780 research outputs found

    STOP 1: Lower Gauja spillway valley at Sigulda

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    I det hÀr arbetet har linjÀr regression anvÀnts för att undersöka om olika sociala faktorer pÄverkar om elever fÄr gymnasiebehörighet. Unders ökningen gjordes med kommunvis aggregerad data och faktorerna som undersöktes var utlÀndsk bakgrund, försörjningsstöd, utbildningsnivÄ, arbetsl öshet, disponibel inkomst, lÀrartÀthet, andel lÀrare med pedagogisk examen och skolornas kostnad. Statistiskt signikanta resultat erhölls för utlÀndsk bakgrund, försörjningsst öd, utbildningsnivÄ, disponibel inkomst och lÀrartÀthet. Enligt undersökningen pÄverkar utlÀndsk bakgrund och försörjningsstöd gymnasiebeh örigheten negativt. UtbildningsnivÄ och disponibel inkomst pÄverkar den positivt. LÀrartÀtheten pÄverkar gymnasiebehörigheten positivt om andelen lÀrare i svenska som andrasprÄk och modersmÄl inte överstiger 10,4 %. Resultaten för resten av de undersökta faktorerna var inte statistiskt signikanta och dÀrför kan inget sÀgas sÀkert om dem utifrÄn den hÀr undersökningen. Observera att inga slutsatser kan dras pÄ individnivÄ. Det som kan sÀgas utifrÄn undersökningen Àr att i kommuner dÀr en stor andel av befolkningen t.ex. fÄr försörjningsstöd tenderar andelen elever som fÄr gymnasiebehörighet att vara lÀgre

    The glacial geomorphology of upper GodthÄbsfjord (Nuup Kangerlua) in south-west Greenland

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    © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of Journal of Maps. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.The Greenland Ice Sheet (GrIS) is known to have experienced widespread retreat over the last century. Information on outlet glacier dynamics, prior to this, are limited due to both a lack of observations and a paucity of mapped or mappable deglacial evidence which restricts our understanding of centennial to millennial timescale dynamics of the GrIS. Here we present glacial geomorphological mapping, for upper GodthÄbsfjord, covering 5800 km 2 at a scale of 1:92,000, using a combination of ASTER GDEM V2, a medium-resolution DEM (error < 10 m horizontal and < 6 m vertical accuracy), panchromatic orthophotographs and ground truthing. This work provides a detailed geomorphological assessment for the area, compiled as a single map, comprising of moraines, meltwater channels, streamlined bedrock, sediment lineations, ice-dammed lakes, trimlines, terraces, gullied sediment and marine limits. Whilst some of the landforms have been previously identified, the new information presented here improves our understanding of ice margin behaviour and can be used for future numerical modelling and landform dating programmes. Data also form the basis for palaeoglaciological reconstructions and contribute towards understanding of the centennial to millennial timescale record of this sector of the GrIS.Peer reviewedFinal Published versio

    A review of glacier outburst floods in Iceland and Greenland with a megafloods perspective

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    The very largest glacier outburst floods have been termed ‘megafloods’ given their volume and peak discharge. That definition might be revised because those floods have become understood due to their distinctive and pervasive landscape impacts. At least three floods in Iceland can be categorized as megafloods since they produced impressive bedrock canyons and giant fluvially-transported boulders. Glacier lake outburst floods (GLOFs) in Greenland might also have megaflood-type attributes given the enormous lake volumes drained. We therefore here present the first review of glacier outburst floods in Greenland: sites Isvand, Russell Glacier, Kuannersuit Glacier, Lake Tininnilik, two unnamed lakes near Amitsulooq Ice Cap, and Iluliallup Tasersua, Base Camp Lake, Lake Hullett, Qorlortorssup Tasia, Imaersartoq, Tordensþ, North Midternés and an outlet glacier of the A. P. Olsen Ice Cap. Overall, megaflood-type landscape impacts in Iceland tend to be best-preserved and most easily identified inland although there has also been extensive offshore sedimentation. There are very few reported impacts of glacier outburst floods in Greenland. In Greenland ice-dam failure causes frequent flooding compared to the volcanically-triggered floods in Iceland and this combined with the proximity of the Greenland glacier lakes to the coast means that most proglacial channels in Greenland are flood-hardened and most landscape impact is likely to be offshore in estuaries and fjords. Future floods with megaflood-type attributes will occur in Iceland induced by volcanic activity. In Greenland they will be induced by extreme weather and rapid ice melt. Any potential landscape impact of these future floods remains open to question

