Supraglacial Debris of G2 Glacier in Hidden Valley, Mukut Himal, Nepal

AbstractField investigations of supraglacial debris were carried out during the monsoon season in 1974 on G2 glacier near Tukche Peak in Hidden Valley, Mukut Himal, Nepal. The thickness of the debris layer was observed to increase down-glacier. Laboratory analysis, however, showed a decrease in particle size in the same direction. This decrease is explained in terms of mixing of particles contained in glacier ice with the original debris as melting proceeds. A simple relation between debris mass and glacier flow is introduced to explain the observed results.

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Crystal Orientation in Glacier and in Experimentally Deformed Ice

Journal of Glaciology ◽

10.3189/s0022143000023716 ◽

1960 ◽

Vol 3 (27) ◽

pp. 589-606 ◽

Cited By ~ 2

Author(s):

George P. Rigsby

Keyword(s):

Crystal Orientation ◽

Laboratory Experiments ◽

Ice Crystals ◽

Equal Area ◽

Fine Grained ◽

Planar Structures ◽

Glacier Ice ◽

Glacier Flow ◽

High Shearing ◽

Universal Stage

AbstractMore than 8,000 ice crystals have been oriented and measured for crystal fabric studies from widely separated temperate and polar glaciers, using a large universal stage and thin-section techniques. Very strong fabrics have been found and a number of laboratory experiments on deformation and recrystallization of ice were conducted in an attempt to solve some of the perplexing problems raised concerning glacier flow.In polar glaciers the c or optic axes of the ice crystals tend to be perpendicular to the foliation plane (alternating planar structures of bubbly and clear ice). In areas of high shearing stress the preferred orientation of the axes reached 39 per cent in 1 per cent of the area when plotted on a Schmidt equal-area projection. In temperate glaciers the optic axes tend to form three or four strong maxima which also appear related to the foliation.Patterns from ice deformed in the laboratory resemble some of the fabric patterns found in polar glaciers. During deformation of laboratory specimens, large crystals have been observed recrystallizing into many smaller ones, while fine-grained ice, after completion of deformation (both glacier ice and laboratory deformed ice), has been annealed at melting temperature into a few large crystals with different orientations from the original pattern.

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Present dynamics and future prognosis of a slowly surging glacier

The Cryosphere ◽

10.5194/tc-5-299-2011 ◽

2011 ◽

Vol 5 (1) ◽

pp. 299-313 ◽

Cited By ~ 49

Author(s):

G. E. Flowers ◽

N. Roux ◽

S. Pimentel ◽

C. G. Schoof

Keyword(s):

Mass Balance ◽

Force Balance ◽

Surface Velocity ◽

Internal Dynamic ◽

Ice Dynamics ◽

Surface Mass ◽

Ice Surface ◽

Glacier Ice ◽

Glacier Flow ◽

Negative Balance

Abstract. Glacier surges are a well-known example of an internal dynamic oscillation whose occurrence is not a direct response to the external climate forcing, but whose character (i.e. period, amplitude, mechanism) may depend on the glacier's environmental or climate setting. We examine the dynamics of a small (∼5 km2) valley glacier in Yukon, Canada, where two previous surges have been photographically documented and an unusually slow surge is currently underway. To characterize the dynamics of the present surge, and to speculate on the future of this glacier, we employ a higher-order flowband model of ice dynamics with a regularized Coulomb-friction sliding law in both diagnostic and prognostic simulations. Diagnostic (force balance) calculations capture the measured ice-surface velocity profile only when non-zero basal water pressures are prescribed over the central region of the glacier, coincident with where evidence of the surge has been identified. This leads to sliding accounting for 50–100% of the total surface motion in this region. Prognostic simulations, where the glacier geometry evolves in response to a prescribed surface mass balance, reveal a significant role played by a bedrock ridge beneath the current equilibrium line of the glacier. Ice thickening occurs above the ridge in our simulations, until the net mass balance reaches sufficiently negative values. We suggest that the bedrock ridge may contribute to the propensity for surges in this glacier by promoting the development of the reservoir area during quiescence, and may permit surges to occur under more negative balance conditions than would otherwise be possible. Collectively, these results corroborate our interpretation of the current glacier flow regime as indicative of a slow surge that has been ongoing for some time, and support a relationship between surge incidence or character and the net mass balance. Our results also highlight the importance of glacier bed topography in controlling ice dynamics, as observed in many other glacier systems.

