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Jean-louis Tison - One of the best experts on this subject based on the ideXlab platform.
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High-resolution distributed vertical strain and velocity from repeat Borehole Logging by optical televiewer: Derwael Ice Rise, Antarctica
Journal of Glaciology, 2020Co-Authors: Bryn Hubbard, Morgane Philippe, Frank Pattyn, Reinhard Drews, Tun Jan Young, Carine Bruyninx, Nicolas Bergeot, Karen Fjosne, Jean-louis TisonAbstract:AbstractDirect measurements of spatially distributed vertical strain within ice masses are scientifically valuable but challenging to acquire. We use manual marker tracking and automatic cross correlation between two repeat optical televiewer (OPTV) images of an ~100 m-long Borehole at Derwael Ice Rise (DIR), Antarctica, to reconstruct discretised, vertical strain rate and velocity at millimetre resolution. The resulting profiles decay with depth, from −0.07 a−1 at the surface to ~−0.002 a−1 towards the base in strain and from −1.3 m a−1 at the surface to ~−0.5 m a−1 towards the base in velocity. Both profiles also show substantial local variability. Three coffee-can markers installed at different depths into adjacent Boreholes record consistent strain rates and velocities, although averaged over longer depth ranges and subject to greater uncertainty. Measured strain-rate profiles generally compare closely with output from a 2-D ice-flow model, while the former additionally reveal substantial high-resolution variability. We conclude that repeat OPTV Borehole Logging represents an effective means of measuring distributed vertical strain at millimetre scale, revealing high-resolution variability along the uppermost ~100 m of DIR, Antarctica.
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Ice shelf density reconstructed from optical televiewer Borehole Logging
Geophysical Research Letters, 2013Co-Authors: Bryn Hubbard, Morgane Philippe, Billie Heene, Terry Malone, Frank Pattyn, Jean-louis Tison, Johannes FreitagAbstract:Optical televiewer luminosity logs are compared with densities measured gravimetrically on 520 snow, firn, and ice samples from two locations of similar annual temperature (~ −14°C) and contrasting accumulation rates (0.23 and 0.43 m water equivalent per year) on the Roi Baudouin Ice Shelf, Antarctica. At the scale of ≥10−1 m, an inverse exponential relationship (R2 = 0.96) is recorded between density and luminosity, indicating (i) that optical televiewing luminosity provides an effective proxy for density at such ice shelves and (ii) that densities may be reconstructed from Boreholes drilled elsewhere by hot water without the need for core material. Our analysis also suggests that this relationship may hold for newly formed ice as well as for snow and firn. At the scale of ≤10−1 m, both luminosity and density show similar patterns, but precise correlation is confounded by detailed differences between the two records.
Bryn Hubbard - One of the best experts on this subject based on the ideXlab platform.
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High-resolution distributed vertical strain and velocity from repeat Borehole Logging by optical televiewer: Derwael Ice Rise, Antarctica
Journal of Glaciology, 2020Co-Authors: Bryn Hubbard, Morgane Philippe, Frank Pattyn, Reinhard Drews, Tun Jan Young, Carine Bruyninx, Nicolas Bergeot, Karen Fjosne, Jean-louis TisonAbstract:AbstractDirect measurements of spatially distributed vertical strain within ice masses are scientifically valuable but challenging to acquire. We use manual marker tracking and automatic cross correlation between two repeat optical televiewer (OPTV) images of an ~100 m-long Borehole at Derwael Ice Rise (DIR), Antarctica, to reconstruct discretised, vertical strain rate and velocity at millimetre resolution. The resulting profiles decay with depth, from −0.07 a−1 at the surface to ~−0.002 a−1 towards the base in strain and from −1.3 m a−1 at the surface to ~−0.5 m a−1 towards the base in velocity. Both profiles also show substantial local variability. Three coffee-can markers installed at different depths into adjacent Boreholes record consistent strain rates and velocities, although averaged over longer depth ranges and subject to greater uncertainty. Measured strain-rate profiles generally compare closely with output from a 2-D ice-flow model, while the former additionally reveal substantial high-resolution variability. We conclude that repeat OPTV Borehole Logging represents an effective means of measuring distributed vertical strain at millimetre scale, revealing high-resolution variability along the uppermost ~100 m of DIR, Antarctica.
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Ice shelf density reconstructed from optical televiewer Borehole Logging
Geophysical Research Letters, 2013Co-Authors: Bryn Hubbard, Morgane Philippe, Billie Heene, Terry Malone, Frank Pattyn, Jean-louis Tison, Johannes FreitagAbstract:Optical televiewer luminosity logs are compared with densities measured gravimetrically on 520 snow, firn, and ice samples from two locations of similar annual temperature (~ −14°C) and contrasting accumulation rates (0.23 and 0.43 m water equivalent per year) on the Roi Baudouin Ice Shelf, Antarctica. At the scale of ≥10−1 m, an inverse exponential relationship (R2 = 0.96) is recorded between density and luminosity, indicating (i) that optical televiewing luminosity provides an effective proxy for density at such ice shelves and (ii) that densities may be reconstructed from Boreholes drilled elsewhere by hot water without the need for core material. Our analysis also suggests that this relationship may hold for newly formed ice as well as for snow and firn. At the scale of ≤10−1 m, both luminosity and density show similar patterns, but precise correlation is confounded by detailed differences between the two records.
