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1
Robinson, Bonnie Jean. "Reconstruction of the glacial history of the Columbia Icefield, Alberta." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0001/MQ30670.pdf.
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Hughes, Anna L. C. "The last British Ice Sheet : a reconstruction based on glacial landforms." Thesis, University of Sheffield, 2008. http://etheses.whiterose.ac.uk/16363/.
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The last British Ice Sheet has been a focus of research for over a century, and yet we have only a generalised picture of its extent and internal geometry. This is a remarkable situation compared to knowledge of the larger former ice sheets of North America and Fennoscandia. The central tenet of this thesis is that the glacial landform record has been neglected as a source of spatial information, hindering our attempts to reconstruct the characteristics of the ice sheet. This motivated systematic mapping of glacial landforms (subglacial bedforms, moraines, eskers, and meltwater channels) for the whole of Britain, yielding the first consistent and countrywide glacial maps. Mapping was achieved primarily using a high resolution (5 m horizontal) digital elevation model to visualise the landscape. Over 60,000 features were identified and mapped, greatly expanding the known distribution and pattern of glacial landforms. Analysis of the landform data permitted a country-wide reconstruction of the pattern of ice sheet retreat. A database of just over 400 dates, compiled from the literature, was used to arrange the pattern of retreat in time. This exercise highlighted various incompatibilities between the presently available dates. Examination of landform patterns enabled the elucidation of some pre-deglacial configurations of ice divides and flow geometry, including ice streams. This revealed the existence of both transient (migrating) and persistent ice divides. In contrast to other and larger palaeo-ice sheets, the majority of flow evidence in Britain exhibits a particularly close association with topography, indicative of an ice sheet thickness comparable with the amplitude of subglacial relief. The retreat pattern, flow geometries and divide configurations that have been identified from this research provide a set of evidence-based constraints at ice sheet scale for future numerical ice sheet modelling experiments.
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James, William Henry Meurig. "A landform based 3D reconstruction of glacier ice at the Last Glacial Maximum in the Southern Alps, New Zealand." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/16345/.
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New Zealand fills a large geographic gap in the global glacial record, with landforms and near-surface deposits preserving a remarkable footprint of Quaternary glaciation. As one of the few land masses in the Southern Hemisphere, the record of glacial geomorphology is of great importance for research into the natural behaviour of the Earth’s climate system. This thesis presents a 3D simulation of the New Zealand Southern Alps glaciers at the Last Glacial Maximum (LGM, c. 30 to 18 ka) in an attempt to constrain glacial geometry of that period. To achieve this, the REVOLTA (Reconstruction of Volume and Topography Automation) model was developed, a Python script tool for ArcGISTM that requires just a DEM of glacier bed conditions and the down-valley extent of glaciation as initial inputs. Ice thickness is initially estimated at points along an automatically generated centreline network based on the perfect-plasticity rheology assumption, taking into account a valley side drag component of the force balance equation. Distributed ice thickness is subsequently interpolated using a glaciologically correct algorithm. Results indicate a total LGM ice volume of 6771.9 km3, in good correspondence of previous studies using a climate-driven ice dynamics approach. Combined with an estimate of contemporary ice volume (50.67 km3), this result reinforces the notion that New Zealand has lost almost the entirety (99.25 %) of its glacial ice since the LGM, although this volume has contributed to just 17.02 mm of global sea level rise. Analysis of the LGM distributed ice thickness output shows a large number of nunataks and exposed ridges in the central Mt. Cook and northern regions, with a localised icefield in the Fiordland area. LGM Equilibrium Line Altitudes (ELAs) automatically calculated using the Accumulation Area Ratio (AAR) method reveals an average lowering of 1074 m from present, with those to the west of main divide 461m lower than those to the east on average. LGM climatic conditions were estimated using the ELAs and scaled versions of contemporary temperature and precipitation distributions, suggesting a temperature reduction of between 5.6°C to 10.3°C and precipitation change of +4.3 % to +100.4% from present. When considering these new estimates in conjunction with critically evaluated previous evidence, an average LGM cooling of 6.5 °C to 8°C is proposed, a refinement on the wide range of previously published values. Importantly, there is large spatial variability between catchments, with eastern regions experiencing significantly greater cooling and greater precipitation increases (or less decrease) than their western counterparts. Increased westerly circulation and reduced sea level altering the relative position of the orographic barrier is a suggested potential mechanism for the predicted precipitation pattern changes, whilst increased southerly flow bringing cool air up the east coast is a possible cause of the temperature change differential predicted. The proportion of precipitation falling as snow or rain was also found to be an important factor when considering New Zealand LGM conditions, with up to 50% estimated to be falling as rain at the LGM ELA, with a strong east-west differential. Input dataset generation for REVOLTA resulted in several important research outcomes. A DEM approximating LGM bed conditions was created, using a variety of novel techniques to modify the existing DEM. These included the estimation of contemporary ice thickness distribution using the VOLTA (Volume and Topography Automation) model for removal from the DEM, merging offshore and lake bathymetry and considering Holocene in-fill sediments. Furthermore, an in-depth review of the most up to date literature and datasets regarding the lateral extent of LGM glaciation was also carried out, generating an updated ‘outline’ of LGM glaciation.
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Stutz, James Edward II. "Reconstruction of LGM and Post LGM Glacial Environment of McMurdo Sound: Implications for Ice Dynamics, Depositional Systems and Glacial Isostatic Adjustment." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1324595182.
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Weremeichik, Jeremy M. "Paleoenvironmental reconstruction by identification of glacial cave deposits, Helderberg Plateau, Schoharie County, New York." Thesis, Mississippi State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1536097.
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Eight dissolution caves from the Helderberg Plateau in Schoharie County, New York were studied to investigate unusual sediment packages previously interpreted to be deposits laid down during stagnant ice-cover conditions of the Wisconsin glaciation. The sediment package, consisting of white finely laminated silts and clays are overlain by coarse gravels, in turn overlain by dark silts and clays. Analysis of 63 sediment samples was inconclusive in terms of organic content, but indicated a higher degree of fine-grained calcite material in the white clays than in the overlying units. The caves with the white clays exist only within the footprint of Glacial Lake Schoharie, with lower elevation caves containing a thicker white clay sequence, a measure of the duration of lake cover. The sediment sequence represents glacial rock flour formed under stagnant lake conditions, overlain by outwash deposits emplaced during lake termination, and more recent sediment from soil-loss deposition.
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Wolff, Ingo Wilhelm. "The Last Glacial Maximum Patagonian Ice Sheet : a GIS-based high-resolution reconstruction approach." Thesis, Aberystwyth University, 2016. http://hdl.handle.net/2160/950c2c84-ce59-49f9-9946-19be41e9c750.
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The Last Glacial Maximum (LGM) Patagonian Ice Sheet (PIS) provides the unique potential to reconstruct the former meridional position and precipitation rates of the Southern Westerly Wind Belt (SWWB) due to its considerable latitudinal distance perpendicular to this global wind system. To use this potential, a high-resolution 3D reconstruction of the LGM PIS would be crucial, but knowledge about even the exact planform of this biggest Quaternary ice sheet on the Southern Hemisphere, excluding Antarctica, is still very poor. The widely accepted limits of the ‘Finiglacial’ ice sheet extent, mapped over 80 years ago by Caldenius (1932), has been identified as the LGM extent at many locations (e.g. Kaplan et al., 2004, 2008a,b; Singer et al., 2004; Hein et al., 2009). However, apart from the broadly correct assignation of the ‘Finiglacial’ limit to the LGM, its resolution remains poor, imperfect, and outdated, despite some later adaptations (e.g. Hollin and Schilling, 1981a; Clapperton, 1993) with small improvements. All attempts to provide 3D reconstructions (Hollin and Schilling, 1981a; Hulton et al., 1994, 2002) date back almost 15 years and did not match the poorly constrained glacial geomorphological record. This study presents a novel attempt to cast all relevant absolute dating locations of glacial landforms into a refined spatio-chronological context of the LGM extent of the PIS. Based on this newly set spatio-chronological context, a geographical information system (GIS)-based high-resolution LGM extent reconstruction, both in planform and in 3D, is presented within this study. In contrast to its predecessors, the applied GIS-based modelling approach enables a grade of reconstruction resolution for an ice sheet, that is as big as Spain and that is otherwise found only in local valley-scale glacier reconstructions. The spatial resolution of the GIS-based 3D ice-sheet reconstruction surface lies at 100 metres, as does the implemented topographic data. This leads to a spatial ice-sheet surface resolution that is at least 200 times higher than any previous attempt to cover the entire LGM PIS. The 3D reconstruction of the LGM PIS using the newly defined extent is in good agreement with observations on vertical ice extents (Boex et al., 2013) and displays, for the first time, a realistic interaction with the complex Patagonian topography. The area of the LGM PIS is, with ca. 504,500 km2 (±8.5%) roughly a fourth of the area of Greenland and represents 554,500 km3 (±10%) of ice or 1.38 metres (±10%) of sea-level equivalent. The now available 3D reconstruction provides a starting point that, after minor revisions, could potentially allow gauging accumulation rates along up to 2,300 km perpendicular to the SWWB and, thus, inferring valuable palaeo-climatic insights from the LGM.
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Williams, Nicola Jane. "The environmental reconstruction of the last glacial cycle at Redhead Lagoon in coastal, eastern Australia." Phd thesis, School of Geosciences, 2005. https://hdl.handle.net/2123/9044.2.
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This study reconstructs the palaeoenvironmental history during the last full glacial cycle (approximately the last
75,000 years) at Redhead Lagoon, an enclosed lake basin located in coastal, eastern New South Wales,
Australia. This has been achieved primarily through sedimentological, palaeoecological and mineral magnetic
analyses of long cores. The sequence adds to the limited number of long-term records in Australia and from
this region in particular.
The chronology of the sediment record is established through AMS radiocarbon and Optically Stimulated
Luminescence (OSL) dating. More than 30 AMS radiocarbon ages, using a variety of pre-treatment methods,
have been obtained for three cores, which makes this one of the most comprehensively dated lake sediment
sequences thus far in Australia.