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Ice Core Studies of Ward Hunt Ice Shelf, 1960

Journal of Glaciology ◽

10.3189/s0022143000028562 ◽

1964 ◽

Vol 5 (37) ◽

pp. 39-59 ◽

Cited By ~ 1

Author(s):

R. H. Ragle ◽

R. G. Blair ◽

L. E. Persson

Keyword(s):

Ice Core ◽

Polarized Light ◽

Ice Cores ◽

Laboratory Analysis ◽

Dartmouth College ◽

The Arctic ◽

Ice Shelf ◽

Glacier Ice ◽

Initial Work ◽

Physical And Chemical

AbstractA four-man party representing the Arctic Institute of North America and the Department of Geology, Dartmouth College, went to the Ward Hunt Ice Shelf in 1960 to obtain ice cores for subsequent laboratory analysis. The overall objective of the project was to study the structural and stratigraphic history of the shelf and its relationship to the environment through laboratory analysis of the cores, using stratigraphic. petrologic, chemical, and physical methods.The four cores obtained were logged, packed, and shipped to Dartmouth College for detailed study. The stratigraphy and structure of the ice were studied under natural and plane polarized light conditions. The results of this initial work showed that the cores were composed of four ice types: glacier ice, lake ice, sea ice, and transition ice. Chlorinity, sulfate, and density profiles complemented megascopic studies and were most useful criteria for plotting stratigraphie changes in ice type.Results of the investigations thus far have yielded new information about the gross structure and stratigraphy of the ice shelf and re-entrant. They have also shown that the physical and chemical techniques employed will be useful in future ice-core analysis.

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Internal Erosion Failure of Uniform Sands under Confinement and Constricted Seepage Exit

Water ◽

10.3390/w12092417 ◽

2020 ◽

Vol 12 (9) ◽

pp. 2417

Author(s):

Kuang-Tsung Chang ◽

Kevin Zeh-Zon Lee ◽

Han-Yu Wu

Keyword(s):

Particle Size ◽

Critical Velocity ◽

Friction Angle ◽

Confining Pressure ◽

Internal Erosion ◽

Seepage Water ◽

Field Investigations ◽

Mechanical Models ◽

Confining Pressures ◽

Experimental Findings

Seepage water may move soil particles and cause internal erosion of soils, leading to sinkholes and the collapse of embankments and slopes. To account for the effects of confinement and constricted seepage exit, a test apparatus was developed to study the internal erosion of granular soils under various confining pressures, particle sizes, and sizes of the seepage exit opening. As indicated in the literature, the behavior of internal erosion has been largely studied by laboratory experiments and field investigations, and mechanical models that help describe the failure mechanism of internal erosion are less prevalent. A hydro-mechanical model that incorporates the fluid drag force and the shear strength of soil was therefore developed for quantifying the internal erosion experiments conducted in this study. The experimental results showed that the greater the confining pressure or the particle size, the greater the critical velocity; the greater the seepage exit opening, the smaller the critical velocity. The critical velocity predicted by the proposed hydro-mechanic model compares reasonably well with the experimental data. In addition to the confining pressure, particle size, and size of the seepage exit opening, the proposed model also showed that the friction angle and porosity of the soil are factors influencing the critical velocity, which is consistent with the experimental findings of this study.

