Textures and fabrics in the Dome F (Antarctica) ice core

AbstractA comprehensive study of ice-crystal fabrics and textures was conducted on the Dome F (Antarctica) ice core. Crystal ,-axis orientations, crystal sizes and crystal shape were measured on thin sections with an automatic ice-fabric analyzer. The general feature of textural and fabric development through a 2500 m long core was obtained by a 20 m interval study. Crystal size steadily increases with depth except for depths of about 500,1800, 2000, 2200 and 2300 m, at which depths crystal size decreases suddenly. There is a clear correlation between crystal-size and ´18O values. Crystals tend to elongate horizontally with depth, and the aspect ratio (long axis vs short axis of a grain) increases twofold at 1600 m depth and fluctuates below that depth. The .-axis orientation fabrics gradually change with depth from a random orientation pattern near the surface to a strong vertical single maximum at 2500 m. These are very similar to those from the GRIP (Greenland) core The observations of crystal shape and the fabric measurements indicate that nucleation-recrystallization does not take place at Dome F.

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Crystal Size and Orientation Patterns in the Wisconsin-Age Ice from Dye 3, Greenland

Annals of Glaciology ◽

10.3189/s0260305500004262 ◽

1988 ◽

Vol 10 ◽

pp. 109-115 ◽

Cited By ~ 7

Author(s):

C.C. Langway ◽

H. Shoji ◽

N. Azuma

Keyword(s):

Crystal Size ◽

Ice Core ◽

Ice Crystal ◽

Axis Orientation ◽

Measuring Device ◽

Thin Sections ◽

Core Samples ◽

Physical Measurements ◽

Ice Crystal Size ◽

Velocity Measuring

Crystal size and c-axis orientation patterns were measured on the Dye 3, Greenland, deep ice core in order to investigate time-dependent changes or alterations in the physical character of the core as a function of time after recovery. The physical measurements were expanded to include depth intervals not previously studied in the field. The recent study focused on core samples located between 1786 m and the bottom of the ice sheet at 2037 m.Manual c-axis measurements were made on 23 new thin sections using a Rigsby-type universal stage. A new semi-automatic ultrasonic wave-velocity measuring device was developed in order to compare the results with the earlier manual measurements and to study an additional 114 ice-core samples in the Wisconsin-age ice. Crystal-size measurements were made on specimen surfaces by inducing evaporation grooves at crystal boundaries and measuring linear intercepts. The ultrasonically measured test samples were subsequently cleaned and analyzed by ion chromatography in order to measure impurity concentration levels of Cl−, NO3− and SO42− and study their effects on crystal growth and c-axis orientation.

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Crystal Size and Orientation Patterns in the Wisconsin-Age Ice from Dye 3, Greenland

Annals of Glaciology ◽

10.1017/s0260305500004262 ◽

1988 ◽

Vol 10 ◽

pp. 109-115 ◽

Cited By ~ 32

Author(s):

C.C. Langway ◽

H. Shoji ◽

N. Azuma

Keyword(s):

Crystal Size ◽

Ice Core ◽

Ice Crystal ◽

Axis Orientation ◽

Measuring Device ◽

Thin Sections ◽

Core Samples ◽

Physical Measurements ◽

Ice Crystal Size ◽

Velocity Measuring

Crystal size and c-axis orientation patterns were measured on the Dye 3, Greenland, deep ice core in order to investigate time-dependent changes or alterations in the physical character of the core as a function of time after recovery. The physical measurements were expanded to include depth intervals not previously studied in the field. The recent study focused on core samples located between 1786 m and the bottom of the ice sheet at 2037 m. Manual c-axis measurements were made on 23 new thin sections using a Rigsby-type universal stage. A new semi-automatic ultrasonic wave-velocity measuring device was developed in order to compare the results with the earlier manual measurements and to study an additional 114 ice-core samples in the Wisconsin-age ice. Crystal-size measurements were made on specimen surfaces by inducing evaporation grooves at crystal boundaries and measuring linear intercepts. The ultrasonically measured test samples were subsequently cleaned and analyzed by ion chromatography in order to measure impurity concentration levels of Cl−, NO3− and SO4 2− and study their effects on crystal growth and c-axis orientation.

