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| 2. |
- Bonow, Johan M., 1969-
(författare)
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Palaeosurfaces and palaeovalleys on North Atlantic previously glaciated passive margins : reference forms for conclusions on uplift and erosion
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Palaeosurfaces and palaeovalleys are landforms under destruction in the present climate and/or tectonic regime, and thus mainly reflect processes not active today. Uplifted palaeosurfaces exist along the formerly glaciated passive continental margins around the North Atlantic. Large-scale landform development has recently become a matter of interest also for geologists and geophysicists as the result of an increasing awareness that a thorough knowledge of uplift, erosion, deposition and development of landforms along continental margins can only be accomplished by combined studies using independent data from different scientific disciplines. The present study focuses on one of these above data sets; the landform record. Two uplifted areas, southern Norway and central West Greenland, were selected for landform analysis of high resolution digital elevation models, aerial photographs, relation between landforms in basement and cover rocks, offshore seismic lines and X-ray diffraction of clay minerals in saprolites. In southern Norway, analysis of slope angles within the range of pediment slopes was combined with analysis of main valley incision. This resulted in the identification of three main planation surfaces in a stepped sequence formed along the main valleys as a consequence of tectonic uplift events, maybe in the Palaeogene, (in total >1000 m). Two phases of late uplift (~900 m), probably in the Neogene, triggered incision of deep fluvial valleys, later reshaped by glacial erosion (up to 300 m). In central West Greenland palaeosurfaces were analysed in relation to cover rock of different age. An exhumed etch surface, characterized by a typical hilly relief, occurs on Disko and south of Disko Bugt, and are by the presence of cover rocks shown to be sub-Palaeocene in origin. To the north, a post-Eocene erosion surface on Nuussuaq, cuts across basement and basalt and was probably formed close to sea level. Uplift in two phases elevated this surface up to 2000 m above present sea level and broke it in differently tilted tectonic blocks. South of Disko Bugt, a planation surface, of probably the same age as the one on Nuussuaq, cuts the tilted etch surface, and also cuts across different bedrock types. The planation surface rises towards the south and splits in two surfaces, separated in altitude up to 300 m, within two highly elevated areas. The separation into two surfaces indicate two uplift events: A first minor event of a few hundred metres in the uplift centres resulted in incision of the lower planation surface. This event was later followed by a major uplift event amounting to >1000 m. Correlation with the offshore sedimentary record suggests that both uplift events occurred in the Neogene. The erosion pattern calculated from one reconstructed palaeosurface to present topography shows large spatial variations. This is interpreted as an effect of differential bedrock resistance and local variations of glacial erosion (400–1300 m in low areas). The results presented in this thesis demonstrate the usefulness of palaeosurfaces and palaeovalleys as tools for deciphering magnitude of uplift events, establishing relative event chronologies and for calculation of erosion. Moreover integrated studies of palaeolandforms, offshore geology and thermal chronologies, are shown to be invaluable when used to solve the spatial and temporal patterns of uplift, erosion and deposition.
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| 3. |
- Jansson, Peter, 1960-, et al.
(författare)
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Spatial and temporal variations in glacier hydrology on Storglaciären, Sweden
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this report is to summarize the experimental work on glacier hydrology and basal hydraulic conditions performed on Storglaciären, northern Sweden, during the years 2003–2005. The aim of the project has been to provide a framework of real conditions within which to interpret theory and extrapolate conditions beneath a future ice sheet over Fennoscandia. Surface fed subglacial hydrological systems are extremely dynamic because the input rates of rain and temperature-contolled surface melt fluctuate and the geometry of flow paths is constantly changing due to ice deformation which tends to close the flow paths. The hydrological system of a glacier is unique since water is flowing through conduits made of its solid phase (ice). A possible analogy is lava flowing through rock of the same composition. Hence understanding the expected dynamic range of the glacier hydrological system is best studied by in situ measurements. The processes studied on Storglaciären can be expected to apply to ice sheet scale, albeit on different spatial scales. Since Storglaciären is a polythermal glacier with a large fraction of ice below freezing and at the melting point and with a surface-fed hydrological system of conduits and tunnels, results apply to the margins (ablation zone) of the past Fennoscandian Ice Sheet, at least along its southern margin. In this report we discuss the measurements made to assess the subglacial conditions that provide an analogue for conditions under the Fennoscandian Ice Sheet. We have also included a large quantity of unpublished data from Storglaciären from different research projects conducted since 1990. Together these data provide a good picture of the temporal and spatial water pressure conditions in and under Storglaciären. The report is the first comprehensive analysis of these subglacial water pressure records.
