Physical modeling of the influence of bedrock topography and ablation on ice flow and meteorite concentration in Antarctica

AbstractAn interpolated bedrock topography is presented for Flask Glacier, one of the tributaries of the remnant part of the Larsen B ice shelf, Antarctic Peninsula. The ice thickness distribution is derived by combining direct but sparse measurements from airborne radio-echo soundings with indirect estimates obtained from ice-flow modelling. The ice-flow model is applied to a series of transverse profiles, and a first estimate of the bedrock is iteratively adjusted until agreement between modelled and measured surface velocities is achieved. The adjusted bedrock is then used to reinterpret the radio-echo soundings, and the recovered information used to further improve the estimate of the bedrock itself. The ice flux along the glacier center line provides an additional and independent constraint on the ice thickness. The resulting bedrock topography reveals a glacier bed situated mainly below sea level with sections having retrograde slope. The total ice volume of 120 ±15 km3 for the considered area of 215 km2 corresponds to an average ice thickness of 560 ± 70 m.

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The bedrock topography of Gries- and Findelengletscher

Geographica Helvetica ◽

10.5194/gh-73-1-2018 ◽

2018 ◽

Vol 73 (1) ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Nadine Feiger ◽

Matthias Huss ◽

Silvan Leinss ◽

Leo Sold ◽

Daniel Farinotti

Keyword(s):

Spatial Interpolation ◽

Thickness Distribution ◽

Estimation Method ◽

Ice Thickness ◽

Glacier Surface ◽

Ice Flow ◽

Bedrock Topography ◽

Abstract Knowledge ◽

Ground Penetrating ◽

Item Item

Abstract. Knowledge of the ice thickness distribution of glaciers is important for glaciological and hydrological applications. In this contribution, we present two updated bedrock topographies and ice thickness distributions for Gries- and Findelengletscher, Switzerland. The results are based on ground-penetrating radar (GPR) measurements collected in spring 2015 and already-existing data. The GPR data are analysed using ReflexW software and interpolated by using the ice thickness estimation method (ITEM). ITEM calculates the thickness distribution by using principles of ice flow dynamics and characteristics of the glacier surface. We show that using such a technique has a significance advantage compared to a direct interpolation of the measurements, especially for glacier areas that are sparsely covered by GPR data. The uncertainties deriving from both the interpretation of the GPR signal and the spatial interpolation through ITEM are quantified separately, showing that, in our case, GPR signal interpretation is a major source of uncertainty. The results show a total glacier volume of 0.28±0.06 and 1.00±0.34 km3 for Gries- and Findelengletscher, respectively, with corresponding average ice thicknesses of 56.8±12.7 and 56.3±19.6 m.

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Longitudinal coupling in ice flow across a subglacial ridge

Annals of Glaciology ◽

10.3189/s026030550001212x ◽

1997 ◽

Vol 24 ◽

pp. 169-174 ◽

Cited By ~ 1

Author(s):

Peter Jansson

Keyword(s):

Numerical Model ◽

Flow Regime ◽

Field Data ◽

Water Pressure ◽

Drastic Change ◽

Surface Velocity ◽

Northern Sweden ◽

Ice Flow ◽

Bedrock Topography ◽

Velocity Variations

A transverse bedrock ridge, or riegel, in the bedrock topography under Storglaciären, northern Sweden, induces a drastic change in flow regime. The part of the glacier located downstream of the riegel exhibits velocity variations correlated to water-pressure variations under this part of the glacier. Similar velocity variations are also observed up-glacier from the riegel despite a lack of significant water-pressure variations there. Field data and a numerical model suggest that the variations in surface velocity observed on the glacier upstream of the riegel are a result of pulling from down-glacier through longitudinal coupling across the riegel.

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Models for strain localization in Law Dome, Antarctica

Annals of Glaciology ◽

10.1017/s0260305500013690 ◽

1996 ◽

Vol 23 ◽

pp. 396-401 ◽

Cited By ~ 2

Author(s):

R. J. M. Rowden-Rich ◽

C. J. L. Wilson

Keyword(s):

Finite Element ◽

Shear Stress ◽

Strain Localization ◽

High Stress ◽

Element Model ◽

Ice Flow ◽

Progressive Development ◽

Bedrock Topography ◽

Ice Cap ◽

Marked Oscillation

A finite-element model was implemented that relates the computed flow to some field and fabric observations recorded on the Law Dome ice cap, East Antarctica. The results of the model suggest that the general ice flow is markedly affected by the bedrock topography. The zones of measured anomalous flow correlate with significant changes in the modelled stress within the ice mass. Stress increases of up to 50% above the reduced model shear stress were obtained in the models where the ice moved over a bedrock rise. Stress relaxation also occurs in the ice mass as the ice moves downward to a lee depression. There is a marked oscillation in the direction of principal stress and this is responsible for the progressive development of a set of high stress zones that are superimposed on the down-slope ice movement.

