ORCID Profile
0000-0003-4444-7851
Current Organisation
Korea Polar Research Institute
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Publisher: Elsevier BV
Date: 2013
DOI: 10.1093/BJA/AES446
Publisher: Elsevier BV
Date: 09-2020
Publisher: Frontiers Media SA
Date: 31-05-2022
DOI: 10.3389/FEART.2022.828313
Abstract: We use high resolution, ground-based observations of ice displacement to investigate ice deformation across the floating left-lateral shear margin of Priestley Glacier, Terra Nova Bay, Antarctica. Bare ice conditions allow us to fix survey marks directly to the glacier surface. A combination of continuous positioning of a local reference mark, and repeat positioning of a network of 33 stakes installed across a 2 km width of the shear margin are used to quantify shear strain rates and the ice response to tidal forcing over an 18-day period. Along-flow velocity observed at a continuous Global Navigation Satellite Systems (GNSS) station within the network varies by up to ∼30% of the mean speed (±28 m a −1 ) over diurnal tidal cycles, with faster flow during the falling tide and slower flow during the rising tide. Long-term deformation in the margin approximates simple shear with a small component of flow-parallel shortening. At shorter timescales, precise optical techniques allow high-resolution observations of across-flow bending in response to the ocean tide, including across-flow strains on the order of 10 –5 . An elastodynamic model informed by the field observations is used to simulate the across-flow motion and deformation. Flexure is concentrated in the shear margin, such that a non-homogeneous elastic modulus is implied to best account for the combined observations. The combined pattern of ice displacement and ice strain also depends on the extent of coupling between the ice and valley sidewall. These conclusions suggest that investigations of elastic properties made using vertical ice motion, but neglecting horizontal displacement and surface strain, will lead to incorrect conclusions about the elastic properties of ice and potentially over-simplified assumptions about the sidewall boundary condition.
Publisher: American Geophysical Union (AGU)
Date: 02-2015
DOI: 10.1002/2014JB011528
Publisher: Wiley
Date: 19-11-2012
DOI: 10.1111/IAR.12003
Publisher: Elsevier BV
Date: 10-2018
Publisher: Copernicus GmbH
Date: 24-08-2022
Abstract: Abstract. Crystallographic preferred orientations (CPOs) are particularly important in controlling the mechanical properties of glacial shear margins. Logistical and safety considerations often make direct s ling of shear margins difficult, and geophysical measurements are commonly used to constrain the CPOs. We present here the first direct comparison of seismic and ultrasonic data with measured CPOs in a polar shear margin. The measured CPO from ice s les from a 58 m deep borehole in the left lateral shear margin of the Priestley Glacier, Antarctica, is dominated by horizontal c axes aligned sub-perpendicularly to flow. A vertical-seismic-profile experiment with hammer shots up to 50 m away from the borehole, in four different azimuthal directions, shows velocity anisotropy of both P waves and S waves. Matching P-wave data to the anisotropy corresponding to CPO models defined by horizontally aligned c axes gives two possible solutions for the c-axis azimuth, one of which matches the c-axis measurements. If both P-wave and S-wave data are used, there is one best fit for the azimuth and intensity of c-axis alignment that matches the measurements well. Azimuthal P-wave and S-wave ultrasonic data recorded in the laboratory on the ice core show clear anisotropy of P-wave and S-wave velocities in the horizontal plane that match that predicted from the CPO of the s les. With quality data, azimuthal increments of 30∘ or less will constrain well the orientation and intensity of c-axis alignment. Our experiments provide a good framework for planning seismic surveys aimed at constraining the anisotropy of shear margins.
No related grants have been discovered for Daeyeong Kim.