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  • 1.
    Cunningham, Laura
    et al.
    School of Geography & Geosciences, University of St Andrews.
    Bishop, Kevin
    Department of Environmental Assessment, Swedish University of Agricultural Sciences.
    Mettävainio, Ewa
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Rosén, Peter
    Climate Impacts Research Centre, Umeå University.
    Paleoecological evidence of major declines in total organic carbon concentrations since the nineteenth century in four nemoboreal lakes2011In: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 45, no 4, p. 507-518Article in journal (Refereed)
    Abstract [en]

    A decade of widespread increases in surface water concentrations of total organic carbon (TOC) in some regions has raised questions about longer term patterns in this important constituent of water chemistry. This study uses near-infrared spectroscopy (NIRS) to infer lake water TOC far beyond the decade or two of observational data generally available. An expanded calibration dataset of 140 lakes across Sweden covering a TOC gradient from 0.7 to 24.7 mg L-1 was used to establish a relationship between the NIRS signal from surface sediments (0-0.5 cm) and the TOC concentration of the water mass. Internal cross-validation of the model resulted in an R (2) of 0.72 with a root mean squared error of calibration (RMSECV) of 2.6 mg L-1. The TOC concentrations reconstructed from surface sediments in four Swedish lakes were typically within the range of concentrations observed in the monitoring data during the period represented by each sediment layer. TOC reconstructions from the full sediment cores of four lakes indicated that TOC concentrations were approximately twice as high a century ago.

  • 2.
    Kylander, Malin M
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lind, Ewa M
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Löwemark, Ludvig
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Recommendations for using XRF core scanning as a tool in tephrochronology2012In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 22, no 3, p. 371-375Article in journal (Refereed)
    Abstract [en]

    X-ray fluorescence (XRF) core scanning is a relatively new arrangement of a classic analytical technique which allows for non-destructive, in situ XRF analysis of sediment cores from submillimetre resolution upwards. In this contribution we explore the use of XRF core scanning for tephrochronology based on the analysis of three gyttja-rich sediment cores from the Faroe Islands. Using a combination of optical and radiographic images, analytical parameters and elemental profiles (Si, K, Ca, Ti, Mn, Fe, Sr and Zr), higher concentration basaltic tephra layers (>1000 shards/cm3) were positively identified. The XRF core scanning did not capture the lower concentration (<850 shards/cm3) rhyolitic layers found in the core. The elemental data generated for the detected tephra layers using XRF core scanning was not comparable to individual shard analysis by electron microprobe. We recommend using XRF core scanning for tephra screening in order to localize depths for high-resolution subsampling and to avoid depths where sediment mixing has caused tailing/mixing of the tephra signal. At the studied site the basaltic Saksunarvatn ash as well as a tephra belonging to the Askja-S/10 ka eruption were identified.

  • 3.
    Lilja, Carl
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lind, Ewa M.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Morén, Björn
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    A Lateglacial-early Holocene tephrochronology for SW Sweden2013In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 42, no 3, p. 544-554Article in journal (Refereed)
    Abstract [en]

    Four cores from southwestern Sweden are presented together with their tephra geochemistry. Two cryptotephra horizons were confirmed geochemically in the cores, the Vedde Ash and the Hässeldalen Tephra. The Lateglacial Hässeldalen Tephra (11 360–11 300 cal. a BP) offers great potential as a regional isochrone to add a new degree of certainty to the deglaciation chronology of southern Sweden, including the extent of glacial Lake Bolmen. In addition, the geographical distribution of the Hässeldalen Tephra has recently been extended outside of Sweden, making it an important time-marker horizon in northern Europe. There are potential difficulties, however. Proper identification of the actual isochrone is complicated by the vertical pattern of shard distribution, which could be the result of several eruptive events, as well as by the fact that shards from the 10-ka Askja horizon (10 500–10 350 cal. a BP) were found in close stratigraphical proximity. The geochemical data presented are the result of improved EPMA methodology, which significantly reduces sodium mobilization. The results therefore have slightly altered values, which has consequences for classifying new finds when they are compared with previous data for geochemically similar tephras. Finally, potential indications of the Borrobol/Penifiler horizon are presented, although the existence of the horizon could not be confirmed geochemically. This highlights the need to retrieve cores from different locations within a basin based on an analysis of basin morphology if horizons are to be located.

