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Sen weichsel isdynamikk og isavsmeltingsmønster av Den fennoskandiske innlandsisen i Gausdal Vestfjell, sentrale Sør-Norge, basert på romlige data
Get PDFEvidence-based geomorphological research (analyses of glacial landform record) is one of the commonly used types of glacial reconstructions applied for studying the past ice sheets. The work covered by this thesis contains a geomorphological data set of more than 17 000 glacial and glacifluvial landforms in Gausdal Vestfjell, south-central Norway. The study area is located in an inner region of the former Fennoscandian Ice Sheet (FIS) and contains a palaeogeological record on the flow pattern evolution and retreat during the Late Weichselian. The geomorphological mapping was carried out by exploiting the accessibility of high resolution LiDAR (Light Detection And Ranging) data and the capabilities provided by the latest advances in Geographical Information System (GIS) technologies such as terrain visualisations in an interactive 3D environment. A consequence of the
‘age of LiDAR’ is the increase in the resolution of the findings with more and smaller-sized landforms being mapped, that earlier were likely to be left out as unrecognised. These small-sized landforms may provide information on relatively short-lived events representing changes of glacial dynamics. This is particularly the case when such landforms are found overlapping other larger landforms. The mapping results have been validated by field observations.
Since the manual mapping of landforms is a time consuming and potentially subjective process, part of the thesis explores the semi-automated mapping (SAM) techniques that may be a reliable and effective alternative for data extraction. Several SAM methods are proposed for glacial streamlined landform extraction, yet none was considered optimal for the extraction of glacial ice flow directions in a complex terrain, such as the study area in the Scandinavian Mountains. Therefore, the potential of the grayscale thinning (skeletonisation) application for the extraction of directional trends from the terrains is explored.
The meltwater landform domain is a valuable source of information on the dynamics of past ice sheets and their deglaciation. Possibly due to the uncertainties in establishing the correlations of spatial and temporal relations of (and, in particular, the marginal) meltwater landforms it has often had only a secondary role. Here, GIS tools were used to introduce a simple reference surface gradient and apply a vertical adjustment of the ‘virtual ice surface’ representing vertical down-wasting of ice
in order to increase the credibility of meltwater landform correlations. This enabled to distinguish several important ice marginal positions and to reconstruct the significant events of deglaciation in a greater detail.
The study reveals a stepwise evolution of the FIS flow pattern during the Late Weichselian where a topography independent ice flow (Phase I) is followed by a regional (Phase II) that is subsequently replaced by a strongly channelized, topography-driven ice flow (Phase III with several substages). Prior to the ice disintegration, the ice flow was increasingly confined into valleys, likely separated by colder, less active ice. The deglaciation is characterised by a vertical down-melting of ice, dynamic evolution of the meltwater drainage systems that included temporary ice-dammed lakes and spillways, and deposition of various glacifluvial landforms.