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Ice Core Studies of Ward Hunt Ice Shelf, 1960

Journal of Glaciology ◽

10.1017/s0022143000028562 ◽

1964 ◽

Vol 5 (37) ◽

pp. 39-59 ◽

Cited By ~ 42

Author(s):

R. H. Ragle ◽

R. G. Blair ◽

L. E. Persson

Keyword(s):

Ice Core ◽

Polarized Light ◽

Ice Cores ◽

Laboratory Analysis ◽

Dartmouth College ◽

The Arctic ◽

Ice Shelf ◽

Glacier Ice ◽

Initial Work ◽

Physical And Chemical

Abstract A four-man party representing the Arctic Institute of North America and the Department of Geology, Dartmouth College, went to the Ward Hunt Ice Shelf in 1960 to obtain ice cores for subsequent laboratory analysis. The overall objective of the project was to study the structural and stratigraphic history of the shelf and its relationship to the environment through laboratory analysis of the cores, using stratigraphic. petrologic, chemical, and physical methods. The four cores obtained were logged, packed, and shipped to Dartmouth College for detailed study. The stratigraphy and structure of the ice were studied under natural and plane polarized light conditions. The results of this initial work showed that the cores were composed of four ice types: glacier ice, lake ice, sea ice, and transition ice. Chlorinity, sulfate, and density profiles complemented megascopic studies and were most useful criteria for plotting stratigraphie changes in ice type. Results of the investigations thus far have yielded new information about the gross structure and stratigraphy of the ice shelf and re-entrant. They have also shown that the physical and chemical techniques employed will be useful in future ice-core analysis.

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Some Comments on Glacier Flow

Journal of Glaciology ◽

10.1017/s0022143000012600 ◽

1950 ◽

Vol 1 (07) ◽

pp. 383-388 ◽

Cited By ~ 11

Author(s):

Richard Finsterwalder

Keyword(s):

Shear Stress ◽

Shear Plane ◽

Critical Value ◽

Ice Flow ◽

Crystalline Materials ◽

Fundamental Point ◽

Glacier Ice ◽

Slow Moving ◽

Glacier Flow ◽

Streaming Flow

Abstract Drs. Orowan and Perutz have shown that glacier ice does not behave as a viscous fluid but is plastic like all crystalline materials. The present author discusses two observed types of ice flow:—(1) the normal, regular streaming flow in slow-moving glaciers; (2) Block-Schollen * movement in swiftly flowing ice. Mention is made of the shear plane or laminar flow theory of Philipp. lt appears that Orowan s thesis is also applicable to Block-Schollen flow. The author agrees with Orowan on the fundamental point that when ice is subjected to shear stress a critical value of the shear stress exists beyond which the ice alters its consistency. But the author disagrees with Orowan in that he believes that below this critical value ice behaves as a viscous material, and he supports this view by reference to many phenomena, measurements and calculations.

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Pollen Analysis of Glaciers in Special Relation to the Formation of Various Types of Glacier Bands

Journal of Glaciology ◽

10.1017/s002214300001008x ◽

1949 ◽

Vol 1 (06) ◽

pp. 325-332 ◽

Cited By ~ 16

Author(s):

H. Godwin

Keyword(s):

Pollen Analysis ◽

Statistical Evidence ◽

General Nature ◽

Special Relation ◽

New Approach ◽

Flow Problems ◽

Pollen Content ◽

Glacier Ice ◽

Glacier Flow ◽

Different Parts

Abstract The author describes the work of Dr. V. Vareschi on the pollen content of glacier ice. A general account of the method of analysis is given. The results of statistical evidence of the analyses on several alpine glaciers are discussed, particularly in regard to the general nature of glacier flow in different parts of the glaciers. Vareschi’s suggestions as to the modes of origin of a certain type of ogive banding and of parallel banding (Pflugfurcheneis) are dealt with in the light of his findings. It is pointed out that what appears to be a valuable new approach to the solution of glacier flow problems needs elaboration before it can be accepted in all its bearings.