During the initial stages of the last glacial period the site was dominated by a mobile dune system with no
permanent water, Supporting only semi-arid vegetation communities. The dune sand was part of a sequence of
cliff-top dunes located on nearby Dudley Bluff emplaced by a process of ‘sand ramping’ during an earlier
Pleistocene phase of lower sea level.
Pollen analysis indicates that the sequence of vegetation changes seen at Redhead Lagoon broadly compares
with the cyclical pattern of climatically induced changes seen in many other pollen records in southeastern
Australia. Alternating open herbaceous and woodland/forest communities correspond with glacial and
interglacial periods respectively. Superimposed on this pattern is a change towards a more open understorey
vegetation assemblage, i.e. increasing values of Poaceae relative to Asteraceae (particularly type B) over the
last 35,000 years.
A sharp increase in the incidence of Casuarinaceae from the height of the last glacial and its subsequent
decline relative to Eucalyptus in the latter stages of the Holocene is evident. While reduced moisture availability
may have initially facilitated the expansion of Casuarinaceae, the restriction of Casuarinaceae during earlier
arid periods indicates that another factor appears to have been in operation. An examination of changing
Chenopodiaceae/Casuarinaceae ratios, an indicator of salt-tolerance, shows that soil salinity may have been a
significant contributor to the incidence of Casuarinaceae at Redhead Lagoon.
The driest period during the last glacial cycle occurred during MIS 2. A hiatus in one core from 0. 28,000 to
12,000 BP may have been caused by the erosion of sediments during the LGM and late glacial period.
However, deposits dating from this period are preserved in a second core. This core indicates the presence of a
Casuarinaceae-dominated open sclerophyll woodland in association with grassland and low water balances
during the height of the last glacial period.
The Holocene marks the start of a period of climatic amelioration. It is characterised by highly organic sediment
deposition, an increase in pollen taxa diversity and the disappearance of several colder and/or drier taxa
indicators (e.g. Asteraceae type B). The highest water balances in the sequence are attained during the early to
mid-Holocene. This is suggested by the development of wet sclerophyll forest and the attainment of maximum
values of taxa such as Pomaderris and Mela/euca. There is also a possible switch to a summer rainfall
dominated climatic regime during this period.
Both microscopic and macroscopic charcoal counting methods have been employed in this study. Importantly,
this has allowed the quantitative assessment of the macroscopic charcoal method over a longer time period
than previously documented in Australian records. An evaluation of the two procedures reveals several notable
differences. In particular, the macroscopic charcoal method records several more local fire events unable to be
distinguished by the microscopic charcoal technique.
The relative importance of climatic and human influences on environmental change has been assessed. The
majority of changes in the vegetation and charcoal records correlate with periods of significant climatic
fluctuation. From around 35,000 years ago the vegetation became more open and ceased to support frequent
or intense fires, resulting in a dramatic reduction in charcoal concentrations. This change may correspond with
the start of a period of increased aridity that has been suggested from geomorphic evidence from southwestern
New South Wales and increased ENSO variability. The small size of the Redhead Lagoon catchment, the close
proximity of other larger and probably more attractive sites for humans, along with the limited population and
nomadic lifestyle of the indigenous Aborigines, were probably major factors contributing to the relatively limited
impact. In addition, the close proximity of the site to the coastline would likely have meant that fishing was an
important activity and the open woodland found on this sandstone catchment is unlikely to have furnished many
useful plant foods. Therefore, there may have been little advantage for humans in a location such as Redhead
lagoon in manipulating the vegetation using fire.
During the mid-Holocene, however, there is evidence of increases in disturbed ground taxa and the ‘fire
adapted’ genus Eucalyptus, along with increased charcoal fragments. In addition, there is a significant increase
in the aquatic wetland plant Typha, which was extensively used by the Aborigines. In the absence of climatic
stress the combination of these increases in various vegetation types and charcoal concentrations suggest that
anthropogenic burning may have caused landscape change from this time.
There have been significant environmental changes since permanent European settlement began in the
catchment. These include the introduction of several exotic vegetation types and significant increases in
sediment accumulation rates, charcoal particles and possibly nutrient levels. In addition, there has been a
decline in the incidence of several tree and rainforest taxa, which may reflect land clearing practices and the
increasing fragmentation of forest communities after the arrival of European settlers. Changes in land use and
human activity have had far more impact on the catchment than climatic and other natural fluctuations during
this most recent period.
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Williams, Nicola Jane. "The environmental reconstruction of the last glacial cycle at Redhead Lagoon in coastal, eastern Australia." Phd thesis, School of Geosciences, 2005. http://hdl.handle.net/2123/9044.
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Standell, Matthew R. "Late glacial (Younger Dryas) glaciers and ice-sheet deglaciation in the Cairngorm Mountains, Scotland : glacier reconstructions and their palaeoclimatic implications." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16159.
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The Cairngorm Mountains contain an outstanding assemblage of glacial landforms from both the deglaciation of the last British Irish Ice Sheet and the Younger Dryas readvance. Glaciers are recognised as sensitive indicators of past and present climate change and, thus, these landforms provide information about past climate and glacier-climate interaction that can be used to contextualise the present climate change. Previous interpretations have left doubt over the extent and style of the Younger Dryas readvance. In addition, the pattern and timing of deglaciation in the southern Cairngorms and, particularly, how local and external ice masses interacted is unclear. New geomorphological mapping from aerial images and fieldwork has been compiled in a GIS for a 600km2 area of the Cairngorm Mountains. This has allowed a complex pattern of ice-dammed lakes and local and regionally sourced ice margins to be reconstructed during the retreat of the last British Irish Ice Sheet. The mapping has been combined with new cosmogenic surface exposure ages taken from areas of hummocky moraine previously subject to differing age interpretations. The effect of moraine denudation on apparent 10Be ages has been checked by inverse modelling of the 10Be concentration vs. boulder height. The results indicate more extensive Younger Dryas glaciation, with glacier reconstructions and equilibrium-line altitudes (ELAs) comparable with the surrounding areas. Reconstruction of both valley and plateau-fed glaciers are presented, with modelling of local topoclimatic factors, such as radiation, avalanche and snow drifting, combined with precipitation gradients, explaining most of the variation within the glacier ELAs. The geomorphological evidence and palaeoclimatic inferences are important, alongside a growing number of palaeoglaciological studies, in acting as evaluation areas for current numerical models of ice-sheet growth and decay.
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Lagerbäck, Adolphi Emma. "Optically Stimulated Luminescence Dating and Last Glacial Climate Reconstruction from the Lingtai Loess Section, Chinese Loess Plateau." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-296666.
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High resolution dating of loess on the Chinese Loess Plateau (CLP) using Optically Stimulated Luminescence (OSL) has increased the understanding of past monsoon climate but also raised questions regarding dust mass accumulation rate (MAR), the presence of disturbances or gaps in the sediment record, a possible teleconnection between North Atlantic and East Asian monsoon climate, and whether these events are due to climate variability, local settings, or age model uncertainties. This study undertakes a detailed (<20cm sampling resolution) -OSL investigation of the Lingtai section to create an independent age model using linear regression, to reconstruct monsoon climate changes using magnetic susceptibility(MS) and grain size (GS) proxies, as well as to calculate MAR for the site. The data shows that between 44-15 ka climate changes from a period of strong summer monsoon to a strong winter monsoon. GS data show variable trends attributed to changes in dust storm activity and local environmental conditions. MAR data does not correlate with grain size and is different from other loess records on the CLP. Such differences are either due to local variations or age model uncertainties. No clear correlation with Heinrich events or teleconnection with North Atlantic climate is visible in the records over the Last Glacial period, and hiatuses or gaps are not obviously present at this site. It is suggested that using linear regression for continuous age model construction from the luminescence ages comes with uncertainties due to subjective bias when fitting the lines and determining shifts in the data, especially during MAR calculations. Further studies are needed to ascertain optimal methods for creating age models, and to constrain the reasons behind the variability between different sites and loess records on the CLP.Högupplöst OSL-datering av loessjordar från CLP har ökat förståelsen av dåtida monsunklimat, men har även lyft frågan gällande MAR, närvaron av avbrott eller småskaliga event i jordsektionerna, möjligheten av en relation mellan de Nordatlantiska och Ostasiatiska monsunklimaten, och om dessa förändringar sker till följd av faktisk klimatvariation, lokala förutsättningar, eller osäkerheter i åldersmodellen. Studien genomförde en detaljerad (<20cm) OSL-undersökning av Lingtai-sektionen för att skapa en oberoende åldersmodell, återge monsunklimatförändringarna genom tillämpning av MS och GS proxies, samt beräkna MAR från platsen. Resultaten påvisar att mellan 44-15 ka förändrades klimatet från en period av stark sommar- till en stark vinter-monsun. Kornstorleks-resultaten påvisar stora variationer vilka kan kopplas till en förändring i sandstormsaktivitet samt de lokala förutsättningarna för deposition av sediment. MAR-resultaten överensstämmer inte med kornstorleksdatan och skiljer sig från den övriga empirin, detta kan bero på lokala variationer i regionen eller osäkerheter i åldermodellen. Det finns ingen klar korrelation mellan "Heinrich events" eller en "teleconnection" i sektionen, och avbrott samt störningar i sektionen är inte förekommande. Avsaknaden av korrelation antyder att användningen av regressionslinjer för att skapa kontinuerliga åldermodeller kommer innebära fortsatta osäkerheter i empirin, speciellt gällande beräking av MAR. Ytterligare studier krävs för att bestämma optimala metoder för att framställa åldersmodeller, samt att utröna orsaken till skillnaden mellan resultat från olika platser på plat
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Logan, K. R. "Late-glacial and early Holocene ocean-climate reconstruction from laminated diatomaceous sediments, Effingham Inlet, British Columbia, Canada." Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517398.
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Morri, Clara Melissa. "The last glacial-interglacial cycle : palaeocurrent reconstruction and sediment response to climate change in the North Atlantic." Thesis, Open University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406404.
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Collins, Lewis G. "High-resolution reconstruction of palaeoceanographic conditions in the glacial Southern Ocean (Scotia Sea and Adelie Land Coast)." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54909/.