  • 4.
    Lilja, Carl
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Lind-Mettävainio, Ewa
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Late Glacial tephra horizons in Southern Sweden2010In: International Field Conference and Workshop on Tephrochronology, Volcanism and Human Activity: Active Tephra in Kyushu, 2010, 2010, p. 54-Conference paper (Other academic)
  • 5.
    Lind, Ewa
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Tephra horizons in the North Atlantic region during the Early Holocene2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Uncertainties about the rate and magnitude of future climate change have drawn attention to the climate variability following the Late Glacial-Early Holocene transition, c. 12-8 ka BP. Tephrochronology is a method that uses volcanic ash as isochrons in order to link, date and synchronise geological and palaeoclimatic records which could provide a better understanding of short rapid climate shifts but also the timing of these.

    The main purpose of this thesis was to improve and refine the Late Younger Dryas-Early Holocene (c. 12-8 ka BP) tephrochronological framework with focus on dating and identification of new and previously known tephra horizons in the North Atlantic region. A special emphasis was to identify tephra horizons contemporary to short rapid climate events that occurred during the period; the Preboreal Oscillation (c. 11.3 ka BP), the Erdalen events (c. 10.0-9.8 ka BP), the 9.3 ka BP and the 8.2 ka BP events. Additional purposes have been to evaluate the potential of XRF ITRAX core-scanning to identify tephra in lake sediments but also as a tool in palaeoclimate studies.

    The potential of tephrochronology for linking climate archives across the North Atlantic region is a main outcome in this thesis. Specific results include five new tephra horizons; four identified on the Faroe Islands and one in Central Norway. Two previously known tephras, the Hässeldalen and Askja-S tephras, were identified on the Faroe Islands for the first time and at new locations in Sweden which confirmed their widespread distribution in NW Europe. Several of these tephras have the potential to become marker horizons for some of the short rapid climate events which occurred during the Late Younger Dryas-Early Holocene but their importance is yet to be determined. Further results show that the XRF core scanner can be used successfully to identify high concentrations of basaltic tephra but also to identify palaeoclimatic events in lake sediments.

  • 6.
    Lind, Ewa
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Olsen, Jesper
    Aarhus University.
    Lacustrine response to short rapid climate shifts during Late Younger Dryas-Early Holocene in Central Norway, registred by XRF and stable isotopesManuscript (preprint) (Other academic)
    Abstract [en]

    There is relatively good knowledge about the climate and the deglaciation pattern during the Late Glacial-Early Holocene transitionin Norway. The origin and mechanisms behind the short, rapid climate shifts that occurred during this period are however notwell known. In this context climate studies in this region can contribute to our understanding of climate patterns. Our specificobjectives in this study were to compare the geochemical response of lake sediments during Late Younger Dryas-Early Holoceneto the general picture of deglaciation in Central Norway and also to evaluate if the Preboreal oscillation (PBO), the Erdalen events,the 9.3 and 8.2 ka cal BP could be detected, superimposed on the general Late Glacial-Early Holocene climate. To address this; highresolutionXRF fluorescence core-scanning, Total organic carbon (TOC), carbon/nitrogen (C/N), stable isotopes of carbon andnitrogen (δ13C, δ15N) and total nitrogen (TN) were made on a palaeolake core from Grønlia fen situated on the Fosen peninsula,Central Norway. The reconstructed Late Younger Dryas-Early Holocene climate from the Grønlia record was noteworthily similarto other reconstructions from the region. The Younger Dryas-Preboreal transition was dated to c. 11 420 cal a BP and five climateshifts were identified in the Early Holocene; c. 11 190 cal a BP, 10 500 cal a BP, 10 200 cal a BP, 9900 cal a BP and 9250 cal a BP.