Frank Pattyn - One of the best experts on this subject based on the ideXlab platform.
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High-resolution distributed vertical strain and velocity from repeat Borehole Logging by optical televiewer: Derwael Ice Rise, Antarctica
Journal of Glaciology, 2020Co-Authors: Bryn Hubbard, Morgane Philippe, Frank Pattyn, Reinhard Drews, Tun Jan Young, Carine Bruyninx, Nicolas Bergeot, Karen Fjosne, Jean-louis TisonAbstract:AbstractDirect measurements of spatially distributed vertical strain within ice masses are scientifically valuable but challenging to acquire. We use manual marker tracking and automatic cross correlation between two repeat optical televiewer (OPTV) images of an ~100 m-long Borehole at Derwael Ice Rise (DIR), Antarctica, to reconstruct discretised, vertical strain rate and velocity at millimetre resolution. The resulting profiles decay with depth, from −0.07 a−1 at the surface to ~−0.002 a−1 towards the base in strain and from −1.3 m a−1 at the surface to ~−0.5 m a−1 towards the base in velocity. Both profiles also show substantial local variability. Three coffee-can markers installed at different depths into adjacent Boreholes record consistent strain rates and velocities, although averaged over longer depth ranges and subject to greater uncertainty. Measured strain-rate profiles generally compare closely with output from a 2-D ice-flow model, while the former additionally reveal substantial high-resolution variability. We conclude that repeat OPTV Borehole Logging represents an effective means of measuring distributed vertical strain at millimetre scale, revealing high-resolution variability along the uppermost ~100 m of DIR, Antarctica.
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Ice shelf density reconstructed from optical televiewer Borehole Logging
Geophysical Research Letters, 2013Co-Authors: Bryn Hubbard, Morgane Philippe, Billie Heene, Terry Malone, Frank Pattyn, Jean-louis Tison, Johannes FreitagAbstract:Optical televiewer luminosity logs are compared with densities measured gravimetrically on 520 snow, firn, and ice samples from two locations of similar annual temperature (~ −14°C) and contrasting accumulation rates (0.23 and 0.43 m water equivalent per year) on the Roi Baudouin Ice Shelf, Antarctica. At the scale of ≥10−1 m, an inverse exponential relationship (R2 = 0.96) is recorded between density and luminosity, indicating (i) that optical televiewing luminosity provides an effective proxy for density at such ice shelves and (ii) that densities may be reconstructed from Boreholes drilled elsewhere by hot water without the need for core material. Our analysis also suggests that this relationship may hold for newly formed ice as well as for snow and firn. At the scale of ≤10−1 m, both luminosity and density show similar patterns, but precise correlation is confounded by detailed differences between the two records.
Morgane Philippe - One of the best experts on this subject based on the ideXlab platform.
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High-resolution distributed vertical strain and velocity from repeat Borehole Logging by optical televiewer: Derwael Ice Rise, Antarctica
Journal of Glaciology, 2020Co-Authors: Bryn Hubbard, Morgane Philippe, Frank Pattyn, Reinhard Drews, Tun Jan Young, Carine Bruyninx, Nicolas Bergeot, Karen Fjosne, Jean-louis TisonAbstract:AbstractDirect measurements of spatially distributed vertical strain within ice masses are scientifically valuable but challenging to acquire. We use manual marker tracking and automatic cross correlation between two repeat optical televiewer (OPTV) images of an ~100 m-long Borehole at Derwael Ice Rise (DIR), Antarctica, to reconstruct discretised, vertical strain rate and velocity at millimetre resolution. The resulting profiles decay with depth, from −0.07 a−1 at the surface to ~−0.002 a−1 towards the base in strain and from −1.3 m a−1 at the surface to ~−0.5 m a−1 towards the base in velocity. Both profiles also show substantial local variability. Three coffee-can markers installed at different depths into adjacent Boreholes record consistent strain rates and velocities, although averaged over longer depth ranges and subject to greater uncertainty. Measured strain-rate profiles generally compare closely with output from a 2-D ice-flow model, while the former additionally reveal substantial high-resolution variability. We conclude that repeat OPTV Borehole Logging represents an effective means of measuring distributed vertical strain at millimetre scale, revealing high-resolution variability along the uppermost ~100 m of DIR, Antarctica.