    Last ice-dammed lake in the Kuray basin, Russian Altai: New results from multidisciplinary research

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    Results from geomorphological, sedimentological and geochronological analyses, together with micropaleontological and mineralogical characteristics of lacustrine deposits in five locations within the Kuray intermountain depression, southeast Altai, mountains of south Siberia, support the thesis of repeated formations of ice-dammed lakes during MIS-2 and their draining by high energy floods. Our data suggest that the timing of one of the last cataclysmic draining events in the area can be estimated by an Optically-Stimulated Luminescence (OSL) age of 19.0 ± 1.1 ka for a sandy layer at the top of the diluvial (i.e. large flood) deposit, revealed in a sedimentary sequence of the 1570 m a.s.l. strandline – one of the lowest preserved strandlines in the western part of the basin. New OSL and radiocarbon ages, augmenting previously published dates, indicate that the last lake to occupy the Kuray depression occurred around 19–16 ka with a depth of at least 170 m in the central part of the basin and to a depth of no less than 220 m near the glacier dam. Lacustrine deposits are represented by two horizons of sandy clays separated by interlayers of mixed-size sands. The mineralogical data, supported by analysis of sedimentological and micropaleontological records, indicate accumulation of a lower lacustrine horizon in a deeper reservoir. Finding of Leucocythere sp.1, Leucocythere sp.2, and Leucocythere dorsotuberosa ostracod species in lacustrine deposits characterizes these reservoirs as periglacial freshwater cold and deep lakes. The presence of well-crystallized mica and chlorite in lacustrine silts and clays from the lower lacustrine horizon indicates cold, dry conditions at the time of their formation, as well as a predominance of physical weathering of rocks within the denudation area. After an abrupt dropping of the lake level around 16 ka, determined from OSL dating, the lake never recovered its former depth. The available radiocarbon ages for organic material in subaerial deposits within the study area and the new OSL ages suggest that the last ice-dammed lake in the Kuray basin was drained between ~16.7 and 9.9 ka. The presence of this lake might explain the absence of late Paleolithic surface finds within the basin that remained generally unsuitable for human habitation until its final drying. The last outburst flood passed along the Chuya and Katun river valleys, which had been already carved by older cataclysmic floods, but did not significantly affect the topography downstream of the Kuray-Chuya intermountain depressions. We numerically simulated the draining of a palaeolake in the Kuray basin with the water level 1650 m a.s.l. (maximal depth about 220 m near the dam) with different scenarios of breaching the ice dam. In contrast to a relatively gradual breach of the ice dam due to thermal erosion, an instantaneous dam break due to structural failure can cause an outburst flood with a peak discharge of around 2 × 106 m3 s−1. The high speeds of the water flow, 1.9–5.6 m s−1, with the maximum Froude numbers of 0.06–0.22, and peak Shields values of 0.03–0.25 indicate competence to mobilize gravel. Generally, the simulated flow remained subcritical, suggesting that bedforms developed under supercritical flows, such as antidunes, could not have developed, although the development of dunes cannot be precluded. Our data also contribute to the issue of correlating the low lake strandlines in the Kuray basin with the landforms associated with cataclysmic outburst floods.The study was supported by State Assignment of IGM SB RAS and partly funded by Russian Foundation for Basic Researches (grant 18-05-00998). We also benefited from the funds of the projects EX-AQUA (1623P) “Palaeohydrological Extreme Events - evidence and archives”, sustained by INQUA TERPRO. The flood modelling contribution by Bohorquez was supported by the Spanish Ministry of Science, Innovation and Universities (MICINN/FEDER, UE) under Grant SEDRETO CGL2015-70736-R
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