Glaciers move through internal deformation and basal sliding
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Peer-reviewed literature, academic books, and reference sources report that glaciers move through a combination of internal ice deformation and basal sliding.
Abstract. Glacial meltwater directly influences glacier dynamics. However, in the case of debris-covered glaciers, the drivers of glacier velocity and the influence of supraglacial lakes have not yet been sufficiently analysed and understood. We present a spatio-temporal analysis of key glacier characteristics for Baltoro Glacier in the Karakoram from October 2016 to September 2022 based on Earth observation data and climate parameters extracted from the High Asia Refined analysis (HAR) data set. For the glacier variables, we used surface velocity, supraglacial lake extent, melt of snow and ice, and proglacial run-off index. For climate variables, we focused on air temperature and precipitation. The surface velocity of Baltoro Glacier was characterized by a spring speed-up, summer peak, and fall speed-up with a relative increase in summer of 0.2–0.3 m d−1 (75 %–100 %) in relation to winter velocities, triggered by the onset of or an increase in basal sliding. Snow and ice melt have the largest impact on the spring speed-up, summer velocity peak, and the transition from inefficient to efficient subglacial drainage. The melt covered up to 64 % (353 km2) of the entirety (debris-covered and debris-free) of Baltoro Glacier and reached up to 4700 m a.s.l. during the first melt peak and up to 5600 m a.s.l. during summer. The temporal delay between the initial peak of seasonal melt and the first relative velocity maximum decreases downglacier. Drainage from supraglacial lakes (3.6–5.9 km2) contributed to the fall speed-up, which showed a 0.1–0.2 m d−1 (20 %–30 %) lower magnitude compared to the summer velocity peak. Most of the run-off can be attributed to the melt of snow and ice. However, from mid-June onward, the lakes play an increasing role, even though their contribution is estimated to be only about half of that of the melt. The observed increase in summer air temperatures leads to a greater extent of melt, as well as to a rise in the number and total area of supraglacial lakes. This tendency is expected to intensify in a future warming climate.
Worldwide, glaciers are receding as a consequence of climate change. Due to the global glacier recession, glaciers are experiencing enhanced melting, which results in an increase in meltwater availability. This increased meltwater has the ability to alter the glacier's hydraulic conditions and ultimately affects the dynamics of glaciers. Glaciers move through a combination of basal motion and internal ice deformation. The motion at the ice-bed interface comprises of both ice sliding along the bed and the deformation of subglacial sediments. Sliding at the bed is partially controlled by the water pressure at the ice-bed interface and therefore, knowledge of the subglacial hydraulic system is paramount in order to predict glacier movement and fundamentally the future evolution of glaciers. To date, our understanding of the glacier’s hydrological system is limited due insufficient field observations. As part of my thesis, I used surface-based geophysical methods to detect and characterise an alpine glacier's hydrological system. The aim is to improve our understanding of the drainage network of temperate alpine glaciers by using active seismic and ground-penetrating radar (GPR) to determine the properties in space and time of the hydrological system. To detect and characterise englacial flow paths, I performed active seismic and GPR on Rhonegletscher (Switzerland). Both geophysical methods detected a hydrological flow path within the glacier. With the use of amplitude-versus-off
An improved understanding of the mechanisms and factors affecting glacial flow is crucial to better predict sea level rise. Glacial ice often contains impurities such as the presence of small insoluble particles. Mixtures of ice and dust can be found in many places throughout the world, specifically in areas of high latitude and altitude (Moore, 2014). This study aims to understand the effect of entrained insoluble debris on processes of glacial motion. Glaciers move through a combination of internal ice deformation and basal sliding. Internal ice deformation, the flow of individual ice grains, has been found to be grain-size dependent in both field and laboratory studies (Goldsby and Kohlstedt, 2001). In an attempt to better understand ice grain size, this study considers the effect of debris on grain growth. Samples of pure ice and ice with debris were fabricated with a standard protocol and maintained at -5°C for controlled annealing. Microstructural characterization was preformed using a light microscope to image the samples, and calculating the average grain sizes using a linear-intercept method. The ice with debris was found to have smaller grain sizes, thought to be associated with grain-boundary pinning. Extrapolated values were used with a flow law, projecting that ice with debris will have lower viscosity, thus flow faster. To address basal sliding, the other form of glacial movement, we conducted a second phase of study. Basal sliding, the process of a glacier slid
glaciers by the com- bination of internal deformation and basal sliding; the latter may account for 90 … p. 417 ablation zone, p. 412 internal deformation, p. 412 basal sliding, p. 412 warm glacier, p. 414 … Barrier spit, 461, 463 Bar scale, 37 Basal load (ice), 418 Basal sliding (glacier ice), 412 Basalt, 271, 274
by the com¬ bination of internal deformation and basal sliding; the latter may account for … 412 ablation zone, p. 412 internal deformation, p. 412 basal sliding, p. 412 warm glacier, p … spit, 461, 463 Bar scale, 37 Basal load (ice), 418 Basal sliding (glacier ice), 412 Basalt,
by the underlying water, and the glacier is afloat. Glaciers may also move by basal sliding, where the base of the glacier is lubricated by the presence
A glacier (US: ; UK: or ) is a persistent body of natural ice, a form of
rock, that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It slowly flows and deforms under stresses induced by gravity, undergoing both ductile and brittle deformation, and acquiring distinguishing surface features, such as
Most of the important processes controlling glacial motion occur in the ice-bed contact—even though it is only a few meters thick. The bed's temperature, roughness and softness define basal shear stress, which in turn defines whether movement of the glacier will be accommodated by motion in the sediments, or if it will be able to slide. A soft bed, with high porosity and low pore fluid pressure, allows the glacier to move by sediment sliding: the base of the glacier may even remain frozen to the bed, where the underlying sediment slips underneath it like a tube of toothpaste. A hard bed cannot deform in this way; therefore the only way for hard-based glaciers to move is by basal sliding, where meltwater forms between the ice and the bed itself. Whether a bed is hard or soft depends on the porosity and pore pressure; higher porosity decreases the sediment strength (thus increases the shear stress τB).
Porosity may vary through a range of methods.
snow or glacier downhill. This is caused by a force, friction, vibration, or internal deformation of the ice, and by sliding over the rocks and sediments
Abrasion is a process of weathering that occurs when material being transported wears away at a surface over time, commonly occurring with ice and glaciers. The primary process of abrasion is physical weathering. Its the process of friction caused by scuffing, scratching, wearing down, marring, and rubbing away of materials. The intensity of abrasion depends on the hardness, concentration, velocit
Abrasion is a process of weathering that occurs when…
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