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  • International Glaciological Society  (16)
  • 1
    Online Resource
    Online Resource
    Short-term surface ice motion variations measured with a ground-based portable real aperture radar interferometer
    International Glaciological Society ; 2011
    In:  Journal of Glaciology Vol. 57, No. 201 ( 2011), p. 53-60
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 57, No. 201 ( 2011), p. 53-60
    Abstract: We report measurements using a portable real aperture radar (Gamma Portable Radar Interferometer (GPRI)) for interferometric imaging of the surface ice motion on Gornergletscher, Switzerland, during the drainage of the adjacent ice-marginal lake Gornersee. The GPRI tracked the surface ice motion in line of sight over an area of ∼3 km 2 down-glacier of Gornersee almost continuously during the drainage event. The displacement maps derived from the acquired interferograms capture the spatial distribution of the surface ice motion. Due to fast acquisition times of the microwave images, the GPRI was able to record sub-daily variations of the ice displacements, most likely caused by the impact of the Gornersee drainage on the ice motion of Gornergletscher. In situ point measurements of the ice displacement agree reasonably well with the results obtained by the GPRI and highlight the use of the GPRI for high-resolution measurements of glacier surface ice motion.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/002214311795306718
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2011
    detail.hit.zdb_id: 2140541-4
    SSG: 14
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  • 2
    Online Resource
    Online Resource
    Modelling mass balance using photogrammetric and geophysical data: a pilot study at Griesgletscher, Swiss Alps
    International Glaciological Society ; 1999
    In:  Journal of Glaciology Vol. 45, No. 151 ( 1999), p. 575-583
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 45, No. 151 ( 1999), p. 575-583
    Abstract: The kinematic boundary condition al the glacier surface can be used to give glacier mass balance at a point as a function of changes in the surface elevation, and of the horizontal and vertical velocities. Vertical velocity can in turn be estimated from basal slope, basal ice velocity and surface strain. In a pilot study on the tongue of Griesgletscher, Swiss Alps, the applicability of the relation for modelling area-wide ice flow and mass-balance distribution is tested. The key input of the calculations, i.e. the area-wide surface velocity field, is obtained using a newly developed photogrammetric technique. Ice thickness is derived from radar-echo soundings. Error estimates and comparisons with stake measurements show an average accuracy of approximately ±0.3 ma -1 for the calculated vertical ice velocity at the surface and ±0.7 ma -1 for the calculated mass balance. Due to photogrammetric restrictions and model-inherent sensitivities the applied model appeared to be most suitable for determining area-wide mass balance and ice flow on flat-lying ablation areas, but is so far not very well suited for steep ablation areas and most parts of accumulation areas. Nevertheless, the study on Griesgletscher opens a new and promising perspective for the monitoring of spatial and temporal glacier mass-balance variations.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/S0022143000001453
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 1999
    detail.hit.zdb_id: 2140541-4
    SSG: 14
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  • 3
    Online Resource
    Online Resource
    Flow dynamics of tidewater glaciers: a numerical modelling approach
    International Glaciological Society ; 2001
    In:  Journal of Glaciology Vol. 47, No. 159 ( 2001), p. 595-606
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 47, No. 159 ( 2001), p. 595-606
    Abstract: The dynamics of grounded tidewater glaciers is investigated with a time-dependent numerical flow model, which solves the full equations for the stress and velocity fields and includes a water-pressure-dependent sliding law. The calving criterion implemented in the model shifts the calving front at each time-step to the position where the frontal ice thickness exceeds flotation height by a prescribed value. With this model, the linear relation between calving rate and water depth proposed on empirical grounds is qualitatively reproduced for the situation of a slowly retreating or advancing terminus, but not for situations of rapid changes. Length changes of tidewater glaciers, i.e. especially rapid changes, are dominantly controlled by the bed topography and are to a minor degree a direct reaction to a mass-balance change. Thus, accurate information on the near-terminus bed topography is required for reliable prediction of the terminus changes due to climate changes. The results also confirm the suggested cycles of slow advance and rapid retreat through a basal depression. Rapid changes in terminus positions preferably occur in places where the bed slopes upwards in the ice-flow direction.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/172756501781831747
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2001
    detail.hit.zdb_id: 2140541-4