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Study of an ice core to the bedrock in the accumulation zone of an Alpine glacier

Journal of Glaciology ◽

10.1017/s0022143000030677 ◽

1976 ◽

Vol 17 (75) ◽

pp. 13-28 ◽

Cited By ~ 72

Author(s):

M. Vallon ◽

J.-R. Petit ◽

B. Fabre

Keyword(s):

Water Content ◽

Ice Core ◽

Ice Crystal ◽

Vertical Orientation ◽

Axis Orientation ◽

Alpine Glacier ◽

Small Crystals ◽

Average Water ◽

Intermediate Size ◽

Average Size

AbstractA water table appearing every summer where the ice begins, at a gerpth of approximately 30 m, accelerates the transformation of firn into ice during the summer (80% of the ice formed every year appears in less than 2 months). The ice formed in this way contains from 0 to 0.6% water. The average water content increases gradually with the gerpth because of the heat of gerformation. But, near bedrock, between 180 and 187 m, the permeability of the blue ice is such that the water content drops (0.3% as compared to 1.3% between 160 and 180 m).From a gerpth of 33 m, a foliation of sedimentary origin gradually gervelops in the ice. Its dip increases regularly to a gerpth of 145 m. At 145 m it jumps sudgernly freom 20° to 40°, then at 170 m freom 40° to 65°, which can be explained by old modifications in the bergschrund. This foliation disappears near bedrock (180-187 m), where there are no bubbles in the ice.The average size of an ice crystal increases slowly in the firn, shows seasonal fluctuations between 30 and 50 m, then jumps freom a diameter of 1 or 2 mm to 10 or 20 mm between 50 and 80 m. Between 180 and 187 m, the ice is mager of large crystals (3-10 cm diameter; the figure, however, is probably inexact due to a recrystallization of the samples).The very strong sub-vertical orientation of the optic axes of the firn crystals disappears quickly, and freom 66 m on, in ice with large crystals, a fabric of multiple maxima appears (generally, 3 or 4 directions, forming a triangle or a rhombus). On the other hand, in the small crystals that form bands parallel to the plane of foliation, only one direction of preferential orientation can be seen, or two close to one another. Crystals of intermediate size (10 to 50 mm) generally have two directions of preferred orientation at an angle of approximately 50° to one another. No matter how big the crystals are, the angle between the most commonc-axis orientation and the vertical does not change freom 60 to 170 m gerpth.

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Crystalline Texture of the 2083 m Ice Core at Vostok Station, Antarctica

Journal of Glaciology ◽

10.1017/s0022143000009321 ◽

1989 ◽

Vol 35 (121) ◽

pp. 392-398 ◽

Cited By ~ 95

Author(s):

V.Ya. Lipenkov ◽

N.I. Barkov ◽

P. Duval ◽

P. Pimienta

Keyword(s):

Enhancement Factor ◽

Crystal Size ◽

Gradual Increase ◽

Ice Core ◽

Impurity Content ◽

Mean Value ◽

Axis Orientation ◽

Vostok Station ◽

The Mean ◽

Convergent Flow

AbstractCrystalline texture andc-axis orientation of the 2083 m ice core at Vostok Station, covering more than 150kyear, reveal the existence of strong anisotropics. Changes in crystal size with depth are compatible with the growth of grains driven by the free energy of grain boundaries. A smaller growth rate appears to be associated with cold periods. A gradual increase in the horizontal elongation of grains was observed between 350 and 680 m. But, the mean value of the coefficient of the linear dimensional orientation of grains does not change below 700 m.Thec-axis orientation of ice grains tends to orientate perpendicular to the direction of the elongation of grains, forming a vertical girdle pattern. This characteristic fabric has been interpreted as resulting from the gradual rotation of grains by basal glide under uniaxial longitudinal tension. The rotation of grains was calculated with respect to the total strain, simulating the formation of the girdle fabric pattern. The fabric-enhancement factor was calculated at various depths. It appears that Vostok ice hardens gradually with depth when considering the transverse convergent flow. No significant variation of the enhancement factor was observed with changes in climate and impurity content.

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Ice crystal c-axis orientation and mean grain size measurements from the Dome Summit South ice core, Law Dome, East Antarctica

10.5194/essd-2015-45 ◽

2016 ◽

Author(s):

A. Treverrow ◽

J. Li ◽

T. H. Jacka

Keyword(s):

Thin Section ◽

Ice Core ◽

Median Number ◽

East Antarctica ◽

Polar Coordinates ◽

Depth Information ◽

Data Set ◽

Axis Orientation ◽

Orientation Data ◽

Thin Sections

Abstract. We present measurements of crystal c-axis orientations and mean grain area from the Dome Summit South (DSS) ice core drilled on Law Dome, East Antarctica. These data are from 185 individual thin sections obtained between a depth of 117 m below the surface and the bottom of the DSS core at a depth of 1196 m. The median number of c-axis orientations recorded in each thin section was 100, with values ranging from 5 through to 111 orientations. The data from all 185 thin sections are provided in a single comma separated value (csv) formatted file which contains the c-axis orientations in polar coordinates, depth information for each core section from which the data were obtained, the mean grain area calculated for each thin section and other data related to the drilling site. The data set is also available as a MATLAB™ structure array. Additionally, the c-axis orientation data from each thin of the 185 thin sections are summarised graphically in figures containing a Schmidt diagram, histogram of c-axis colatitudes and rose plot of c-axis azimuths. All of these data are referenced by doi:10.4225/15/5669050CC1B3B and are available free of charge at https://data.antarctica.gov.au.