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An iterative inverse method to estimate basal topography and initialize ice flow models

The Cryosphere Discussions ◽

10.5194/tcd-7-873-2013 ◽

2013 ◽

Vol 7 (2) ◽

pp. 873-920

Author(s):

W. J. J. van Pelt ◽

J. Oerlemans ◽

C. H. Reijmer ◽

R. Pettersson ◽

V. A. Pohjola ◽

...

Keyword(s):

Inverse Method ◽

Thickness Distribution ◽

Radar Data ◽

Time Dependent ◽

Climate Forcing ◽

Ice Flow ◽

Flow Models ◽

Ice Caps ◽

Inverse Approach ◽

Bedrock Topography

Abstract. We present and evaluate an inverse approach to reconstruct two-dimensional fields of bedrock topography and simultaneously initialize an ice flow model. The inverse method involves an iterative procedure in which an ice dynamical model (PISM) is run multiple times over a prescribed period, while being forced with space and time-dependent climate input. After every iteration bed heights are adjusted using information of the remaining misfit between observed and modeled surface topography. The inverse method is first applied in synthetic experiments with a constant climate forcing to verify convergence and robustness of the approach. In a next step, the inverse approach is applied to Nordenskiöldbreen, Svalbard, forced with height- and time-dependent climate input since 1300 AD. An L-curve stopping criterion is used to prevent overfitting. Validation against radar data reveals a high correlation (up to R = 0.89) between modeled and observed thicknesses. Remaining uncertainties can mainly be ascribed to inaccurate model physics, in particular uncertainty in the description of sliding. Results demonstrate the applicability of this inverse method to reconstruct the ice thickness distribution of glaciers and ice caps. In addition to reconstructing bedrock topography, the method provides a direct tool to initialize ice flow models for forecasting experiments. Application of the method is not constrained to a single model or glacier, indicating the potential to use the approach to compute the detailed thickness distribution of a single glacier, as well as the volume contained in a set of glaciers and ice caps.

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Longitudinal coupling in ice flow across a subglacial ridge

Annals of Glaciology ◽

10.1017/s026030550001212x ◽

1997 ◽

Vol 24 ◽

pp. 169-174 ◽

Cited By ~ 7

Author(s):

Peter Jansson

Keyword(s):

Numerical Model ◽

Flow Regime ◽

Field Data ◽

Water Pressure ◽

Drastic Change ◽

Surface Velocity ◽

Northern Sweden ◽

Ice Flow ◽

Bedrock Topography ◽

Velocity Variations

A transverse bedrock ridge, or riegel, in the bedrock topography under Storglaciären, northern Sweden, induces a drastic change in flow regime. The part of the glacier located downstream of the riegel exhibits velocity variations correlated to water-pressure variations under this part of the glacier. Similar velocity variations are also observed up-glacier from the riegel despite a lack of significant water-pressure variations there. Field data and a numerical model suggest that the variations in surface velocity observed on the glacier upstream of the riegel are a result of pulling from down-glacier through longitudinal coupling across the riegel.

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The bedrock topography of Starbuck Glacier, Antarctic Peninsula, as determined by radio-echo soundings and flow modeling

Annals of Glaciology ◽

10.3189/2014aog67a025 ◽

2014 ◽

Vol 55 (67) ◽

pp. 22-28 ◽

Cited By ~ 17

Author(s):

Daniel Farinotti ◽

Edward C. King ◽

Anika Albrecht ◽

Matthias Huss ◽

G. Hilmar Gudmundsson

Keyword(s):

Antarctic Peninsula ◽

Thickness Distribution ◽

Flow Speed ◽

Ice Thickness ◽

Ice Flow ◽

Bedrock Topography ◽

Radio Echo Sounding ◽

Field Season ◽

Thickness Measurements

AbstractA glacier-wide ice-thickness distribution and bedrock topography is presented for Starbuck Glacier, Antarctic Peninsula. The results are based on 90 km of ground-based radio-echo sounding lines collected during the 2012/13 field season. Cross-validation with ice-thickness measurements provided by NASA's IceBridge project reveals excellent agreement. Glacier-wide estimates are derived using a model that calculates distributed ice thickness, calibrated with the radio-echo soundings. Additional constraints are obtained from in situ ice flow-speed measurements and the surface topography. The results indicate a reverse-sloped bed extending from a riegel occurring ~ 5 km upstream of the current grounding line. The deepest parts of the glacier are as much as 500 m below sea level. The calculated total volume of 80.7 ± 7.2 km3 corresponds to an average ice thickness of 312 ± 30 m.