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Antarctic sea-ice is a critical component of the climate system, an enhancer of glacial climate and, as recently hypothesised by modelling studies, a potential driver of the millennial scale climate variability that dominated the last glacial cycle (LGC). Unfortunately a severe lack of glacial sea-ice records from the Southern Ocean has so far prevented the testing of this hypothesis with field data. In this thesis, I present detailed reconstructions of Antarctic sea-ice and ocean conditions derived from diatom assemblages and the first application of highly branched isoprenoid biomarkers to glacial sediments. These sea-ice sensitive proxies were measured in high-resolution, glacial sediment cores from the Scotia Sea (Southwest Atlantic, West Antarctica) and the Adelie Land Coast (Australia Antarctica Basin, East Antarctica). Good chronological control for the past 50 kyrs was achieved through the correlation of geochemical tracers with an oxygen isotope stack, a combination of biostratigraphic datums and relative geomagnetic palaeointensity data, and the identification of the Laschamp geomagnetic excursion at its most southerly site to date. These records permit a critical assessment of the contemporaneous nature of the regional extent, duration and seasonality of summer and winter sea-ice in West and East Antarctica during the LGC, and further afford an opportunity to determine validity of the proposed role played by Antarctic sea-ice in millennial-scale climate change through its influence on oceanography and climate. Results show that the environmental response to climate perturbations in West and East Antarctica was heterogeneous between 46.9 cal ka B.P. and 25 cal ka B.P. and broadly homogenous between ""25 cal ka B.P. and deglaciation. This study builds on existing Last Glacial Maximum (LGM) sea-ice reconstructions and shows greater summer sea-ice expansion in the Scotia Sea than previously recognised, a reduced maximum winter sea-ice extent along the Adelie Land Coast, a circum-Antarctic sea-ice maximum earlier than the LGM, decreased sea-ice seasonality in the Scotia Sea prior to maximum conditions, and an extensive period of extended sea-ice seasonality after maximum conditions. Further, this investigation has revealed close relationships between these new glacial reconstructions of Antarctic sea-ice and Antarctic Isotope Maxima, Dansgaard/Oeschger events, atmospheric CO2 variability and deep-water formation, confirming the likely importance of Antarctic sea-ice in the propagation of global millennial-scale climate change during the LGC.
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Balakauskas, Lauras. "Development of the Late Glacial and Holocene forest vegetation in Lithuania, according to LRA (Landscape Reconstruction Algorithm) modelling data." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20121001_093432-89436.
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Most widely used applications of quantitative past vegetation reconstruction are based on pollen-vegetation relationship functions. To carry out detail vegetation reconstruction using this method, large amount of geographic data pre-processing is necessary. For this reason, large scale vegetation reconstructions are extremely rare. In this study data processing is carried out using automated GIS tools. Application of GIS enabled precise and detail reconstruction of the Late Glacial and Holocene forest vegetation composition, as well as the development of vegetation in Lithuania. New pollen investigations from cores and outcrops, created Lithuanian pollen database, evaluation of pollen-vegetation relationship functions in the environment of Lithuania and reconstruction of main tree species composition in the Late Glacial and Holocene, according to pollen database and selected pollen-vegetation relationship function are presented in this study. The created palaeovegetation maps enbled considerable detalization of knowledge about past vegetation in Lithuania. Consequently, main vegetation migration and distribution patterns were defined.Plačiausiai naudojami kiekybinio praeities augalijos taksonominės sudėties atkūrimo pagal žiedadukių duomenis metodai remiasi žiedadulkių-augalijos priklausomybės funkcijomis. Norint atlikti detalų augalijos sudėties atkūrimą šiuo metodu, reikalingos itin didelės apimties geografinių duomenų apdorojimo procedūros, todėl stambiu masteliu augalijos sudėtis atkūriama itin retai. Šiame darbe duomenų apdorojimas atliekamas automatizuotomis GIS priemonėmis. GIS panaudojimas leido tiksliai ir detaliai atkurti Lietuvos vėlyvojo ledynmečio ir holoceno miško augalijos taksonominę sudėtį bei augalijos vystymosi raidą. Disertaciniame darbe pristatomi nauji gręžinių ir atodangų nuosėdų žiedadulkių tyrimai, sudaryta Lietuvos žiedadulkių duomenų bazė, atliktas įvairių žiedadulkių-augalijos priklausomybės funkcijų įvertinimas Lietuvos sąlygose, žiedadulkių duomenų bazės pagrindu pagal pasirinktą priklausomybės funkciją atkurta pagrindinių medžių taksonų sudėtis eilei vėlyvojo ledynmečio ir holoceno laikotarpių. Sudarytais praeities augalijos paplitimo žemėlapiais reikšmingai detalizuotos žinios apie praeities augaliją Lietuvoje, nustatyti pagrindiniai augalijos migracijos keliai ir jos paplitimo dėsningumai.
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van, Woerkom Anne. "Ancient DNA from soils and sediments from the Krigstjärn area, northern Sweden : Preservation and detection of Holocene mammal sedaDNA." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-127680.
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Current knowledge of past vegetation and faunal diversity has been based on pollen and macrofossil analysis from lake sediments. The innovative method of sedimentary ancient DNA (sedaDNA) is a promising, complementary proxy to reconstruct information about past environments. However, to what extent animal DNA can be extracted from old sediments and soils has not been frequently studied. This study explored if ancient DNA of moose (Alces alces), reindeer (Rangifer tarangus), goat (Capra aegagrus) and plants could be extracted from millennia old lake sediments of Lake Krigstjärn and archaeological soil samples in northern Sweden. SedaDNA was successfully extracted and detected from both reindeer and plants DNA, while goats sedaDNA was absent in all sediments. Moose ancient DNA (aDNA) was only detected in the archaeological soils. Yet, there were signs that the applied moose primer set was not optimal for heavily degraded DNA and the validity of this primer needs further research. Earliest detections of reindeer DNA can be dated to ~6500 c. years ago. Oldest sediments contained DNA, indicating sufficient DNA preservation conditions in the sediments of Lake Krigstjärn. Finds of plants DNA in pre-deglaciational sediments may indicate the existence of >9500 year old glacial vegetation. Altogether is sedaDNA a highly promising tool to reconstruct diversity, origin and immigration routes of mammals, but technical issues such as primer set specificity and its purpose should be considered and tested carefully in advance.
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Xiao, Xiaotong [Verfasser], Ruediger [Akademischer Betreuer] Stein, and Gesine [Akademischer Betreuer] Mollenhauer. "Last Glacial Maximum to Holocene Arctic sea-ice variability: Reconstruction from biomarkers / Xiaotong Xiao. Gutachter: Ruediger Stein ; Gesine Mollenhauer. Betreuer: Ruediger Stein." Bremen : Staats- und Universitätsbibliothek Bremen, 2014. http://d-nb.info/107222576X/34.
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Mischel, Simon André [Verfasser]. "Multi-proxy reconstruction of Holocene and Late Glacial climate variability using precisely dated speleothems from the Herbstlabyrinth, central Germany / Simon André Mischel." Mainz : Universitätsbibliothek Mainz, 2016. http://d-nb.info/1119102847/34.
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Dietrich, Stephan [Verfasser]. "Palaeo wind system reconstruction of the last glacial period over Europe, using high resolution proxy data and model-data-comparison / Stephan Dietrich." Mainz : Universitätsbibliothek Mainz, 2011. http://d-nb.info/1025052528/34.
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Iizuka, Yoshinori, Torbjorn Karlin, and Margareta Hansson. "Sulphate and chloride aerosols during Holocene and last glacial periods preserved in the Talos Dome Ice Core, a peripheral region of Antarctica." Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-90812.
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Antarctic ice cores preserve the record of past aerosols, an important proxy of past atmospheric chemistry. Here we present the aerosol compositions of sulphate and chloride particles in the Talos Dome (TD) ice core from the Holocene and Last Glacial Period. We find that the main salt types of both periods are NaCl, Na2SO4 and CaSO4, indicating that TD ice contains relatively abundant sea salt (NaCl) from marine primary particles. By evaluating the molar ratio of NaCl to Na2SO4, we show that about half of the sea salt does not undergo sulphatisation during late Holocene. Compared to in inland Antarctica, the lower sulphatisation rate at TD is probably due to relatively little contact between sea salt and sulphuric acid. This low contact rate can be related to a reduced time of reaction for marine-sourced aerosol before reaching TD and/or to a reduced post-depositional effect from the higher accumulation rate at TD. Many sulphate and chloride salts are adhered to silicate minerals. The ratio of sulphate-adhered mineral to particle mass and the corresponding ratio of chloride-adhered mineral both increase with increasing dust concentration. Also, the TD ice appears to contain Ca(NO3)(2) or CaCO3 particles, thus differing from aerosol compositions in inland Antarctica, and indicating the proximity of peripheral regions to marine aerosols.AuthorCount:9;
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Allègre, Xavier. "Different generation of controlled moraines in the glacier foreland of Midtdalsbreen, Norway." Thesis, Stockholms universitet, Institutionen för naturgeografi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-175533.