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  • 4
    Online Resource
    Online Resource
    Glacier-dammed lake outburst events of Gornersee, Switzerland
    International Glaciological Society ; 2007
    In:  Journal of Glaciology Vol. 53, No. 181 ( 2007), p. 189-200
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 53, No. 181 ( 2007), p. 189-200
    Abstract: Gornersee, Switzerland, is an ice-marginal lake, which drains almost every year, subglacially, within a few days. We present an analysis of the lake outburst events between 1950 and 2005, as well as results of detailed field investigations related to the lake drainage in 2004 and 2005. The latter include measurements of lake geometry, water pressure in nearby boreholes and glacier surface motion. A distributed temperature-index melt model coupled to a linear-reservoir runoff model is used to calculate hourly discharge from the catchment of Gornergletscher in order to distinguish between the melt/precipitation component and the outburst component of the discharge hydrograph. In this way, drainage volume and timing are determined. From 1950 there is a clear trend for the outburst flood to occur earlier in the melt season, but there is no trend in lake discharge volumes. Peak discharges from the lake lie significantly below the values obtained using the empirical relation proposed by Clague and Mathews (1973). The shapes of the 2004 and 2005 lake outflow hydrographs differ substantially, suggesting different drainage mechanisms. From water balance considerations we infer a leakage of the glacier-dammed lake in 2005, starting 1 week prior to the lake outburst. During the drainage events, up to half of the lake water is temporarily stored in the glacial system, causing substantial uplift of the glacier surface.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/172756507782202784
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2007
    detail.hit.zdb_id: 2140541-4
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  • 5
    Online Resource
    Online Resource
    The ice-thickness distribution of Unteraargletscher, Switzerland
    International Glaciological Society ; 2003
    In:  Annals of Glaciology Vol. 37 ( 2003), p. 331-336
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 37 ( 2003), p. 331-336
    Abstract: Results from 15 years of work on glacier-bed mapping by radio-echo soundings on Finsteraar-, Lauteraar- and Unteraargletscher, Switzerland, are summarized, and a new and greatly improved map of the ice-thickness distribution presented. In contrast to the tongue of Unteraargletscher, its two main tributaries, Lauteraar and Finsteraar, are both deep and narrow, and ice-thickness determination depends on the detection of more than just the primary reflection. Migrating the data led to considerably improved bed determination. Wherever possible, additional information on ice thicknesses gained from numerous hot-water drillings to the glacier bed is used as an independent verification of the results of the radar measurements, and a fair agreement is found.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/172756403781815852
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2003
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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  • 6
    Online Resource
    Online Resource
    Homogenization of long-term mass-balance time series
    International Glaciological Society ; 2009
    In:  Annals of Glaciology Vol. 50, No. 50 ( 2009), p. 198-206
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 50, No. 50 ( 2009), p. 198-206
    Abstract: The re-analysis of long-term mass-balance time series is important to provide bias-corrected mass-balance data for climate-change impact studies. A method to homogenize time series of comprehensive mass-balance monitoring programmes is presented and applied to the nearly 50 year mass-balance records of Griesgletscher and Silvrettagletscher, Switzerland. Using a distributed mass-balance model in daily resolution we correct the mass-balance data for varying observation dates. Direct point measurements are combined with independent geodetic mass changes, a prerequisite for a thorough homogenization of mass-balance records. Differences between mass balance evaluated in the hydrological year or according to the measurement period and the stratigraphic system are analysed and may be up to ± 0.5mw.e. a − 1. Cumulative mass balance of both glaciers based on the glaciological method generally agrees well with geodetic mass change on the investigated glaciers. However, for Silvretta-gletscher a significant bias of +0.37mw.e. a − 1 has been detected and corrected for since 1994.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/172756409787769627
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2009
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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  • 7
    Online Resource
    Online Resource
    A method to estimate the ice volume and ice-thickness distribution of alpine glaciers
    International Glaciological Society ; 2009
    In:  Journal of Glaciology Vol. 55, No. 191 ( 2009), p. 422-430
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 55, No. 191 ( 2009), p. 422-430