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The ATAL and its aerosol microphysical properties in the Asian Monsoon Anticyclone

10.5194/egusphere-egu2020-6759 ◽

2020 ◽

Author(s):

Christoph Mahnke ◽

Stephan Borrmann ◽

Ralf Weigel ◽

Francesco Cairo ◽

Armin Afchine ◽

...

Keyword(s):

Particle Size ◽

Asian Monsoon ◽

Extreme Values ◽

Monsoon Season ◽

Measurement Techniques ◽

Potential Temperature ◽

Particle Diameter ◽

Size Distributions ◽

Particle Size Distributions ◽

Microphysical Properties

During the StratoClim 2017 measurement campaign in Nepal, within the Asian Monsoon Anticyclone (AMA), measurements of the aerosols&#8217; microphysical properties up to UT/LS altitudes were successfully completed with a modified version of the commercially available (Droplet Measurement Technologies Inc.) aerosol spectrometer UHSAS-A. Technical rearrangements of parts of the UHSAS-A were developed and implemented, which improve the instrument&#8217;s measuring performance and extend its airborne application range from around 12 km altitude to the extreme ambient conditions in the stratosphere at heights of 20 km. The measurement techniques used for this purpose were characterized by laboratory experiments.Within the AMA region, extreme values of the particle mixing ratio (PMR) ranging between 6 mg-1 and about 10000 mg-1 were found with the UHSAS-A (particle diameter range: 65 nm to 1000 nm). The median of the PMR for all research flights was about 1300 mg-1 close to the ground. Within tropospheric altitudes, the PMR was highly variable and median values between 70 mg-1 and 400 mg-1 were observed. &#160;At levels of 370 K potential temperature, the median PMR maximally reaches about 700 mg-1 while the 1 Hz resolved measurements show values up to about 10000 mg-1. Between 450 K and 475 K, median PMR between 40 mg-1 and 50 mg-1 were observed. The aerosol size distributions (measured by the UHSAS-A) were extended by an additional diameter size bin obtained from the 4-channel Condensation Particle counting System (COPAS), i.e. for aerosol diameter between 10&#160;nm and 65&#160;nm.The UHSAS-A measured aerosol particle size distributions were compared with balloon-borne measurements (by T. Deshler et al., Dep. of Atmospheric Science, University of Wyoming, USA) at altitudes of up to 20 km. These show that the size distributions measured during the StratoClim 2017 campaign fit well within the range of the balloon-borne measurements during the Asian Monsoon season over India (Hyderabad) in 2015 and the USA (Laramie) in 2013. Further analyses of measured particle size distributions by means of backscatter ratio show remarkable consistency with CALIOP satellite observations of the ATAL during the StratoClim mission period.

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A Contribution to the Study of the Glacier Grain

Journal of Glaciology ◽

10.3189/s0022143000010078 ◽

1949 ◽

Vol 1 (6) ◽

pp. 320-324

Author(s):

André Renaud

Keyword(s):

Electrical Conductivity ◽

Melting Point ◽

The Other ◽

Other Hand ◽

Glacier Ice ◽

Glacier Flow

AbstractThe melting of glacier ice always begins at the surface of the glacier grains. A mass of glacier ice at a temperature near its melting point is therefore an aggregate of crystals separated by a film of liquid. The electrical conductivity of ice subjected to differential melting differs considerably according to whether the fractions come from the grain surfaces or from the crystal centres, being much the higher in the former case. It is concluded therefore that the glacier grain consists of a crystal of pure ice with a surrounding film of brine, thus verifying the hypotheses of Buchanan and of Quincke on the formation of natural and artificial ice.The growth of the grain is facilitated by the elimination of the saline skin between neighbouring crystals, the resulting coalescence having the character of autogenous welding. On the other hand, the intergranular film of liquid may act as a lubricant in the as yet inadequately explained mechanism of glacier flow.

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