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A series of small mounds (< 3m) were sampled in the foreland of Midtdalsbreen outlet glacier, southern Norway. These landforms were interesting, especially at site number 1 because they were located very close to a higher Little Ice Age (LIA) moraine (> 5 m), thereby informing the dynamic of the glacier after the LIA at this location. It was yet to determine if these specific mounds are controlled moraines. If they are controlled moraines, then this would have implication for the glacier dynamics and the geometry of the snout after the LIA. It could be determined, based on the landform record evidence, whether the ice at the snout of Midtdalsbreen was thin and cold shortly after the LIA. Furthermore, whether the landscape was deglaciated by downwasting and then by backwasting was the main question addressed in relation to the nature of the mound and the thickness of ice at the snout during and after the LIA. In order to better understand the nature of the landform record and the mounds near the LIA moraine, satellite imagery coupled with careful field investigations were used in the foreland of the Midtdalsbreen outlet glacier. A geomorphological map was produced, and it was useful to put the mounds in a geographical context. Further sedimentological investigation; including clast-shape analyze, produced more evidence about the inner nature of these landforms. Both few controlled moraines and other landforms throughout the glacier foreland indicate that the ice geometry for Midtdalsbreen, shortly after the LIA was such that the snout of the glacier was a thin sheet of ice flowing against the previously deposited LIA moraine. The sedimentology of the controlled moraine is such that the sediments are deposited in steeply dipping layers, and they could even be misinterpreted as permafrost terrains at first glimpse. However, other sedimentological evidences such as the presence of sorted sand and sometimes dipping beds of gravels in addition to the geomorphological mapping make it meaningful to interpret few of the mounds as controlled moraines. A modern analogue to these controlled moraines is dirt cones present on top of the glacier snout as well as controlled moraines a few hundred of meter from the snout. Observations both on the glacier snout and on the foreland involve that dirt-cones later evolve into these sedimentological hummocky units with steeply dipping layers within the paleo-landscape. These observations constrain the thickness of ice at the snout of Midtdalsbreen after the LIA as well as the glacier dynamic during its melt: for controlled moraines to be generated by glaciers, these accumulations of sediments would have to thaw by downwasting and then by backwasting, directly at the glacier snout. This process -comprising of different stages- allows enough time to deposit controlled moraine. It is then a thin, cold-based sheet of ice which is by the end responsible for the deposition of such a landform record. There was even dead-ice present on the landscape at that point. After deposition of dirt cones on top of the ice, important meltwater action is contributing to the glacifluvial origin of these hummocks which evolve from dirt-cones onto the glacier, to ice-cored moraines, and then to controlled moraines onto the foreland. Details about the multistage processes leading to the formation of controlled moraines is also at the center of the investigations.Updated version, september 2019.
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Li, Lingwei. "Understanding Antarctic Circumpolar Current Transport at the LGM Using an Isotope-enabled Ocean Model." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555594394056462.
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Le, Mezo Priscilla. "Variabilité des écosystèmes marins de l'échelle inter-annuelle au dernier cycle glaciaire-interglaciaire." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLV003/document.
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La variabilité du système climatique influence la productivité et la distribution des espèces marines sur toutes les échelles de temps, de la variabilité saisonnière et inter-annuelle aux cycles glaciaires-interglaciaires. Mais ces liens entre climat et écosystèmes marins sont encore largement méconnus, de telle sorte que les prévisions des changements à venir sont difficiles. De plus, parce que les indicateurs paléoclimatiques issus des archives marines sont souvent liés au fonctionnement de l’écosystème, cette méconnaissance limite la fiabilité de la reconstruction de la variabilité climatique passée.Ce travail de thèse vise à améliorer notre connaissance de ces liens entre climat et écosystèmes marins : nous nous sommes intéressés aux changements de productivité marine au cours du dernier cycle glaciaire-interglaciaire, et nous nous sommes aussi penchés sur la réponse de l’écosystème, incluant l'ensemble des niveaux de la chaine trophique, à la variabilité inter-annuelle à décennale en climat pré-industriel. Ce travail est basé sur l’utilisation d’un modèle climatique (IPSL-CM), d’un modèle de biogéochimie marine (PISCES) et d’un modèle de niveaux trophiques supérieurs (APECOSM).Dans un premier temps, nous montrons que le lien entre l’intensité de la mousson indienne et la productivité primaire marine, en été boréal dans la mer d’Arabie, n’est pas direct. En effet, il apparait indispensable pour comprendre les changements de productivité de considérer, en plus de l'intensité de la mousson, la structure de la mousson. En particulier, la position du Jet de Findlater par rapport à la côte de la péninsule arabique est un paramètre important puisqu'elle conditionne la dynamique d'Ekman dans la région.Dans un second temps, nous avons étudié les variations de la productivité marine au large de l'embouchure du fleuve Congo et leurs liens avec le fleuve et les changements de dynamique atmosphérique africaine. Ce travail a mis en évidence que la relation entre l'intensité de la mousson et l'intensité des alizés, souvent utilisée dans les reconstructions climatiques, n'est pas toujours vérifiée. Selon le climat étudié, l'importance des effets thermiques ou dynamiques sur les changements de précipitations et de vents simulés est différente.Dans un troisième temps, nous avons étudié l'effet de la variabilité inter-annuelle sur les changements de productivité passés et sur le signal climatique potentiellement enregistré par des indicateurs climatiques biologiques.Enfin, la dernière partie de cette thèse se focalise sur la réponse des organismes marins des haut-niveaux trophiques à la variabilité climatique à différentes fréquences. Ce travail a révélé que les organismes marins répondent de façons différentes aux variations environnementales en fonction de leur taille et de leur habitatClimate variability influences marine primary productivity and marine species distribution over all timescales, from seasonal to interannual variability and glacial-interglacial cycles. The links between climate and marine ecosystems are still sparsely known so that the predictions of futur changes are difficult. Moreover, because paleoclimate recorders extracted from marine archives are often linked to the functionning of the ecosystem, this lack of knowledge limits our ability to reconstruct past climate variability.This thesis work aims at improving our knowledge of these links between climate and marine ecosystems : we have looked into marine productivity changes during the last glacial-interglacial cycle, but we also examined the "end-to-end" ecosystem response to inter-annual to decadal variability in a pre-industrial climate. This work uses a climate model (IPSL-CM), a bio-geochemical model (PISCES) and a model of high trophic levels (APECOSM).First, we show that the link between Indian summer monsoon intensity and marine primary productivity in the Arabian Sea is indirect. Indeed, it appears necessary to consider the monsoon pattern, such as the Findlater Jet position, which drives the Ekman dynamics in the region, as well as its intensity to understand the productivity changes.Second, we study the marine productivity changes off the Congo river mouth and their links with the river runoff and the African atmospheric dynamics. This work shows that the relationship between monsoon intensity and trade winds intensity, often used to reconstruct past changes, is not always verified. Depending on the climate, thermal or dynamical effects are more or less prominent drivers of the simulated changes in precipitation and winds. Productivity off the Congo river mouth, which is mainly located in the subsurface, seems more affected by the ocean and atmosphere dynamics than by the river supply in nutrients.Third, we study the inter-annual variability effects over past productivity changes and over the climatic signal potentially recorded in the biological climate proxies.Finally, the last part of the thesis focuses on high trophic levels marine organisms response to climate variability at different frequencies. This study shows that marine organisms response to environmental changes varies with the organism' size and habitat
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Rivera, Rondón Carlos Alberto. "Diatom-based reconstruction of Late Glacial and Early Holocene environment in the Pyrenees = Reconstrucción ambiental del Tardiglaciar y el Holoceno Temprano en los Pirineos utilizando el registro sedimentario de diatomeas." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/133010.
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Lakes are ecosystems exposed to the combined influence of climate and catchment processes. Lakes collect and archive evidence of these forcings in their sediments through of a complex interaction with internal processes. Deciphering and extracting information from the sediments is a challenging task because, in addition to the inter-dependence between the forcing agents, the lake ontogeny affects the way in which the system responds to them. Among the sub-fossil material, diatoms occupy an outstanding position. The remains can be identified to the species level, due to the siliceous composition of their valves. This fact, added to the rich community that at any instant exists in the lake, make diatoms an excellent proxy for environmental reconstructions. In this study, the focus is placed on the diatom assemblages of the lakes of the Pyrenees and their potential as indicators of environmental conditions. The findings are applied to the sedimentary sequence of the former Burg Lake to reconstruct the lake conditions during Late Glacial and early Holocene periods.
The regional variability of diatom distributions is usually explained by pH or acid neutralising capacity gradients in alpine and temperate areas. However, there is a large remaining unexplained variability, which is related to other environmental factors, and could be also used in environmental reconstructions. Some researchers question the feasibility of independent reconstructions of several variables from a single diatom record; they argue that the high temporal autocorrelation of the local assemblages might obscure secondary influences. However, some others sustain that it is possible to perform reconstructions, even of particularly dependent variables if they present contrasting trends at some sites.
Accordingly, it was carried out an extensive taxonomical study of diatom of the mountain lakes of the Pyrenees. After this, were explored the environmental factors that, besides pH, explains the diatom distribution in the lakes of the Pyrenees, including in-lake proximal factors as well as general descriptors of catchment characteristics and using indicator analysis approach. In order to demonstrate that it is possible to reconstruct different independent variables from a unique diatom data set were developed transfer functions for selects variables and analysed the reliability and the independence of models performed. The analysis was carried out by comparing the performance of two sample data-sets (bottom surface sediment and epilithon samples). The ratio between Chrysophycean cysts and diatoms was analysed as a potential environmental indicator. Indicator species and the transfer functions were applied to the diatoms of the sedimentary sequence of Burg Lake covering Late Glacial and Early Holocene. The reconstructed variables were analysed in terms of in-lake processes and their eventual link with climate and catchment processes. An interpretation of the reconstruction of climate during Late Glacial and Early Holocene in the Pyrenees is shown.Los lagos son ecosistemas expuestos a la influencia combinada del clima y la entrada de materiales y nutrientes desde la cuenca. La información de estos procesos y de la dinámica interna del sistema suele archivarse en los sedimentos mediante la acumulación de los materiales externos y los producidos por el sistema. Dentro de los materiales acumulados en los sedimentos, las valvas de diatomeas pueden aportar información limnológica que es difícil de obtener con otros indicadores. El objetivo principal de esta tesis fue explorar el potencial de las diatomeas para realizar reconstrucciones ambientales multivariadas del pasado, con una aplicación a la secuencia sedimentaria del Holoceno Temprano y el Tardiglaciar del lago Burg (Pirineos). La variabilidad regional de la distribución de diatomeas en zonas alpinas y templadas es generalmente explicada por el gradiente de pH y alcalinidad. Sin embargo, existe una gran variabilidad que está relacionada con otros factores ambientales y que podría también ser utilizada en el desarrollo de la reconstrucción del ambiente acuático. Algunos autores ponen en duda la viabilidad de realizar reconstrucciones independientes, utilizando un único registro de diatomeas, argumentando que la correlación entre las variables puede alterar las señales que son reconstruidas. Sin embargo, otros autores sostienen que es posible realizar reconstrucciones, si existen conjuntos de especies con respuestas distintas. De acuerdo con esto, inicialmente se realizó un estudio taxonómico y ecológico de las diatomeas de 80 lagos de montaña de los Pirineos. Se exploraron los factores ambientales que, además del pH, explican la distribución de diatomeas en los lagos pirenaicos, incluyendo factores próximos al lago y descriptores generales de la cuenca. Este análisis se realizó siguiendo la aproximación de especies indicadoras. Así mismo, se desarrollaron funciones de transferencia para reconstruir diferentes variables independientes a partir de un mismo conjunto de datos de diatomeas. Posteriormente, se aplicaron los resultados las especies indicadoras y las funciones de transferencia en la secuencia sedimentaria del lago Burg cubriendo el Tardiglaciar y el Holoceno Temprano. Finalmente, se analizan los resultados encontrados en términos de los procesos internos del lago y su eventual vinculación con procesos relacionados con el clima y la cuenca.
