Application of a general sliding law to simulating flow in a glacier cross-section

Harbor, Jonathan M.

doi:10.1017/s0022143000009710

Cited by 29 publications

(16 citation statements)

References 31 publications

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“…In younger erosional events the erosion is instead focused on the valley margins (Figures 5 and 6). This is in agreement with the conceptual model of Brook et al (2006), the model simulations of Hirano and Aniya (1988) and Harbor (1992), and erosion estimates from TCN studies from northern Sweden (Li et al, 2005), and it supports the formation of glacial valleys from fluvial precursors over multiple glacial cycles (Harbor, 1992;Kirkbride and Matthews, 1997;Li et al, 2005;Brook et al, 2006). The correspondence between expected and reconstructed overall patterns and rates of glacial erosion, however, does not imply that other processes were unimportant.…”

Section: Discussionsupporting

confidence: 85%

“…Stroeven et al, 2006), (ii) valleys terminating in large glacial troughs have been shortened by glacial erosion (Kleman and Stroeven, 1997), and (iii) the preference for glacial erosion of steep slopes rather than valley bottoms in large troughs (Figures 5 and 6; cf. Harbor, 1992).…”

Section: Erosional Pattern Of the Riksgränsen Areamentioning

confidence: 99%

“…Firstly, temporal patterns of erosion can be evaluated at the landform scale, such as by comparing glacial valley evolution with existing models for valley formation (e.g. Svensson, 1959;Graf, 1970;Shoemaker, 1986;Hirano and Aniya, 1988;Augustinus, 1992Augustinus, , 1995Harbor, 1992Harbor, , 1995Pattyn and Decleir, 1995;James, 1996;Hebdon et al, 1997;Kirkbride and Matthews, 1997;MacGregor et al, 2000;Li et al, 2001;Montgomery, 2002;Fabel et al, 2004;Anderson et al, 2006;Brook et al, 2006Brook et al, , 2008. Secondly, spatial patterns of erosion can be compared to mapped patterns of erosion for a specific region (in this study we compare results generated by the filtering technique with the pattern of erosion in a PDL test area of NW Scandinavia; Kleman and Stroeven, 1997;Fabel et al, 2002;Stroeven et al, 2002aStroeven et al, , 2002bStroeven et al, , 2006Li et al, 2005;.…”

Section: Introductionmentioning

confidence: 99%

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Using a GIS filtering approach to replicate patterns of glacial erosion

Jansson

Stroeven

Alm

et al. 2010

Earth Surf Processes Landf

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Jansson, K. N., Stroeven, A. P., Alm, G., Dahlgren, K. I. T., Glasser, N. F., Goodfellow, B. W. (2011). Using a GIS filtering approach to replicate patterns of glacial erosion. Earth Surface Processes and Landforms, 36, (3), 408-418.In order to extend our knowledge of glacial relief production in mountainous areas new methods are required for landscape reconstructions on a temporal resolution of a glacial cycle and a spatial resolution that includes the most important terrain components. A generic data set and a 50 m resolution digital elevation model over a study area in northern Sweden and Norway (the present day landscape data set) were employed to portray spatial patterns of erosion by reconstructing the landscape over successive cycles of glacial erosion. A maximum-value geographic information system (GIS) filtering technique using variable neighbourhoods was applied such that existing highpoints in the landscape were used as erosional anchor points for the reconstruction of past landscape topography. An inherent assumption, therefore, is that the highest surfaces have experienced insignificant down-wearing over the Quaternary. Over multiple reconstruction cycles, proceeding backwards in time, the highest summits increase in area, valleys become shallower, and the valley pattern becomes increasingly simplified as large valleys become in-filled from the sides. The sum of these changes reduces relief. The pattern of glacial erosion, which is to 60% correlated to slope angle and to 70% correlated to relative relief, is characterized by (i) an abrupt erosional boundary below preserved summit areas, (ii) enhanced erosion in narrow valleys, (iii) restricted erosion of smooth areas, independently of elevation, (iv) eradication of small-scale irregularities, (v) restricted erosion on isolated hills in low-relief terrain, and (vi) a valley widening independent of valley directions. The method outlined in this paper shows how basic GIS filtering techniques can mimic some of the observed patterns of glacial erosion and thereby help deduce the key controls on the processes that govern large-scale landscape evolution beneath ice sheets. Copyright (C) 2010 John Wiley & Sons, Ltd.Peer reviewe