  • 7.
    Lind, Ewa
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Wastegard, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Larsen, Jeppe J.
    Univ Copenhagen, Dept Geosci & Nat Resource Management.
    A Late Younger Dryas-Early Holocene tephrostratigraphy for Fosen, Central Norway2013In: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 28, no 8, p. 803-811Article in journal (Refereed)
    Abstract [en]

    A number of rapid climate oscillations occur during the Lateglacial-Early Holocene, 15-8 ka BP period and a well-developed tephrostratigraphy in association with these oscillations increases the possibilities to correlate climate archives around the North Atlantic. This paper presents a tephrostratigraphy for Fosen peninsula, Central Norway. Both the Vedde Ash ca.12.1 ka BP and the Saksunarvatn Ash approximate to 10.3 ka BP are important isochrones for correlations of Late Quaternary palaeoenvironmental records in the North Atlantic region and have been assigned ages in GICC05. Beside these tephras we have also identified a new tephra, the Fosen Tephra, with a Borrobol-type geochemistry that occurs above both the Vedde Ash and the Saksunarvatn Ash with an age approximate to 10.2 ka BP. Several tephras with Borrobol-type geochemistry have been identified around the North Atlantic. One group is the Borrobol/Penifiler tephras dated to Greenland Interstadial-1 and another group is dated to the Early Holocene. We suggest that some of the Early Holocene Borrobol-type tephras and the Fosen Tephra may actually be the same layer. If so, the Fosen Tephra is spread over a large area of the North Atlantic and has the potential to become an important marker for short-term climate variability in Scandinavia and in the northern hemisphere.

  • 8.
    Lind, Ewa
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Tephra horizons contemporary with short early Holocene climate fluctuations: New results from the Faroe Islands2011In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 246, p. 157-167Article in journal (Refereed)
    Abstract [en]

    The climate of the North Atlantic region was relatively unstable after the last Termination.At least three cold events superimposed upon a general warming took place during the earliest part of the Holocene: the Preboreal oscillation (11,300-11,100 cal. yr BP), the Erdalen event (10,300-10,200 cal. yr BP) and the 9.3 ka BP event. New results from the Faroe Islands could give the opportunity to test hypothesis regarding synchronous or non-synchronous response to climate forcing in the North Atlantic area. Seven tephra layers have been identified in a palaeo-lake core from the island of Sandoy on the Faroe Islands, dated to 11,700-9750 cal. yr BP. Three tephras were found below the visible Saksunarvatn Ash (ca. 10,300 cal. yr BP) and three above it. The rhyolitic Hässeldalen Tephra dated to ca. 11,350 cal. yr BP and previously only found in Sweden, a double-peaked basaltic tephra from the Veidivötn-Bárdarbunga volcanic system at the same depth and another rhyolitic tephra from the Askja volcanic system dated to ca. 10,400 cal. yr BP, tentatively correlated with the Askja-S/10 ka Tephra. Askja-S has earlier been found in large parts of the terrestrial North Atlantic region but not on the Faroe Islands. The three tephra layers above the Saksunarvatn Ash are all unreported tephras. A rhyolitic tephra with an age of ca. 10,200 cal. yr BP, that is still unidentified, one silicic layer from the Katla volcano (SILK) and a tephra correlated with the Torfajökull volcanic system, both with an estimated age of ca. 9700 cal. yr BP. These tephra horizons provide a unique potential to link not only the terrestrial records from NW Europe but alsotocorrelate them to ice-cores from Greenland. The findings of the Hässeldalen Tephra, the Askja-S Tephra and the new tephra correlating toTorfajökullvolcanic systemcould become important time-markers for correlating the Preboreal Oscillation and the Erdalen event around the North Atlantic region.

  • 9.
    Lind Mettävainio, Ewa
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Tephrochronology of the north Atlantic region during the early Holocene2010Other (Other academic)
  • 10.
    Lind Mettävainio, Ewa
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    New Early Holocene tephra horizons from the Faroe Islands:  2010In: International Field Conference and Workshop on Tephrochronology, Volcanism and Human Activity.: Active Tephra in Kyushu 2010, 2010, p. 60-Conference paper (Other academic)
    Abstract [en]