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Krauß, Lydia [Verfasser], Frank [Akademischer Betreuer] Lehmkuhl, and Eileen Sandra [Akademischer Betreuer] Eckmeier. "Paleoenvironmental reconstruction of the last interglacial-glacial cycle of the quaternary in Central Europe applying a multi-proxy approach investigating loess-paleosol sequences / Lydia Krauß ; Frank Lehmkuhl, Eileen Sandra Eckmeier." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1162450932/34.
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Geiger, Alessa J. "Patagonian glacial reconstructions at 49°S." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6404/.
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Patagonia has one of the most extensive and well preserved glacial geomorphic records of anywhere else in the world. This study provides empirical constraints of Patagonian Ice Sheet (PIS) configuration and dynamics during the last two glacial cycles and the Holocene at 49°S. In particular a chronology of palaeo-ice surface elevations, thickness changes and ice-thinning rates is developed. Cosmogenic surface exposure dating across eight mountain transects at Hielo Patagonico Sur (HPS) outlet glaciers' Viedma and Chico, and from eastern facing mountain valley glaciers, is utilised to reconstruct PIS ice-surface elevation changes through time. The earliest dated glacier ice thickness marker falls into MIS6 (Marine Isotope Stage). The last glacial cycle is characterised by continuous ice-surface elevation lowering from a maximum at MIS5a to the Antarctic Cold Reversal (ACR). Large scale PIS cover occurred between ca. 40-47 kyrs, in both the HPS outlet glaciers and the eastern mountain valleys. This regional ice-cover considerably pre-dates the global Last Glacial Maximum (gLGM). A gLGM vertical ice surface expression is absent from the study area. A minor re-advance and/or stillstand at ca. 18 kyrs is recorded by the valley glaciers, but is not evident at the HPS outlet glaciers. Glacier Viedma records a prominent ice elevation during the ACR with rapid thinning at the end of the climate perturbation. Ice-surface lowering from the ACR limit continues with acceleration toward the late-Holocene. The PIS palaeo-ice elevation and thinning record presented here is sensitive to internal PIS dynamics, local and global climate forcing acting on different timescales, with glacier response to climate perturbation strongly linked to glacier catchment size and distance from the main source of precipitation at 49°S.
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Adams, Jonathan M. "The role of terrestrial ecosystems in glacial-to-interglacial changes in the global carbon cycle : an approach based on reconstruction of paleovegetation : l'Influence des écosystèmes terrestres sur les changements du cycle global du carbone, entre les aires glaciaires et interglaciaires : une approche par la reconstruction de la paléovégétation." Aix-Marseille 2, 1995. http://www.theses.fr/1995AIX22054.
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Les changements du taux atmospherique du co#2 sont d'une grande importance pour l'explication des fluctuations climatiques pendant le quaternaire. Le carbone organique dans les ecosystemes continentaux peut jouer un grand role dans la modification et la direction des fluctuations glaciaire-interglaciaires. Une base de donnees paleo-environnementale est utilisee pour construire des cartes de la vegetation des continents, a 18000, 8000 et 5000 ans. Ces cartes permettent de calculer les bilans du carbone pour chaque periode. Les calculs indiquent qu'il y a une augmentation d'environ 1700 gt (+/- 600 gt) de carbone entre le maximum glaciaire et l'holocene. Ce chiffre est bien superieur a toutes les autres estimations qui ont ete publiees jusqu'a present. Si cette estimation est exacte, elle est importante pour la modelisation du cycle global du carbone et du co#2 pendant le quaternaire superieur
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Martin, Céline. "Reconstruction des températures continentales en Europe de l'Ouest à partir de l'étude des tétraéthers ramifiés dans les sédiments du lac de Saint-Front (Massif Central, France)." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0326/document.
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Cette thèse a pour but de reconstituer le climat des 100 000 dernières années en Europe de l’ouest. L’étude du climat du passé permet de mieux comprendre la variabilité naturelle du climat sur laquelle se surimpose aujourd’hui le réchauffement climatique d’origine anthropique. Ce sont des molécules fossiles bactériennes dont la structure varie en fonction des conditions environnementales qui ont permis dans cette étude de reconstituer le paléoclimat à partir des sédiments du lac St Front dans le Massif Central. Les indices dérivés de ces molécules révèlent la variabilité climatique à long terme mais également les évènements rapides de changement climatique ainsi qu’une forte action anthropique en surimposition des changements climatiques régionaux sur les 5000 dernières années. Ce travail montre l’importance de la compréhension de l’outil utilisé et du fonctionnement du système naturel dans lequel il est étudié, préalables indispensables à l’obtention d’une séquence climatique crédibleThis thesis aims to reconstruct the climate of the last 100,000 years in western Europe. The study of past climate allows to better understand the natural variability of climate on which human-induced global warming is superimposed today. Bacterial fossil molecules whose structure varies according to the environmental conditions were used in this study to reconstruct the paleoclimate from the sediments of lake St Front in the Massif Central. The indices derived from these molecules reveal the long-term climatic variability but also the rapid events of climate change as well as a strong anthropogenic action in superimposition of the regional climatic changes over the last 5000 years. This work shows the importance of understanding the tool used and the functioning of the natural system in which it is studied, essential prerequisites for obtaining a credible climate reconstruction
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Driscoll, Robin Eleanor. "PaleoENSO reconstructions of the Holocene and Last Glacial Period." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/17944.
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In this study, specimens of Tridacna sp., which are reef dwelling bivalve molluscs and have been shown to live up to 60 years, collected from the Huon Peninsula, Papua New Guinea, were sampled for geochemical profiles. The Huon Peninsula is in the heart of the Western Pacific Warm Pool (WPWP), which plays a key role in ENSO dynamics. The uplifted reef terraces of the Huon Peninsula have been extensively studied, and are well dated, which gives the opportunity to reconstruct the local climate of this region at key intervals during the past. Previous work on Tridacna sp. has shown that they precipitate their aragonite shell in equilibrium with the surrounding seawater, and the δ18O profile of a modern T. gigas from the Huon Peninsula has been shown to correlate with precipitation and temperature anomalies, and the Niño 3.4 temperature anomaly record. Fossil samples from this region are therefore assumed to have the ability to capture changes in δ18O attributable to ENSO. Seasonally resolved δ18O measurements from Tridacna sp. from early Holocene and Marine Isotope Stage 3 (MIS3) reefs were used to reconstruct changes in mean climate, seasonality and inter-annual variability (e.g. ENSO). Reconstructions of the mean state tend to agree with previously published studies of Holocene and MIS3 climate, showing similar temperatures to today during the early Holocene, and an average cooling of 2- 3°C during MIS3. The early Holocene Tridacna sp. samples show a reduction in seasonality, consistent with the reduction in seasonal insolation at this time, while those from MIS3 show variable seasonality between 30-60ka. ENSO appears to have been supressed during the early Holocene by up to 50% compared with the late 20th century, which is consistent with coral data and modelling studies. During MIS3, ENSO appears to have been more variable with some records showing anomalous warm and cool events as strong as those seen in the modern T. gigas, used here as a benchmark. Trace element profiles derived from the Tridacna sp. used in this study show a tentative link with temperature and local productivity, but these relationships are subject to species specific and intra-shell effects.
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Allen, Robert. "Reconstructing the last glacial maximum climate of Europe and Russia using the glacial-geological record." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439675.
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Margold, Martin. "Retreat pattern and dynamics of glaciers and ice sheets: reconstructions based on meltwater features." Doctoral thesis, Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-68958.
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Glaciers and ice sheets covered extensive areas in the Northern Hemisphere during the last glacial period. Subsequently to the Last Glacial Maximum (LGM), they retreated rapidly and, except for Greenland and some other ice caps and glaciers, they vanished after the last glacial termination. This thesis examines the dynamics of deglacial environments by analysing the glacial geomorphological record with focus on the landforms created by glacial meltwater. The aims are (i) to evaluate the data available for mapping glacial meltwater features at the regional scale, and (ii) to demonstrate the potential of such features for regional ice retreat reconstructions in high-relief landscapes. Meltwater landforms such as ice-marginal meltwater channels, eskers, deltas and fossil glacial lake shorelines are used to infer former ice surface slope directions and successive positions of retreating ice margins. Evaluated high-resolution satellite imagery and digital elevation models reveal their potential to replace aerial photographs as the primary data for mapping glacial meltwater landforms. Following a methods study, reconstructions of the deglacial dynamics are carried out for central Transbaikalia, Siberia, Russia, and for the Cordilleran Ice Sheet (CIS) in central British Columbia, Canada, using regional geomorphological mapping surveys. Mapped glacial landforms in central Transbaikalia show evidence of a significant glaciation that possibly extended beyond the high mountain areas. Large glacial lakes were formed as advancing glaciers blocked rivers, and of these, Glacial Lake Vitim was the most prominent. Deglacial dynamics of the CIS reveals that the ice divide shifted to the Coast Mountains in north-central British Columbia and the eastern ice margin retreated towards the ice divide in late glacial time. This thesis demonstrates the potential to reconstruct ice retreat patterns and deglacial dynamics at regional scales by interpretation of the meltwater landform record.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Submitted. Paper 6: Manuscript.
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Saha, Sourav. "Reconstructing High-frequency Holocene Glacial Chronostratigraphies in the Himalayan-Tibetan Orogen." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543920897036039.