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Crystalline Texture of the 2083 m Ice Core at Vostok Station, Antarctica

Journal of Glaciology ◽

10.3189/s0022143000009321 ◽

1989 ◽

Vol 35 (121) ◽

pp. 392-398 ◽

Cited By ~ 2

Author(s):

V.Ya. Lipenkov ◽

N.I. Barkov ◽

P. Duval ◽

P. Pimienta

Keyword(s):

Enhancement Factor ◽

Crystal Size ◽

Gradual Increase ◽

Ice Core ◽

Impurity Content ◽

Mean Value ◽

Axis Orientation ◽

Vostok Station ◽

The Mean ◽

Convergent Flow

AbstractCrystalline texture and c-axis orientation of the 2083 m ice core at Vostok Station, covering more than 150kyear, reveal the existence of strong anisotropics. Changes in crystal size with depth are compatible with the growth of grains driven by the free energy of grain boundaries. A smaller growth rate appears to be associated with cold periods. A gradual increase in the horizontal elongation of grains was observed between 350 and 680 m. But, the mean value of the coefficient of the linear dimensional orientation of grains does not change below 700 m.The c-axis orientation of ice grains tends to orientate perpendicular to the direction of the elongation of grains, forming a vertical girdle pattern. This characteristic fabric has been interpreted as resulting from the gradual rotation of grains by basal glide under uniaxial longitudinal tension. The rotation of grains was calculated with respect to the total strain, simulating the formation of the girdle fabric pattern. The fabric-enhancement factor was calculated at various depths. It appears that Vostok ice hardens gradually with depth when considering the transverse convergent flow. No significant variation of the enhancement factor was observed with changes in climate and impurity content.

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Complete determination of ice crystal orientation using Laue X-ray diffraction method

Journal of Glaciology ◽

10.3189/002214311795306754 ◽

2011 ◽

Vol 57 (201) ◽

pp. 103-110 ◽

Cited By ~ 13

Author(s):

Atsushi Miyamoto ◽

Ilka Weikusat ◽

Takeo Hondoh

Keyword(s):

Crystal Orientation ◽

Ice Core ◽

Ice Sheets ◽

Diffraction Method ◽

Ice Cores ◽

Ice Crystals ◽

Ice Crystal ◽

X Ray Diffraction ◽

Axis Orientation ◽

X Ray

AbstractIce crystal orientation fabric data from ice cores contain important information concerning the internal structure and the flow behaviour of ice sheets. When ice cores are recovered from the Antarctic and Greenland ice sheets, crystal orientation measurements are performed immediately to obtain fundamental physical property information. In the past, we have measured the c-axis orientation of ice crystals by a manual optical method using a universal stage. This method is very time-consuming, involving tedious work in a cold laboratory. Recently, automated systems have been developed that enable measurement of c-axis orientation, grain size and other microstructures. However, in order to detect the full crystal orientation of an ice crystal, we also need information on its a-axis orientation. A variety of other crystal orientation measurement methods have previously been discussed, but some shortcomings for ice-core studies cannot be neglected. We have developed a crystal-orientation analysing device using the Laue X-ray diffraction method. As this device can measure the orientations of all crystal axes with high accuracy, it is possible to obtain new microstructure information on natural ice crystals. For the first time, we are able to quantify very low subgrain misorientation angles in polar ice-core samples, allowing us to investigate micro-deformation features of individual crystals. Here we discuss the analysis process, which is customized to measure standard ice thin sections, and show preliminary results.

