| 21. |
- Lundqvist, Jan
(författare)
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DEPOSITS FROM LANDSLIDES AND AVALANCHES TRIGGERED BY SEISMIC ACTIVITY IN SWEDISH LAPLAND
- 2010
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 92A:3, s. 411-420
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Tidskriftsartikel (refereegranskat)abstract
- In the mountain area of Swedish Lapland, landforms with semicircular or horse-shoe ridges encircling hummocky ground occur They are interpreted as landslide or avalanche deposits directly upon, from or adjacent to down-wasting ice Since they are restricted to the vicinity of fault scarps in the Parvie fault system the releasing factor is suggested to be displacement of bedrock blocks or related seismic activity.
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| 22. |
- Margold, Martin, et al.
(författare)
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Snowpatch hollows and pronival ramparts in the krkonoše mountains, Czech Republic : distribution, morphology and chronology of formation
- 2011
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 93A:2, s. 137-150
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Tidskriftsartikel (refereegranskat)abstract
- Two types of landforms attributed to the geomorphological effects of long-lasting snow accumulations, snowpatch hollows and pronival ramparts, were studied in the Krkonose Mountains, Czech Republic. Factors influencing the distribution and morphology of snowpatch hollows were examined using statistical analysis of field-measured and DEM-modelled snowpatch hollow characteristics. Snowpatch hollows were classified into two groups. The first group comprises hollows developed mainly in erosional incisions from streams on low-relief summit planation surfaces. The hollows of this group are relatively small and display signs of recent activity, with development during the Holocene. The second group consists of larger snowpatch hollows developed in debris-covered slopes of the highest summits, closely related to the cryoplanation terraces occurring in the area. The hollows of this group are suggested to have developed in the periglacial environment of the glacial periods. The age and degree of activity of pronival ramparts, occurring only at two sites in the study area, were determined using several methods (Schmidt hammer, lichenometry, pollen analysis, and radiocarbon dating). The appearance of these pronival ramparts differs between the two sites as a result of the different geological setting. Both the ramparts in the Harrachova jama cirque, consisting of coarse granite debris, and the rampart in the Upska jama cirque, developed of mica-schist clasts, have been active during the late Holocene and are considered to be active even today.
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| 23. |
- Moeller, Marco, et al.
(författare)
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Snowpack Characteristics of Vestfonna and De Geerfonna (Nordaustlandet, Svalbard) : A Spatiotemporal Analysis Based on Multiyear Snow-Pit Data
- 2011
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 93A:4, s. 273-285
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Tidskriftsartikel (refereegranskat)abstract
- Extensive glaciological field measurements were carried out on the ice cap Vestfonna as well as on the minor ice body De Geerfonna (Nordaustlandet, Svalbard) within the framework of IPY Kinnvika. Field campaigns were conducted during the period 20072010 in spring (April/May) and summer (August). In this study we compile and present snow cover information obtained from 22 snow pits that were dug on Vestfonna during this period. Locations are along two transects on the northwestern, land terminating slope of the ice cap, on its central summit, Ahlmann Summit, and at a set of several other locations in the eastern and northern part of the ice cap. Snow-cover information acquired from four snow pits on adjacent De Geerfonna is also incorporated in this study. Field data are analysed regarding snow stratigraphy, snow density, snow hardness and snow temperature. Results reveal mean snow densities of around 400 kg m-3 for the snowpack of Vestfonna with no apparent spatial or interannual variability. A distinctly higher value of more than 450 kg m-3 was obtained for De Geerfonna. A spatial comparison of snow water equivalents above the previous end-of-summer surface serves for obtaining insights into the spatial distribution of snow accumulation across Vestfonna. Altitude was found to be the only significant spatial parameter for controlling snow accumulation across the ice cap.
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| 24. |
- Mörner, Nils-Axel, et al.
(författare)
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Heimdall's stones at Vitemölla in Sweden and the chronology and stratigraphy of the surroundings
- 2009
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 91A:3, s. 205-213
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Tidskriftsartikel (refereegranskat)abstract
- Heimdall's Stones at Vitemolla is an archaeological monument of stones arranged in circles and where sightlines can be identified of the sunrise and sunset at winter and summer solstices and spring and autumn equinoxes. Therefore, this stone monument is likely to have served as an archaeoastronomic observatory. It is founded in a fossil land surface now covered by half a metre of eolian sand. In order to date this sand drift, sediment coring was performed in the nearby Sandefloen bog. Seven levels were subjected to AMS C14 dating. The first sand drift, correlated with the sand drift covering Heimdall's Stones, was dated at 500-600 cal. bc. Consequently, the observatory has to date back to the Bronze Age, fitting well with its Sun cult and with the rock carvings recorded on the individual stones. At the seashore 500 m east of the observatory and the bog, we were able to reconstruct the sea-level changes. In conclusion, we combine the recorded sea-level changes with the C14-dated bog stratigraphy and the observed stratigraphy at Heimdall's Stones (covering an area of 500x500 m) into one unified picture. The chronostratigraphic position of Heimdall's Stones agrees well with the dating of the Kivik grave. The Vitemolla area is likely to have been an important cultural centre in the Bronze Age.
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| 25. |
- Nel, Werner, et al.