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Bromley, Gordon R. M. "Reconstructing the History of Reedy Glacier, Antarctica." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/BromleyGRM2005.pdf.
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Partin, Judson Wiley. "Stalagmite reconstructions of western tropical pacific climate from the last glacial maximum to present." Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22556.
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The West Pacific Warm Pool (WPWP) plays an important role in the global heat budget and global hydrologic cycle, so knowledge about its past variability would improve our understanding of global climate. Variations in WPWP precipitation are most notable during El Niño-Southern Oscillation events, when climate changes in the tropical Pacific impact rainfall not only in the WPWP, but around the globe. The stalagmite records presented in this dissertation provide centennial-to-millennial-scale constraints of WPWP precipitation during three distinct climatic periods: the Last Glacial Maximum (LGM), the last deglaciation, and the Holocene. In Chapter 2, the methodologies associated with the generation of U/Th-based absolute ages for the stalagmites are presented. In the final age models for the stalagmites, dates younger than 11,000 years have absolute errors of ±400 years or less, and dates older than 11,000 years have a relative error of ±2%. Stalagmite-specific 230Th/232Th ratios, calculated using isochrons, are used to correct for the presence of unsupported 230Th in a stalagmite at the time of formation. Hiatuses in the record are identified using a combination of optical properties, high 232Th concentrations, and extrapolation from adjacent U/Th dates. In Chapter 3, stalagmite oxygen isotopic composition (d18O) records from N. Borneo are presented which reveal millennial-scale rainfall changes that occurred in response to changes in global climate boundary conditions, radiative forcing, and abrupt climate changes. The stalagmite d18O records detect little change in inferred precipitation between the LGM and the present, although significant uncertainties are associated with the impact of the Sunda Shelf on rainfall d18O during the LGM. A millennial-scale drying in N. Borneo, inferred from an increase in stalagmite d18O, peaks at ~16.5ka coeval with timing of Heinrich event 1, possibly related to a southward movement of the Intertropical Convergence Zone (ITCZ). An inferred precipitation maximum (stalagmite d18O minimum) during the mid-Holocene in N. Borneo supports La Niña-like conditions and/or a southward migration of the ITCZ over the course of the Holocene as likely mechanisms for the observed millennial-scale trends. In Chapter 4, stalagmite Mg/Ca, Sr/Ca, and d13C records reflect hydrologic changes in the overlying karst system that are linked to a combination of rainfall variability and cave micro-environmental effects. Dripwater and stalagmite geochemistry suggest that prior calcite precipitation is a mechanism which alters dripwater geochemistry in slow, stalagmite-forming drips in N. Borneo. Stalagmite Mg/Ca ratios and d13C records suggest that the LGM climate in N. Borneo was drier and that ecosystem carbon cycling may have responded to the drier conditions. Large amplitude decadal- to centennial-scale variability in stalagmite Mg/Ca, Sr/Ca and d13C during the deglaciation may be linked to deglacial abrupt climate change events.
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Read, Sarah Louise. "The last glacial holocene transition in Germany : palaeoenvironmental reconstructions based on fossil coleopteran assemblages." Thesis, Royal Holloway, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271129.
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Boulter, C. H. "Reconstructing the palaeoenvironmental dynamics of East Central Texas since the Last Glacial Maximum." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505366.
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Thornton, Rachel M. "36Cl Chronologies and ELA reconstructions from the northern boundary of the South American Arid Diagonal." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552399052152741.
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Heard, Joshua Andrews. "Late Pleistocene and Holocene Aged Glacial and Climatic Reconstructions in the Goat Rocks Wilderness, Washington, United States." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/557.
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Eight glaciers, covering an area of 1.63 km2, reside on the northern and northeastern slopes of the Goat Rocks tallest peaks in the Cascades of central Washington. At least three glacial stands occurred downstream from these glaciers. Closest to modern glacier termini are Little Ice Age (LIA) moraines that were deposited between 1870 and 1899 AD, according to the lichenometric analysis. They are characterized by sharp, minimally eroded crests, little to no soil cover, and minimal vegetation cover. Glacier reconstructions indicate that LIA glaciers covered 8.29 km2, 76% more area than modern ice coverage. The average LIA equilibrium line altitude (ELA) of 1995 ± 70 m is ~150 m below the average modern ELA of 2149 ± 76 m. To satisfy climate conditions at the LIA ELA, the winter snow accumulation must have been 8 to 43 cm greater and mean summer temperatures 0.2 to 1.3 ºC cooler than they are now. Late Pleistocene to early Holocene (LPEH) aged moraines are located between 100 and 400 m below the LIA deposits. They have degraded moraine crests, few surface boulders, and considerable vegetation and soil cover. Volcanic ashes indicate LPEH moraines were deposited before 1480 AD while morphometric data suggest deposition during the late Pleistocene or early Holocene. The average LPEH ELA of 1904 ± 110 m is ~ 240 m and ~90 m below the modern and LIA ELAs, respectively. The climate change necessary to maintain a glacier with an ELA at that elevation for LPEH conditions requires the winter accumulation to increase by 47 to 48 cm weq and the mean summer temperature to cool by 1.4 to 1.5 ºC. Last glacial maximum (LGM) moraines are located more than 30 km downstream from modern glacial termini. They are characterized by hummocky topography, rounded moraine crests, complete vegetation cover, and well developed soil cover. Moraine morphometry, soil characteristics, and distance from modern glacial termini indicate that deposition occurred at least 15 ka BP during an expansive cooling event, the last being the LGM. The LGM ELA of 1230 m is ~920 m below the modern ELA. The climate change necessary to maintain a glacier with an ELA at that elevation for LGM conditions requires the mean summer temperature to cool by 5.6 ºC with no change in precipitation.
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Huh, Kyung In. "Reconstructing Holocene Glacier changes in West Greenland from multispectral imagery." The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407141572.
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Mansilla, Claudia A. "Palaeoenvironmental changes in southern Patagonia during the Late-glacial and the Holocene : implications for forest establishment and climate reconstructions." Thesis, University of Stirling, 2015. http://hdl.handle.net/1893/21979.
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Three continuous terrestrial high-resolution palaeoenvironmental records for the Late-glacial and the Holocene have been reconstructed for different ecosystems in Fuego-Patagonia on a longitudinal transect at latitude 53°S. The records describe the nature and extent of environmental and climatic changes inferred from palynological evidence supported by lithostratigraphy, tephrochronology and radiocarbon dating. The environmental changes recorded at the three sites displays a significant degree of synchrony in response to similar large-scale climatic changes. Clear stratigraphical evidence alongside the pollen record indicates a shift to warmer interstadial conditions between c. 14,800 Cal yr BP and 14,400 Cal yrs BP. During the period coeval with ACR the vegetation was dominated by cold resistant dry land herbs such as Poaceae, Asteraceae (Suf. Asteroideae) and Acaena, by c. 13,200 Cal yr BP the vegetation changed from the dominance of cold resistant dry land herbs towards more mesic conditions and the expansion of steppe dominated by Poaceae with patches of Nothofagus forest. The establishment of the forest and an eastward shift of the forest-steppe ecotone by c. 12,500 Cal yr BP from which a gradual shift from colder to warmer conditions and the relatively stronger influences of the SSWs is inferred. The sequence of Late-glacial environmental changes places Fuego-Patagonia within the new palaeoecological data provided by this study includes “the earliest” evidence for the establishment of subantarctic Nothofagus forest during the LGIT in Fuego-Patagonia. During the Early-Holocene two major phases of Nothofagus forest expansion were registered between c. 11,700 - 10,500 Cal yr BP and c. 9,500 - 8,200 Cal yr BP. These intervals of expansion of Nothofagus forest are separated by an interval of forest contraction in response to lower effective moisture between c. 10,500 - 9,500 Cal yr BP. An intense arid phase is inferred between c. 8,250 Cal yr BP and 6,800 Cal yr BP and probably leading to an increase in the amount of dry fuel available during the mid-Holocene in Fuego-Patagonia leading to the highest fire activity promoted by very weak SSWs at this time. The later Holocene was characterised by an increase in humidity and an inferred intensification of the SSWs.
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Zech, Roland. "Glacier and climate reconstruction in the Central Andes based on ¹°Be surface exposure dating /." Bern : [s.n.], 2006. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Palmgren, Rikard. "Reconstructing the Long-Term Mass Balance of Brewster Glacier, New Zealand, Using a Degree-Day Approach." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-324325.
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Varmare klimat är något som kontinuerligt påverkar glaciärer planeten över och har under det senaste århundrandet vidtagit en global ökning av negativa massbalanser. Denna trend kan bidra till variationer i havsnivån och orsaka problem med översvämningar över hela världen. Övervakning och observation av världens glaciärer är därför väldigt viktigt och genom att skapa modeller som tillåter insyn i glaciärernas respons till atmosfärisk fluktuation går det att åstadkomma en djupare förståelse för hur den globala uppvärmningen kommer att utvecklas. I detta projektet återskapas massbalansen för Brewster Glacier, Nya Zeeland, för perioden 2005 – 2015 genom tillämpning av graddagar. Modellen har försetts med data från ett nyligen genomfört nedskalningsprojekt som har producerat atmosfäriska data för perioden 1979 – 2015 vilket tillåter modellen att köras. Resultaten som presenteras kommer att bidra till större inblick i graddags-modellen om huruvida tillvägagångssättet att använda enkel temperatur- och nederbördsdata är tillförlitligt för att porträttera massbalansen för glaciärer.Warmer climate is something that is continuously affecting glaciers across the planet and has during the last century gained a global increase in negative mass balances. This trend has contributed to sea-level rise and had other impacts on water resources. Monitoring and observing the worlds glaciers is therefore very important and by creating models that allows insight in the glacier response to atmospheric fluctuation, it is possible to obtain deeper knowledge on how the global warming will develop. In this project, the mass balance of Brewster Glacier, New Zealand, is reconstructed for the period 2005 – 2015 using a degree-day approach. The input for the model has been obtained from a recent downscaling project that has produced atmospheric data over the period 1979 – 2015 that allows the model to run at a daily temporal resolution. The results presented are going to contribute to a greater insight in the degree-day model as to whether the approach of using simple air temperature and precipitation data are reliable to portray the mass balance of glaciers.