    Abstract: Sound knowledge of the ice volume and ice-thickness distribution of a glacier is essential for many glaciological applications. However, direct measurements of ice thickness are laborious, not feasible everywhere and necessarily restricted to a small number of glaciers. In this paper, we present a method to estimate the ice-thickness distribution and the total ice volume of alpine glaciers. This method is based on glacier mass turnover and principles of ice-flow mechanics. The required input data are the glacier surface topography, the glacier outline and a set of borders delineating different ‘ice-flow catchments’. Three parameters describe the distribution of the ‘apparent mass balance’, which is defined as the difference between the glacier surface mass balance and the rate of ice-thickness change, and two parameters define the ice-flow dynamics. The method was developed and validated on four alpine glaciers located in Switzerland, for which the bedrock topography is partially known from radio-echo soundings. The ice thickness along 82 cross-profiles can be reproduced with an average deviation of about 25% between the calculated and the measured ice thickness. The cross-sectional areas differ by less than 20% on average. This shows the potential of the method for estimating the ice-thickness distribution of alpine glaciers without the use of direct measurements.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/002214309788816759
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2009
    detail.hit.zdb_id: 2140541-4
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  • 8
    Online Resource
    Online Resource
    Comment on ‘Integrated monitoring of mountain glaciers as key indicators of global climate change: the European Alps’ by Haeberli and others
    International Glaciological Society ; 2008
    In:  Journal of Glaciology Vol. 54, No. 184 ( 2008), p. 199-200
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 54, No. 184 ( 2008), p. 199-200
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/S0022143000210009
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2008
    detail.hit.zdb_id: 2140541-4
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  • 9
    Online Resource
    Online Resource
    Ice-volume changes of selected glaciers in the Swiss Alps since the end of the 19th century
    International Glaciological Society ; 2007
    In:  Annals of Glaciology Vol. 46 ( 2007), p. 145-149
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 46 ( 2007), p. 145-149
    Abstract: The evolution of surface topography of glaciers in the Swiss Alps is well documented with high-resolution aerial photographs repeatedly recorded since the 1960s and further back in time with topographic maps including elevation contour lines first surveyed in the mid-19th century. In order to quantify and interpret glacier changes in the Swiss Alps, time series of volume changes over the last 100–150 years have been collected. The available datasets provide a detailed spatial resolution for the retreat period since the end of the Little Ice Age. The spatial distribution as well as temporal variations of the thickness change were analyzed. A significant ice loss since the end of the 19th century was observed in the ablation area, while the changes in the accumulation area were small. We found moderate negative secular rates until the 1960s, followed by steady to positive rates for about two decades and strong ice loss starting in the 1980s which has lasted until the present. An evaluation of 19 glaciers revealed a total ice volume loss of about 13km 3 since the 1870s, of which 8.7 km 3 occurred since the 1920s and 3.5 km 3 since 1980. Decadal mean net balance rates for the periods 1920–60, 1960–80 and 1980–present are –0.29, –0.03 and –0.53ma –1 w.e., respectively.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/172756407782871701
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2007
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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  • 10
    Online Resource
    Online Resource
    Tidewater glaciers: frontal flow acceleration and basal sliding
    International Glaciological Society ; 2000
    In:  Annals of Glaciology Vol. 31 ( 2000), p. 217-221
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 31 ( 2000), p. 217-221
    Abstract: A numerical glacier-flow model (finite-element method) is used to suggest the processes that control the flow behind the calving front of a tidewater glacier. The model is developed for grounded calving glaciers and includes an effective-pressure-dependent sliding law The sliding law is implemented by adding a soft basal layer with a variable viscosity The model is applied on Hansbreen, a tidewater calving glacier in Svalbard. Comparison between modeled surface velocities and observed velocity data shows good agreement. We conclude that the flow of a grounded calving glacier can be modeled with an effective-pressure-dependent sliding law
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/172756400781820417
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2000
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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