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Section: Discussionsupporting

confidence: 85%

Section: Erosional Pattern Of the Riksgränsen Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Using a GIS filtering approach to replicate patterns of glacial erosion

Jansson

Stroeven

Alm

et al. 2010

Earth Surf Processes Landf

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“…We have not succeeded in identifying a characteristic signature of a basal till layer in surface measurements. As far as the velocity distribution in a transverse section is concerned, this can already be recognized by comparing our results with the modeling of Reynaud (1973) and Harbor (1992), who used a friction law and a sliding law, respectively. They obtained results that were somewhat similar to ours.…”

Section: Till Versus Bedrockmentioning

confidence: 62%

Implications of till deformation on glacier dynamics

2001

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The dynamics of glacier motion is governed, to a large extent, by the properties of the basal interface. In this paper we address the interaction of a glacier with a layer of till at its bed in an attempt to test whether our physical understanding of till is sufficient to explain general features of the observed flow field and changes in geometry of Black Rapids Glacier, Alaska. We also investigate whether or not a till layer has a clear surface-observable signature in the dynamics of the glacier. Towards this end we use a finite element ice-flow model with a Coulomb failure criterion within the basal till layer. We find that simple 'till physics' can be used to describe decadal, seasonal, and short term (hours to days) velocity variations, and possibly uplift events. Mechanisms for each of these variations involve an increase in the extent of till at failure, a transfer of shear stress across the bed, and a consequent increase in ice deformation. 'Effective shape factors' are calculated to permit a simple incorporation of this boundary condition into glacier response models. Our analyses, however, have not resulted in the identification of a clear and unique signature of a till layer in the surface dynamics of the glacier.

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“…Erosion by rivers and glaciers, which is responsible for shaping the large-scale topography of mountain ranges, is dependent on accumulated precipitation in drainage basins (e.g., Hallet 1979Hallet , 1996Oerlemans 1984;Harbor 1992;Howard 1994;Whipple 2004). The impact of billion-year-old rain shadows can be seen in the filling of sedimentary basins in eastern North America (Hoffman and Grotzinger 1993).…”

Section: Simple Models Of Precipitation In the Olympicsmentioning

confidence: 99%

Small-Scale Spatial Gradients in Climatological Precipitation on the Olympic Peninsula

Anders

Roe

Durran

et al. 2007

Journal of Hydrometeorology

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Persistent, 10-km-scale gradients in climatological precipitation tied to topography are documented with a finescale rain and snow gauge network in the Matheny Ridge area of the Olympic Mountains of Washington State. Precipitation totals are 50% higher on top of an ϳ800-m-high ridge relative to valleys on either side, 10 km distant. Operational fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5) runs on a 4-km grid produce similar precipitation patterns with enhanced precipitation over high topography for 6 water years.The performance of the MM5 is compared to the gauge data for 3 wet seasons and for 10 large precipitation events. The cumulative MM5 precipitation forecasts for all seasons and for the sum of all 10 large events compare well with the precipitation measured by the gauges, although some of the individual events are significantly over-or underforecast. This suggests that the MM5 is reproducing the precipitation climatology in the vicinity of the gauges, but that errors for individual events may arise due to inaccurate specification of the incident flow.A computationally simple model of orographic precipitation is shown to reproduce the major features of the event precipitation pattern on the windward side of the range. This simple model can be coupled to landscape evolution models to examine the impact of long-term spatial variability in precipitation on the evolution of topography over thousands to millions of years.

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Application of a general sliding law to simulating flow in a glacier cross-section

Cited by 29 publications

References 31 publications

Using a GIS filtering approach to replicate patterns of glacial erosion

Using a GIS filtering approach to replicate patterns of glacial erosion

Implications of till deformation on glacier dynamics

Small-Scale Spatial Gradients in Climatological Precipitation on the Olympic Peninsula

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