Although the presented work can be considered as a local study from Gausdal Vestfjell, it improves our knowledge on the evolution and retreat of the FIS. Further, the proposed methods may find useful applications in other glacial geomorphology studies elsewhere.Bevisbaserte geomorfologiske undersøkelser (analyser av glasiale landformer) er en av de vanligste måtene å rekonstruere tidligere innlandsiser. Arbeidet som omfattes av denne avhandlingen inneholder et geomorfologisk datasett med mer enn 17 000 glasiale og glasifluviale landformer i Gausdal Vestfjell, midtre Sør-Norge. Studieområdet ligger i indre region av Den fennoskandiske innlandsisen (FIS) og inneholder et verdifullt geologisk arkiv om utviklingen av strømningsmønsteret og isavsmeltingen i sein weichsel. Geomorfologisk kartlegging ble utført ved å utnytte tilgjengeligheten av høyoppløselig LiDAR-data (Light Detection And Ranging) og å anvende de nyeste teknologiske framskrittene innen geografiske informasjonssystemer (GIS) som interaktive 3Dvisualiseringer av terrenget. En konsekvens av denne ‘LiDAR-epoken’ er høyere oppløsning av kartleggingsfunnene med forekomst av langt flere og mindre landformer som sannsynligvis ville blitt oversett tidligere. Disse små-skala landformene kan gi informasjon om relativt kortvarige hendelser som representerer endringer i isdynamikken. Dette gjelder spesielt når slike landformer er funnet oppå andre større landformer. Kartleggingsresultatene er stadfestet med feltobservasjoner.Pierādījumos balstītie ģeomorfoloģiskie pētījumi (glaciālo reljefa formu analīze) ir viens no biežāk pielietotajiem rekonstruckiju veidiem pagātnes ledusvairogu pētījumos. Doktora disertācijas ietvaros veiktais pētījums sevī ietver informāciju par vairāk kā 17 tūkstošiem dažādu glacigēno un ledāja kušanas ūdeņu reljefa formām no Gausdālas Vestfjelas (Gausdal Vestfjell) apkārtnes, centrālajā Dienvidnorvēģijā. Pētījuma teritorija atrodas bijušā Fenoskandijas ledusvairoga centrālā apgabala iecirknī, un tājā ir atrodamas vērtīgas paleoģeoloģiskās liecības par apledojuma plūsmu attīstību vēlā Vislas apledojuma laikā un ledusvairoga kušanu leduslaikmeta beigu posmā. Ģeomorfoloģiskā kartēšana tika veikta izmantojot augstas izšķirtspējas LiDAR (lāzerskenēšanas) datu pieejamību un Ģeogrāfisko Informācijas Sistēmu (ĢIS) sniegtās iespējas, kā piemēram, reljefa vizualizāciju interaktīvajā 3-dimensiju vidē. Likumsakarīgi, ka LiDAR laikmets ir atnesis izšķirtspējas pieaugumu, kā rezultātā ir iespējams kartēt un datu kopā ietvert vairāk un izmēros mazākas reljefa formas, kuras agrāk būtu palikušas nepamanītas. Šīs mazizmēra reljefa formas iespējams var sniegt ieskatu relatīvi īslaicīgos notikumos ledus plūsmu dinamikas attīstībā. Tas jo īpaši ir attiecināms gadījumos, kad šīs mazizmēra reljefa formas ir atrodamas pārklājamies uz citām, lielākām reljefa formām. Pētījuma ietvaros iegūtie kartēšanas rezultāti ir apstiprināti ar lauka darbos gūtajiem novērojumiem.
Tā kā manuāla reljefa formu kartēšana ir laikiepiltīgs un potenciāli subjektīvs process, daļa no doktora disertācijā ietvertā pētījuma apskata (semi-)automātiskās kartēšanas metodžu pielietošanu kā potenciāli uzticamu un efektīvu alternatīvu datu ieguvei. Kaut arī pastāv dažas reljefa formu automātiskās atpazīšanas metodes, neviena no esošajām metodēm nav uzskatāma par piemērotu datu par ledus plūsmu virzieniem ieguvei sarežģītos reljefa apstākļos, kādi ir satopami pētījuma teritorijā, Skandināvijas kalnu grēdas centrālajā apgabalā. Tāpēc pelēktoņu (grayscale) retināšanas rīkā balstīta reljefa virzienu noteikšanas metode, tiek apskatīta kā alternatīva esošajām metodēm.
Ledājkušanas ūdeņu reljefa formas sevī ietver vērtīgu informācijas avotu par ledusvairogu plūsmas dinamiku un to atkāpšanos leduslaikmeta beigu posmā. Taču, iespējams tieši neskaidrību un problemātikas dēļ, kāda pastāv saistībā ar ledāja kušanas reljefa formu (un jo īpaši marginālo) korelāciju izveidošanu, ledājkušanas ūdeņu reljefa formām bieži ir bijusi tikai otršķirīga nozīme. Šī darba ietvaros tika pielietoti ĢIS rīki, lai ieviestu vienkāršotu atsauces virsmu - ‘virtuālo ledāja virsmu’, ar mērķi uzlabot marginālo ledājkušanas ūdeņu reljefa formu korelācijas. Šādas atskaites virsmas ieviešana ir veicinājusi ledāja marginālo pozīciju noteikšanu un galciālo rekonstrukciju izveidi daudz augstākā detaizācijas pakāpē kā līdz šim.