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| 4. |
- Johansson, Emma, et al.
(författare)
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Hydrological and meteorological investigations in a periglacial lake catchment near Kangerlussuaq, west Greenland - presentation of a new multi-parameter data set
- 2015
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 7:1, s. 93-108
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Tidskriftsartikel (refereegranskat)abstract
- Few hydrological studies have been conducted in Greenland, other than on glacial hydrology associated with the ice sheet. Understanding permafrost hydrology and hydroclimatic change and variability, however, provides key information for understanding climate change effects and feedbacks in the Arctic landscape. This paper presents a new, extensive, and detailed hydrological and meteorological open access data set, with high temporal resolution from a 1.56 km(2) permafrost catchment, with a lake underlain by a through-talik close to the ice sheet in the Kangerlussuaq region, western Greenland. The paper describes the hydrological site investigations and utilized equipment, as well as the data collection and processing. The investigations were performed between 2010 and 2013. The high spatial resolution, within the investigated area, of the data set makes it highly suitable for various detailed hydrological and ecological studies on catchment scale. The data set is available for all users via the PANGAEA database, http://doi.pangaea.de/10.1594/PANGAEA.836178.
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| 5. |
- Kjellström, Erik, et al.
(författare)
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Simulated climate conditions in Europe during the Marine Isotope Stage 3 stadial
- 2010
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 39:2, s. 436-456
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Tidskriftsartikel (refereegranskat)abstract
- State-of-the-art climate models were used to simulate climate conditions in Europe during Greenland Stadial (GS) 12 at 44 ka BP. The models employed for these simulations were: (i) a fully coupled atmosphere-ocean global climate model (AOGCM), and (ii) a regional atmospheric climate model (RCM) to dynamically downscale results from the global model for a more detailed investigation of European climate conditions. The vegetation was simulated off-line by a dynamic vegetation model forced by the climate from the RCM. The resulting vegetation was then compared with the a priori vegetation used in the first simulation. In a subsequent step, the RCM was rerun to yield a new climate more consistent with the simulated vegetation. Forcing conditions included orbital forcing, land-sea distribution, ice-sheet configuration, and atmospheric greenhouse gas concentrations representative for 44 ka BP. The results show a cold climate on the global scale, with global annual mean surface temperatures 5 degrees C colder than the modern climate. This is still significantly warmer than temperatures derived from the same model system for the Last Glacial Maximum (LGM). Regional, northern European climate is much colder than today, but still significantly warmer than during the LGM. Comparisons between the simulated climate and proxy-based sea-surface temperature reconstructions show that the results are in broad agreement, albeit with a possible cold bias in parts of the North Atlantic in summer. Given a prescribed restricted Marine Isotope Stage 3 ice-sheet configuration, with large ice-free regions in Sweden and Finland, the AOGCM and RCM model simulations produce a cold and dry climate in line with the restricted ice-sheet configuration during GS 12. The simulated temperature climate, with prescribed ice-free conditions in south-central Fennoscandia, is favourable for the development of permafrost, but does not allow local ice-sheet formation as all snow melts during summer.
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| 6. |
- Kjellström, Erik, et al.