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Gessese, Alelign Fekade. "Algorithms for Bed Topography Reconstruction in Geophysical Flows." Thesis, University of Canterbury. Mechanical Engineering, 2013. http://hdl.handle.net/10092/8673.
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Bed topography identification in open channel and glacier flows is of paramount importance for the study of the respective flows. In the former, the knowledge of the channel bed topography is required for modelling the hydrodynamics of open channel flows, fluvial hydraulics, flood propagation, and river flow monitoring. Indeed, flow models based on the Shallow Water Approximation require prior information on the channel bed topography to accurately capture the flow features. While in the latter, usable bedrock topographic information is very important for glacier flow modellers to accurately predict the flow characteristics. Experimental techniques to infer the bed topography are usually used but are mostly time consuming, costly, and sometimes not possible due to geographical restrictions. However, the measurement of free surface elevation is relatively easy. Alternative to experimental techniques, it is therefore important to develop fast, easy-to-implement, and cost-effective numerical methods.
The inverse of the classical hydrodynamic problem corresponds to the determination of hydraulic parameters from measurable quantities. The forward problem uses model parameters to determine measurable quantities. New one-shot and direct pseudo-analytical and numerical approaches for reconstructing the channel bed topography from known free surface elevation data is developed for one-dimensional shallow water flows. It is shown in this work that instead of treating this inverse problem in the traditional partial differential equation (PDE)-constrained optimization framework, the governing equations of the direct problem can be conveniently rearranged to obtain an explicit PDE for the inverse problem. This leads to a direct solution of the inverse problem which is successfully tested on a range of benchmark problems and experimental data for noisy and noiseless free surface data. It was found that this solution approach creates very little amplification of noise.
A numerical technique which uses the measured free surface velocity to infer the channel bed topography is also developed. The one-dimensional shallow water equations along with an empirical relationship between the free surface and the depth averaged velocities are used for the inverse problem analysis. It is shown that after a series of algebraic manipulation and integration, the equation governing the inverse problem simplifies to a simple integral equation. The proposed method is tested on a range of analytical and experimental benchmark test cases and the results confirm that, it is possible to reconstruct the channel bed topography from a known free surface velocity distribution of one-dimensional open channel flows.
Following the analysis of the case of one-dimensional shallow water flows, a numerical technique for reconstructing the channel bed topography from known free surface elevation data for steep open channel flows is developed using a modified set of equations for which the zero-inertia shallow water approximation holds. In this context, the shallow water equations are modified by neglecting inertia terms while retaining the effects of the bed slope and friction terms. The governing equations are recast into a single first-order partial differential equation which describes the inverse problem. Interestingly, the analysis shows that the inverse problem does not require the knowledge of the bed roughness. The forward problem is solved using MacCormack’s explicit numerical scheme by considering unsteady modified shallow water equations. However, the inverse problem is solved using the method of characteristics. The results of the inverse and the forward problem are successfully tested against each other.
In the framework of full two-dimensional shallow water equations, an easy-to-implement and fast to solve direct numerical technique is developed to solve the inverse problem of shallow open channel flows. The main underlying idea is analogous to the idea implemented for the case of one-dimensional reconstruction. The technique described is a “one-shot technique” in the sense that the solution of the partial differential equation provides the solution to the inverse problem directly. The idea is tested on a set of artificial data obtained by first solving the forward problem.
Glaciers are very important as an indicator of future climate change or to trace past climate. They respond quickly compared to the Antarctica and Greenland ice sheets which make them ideal to predict climate changes. Glacier bedrock topography is an important parameter in glacier flow modelling to accurately capture its flow dynamics. Thus, a mathematical technique to infer this parameter from measured free surface data is invaluable. Analogous to the approaches implemented for open channel flows, easy-to-implement direct numerical and analytical algorithms are developed to infer the bedrock topography from the knowledge of the free surface elevation in one space dimension. The numerical and analytical methods are both based on the Shallow Ice Approximation and require the time series of the ablation/accumulation rate distribution. Moreover, the analytical method requires the knowledge of a non-zero glacier thickness at an arbitrary location. Numerical benchmark test cases are used to verify the suitability and applicability of the algorithms.
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Sagredo, Esteban A. "Glacier sensitivity along the Andes: implication for paleoclimatic reconstructions of the Little Ice Age." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342103681.
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Muñoz-Cobo, Belart Joaquín. "Bilan de masse des glaciers islandais depuis 1945 : reconstruction et relation avec la variabilité climatique." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30236.
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Le bilan de masse des glaciers est fortement lié au climat. Aux hautes latitudes, l'accumulation de neige pendant l'hiver et la fonte de glace pendant l'été sont les principales composantes du bilan de masse. En Islande, le bilan de masse des trois plus larges calottes glaciaires (~600-~8000 km²) a été suivi régulièrement depuis 25 ans notamment grâce à des mesures in situ. Mais les bilans de masse des autres glaciers et calottes glaciaires islandaises ont été très peu étudiés. Aujourd'hui, les données de télédétection, notamment via la comparaison des modèles numériques du terrain (MNT), permettent de mesurer le bilan de masse par la méthode géodésique. Pour ces glaciers et calottes de plus petites tailles (de 1 km² et à quelques centaines de km²), les photographies aériennes, l'imagerie satellitaire stéréoscopique sub-métriques, et le lidar aérien sont parfaitement adaptées. Cette thèse se focalise donc sur l'estimation des bilans de masse des " petits " glaciers et calottes islandaises depuis le pas de temps saisonnier jusqu'à pluri-décennal et leur relation avec les variations spatiales et temporelles du climat. Le bilan de masse hivernal de la calotte du Drangajökull (NO-Islande) a été mesuré par des images satellitaires stéréoscopiques sub-métriques (données Pléiades et WorldView-2) acquises au début, milieu et à la fin de l'hiver 2014-2015. Les changements de volume ont été convertis en bilan de masse grâce à des mesures in situ de densité de neige, et validés avec des mesures in situ de profondeur de neige. Ce travail permet d'envisager désormais un suivi du bilan de masse saisonnier sans un laborieux travail de terrain. Une importante archive de photographies aériennes est disponible en Islande depuis 1945. Ces données offrent une revisite de 5 à 20 ans pour la majorité des glaciers. De plus, depuis 2000, cette archive est complétée par les données des capteurs satellitaires stéréoscopiques et de lidar aérien acquis entre 2008 et 2013. Cet ensemble de données est exploité pour créer une série temporelle de 70 ans de bilan de masse en Islande. La calotte d'Eyjafjallajökull (~70 km²) sert de zone test pour la création et l'automatisation d'une chaîne de traitement, basée sur des logiciels libres. [....]The mass balance of a glacier is strongly connected to climate. At high latitudes, mass balance is typically controlled by snow accumulation during the winter and the glacier ablation during the summer. In Iceland, direct mass balance observations have been mostly focused on the three largest ice caps (~600 to ~8000 km2), measured in situ for the last 25 years. There are, however, glaciers and ice caps distributed over all quarters of the country that lack mass balance observations. Remote sensing data with the capability to retrieve the glacier surface geometry through Digital Elevation Models (DEMs) are valuable tools to measure mass balance using the geodetic method. For a typical Icelandic glacier (with an area between 1 km2 and hundreds of km2), this can be optimally achieved from optical stereoscopic imagery, emplaced in airborne or spaceborne sensors, and from airborne lidar. This thesis focuses on remote sensing techniques to accurately measure geodetic mass balance from seasonal to decadal time spans and the relationship of mass balance to climate. As an example of seasonal mass balance, the winter mass balance of Drangajökull was measured from satellite sub-meter stereo images at the beginning, middle and end of the 2014-2015 winter using data from the Pléiades and WorldView-2 satellites. The results were complemented with in situ snow density measurements and validated with snow thickness measurements. The study concludes that images from the sensors mentioned above may often be used to monitor seasonal mass balance without tedious field logistics. A vast archive of aerial photographs exists for Iceland extending back to 1945. Since then, most glaciers were surveyed every 5 to 20 years. In addition, a wealth of modern satellite stereo images is available since the early 2000s as well as airborne lidar data in 2008-2013. This creates a unique dataset to construct a 70-year time series of geodetic mass balances.[...]
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Marcott, Shaun Andrew. "A Tale of Three Sisters: Reconstructing the Holocene glacial history and paleoclimate record at Three Sisters Volcanoes, Oregon, United States." PDXScholar, 2005. https://pdxscholar.library.pdx.edu/open_access_etds/3386.
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At least four glacial stands occurred since 6.5 ka B.P. based on moraines located on the eastern flanks of the Three Sisters Volcanoes and the northern flanks of Broken Top Mountain in the Central Oregon Cascades. The youngest of these advances was the Little Ice Age (LIA) glaciation, which reached its maximum advance 150-200 yrs. B.P. and is defined by the large sharp crested and unvegetated moraines adjacent to the modern glaciers. In isolated locations less than 100 m downslope from these moraines, a second set of sparsely vegetated lateral moraines marks the Late-Neoglacial stand of the glaciers between 2.1 ± 0.4 and 7.7 ka B.P, A third set of Early-Neoglacial end moraines is 300-700 meters downslope of the modern glacier termini, and postdates 7.7 ka B.P. From SST temperature data (Barron et al., 2003) and a speleothem record (Vacco, 2003), we infer that this advance occurred between 4.5 and 6.5 ka B.P. Finally, the Fountonnor stand is marked by moraines 500-900 meters downslope of the modern glacier termini, and we infer these are latest Pleistocene or early Holocene.
Modem equilibrium line altitudes (ELAs) at the Three Sisters and Broken Top are approximately 2500 - 2600 m. During the LIA, the ELAs were 40 - 180 m lower, requiring cooler mean summer temperatures by 0.7 - 1.0°C and winter snowfall to increase by 10 - 60 cm water equivalent. The average Early Neoglacial and Fountonnor ELAs were 130 - 300 m and 290 - 320 m lower than modem glaciers, respectively, requiring air temperatures to be 0.7 - 1.6°C and 1.5 - 1.7°C cooler during the summer and winter snowfall to be 40 - 100 cm water equivalent and 90 - 100 cm water equivalent greater.