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Derivation of ice thickness and bedrock topography in data-gap regions over Antarctica

Annals of Glaciology ◽

10.3189/172756400781820011 ◽

2000 ◽

Vol 31 ◽

pp. 191-197 ◽

Cited By ~ 17

Author(s):

Roland C. Warner ◽

W. F. Budd

Keyword(s):

Ice Sheet ◽

Ice Thickness ◽

Ice Flow ◽

Sheet Surface ◽

Bedrock Topography ◽

Ice Accumulation ◽

Data Gap ◽

Lambert Glacier ◽

The Antarctic ◽

Lambert Glacier Basin

AbstractAn approach to deriving the thickness of the Antarctic ice sheet and inferring the bedrock elevation to fill in gaps in the compilations of ice-thickness observations is presented. It combines assumptions about the general state of balance of the ice sheet and of the dynamics of ice flow, with information about ice accumulation and the topography of the ice-sheet surface elevation to infer the ice thickness and bedrock. A simplified version of the scheme already shows the potential of this approach, as is demonstrated by an application to the Lambert Glacier basin, East Antarctica.

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An iterative inverse method to estimate basal topography and initialize ice flow models

The Cryosphere ◽

10.5194/tc-7-987-2013 ◽

2013 ◽

Vol 7 (3) ◽

pp. 987-1006 ◽

Cited By ~ 38

Author(s):

W. J. J. van Pelt ◽

J. Oerlemans ◽

C. H. Reijmer ◽

R. Pettersson ◽

V. A. Pohjola ◽

...

Keyword(s):

Inverse Method ◽

Thickness Distribution ◽

Radar Data ◽

Three Dimensions ◽

Time Dependent ◽

Ice Flow ◽

Flow Models ◽

Ice Caps ◽

Inverse Approach ◽

Bedrock Topography

Abstract. We evaluate an inverse approach to reconstruct distributed bedrock topography and simultaneously initialize an ice flow model. The inverse method involves an iterative procedure in which an ice dynamical model (PISM) is run multiple times over a prescribed period, while being forced with space- and time-dependent climate input. After every iteration bed heights are adjusted using information of the remaining misfit between observed and modeled surface topography. The inverse method is first applied in synthetic experiments with a constant climate forcing to verify convergence and robustness of the approach in three dimensions. In a next step, the inverse approach is applied to Nordenskiöldbreen, Svalbard, forced with height- and time-dependent climate input since 1300 AD. An L-curve stopping criterion is used to prevent overfitting. Validation against radar data reveals a high correlation (up to R = 0.89) between modeled and observed thicknesses. Remaining uncertainties can mainly be ascribed to inaccurate model physics, in particular, uncertainty in the description of sliding. Results demonstrate the applicability of this inverse method to reconstruct the ice thickness distribution of glaciers and ice caps. In addition to reconstructing bedrock topography, the method provides a direct tool to initialize ice flow models for forecasting experiments.

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Contemporaneous, localized, basal ice-flow variations: implications for bedrock erosion and the origin of p-forms

Journal of Glaciology ◽

10.3189/172756500781833197 ◽

2000 ◽

Vol 46 (154) ◽

pp. 470-476 ◽

Cited By ~ 16

Author(s):

Brice R. Rea ◽

David J. A. Evans ◽

Tom S. Dixon ◽

W. Brian Whalley

Keyword(s):

Flow Direction ◽

Flow Patterns ◽

Stress Regime ◽

Flow Paths ◽

Ice Flow ◽

Mechanical Abrasion ◽

Bedrock Topography ◽

Basal Ice ◽

Bedrock Erosion ◽

Bed Roughness

AbstractA detailed study of a proglacial bedrock site and a subglacial cavity of an outlet of Øksfjordjøkelen, Norway, is presented together with observations from the foreland of Konowbreen, Spitsbergen. Striation directions and subglacial observations indicate that local ice-flow paths were highly variable, deviating at angles of approximately 90° from the main ice-flow direction. Stepped bedrock topography appears conducive to the production of highly variable ice-flow paths, because the high bed roughness creates a locally variable stress regime within the ice, including low-pressure, lee-side areas into which ice can flow. If ice flow is sustained along a specific path and the ice contains debris, then abrasion should produce an erosional bedform. Models are proposed whereby locally variable ice-flow patterns could produce erosional bedforms, which would be described as p-forms, purely through mechanical abrasion.

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