(författare)
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Simulated climate conditions in Fennoscandia during a MIS 3 stadial
- 2010
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 39:2, s. 436-456
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Tidskriftsartikel (refereegranskat)abstract
- State-of-the-art climate models were used to simulate climate conditions in Europe during Greenland Stadial (GS) 12 at 44 ka BP. The models employed for these simulations were: (i) a fully coupled atmosphere–ocean global climate model (AOGCM), and (ii) a regional atmospheric climate model (RCM) to dynamically downscale results from the global model for a more detailed investigation of European climate conditions. The vegetation was simulated off-line by a dynamic vegetation model forced by the climate from the RCM. The resulting vegetation was then compared with the a priori vegetation used in the first simulation. In a subsequent step, the RCM was rerun to yield a new climate more consistent with the simulated vegetation. Forcing conditions included orbital forcing, land–sea distribution, ice-sheet configuration, and atmospheric greenhouse gas concentrations representative for 44 ka BP. The results show a cold climate on the global scale, with global annual mean surface temperatures 5 °C colder than the modern climate. This is still significantly warmer than temperatures derived from the same model system for the Last Glacial Maximum (LGM). Regional, northern European climate is much colder than today, but still significantly warmer than during the LGM. Comparisons between the simulated climate and proxy-based sea-surface temperature reconstructions show that the results are in broad agreement, albeit with a possible cold bias in parts of the North Atlantic in summer. Given a prescribed restricted Marine Isotope Stage 3 ice-sheet configuration, with large ice-free regions in Sweden and Finland, the AOGCM and RCM model simulations produce a cold and dry climate in line with the restricted ice-sheet configuration during GS 12. The simulated temperature climate, with prescribed ice-free conditions in south-central Fennoscandia, is favourable for the development of permafrost, but does not allow local ice-sheet formation as all snow melts during summer.
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| 7. |
- Lidmar-Bergström, Karna, et al.
(författare)
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Cenozoic landscape development on the passsive margin of northern Scandinavia
- 2007
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Ingår i: Norwegian Journal of Geology. ; 87:1 & 2, s. 181-196
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Tidskriftsartikel (refereegranskat)abstract
- The geometry of major bedrock landforms in a central part of the Northern Scandes has been examined for interpretation of landforming events and their chronology. Analysis of palaeosurfaces and palaeovalleys was undertaken based on digital elevation data. Four major landscape generations, governed by different base levels, were reconstructed within the mountains. In the east the generations more or less merge and form plains with residual hills. The configuration of the landscape generations suggests an asymmetrical uplift with maximum uplift in the west caused by discrete events during the Cenozoic and guided by reactivated Mesozoic faults west of the study area. The style and amount of uplift differs from the Southern Scandes and a hinge line is defined in between. The landscape generations were also used for estimations of the amount of glacial/fluvial erosion since the beginning of the Late Cenozoic glaciations. Erosion amounted up to 200 - 400 m in the valleys that hosted the major outlet glaciers, while the eastern plateaux and the plains with residual hills have experienced no or limited glacial erosion.
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| 10. |
- Näslund, Jens-Ove, 1965-
(författare)
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Ice Sheet, Climate, and Landscape Interactions in Dronning Maud Land, Antarctica
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The impact of glaciers and ice sheets on the subglacial landscape are of fundamental importance for studies of glacial history and landscape development, both in previously glaciated areas and in areas that are glaciated today. The thesis concerns the present and past erosive capacity of the ice sheet in Dronning Maud Land, East Antarctica. Large-scale subglacial landforms, mainly glacial valleys and cirques, were mapped by radar soundings and basal ice temperatures were calculated. The hypothesis that the alpine landscape in western and central Dronning Maud Land predates the ice sheet was tested. It was found that the ice sheet covering localities at high altitudes within the landscape today are covered by cold-based, and thus non-erosive, ice and that this probably also was the case during late Cenozoic glacial/interglacial cycles. It was concluded that the high-altitude alpine landscape commonly found within the coastal mountain ranges of Dronning Maud Land was formed by local wet-based mountain glaciers during the middle Cenozoic. In the late Cenozoic, the high-altitude alpine landscape has been preserved by cold-based ice coverage. Glacial preservation of a subglacial large-scale sediment accumulation, interpreted as a pre-glacial floodplain or valley delta, was also inferred. Intermediate altitudes within the landscape may have experienced alternating phases of cold-based and wet-based conditions during the late Cenozoic. The lowest parts of the Dronning Maud Land landscape constitute troughs of tectonic origin, exemplified by the prominent Penck-Jutul Trough. In these depressions wet-based conditions have prevailed up to the present day due to the presence of fast flowing ice streams such as Jutulstraumen and Veststraumen. Ice stream erosion has probably been important for the continued deepening of these troughs, and it is feasible that erosion by ice streams today still increases the already significant landscape relief. The alpine landscape of Dronning Maud Land is incised in considerably older large-scale morphology consisting of an elevated Paleozoic planation surface and a passive continental margin escarpment. An attempt is made to synthesise major events in the long-term landscape development of central and western Dronning Maud Land since the time of break-up of the Gondwana continent. The role of glacial erosion in the development of this passive continental margin is assessed.
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