the absence of complete recrystallization. The age of the Cl-poor end-member WM approximates the age of the HP event, 38 Ma. Ar inheritance in Cretaceous mica relicts is heterogeneous at the single-grain scale. Comparing the degassing rates of the WM fractions rules out ‘multidomain’ diffusion. As no sample is monomineralic, the degassing rate of each polygenetic mica is instead controlled by the mass balanced sum of the unrelated rate constants of its constituent minerals. Given the commonness of zoned and composite micas, the approach detailed here is potentially useful for reconstructing polyphase metamorphic histories worldwide.
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