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Booth, Laura M. "Geomorphic reconstruction and 3D visualisation of a tenth century volcanic jökulhlaup at Sólheimajökull Glacier, south Iceland." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/0fd212f2-75bf-477b-bbc7-c21dd4533129.
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Jökulhlaup (glacial outburst floods) present a recurring natural hazard to the inhabitants and infrastructure along Iceland’s south coast. The high-energy, debris-rich floods are capable of eroding, transporting and depositing vast quantities of sediment; and in some cases, can completely re-shape sandur topography within a single flood event. They can be triggered by drainage of ice-dammed lakes or by meltwater released during sub-glacial volcanic eruptions; or a combination of both. This research reconstructs a Tenth Century jökulhlaup at Sólheimajökull; a southern outlet glacier of Mýrdalsjökull ice cap overlying Katla volcano. The flood permanently altered sandur topography and marked an important shift in changing flood routes and resultant flood deposits at the site since. Collection and synthesis of field evidence provides detailed information about the jökulhlaup, the route it took, the contemporaneous glacier margin, and environmental conditions at the time. As Sólheimasandur’s last major jökulhlaup, this event is important, not just in terms of scale and magnitude (comparable with the largest floods known to have occurred at the site); but also because of its geomorphic and sedimentary signature. This research records and compiles the remnant features of the Tenth Century flood, some of which are still evident at Sólheimasandur today. The outcome is a template for linking jökulhlaup sources, pathways and deposits, focusing in particular on ice- proximal flood routeways as a determining control over the nature of flood deposit. Geomorphic, sedimentological and tephrostratigraphic techniques have been used to recreate the origin, mechanics, and impacts of this flood through analysis of its deposits. In the same manner the regional Holocene jökulhlaup chronology is refined for Sólheimasandur, supported by a dating framework of volcanic eruptions and glacial fluctuations. An innovative 3D visual simulation, VolcVis, has been created, which models the field site as it might have looked in the Tenth Century, based on field data collected in reconstructing the Tenth Century flood. The ability of the prototype simulation to assist in palaeo-geomorphic reconstruction, is tested by visually simulating the Tenth Century volcanic jökulhlaup for the first time. The model distills complex and often spatially disparate field data into an interactive, user-friendly tool, with wider applicability in communicating results to the general public, aiding hazard mitigation authorities and informing the designation of evacuation routes. Identification of the pathways, magnitudes and frequencies of past jökulhlaup at Sólheimajökull allows a greater accuracy in predicting contemporary flood routes, when other major subglacial eruptions occur in this region of Iceland. The value of this research is timely given recent volcanically-generated jökulhlaup at Eyjafjallajökull (2010) and Grímsvötn (2011); illustrating how heightening awareness of past (and present) glacio-volcanic hazards in this region of South Iceland ensures better preparedness for future events.
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Jeong, Seongsu. "Time Series Reconstruction of Surface Flow Velocity on Marine-terminating Outlet Glaciers." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437602064.
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Gerbaux, Martin. "Reconstruction du bilan de masse des glaciers alpins et impact d'un changement climatique." Phd thesis, Université Joseph Fourier (Grenoble), 2005. http://tel.archives-ouvertes.fr/tel-00011324.
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Dans ce travail, nous avons adapté et mis en oeuvre le modèle de neige CROCUS pour le calcul et la reconstruction du bilan de masse des glaciers alpins. Le bilan de masse est calculé au pas horaire à partir des données de température, vitesse du vent, humidité, précipitations, rayonnement infra-rouge, rayonnement solaire direct et diffus et nébulosité. Il est spatialisé sur l'ensemble de la surface du glacier avec un pas horizontal de 200 m. Les données météorologiques pour la validation du modèle proviennent du modèle SAFRAN. La glace de glacier a été introduite dans CROCUS (albédo, rugosité), et la chaîne SAFRAN/CROCUS a été validée à partir de mesures de terrain et de reconstructions photogrammétriques du bilan de masse de surface et d'images satellite de la ligne de neige. Le bilan de masse pour la période 1981-2004 est reconstruit pour les glaciers de St Sorlin et d'Argentière, en bon accord avec les données disponibles.Le modèle permet de tester la sensibilité du bilan de masse des glaciers aux paramètres météorologiques. Pour des amplitudes de variations des paramètres météorologiques compatibles avec un changement climatique réaliste (prévisions climatiques de type IPCC), la température se révèle le paramètre dominant, et la sensibilité de l'altitude de la ligne d'équilibre est de 125 m.K-1, ou même 160 m.K-1 si la variation concomitante du rayonnement infra-rouge est prise en compte. L'impact de la variabilité des paramètres et des combinaisons de paramètres entre eux n'est pas négligeable par rapport à l'impact d'un changement de la moyenne météorologique (tendance).
Des simulations longues de bilan de masse ont été effectuées sur la période 1800-2165, en utilisant des résultats de simulations climatiques réalisées par plusieurs modèles de circulation générale dans le cadre de l'IPCC AR4. D'après le modèle, le glacier de St Sorlin devrait disparaître avant 2100.
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Dumont, Marie. "Détermination de l'albédo des surfaces enneigées par télédétection : application à la reconstruction du bilan de masse du glacier de Saint Sorlin." Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00582925.
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L'albédo, fraction de rayonnement réfléchi dans le spectre solaire, est une variable clef du bilan énergétique des surfaces enneigées et englacées. Cette grandeur possède une forte variabilité spatio-temporelle ce qui fait de la télédétection un outil adapté pour son étude. L'albédo dépend à la fois des propriétés physiques du milieu considéré et des caractéristiques du rayonnement incident. Les différentes grandeurs liées à l'albédo sont fonction des domaines angulaires et spectraux des radiations considérées. Les mesures de répartition angulaire du rayonnement réfléchi par la neige ont montré que l'hypothèse lambertienne pouvait conduire à des erreurs non négligeables lors de la détermination de l'albédo par télédétection. La connaissance des caractéristiques de la répartition angulaire du rayonnement réfléchi par la neige permet de développer une nouvelle méthode de détermination de l'albédo en zones montagneuses. Cette méthode prend en compte les effets liés à la forte variabilité topographique des terrains de montagne, à l'anisotropie du rayonnement réfléchi par la neige et par la glace ainsi que les variations spectrales de l'albédo en fonction des propriétés physiques de la surface. Elle a été appliquée à deux types de données : des photographies terrestres visibles et proche infrarouges (résolution spatiale 10 m) et des images MODIS (résolution spatiale 250 m). L'incertitude sur la valeur de l'albédo ainsi déterminée est évaluée à ±10% grâce aux mesures de terrain effectuées sur le glacier de Saint Sorlin (massif des Grandes Rousses, France). L'étude des cartes d'albédo issues de dix années (2000-2009) d'images MODIS montre qu'il n'y a pas de décroissance marquée de la valeur de l'albédo en zone d'ablation au contraire de ce qui a été prouvé pour le glacier du Morteratsch (Suisse). De plus, il existe une corrélation très élevée entre la valeur minimale de la moyenne de l'albédo sur le glacier, i.e. l'albédo moyen du glacier le jour où la ligne de neige est proche de la ligne d'équilibre, et la valeur du bilan de masse annuel spécifique. L'assimilation des données d'albédo obtenues grâce aux images MODIS et aux photographies terrestres dans le modèle de neige CROCUS permet une bonne estimation du bilan de masse spatialisé du glacier de Saint Sorlin (rmse=0.5 m w.e. pour les cinq années hydrologiques étudiées). Les forçages météorologiques utilisés pour cette étude sont de moyenne échelle. L'analyse succincte de la contribution des différents flux atmosphériques au bilan d'énergie de surface montre qu'en zone d'ablation comme en zone d'accumulation, le bilan radiatif net courtes longueurs d'ondes constitue la source principale d'énergie et que la variabilité de ce flux explique la majeure partie de la variabilité journalière de la somme des flux atmosphériques. Appliquées à d'autres glaciers, ces méthodes permettraient de savoir si les conclusions établies pour notre seul glacier d'étude sont valables pour d'autres glaciers. Elles rendraient également possibles la reconstruction du bilan de masse spatialisé sur 10 ans d'autres glaciers et potentiellement une meilleure quantification des processus physiques mis en jeu dans le bilan de masse de ces glaciers tempérés
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Smith, J. G. "Reconstructing Holocene glacier fluctuations from glaciolacustrine sediments : a new approach using modern analogues in southern Norway." Thesis, Swansea University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639069.
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A new technique for reconstructing Holocene glacier variations was developed using a modern analogue approach on glaciolacustrine sediments. Glaciolacustrine sediments record alternations between minerogenic (active glaciers) and organic sedimentation (reduced glacier extent) with high resolution and have been used widely to infer regional glacier history. The approach has been particularly prevalent in southern Norway, where relatively extensive Little Ice Age glaciers destroyed much of the evidence for earlier episodes. Surface sediments from 53 pro-glacial lakes in southern and western Norway were sampled and variations in grain-size, organic matter and magnetic susceptibility were related to catchment variables through correlation and multiple regression analyses. This modern analogue sample was used to test directly the accepted model of glaciolacustrine sedimentation by investigating glacial signals in established sedimentary indicators on a quantitative basis. In relation to grain-size, percentage data were insensitive indicators of glacier extent, while estimated sedimentation rates (derived from an independent training set) were very sensitive. Glacial signal strength of up to 83 % for regional and other sub-sets and up to 50 % for the total data set were recorded. The glacial signal occurs in the fine size grades, particularly fine silt and clay. Organic matter and magnetic susceptibility are insensitive to glacier size and carry noisy signals with no systematic relationship to catchment variables. The analyses also identified and quantified non-glacial sediment sources. The optimum models for grain-size were applied to dated sediment cores from southern Norway in order to reconstruct Holocene glacier variations on a quantitative basis. The reconstructions were reasonably successful in Jotunheimen and Breheimen lakes, but unsuccessful in Jostedalsbreen, where the models were not applicable to the available sediment cores. The quantification of glacier size variations is a significant methodological advance in reconstructing Holocene glacier variations and its potentially a powerful tool for reconstructing Holocene climatic change.