(författare)
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The effect of synoptic scale weather systems on sub-surface soil temperatures in a diurnal frost environment : preliminary observations from sub-antarctic Marion Island
- 2009
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 91:4, s. 313-319
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Tidskriftsartikel (refereegranskat)abstract
- Marion Island in the South Indian Ocean has a maritime climate dominated by diurnal frost processes in the landscape. We test the hypothesis that synoptic time-scale measurements are essential in understanding the drivers of diurnal frost processes. Preliminary results from automated microclimate measurements in a polar desert habitat show that diurnal soil surface temperatures on Marion Island are influenced by a complex interaction of radiation balance, air mass circulation, cloud cover and snow. The passage of synoptic scale weather systems influences soil thermal characteristics through changes in dominance of the radiation budget. Soil frost on Marion appears to be dependent on clear skies, while synoptic weather systems affect the duration and intensity of soil frost processes and non-radiative heat fluxes. Air circulation patterns at Marion Island influence diurnal scale temperature fluctuations and its direct and indirect interactions with ecosystem processes. The data suggest that in a maritime sub-Antarctic environment the climatic drivers of soil frost occur at a finertemporal resolution than for seasonal and permafrost environments and needs to be measured at a diurnal time-scale to be meaningful.
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| 26. |
- Olvmo, Mats, 1956, et al.
(författare)
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Saprolite remnants as indicators of pre-glacial landform genesis in southeast Sweden
- 2005
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Ingår i: Geografiska Annaler Series a-Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 87A:3, s. 447-460
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Tidskriftsartikel (refereegranskat)abstract
- Twenty-six sites with remnants of gravelly saprolites (grus) have been located in southeast Sweden. Joint block hills (castle kopjes) and steep rock walls with weathered joints as well as rounded boulders are documented to have an origin in deep weathering and subsequent stripping of saprolites. The saprolite remnants and landforms result from the fragmentation of the re-exposed sub-Cambrian peneplain along fracture systems. Only shallow saprolites occur on the elevated intact parts of the sub-Cambrian peneplain, while saprolites up to 20 m thick are encountered in areas where the sub-Cambrian peneplain is fractured and dissected. Neogene uplift with reactivation of the weathering system is thought to be the main cause of saprolite formation. Deep weathering is thus judged to have been the major agent of landform formation in the study area, while glacial and glaciofluvial erosion has contributed mainly by stripping saprolites, detaching corestones, and plucking joint blocks along weathered joints.
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| 27. |
- Ostwald, Madelene, 1966-, et al.
(författare)
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Relation between vegetation changes, climate variables and land-use policy in Shaanxi Province, China
- 2007
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 89:4, s. 223-236
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Tidskriftsartikel (refereegranskat)abstract
- Shaanxi Province in China has been exposed to climate variability and dramatic land-use policies. The aim here is to examine vegetation changes in this area on a regional scale from 2000 to 2004 in relation to land-use changes and climate traits. The data in this assessment include remote sensing information from moderate-resolution imaging spectro-radiometer normalized difference vegetation index from 2000 to 2004, and climate data (precipitation and temperature) from 1956 to 2000. The results show an increase in vegetation production from 2000 to 2004, particularly in the north, which cannot be explained solely by climate impacts. Since the vegetation in the north is more dependent on climate variation than the other parts of Shaanxi due to more serious water limitation, the results suggest that the large-scale land-use policy implemented over the last decade, with a focus on northern Shaanxi, is possibly having an impact on the overall vegetation.
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| 28. |
- Pettersson, Rickard, et al.
(författare)
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Ice thickness and basal conditions of Vestfonna ice cap, eastern Svalbard
- 2011
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 93A:4, s. 311-322
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Tidskriftsartikel (refereegranskat)abstract
- We combined ground-based pulsed radar data collected in 20082009 with airborne radio-echo sounding data acquired in 1983 and 1986 over Vestfonna ice cap, Svalbard. The airborne dataset mainly covers the fast-flowing outlet glaciers and the marginal zone, while the ground-based data explicitly cover the interior part of the ice cap. The data presented here are thus the first complete estimate of bed topography and ice thickness. The subglacial landscape undulates with elevations between -160 and +410 m above sea level. The mean ice thickness is 186 m and the total ice area and volume are 2402 km2 and 442 +/- 0.6 km3, respectively. This is a much smaller volume than those derived from empirical volume-area scaling relationships currently used to estimate regional-to-global glacier volumes. This difference may depend on local conditions for Vestfonna and emphasizes the need to include more volume observations in the derivations of volume-area scaling parameters. We also derive basal reflectivity as a proxy for thermal conditions at the bed. Basal reflectivity values suggest that fast-flowing outlet glaciers are underlain by temperate conditions. The geometric boundaries and basal conditions for Vestfonna will be critical additions to the development of numerical models of the ice cap and to the estimation of more accurate area-volume scaling parameters.
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| 29. |
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| 30. |
- Pohjola, Veijo A, 1960-, et al.
(författare)
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Spatial distribution and change in the surface ice-velocity field of Vestfonna ice cap, Nordaustlandet, Svalbard, 1995-2010 using geodetic and satellite interferometry data
- 2011
-
Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 93:4, s. 323-335
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Tidskriftsartikel (refereegranskat)abstract
- During 2007 we launched a geodetic campaign on the Svalbard ice cap Vestfonna in order to estimate the velocity field of the ice cap. This was done within the frame of the IPY project KINNVIKA. We present here the velocity measurements derived from our campaigns 2007–2010 and compare the geodetic measurements against InSAR velocity fields from satellite platforms from 1995/96 and 2008. We find the spatial distribution of ice speeds from the InSAR is in good agreement within the uncertainty limits with our geodetic measurements. We observe no clear indication of seasonal ice speed differences, but we find a speed-up of the outlet glacier Franklinbreen between the InSAR campaigns, and speculate the outlet is having a surge phase.
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