    The early Holocene climate in the North Atlantic region was rather unstable and three cold events superimposed upon a general warming took place during the earliest part of the Holocene: the Preboreal oscillation (11.3-11.1 ka BP), the Erdalen event (10.3-10.2 ka BP) and the 9.3 ka BP event (e.g. Dahl et al., 2002; Rasmussen et al. 2007). There is relatively little known about early Holocene tephrochronology in comparison to the Last Glacial/Interglacial transition and the mid to late Holocene, although there is no reason to believe that Icelandic eruptions were less frequent during the early Holocene. The main focus of the present study is improve the dating and geochemical identification of early Holocene tephras on the Faroe Islands, using wiggle-match or Bayesian techniques for age-depth modelling and EMPA analyses for geochemical fingerprinting of tephras. Identification of tephras is also aided by XRF core scanning. While this method is still in its infancy, some promising results have been reported recently regarding the identification of cryptotephra in marine and lacustrine sediments. The Faroe Islands is an ideal area to test the method, since tephras ranging from basaltic to rhyolitic are abundant but usually not visible to the naked eye (Wastegård, 2002). We have investigated new cores taken in 2009 from previously studied sites and new sites with high sediment accumulation rates during the early Holocene. Results from the first analyzed peat and lake sediment cores from the Faroe Islands show that several previously unreported tephra horizons occur below the visible Saksunarvatn tephra dated to c. 10 300 cal. yr BP (Rasmussen et al. 2007). Two layers are rhyolitic, one dacitic and one basaltic. The XRF core-scanner data has been especially useful for identifying basaltic cryptotephra horizons.

  • 11. Telesinski, Maciej M.
    et al.
    Spielhagen, Robert F.
    Lind, Ewa M.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    A high-resolution Lateglacial and Holocene palaeoceanographic record from the Greenland Sea2014In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 43, no 2, p. 273-285Article in journal (Refereed)
    Abstract [en]

    We present an unprecedented multicentennial sediment record from the foot of Vesterisbanken Seamount, central Greenland Sea, covering the past 22.3 thousand years (ka). Based on planktic foraminiferal total abundances, species assemblages, and stable oxygen and carbon isotopes, the palaeoenvironments in this region of modern deepwater renewal were reconstructed. Results show that during the Last Glacial Maximum the area was affected by harsh polar conditions with only episodic improvements during warm summer seasons. Since 18 ka extreme freshwater discharges from nearby sources occurred, influencing the surface water environment. The last major freshwater event took place during the Younger Dryas. The onset of the Holocene was characterized by an improvement of environmental conditions suggesting warming and increasing ventilation of the upper water layers. The early Holocene saw a stronger Atlantic waters advection to the area, which began around 10.5 and ended quite rapidly at 5.5 ka, followed by the onset of Neoglacial cooling. Surface water ventilation reached a maximum in the middle Holocene. Around 3 ka the surface water stratification increased leading to subsequent amplification of the warming induced the North Atlantic Oscillation at 2 ka.

  • 12.
    Wastegård, Stefan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gudmundsdóttir, Esther R.
    Lind, Ewa M.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Timms, Rhys G. O.
    Björck, Svante
    Hannon, Gina E.
    Olsen, Jesper
    Rundgren, Mats
    Towards a Holocene tephrochronology for the Faroe Islands, North Atlantic2018In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 195, p. 195-214Article in journal (Refereed)
    Abstract [en]

    The Faroe Islands hold a key position in the North Atlantic region for tephra studies due to their relative proximity to Iceland. Several tephras have been described over the last 50 years in peat and lake sediment sequences, including the type sites for the Saksunarvatn and Mjauvotn tephras. Here we present a comprehensive overview of Holocene tephras found on the Faroe Island. In total 23 tephra layers are described including visible macrotephras such as the Saksunarvatn and Hekla 4 tephras and several cryptotephras. The importance of tephras originally described from the Faroe Islands is highlighted and previously unpublished results are included. In addition, full datasets for several sites are published here for the first time. The Saksunarvatn Ash, now considered to be the result of several eruptions rather than one major eruption, can be separated into two phases on the Faroe Islands; one early phase with two precursor eruptions with lower MgO concentrations (4.5-5.0 wt%) than the main eruption and a later phase with higher MgO concentrations (5.5-6.0 wt%), including the visible Saksunarvatn Ash. The Tjornuvik Tephra, previously considered to be a primary deposit, is now interpreted as a reworked tephra with material from at least two middle Holocene eruptions of Hekla. Several of the tephras identified on the Faroe Islands provide useful isochrons for climate events during the Holocene.

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