Veiktais pētījums atklāj pakāpeniskumu Fenoskandijas ledusvairoga ledus plūsmu dinamiskas attīstībā vēlā Vislas apledojuma laikā, kur no topogrāfiski neatkarīgas plūsmas (fāze I) tā pāriet reģionālā (fāze II) ar zināmu zemledāja topogrāfijas ietekmi, līdz tā iegūst izteiktu kanālveida (fāze III un tās paveidi) raksturu. Pirms ledusvairoga aprimšanas, ledus plūsma pakāpeniski tika arvien vairāk novirzīta ielejās, starp tām valdot stagnata un aprimuša ledus apstākļiem. Deglaciāciju galvenokārt raksturo ledus biezuma pakāpeniska samazināšanās un dinamiska ledājkušanas ūdeņu sistēmu attīstību, kura ietver īslaicīgu ledājkušanas ūdeņu baseinu, ledājkušanas ūdeņu pārteces kanālu eksistenci kā arī akumulatīvo ledājkušanas ūdeņu reljefa formu veidošanos.
Kaut arī šis pētījums ir raksturojams kā lokālas nozīmes pētījums Gausdālas Vestfjelas apkārtnei, tas sniedz nozīmīgu papildinājumu mūsu zināšanās par Fenoskandijas ledusvairoga attīstību un deglacācijas gaitu. Turklāt, šī darba ietvaros piedāvātās metodes ir potenciāli pielietojamas glaciālās ģeomorfoloģijas pētījumos citviet seno apledojumu skartajās teritorijās
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Holocene glacial advances and moraine formation at Albrechtbreen, Edgeøya, Svalbard
No full textTerrace remnants close to the marine limit as well as two separate moraine ridges are observed in front of the glacier Albrechtbreen. The stacking of marine sediments from an original elevation of ca. 60–80 m a.s.l. into the Little Ice Age Moraine gives evidence for a considerably smaller glacier following the early Holocene deglaciation compared to that of the present. The outer moraine is composed of glacial diamicton. Radiocarbon datings of whale ribs, shell fragments and a log taken from sediment in front of Albrechtbreen indicate that the initial deglaciation occurred before 9, 400 B.P. and that the outer moraine was formed during a younger Holocene glacial advance. Lithological differences between the two moraine ridges suggest that the first ice advance occurred during a period with limited permafrost, whereas permafrost was more extensive during the Little Ice Age
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
The PONAM project in eastern Svalbard
No full textWhy would the modern scientist choose to travel to the most remote islands of the Svalbard archipelago, spending days travelling, living in primitive field camps, carrying heavy equipment for long distances, and exposing him- or herself to the dangers of a desolate country and its wildlife
Glaciation development and interstadial sea-level on central Spitsbergen, Svalbard
No full textAbove the marine limit in Gangdalen, Nordenskiold Land, a 2Om thick sequence of unconkolidated sediments occurs. On the top of striated bedrock it is composed of a 2m thick till bed, 15m gravel interpreted to be deposited as a sandur, and another till bed on the top. A solifluction deposit is capping the section. Fabric analyses and erratics in the two tills indicate a similar development in glacial transport directions during the two glaciations. starting with a local glaciation which subsequently turns into a larger glaciation centred over the eastern part of Svalbard. Co-existence of different ice domes over Spitsbergen is suggested. f h e sandur was deposited during an ice free period with a sea-level 4&80 m higher than at present. The section is undated. Above the marine limit in Gangdalen, Nordenskiold Land, a 2Om thick sequence of unconkolidated sediments occurs. On the top of striated bedrock it is composed of a 2m thick till bed, 15m gravel interpreted to be deposited as a sandur, and another till bed on the top. A solifluction deposit is capping the section. Fabric analyses and erratics in the two tills indicate a similar development in glacial transport directions during the two glaciations. starting with a local glaciation which subsequently turns into a larger glaciation centred over the eastern part of Svalbard. Co-existence of different ice domes over Spitsbergen is suggested. f h e sandur was deposited during an ice free period with a sea-level 4&80 m higher than at present. The section is undated
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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