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Seasonal variability in ice crystal properties at NorthGRIP: a case study around 301 m depth

Annals of Glaciology ◽

10.3189/172756403781815582 ◽

2003 ◽

Vol 37 ◽

pp. 119-122 ◽

Cited By ~ 6

Author(s):

Anders Svensson ◽

Pauli Baadsager ◽

Asbjørn Persson ◽

Christine Schøtt Hvidberg ◽

Marie-Louise Siggaard-Andersen

Keyword(s):

Seasonal Variability ◽

Ice Core ◽

Ice Crystal ◽

Axis Orientation ◽

Annual Cycles ◽

Average Value ◽

The North ◽

Chemical Impurities ◽

Crystal Properties

AbstractThe aim of this case study is to quantify the seasonal variability in crystal properties and to discuss the reason for the variability. A continuous 1.10 m long vertical thin-section profile covering approximately five annual cycles has been obtained from the North Greenland Icecore Project (NorthGRIP) ice core at around 301 m depth. The crystal outline and the c-axis orientation of more than 13000 crystals in the profile have been measured on a new Australian automated ice-crystal analyzer. In 2.5 cm resolution we observe a strong seasonal variability in crystal areas of >30%deviation from the average value of 6.7 mm2. Each year, a band of smaller crystals is observed in ice deposited during spring. The area distribution function is found to be close to a lognormal distribution. The crystal areas are compared to the concentration of chemical impurities in the ice; at a 5 cm resolution, the best correlation is found with the concentration of Ca2+. Our results show no seasonal variability of the average c-axis orientation of ice crystals.

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Properties of GRIP ice crystals from around Greenland interstadial 3

Annals of Glaciology ◽

10.3189/172756402781816834 ◽

2002 ◽

Vol 35 ◽

pp. 531-537 ◽

Cited By ~ 4

Author(s):

Kaj M. Hansen ◽

Anders Svensson ◽

Yun Wang ◽

Jørgen Peder Steffensen

Keyword(s):

Ice Core ◽

Ice Crystal ◽

Vertical Orientation ◽

Thin Sections ◽

Area Distribution ◽

Before And After ◽

Manual Methods ◽

Log Normal ◽

Log Normal Distribution ◽

Automated Methods

AbstractIce-crystal textures (sizes and shapes) and fabrics (c-axis orientations) have been determined in 3 m of vertical thin sections from the Greenland Icecore Project (GRIP) ice core. the samples cover ice from before, during and after Greenland interstadial 3 (IS3) that occurred about 25 kyr BP. the texture of 60 000 crystals has been obtained from stacked digital images by semi-automated methods, and the fabric of 5000 selected crystals has been measured on the Automatic Ice Fabric Analyzer at the Alfred Wegener Institute, Bremerhaven. the area distribution function of the crystals is close to a log normal distribution, and the mean area is found to be 3.36 mm2 in ice from IS3, and 3.04 mm2 in ice from colder periods before and after IS3. the overall c-axis orientations show a strong single maximum with vertical orientation. These results agree well with earlier GRIP fabric studies obtained by manual methods. from comparisons of crystal areas with the concentrations of dust, Ca2+, SO42–, Cl– and NO3– in the ice we determine that NO3– correlates best with crystal areas. Crystals within clearly visible cloudy bands are significantly smaller than the surrounding crystals, and their c-axis orientations are less well confined than the average.

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Shallow-ice microstructure at Dome Concordia, Antarctica

Annals of Glaciology ◽

10.3189/172756400781820813 ◽

2000 ◽

Vol 30 ◽

pp. 8-12 ◽

Cited By ~ 11

Author(s):

Laurent Arnaud ◽

Jérôme Weiss ◽

Michel Gay ◽

Paul Duval

Keyword(s):

Crystal Size ◽

Accumulation Rate ◽

Ice Core ◽

Processing Technique ◽

Image Processing Technique ◽

Size Distributions ◽

Thin Sections ◽

Crystal Size Distributions ◽

Size Profile ◽

The Mean

AbstractThe shallow-ice microstructure at Dome Concordia, Antarctica, has been studied between 100 m and 580 m. An original digital-image-processing technique has been specially developed to extract ice microstructure (grain boundaries) from thin sections prepared during the two first scientific EPICA field seasons (1997/98 and 1998/99). Using this, not only the mean crystal size, but also crystal-size distributions and shape anisotropy were determined. The mean crystal-size profile as well as crystal-size distributions reveal normal grain growth up to 430 m. Between 430 m and 500 m, a marked decrease of crystal size is observed and compared with a similar trend obtained in the "old" Dome C ice core formerly associated with the Holocene/Last Glacial transition (Duval and Lorius, 1980). This seems to indicate a slightly lower accumulation rate (by <10%) at Dome C. The shapes of the crystal-size distributions, though very similar, do evolve with depth and seem to be sensitive to climatic changes. An increasing flattening of crystal shape is observed with depth. This allowed estimation of the vertical strain rate in the shallow part of the ice sheet.

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