Journal ArticleDOI
Sliding motion of glaciers: Theory and observation
TLDR
In this article, the sliding motion of glacier ice over bedrock, which contributes about half the flow velocity of temperate glaciers, is analyzed for arbitrary bedrock topography of low roughness.Abstract:
The sliding motion of glacier ice over bedrock, which contributes about half the flow velocity of temperate glaciers, is analyzed for arbitrary bedrock topography of low roughness. Fourier-analyzed topography is represented by a roughness spectral function ζ(h, k) defined in terms of the mean square topographic amplitude. From an essentially exact solution of the sliding problem for linear ice-flow rheology, an approximate solution for the actual nonlinear rheology is built on the assumption that the second strain-rate invariant depends only on distance from the ice-bedrock contact. The transition wavelength λ0 between regelation and plastic flow, constant in the linear theory, is replaced in the nonlinear theory by a velocity- and roughness-dependent parameter λα that plays a similar role. Detailed results are given for three special types of ζ(h, k): (1) white roughness (|ζ| constant); (2) truncated white roughness (|ζ| constant for all wavelengths above a certain lower limit); (3) a single wavelength; and (4) cross-corrugated sinusoidal waves. The results are tested against field observations of sliding. Given sliding velocity υ, basal shear stress τ, and rheological parameters, the theory predicts roughness values ζ for the different types of ζ(h, k). When compared with ζ values inferred from observed bedrock outcrops, predicted values for white roughness are somewhat too small, whereas for white roughness truncated at 3.53 meters, they are of the expected size (ζ ∼ 0.05). Predicted λα values range from 3 to 112 cm; high υ (>20 m yr−1) generally gives λα in the range 10–40 cm, and low υ (<6 m yr−1) 30–70 cm. The predicted thickness of the regelation layer (1–10 mm) agrees with observation, but the predicted λα values appear to be somewhat too small. Extensive separation of the ice sole from bedrock, due to tensile stresses set up in sliding, is predicted in icefalls, whereas for valley glaciers little separation is predicted, unless meltwater under a head of pressure comparable to half the glacier thickness has access to the bed. Extensive separation is not needed to account for typical sliding velocities, provided that the roughness spectrum is truncated. Observed features of glaciated bedrock indicate truncation, which results from glacial abrasion. For the truncated spectrum, the predicted dependence of υ on τ is much more highly nonlinear than for the full white spectrum; this implies a relatively high sensitivity of sliding velocity to changes in glacier thickness or surface slope.read more
Citations
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Journal ArticleDOI
Topography, climate and ice masses: a review
TL;DR: Topography acts as a filter between regional climate and the consequent response of a glacier or ice sheet and influences the mass and energy inputs and modifies the ice dynamics as mentioned in this paper.
Journal ArticleDOI
The role of bed separation and friction in sliding over an undeformable bed
Jürg Schweizer,Almut Iken +1 more
TL;DR: In this paper, the authors investigated the influence of debris concentration on the sliding process and the effect of subglacial water pressure and friction on a sliding motion over an undulating bed.
Journal ArticleDOI
Meltwater influences on deep stick‐slip icequakes near the base of the Greenland Ice Sheet
Claudia Roeoesli,Claudia Roeoesli,Agnès Helmstetter,Fabian Walter,Fabian Walter,Fabian Walter,Edi Kissling +6 more
Journal ArticleDOI
Characterization of subglacial landscapes by a two-parameter roughness index
Xin Li,Bo Sun,Martin J. Siegert,Robert Bingham,Xueyuan Tang,Dong Zhang,Xiangbin Cui,XiangPei Zhang +7 more
TL;DR: In this paper, a two-parameter Fourier transformation (FT) roughness index is proposed for subglacial terrain, based on elevation and bed-slope profile.
Journal ArticleDOI
Experimental determination of a double-valued drag relationship for glacier sliding
Lucas K. Zoet,Neal R. Iverson +1 more
TL;DR: In this paper, the authors demonstrate empirically for the first time a double-valued drag relationship like that suggested by some sliding theories: steady drag on a rigid, sinusoidal bed increases, peaks and declines at progressively higher sliding speeds due to growth of cavities in the lee sides of bed undulations.
References
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Journal ArticleDOI
On the Sliding of Glaciers
TL;DR: In this article, a model is proposed to explain the sliding of any glacier whose bottom surface is at the pressure melting point, and two mechanisms are considered: pressure melting and creep rate enhancement through stress concentrations.
Journal ArticleDOI
What are glacier surges
Mark F. Meier,Austin Post +1 more
TL;DR: A total of 204 surging glaciers has been identified in western North America as discussed by the authors, and these glaciers surge repeatedly and probably with uniform periods (from about 15 to greater than 100 years).
Journal ArticleDOI
General theory of subglacial cavitation and sliding of temperate glaciers
TL;DR: In this article, a more realistic model of the bed consisting of a superposition of sine waves all having the same roughness r, and a decreasing in a geometrical progression is considered.