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Ice shelf density reconstructed from optical televiewer Borehole Logging
Geophysical Research Letters, 2013Co-Authors: Bryn Hubbard, Morgane Philippe, Billie Heene, Terry Malone, Frank Pattyn, Jean-louis Tison, Johannes FreitagAbstract:Optical televiewer luminosity logs are compared with densities measured gravimetrically on 520 snow, firn, and ice samples from two locations of similar annual temperature (~ −14°C) and contrasting accumulation rates (0.23 and 0.43 m water equivalent per year) on the Roi Baudouin Ice Shelf, Antarctica. At the scale of ≥10−1 m, an inverse exponential relationship (R2 = 0.96) is recorded between density and luminosity, indicating (i) that optical televiewing luminosity provides an effective proxy for density at such ice shelves and (ii) that densities may be reconstructed from Boreholes drilled elsewhere by hot water without the need for core material. Our analysis also suggests that this relationship may hold for newly formed ice as well as for snow and firn. At the scale of ≤10−1 m, both luminosity and density show similar patterns, but precise correlation is confounded by detailed differences between the two records.
Freudenthal Tim - One of the best experts on this subject based on the ideXlab platform.
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Acoustic Borehole Logging of MeBo sediment core GeoB23730-1
PANGAEA, 2020Co-Authors: Freudenthal TimAbstract:Logging was performed with the sea floor drill rig MARUM-MeBo70 in a Borehole drilled with a 103 mm diameter bit. The 1343 Slimhole Memory Acoustic instrument developed by ANTARES Datasystems GmbH was used. The probe consists of 1 transmitter and two receivers in 0.9 and 1.0 m distance, respectively. Sound velocity in the formation was calculated from the time difference of signal arrival at both receivers using the waveform processing module of the Antares software GeoBase 6.22. The vertical resolution is about 10 cm. The accuracy is better than 10 m/s
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Acoustic Borehole Logging of MeBo sediment core GeoB23711-3
PANGAEA, 2020Co-Authors: Freudenthal TimAbstract:Logging was performed with the sea floor drill rig MARUM-MeBo70 in a Borehole drilled with a 103 mm diameter bit. The 1343 Slimhole Memory Acoustic instrument developed by ANTARES Datasystems GmbH was used. The probe consists of 1 transmitter and two receivers in 0.9 and 1.0 m distance, respectively. Sound velocity in the formation was calculated from the time difference of signal arrival at both receivers using the waveform processing module of the Antares software GeoBase 6.22. The vertical resolution is about 10 cm. The accuracy is better than 10 m/s
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Magnetic susceptibility Borehole Logging of MeBo sediment core GeoB23702-5
PANGAEA, 2020Co-Authors: Freudenthal TimAbstract:Logging was performed with the sea floor drill rig MARUM-MeBo70 in a Borehole drilled with a 103 mm diameter bit. The 1188 Slimhole Memory Magnetic Susceptibility instrument developed by ANTARES Datasystems GmbH was used. Three coils are used for measuring the apparent magnetic susceptibility with an alternating magnetic field tuned to resonate at 1 kHz. The accuracy is within 5 %. The vertical resolution is about 20 cm. The probe was deployed in the memory mode with the Logging string being inserted into the drill string and the sensors located below the drill bit. The measurement was conducted as upcast while the drill string was pulled back to the seafloor out of the Borehole. The trip out speed was about 1 cm/s and the Logging frequency was 0.5 Hz. Data Processing was conducted using the Antares software GeoBase 6.22.
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Magnetic Susceptibility Borehole Logging of MeBo sediment core Geob23725-2
PANGAEA, 2020Co-Authors: Freudenthal TimAbstract:Logging was performed with the sea floor drill rig MARUM-MeBo70 in a Borehole drilled with a 103 mm diameter bit. The 1188 Slimhole Memory Magnetic Susceptibility instrument developed by ANTARES Datasystems GmbH was used. Three coils are used for measuring the apparent magnetic susceptibility with an alternating magnetic field tuned to resonate at 1 kHz. The accuracy is within 5 %. The vertical resolution is about 20 cm. The probe was deployed in the memory mode with the Logging string being inserted into the drill string and the sensors located below the drill bit. The measurement was conducted as upcast while the drill string was pulled back to the seafloor out of the Borehole. The trip out speed was about 1 cm/s and the Logging frequency was 0.5 Hz. Data Processing was conducted using the Antares software GeoBase 6.22.
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Spectrum gamma ray Borehole Logging of MeBo sediment core GeoB23711-5
PANGAEA, 2020Co-Authors: Freudenthal TimAbstract:Logging was performed with the sea floor drill rig MARUM-MeBo70 in a Borehole drilled with a 103 mm diameter bit. The 1460 Slimhole Memory SGR instrument developed by ANTARES Datasystems GmbH was used. A CsI(Na) crystal with outer diameter of 37 mm and 250 mm length is used as detector. The probe provides Natural Gamma Ray counts and analyses the spectrum for the concentrations of the natural gamma ray emitters potassium, thorium and uranium with an accuracy of about 10%. The probe was deployed in the memory mode with the Logging string being inserted into the drill string. The measurement was conducted as upcast hooking up the Logging string with a wire inside the drill string. Wire speed was about 2 cm/s and the Logging frequency was 0.5 Hz. Data Processing including the correction for bore hole diameter and signal attenuation by the drill string was conducted using the Antares software GeoBase 6.22.