• Korean Journal of Remote Sensing
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• v.37 no.1
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• pp.1-11
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• 2021

This study measures the change of ice flow velocity of David Glacier, one of the fast-moving glaciers in East Antarctica that drains through Drygalski Ice Tongue. In order to effectively observe the rapid flow velocity, we applied the offset tracking technique to Sentinel-1A SAR images obtained from 2016 to 2020 with 36-day temporal baseline. The resulting velocity maps were averaged and the two relatively fast points (A1 and A2) were selected for further time-series analysis. The flow velocity increased during the Antarctic summer (around December to March) over the four years' observation period probably due to the ice surface melting and reduced friction on the ice bottom. Bedmap2 showed that the fast flow velocities at A1 and A2 are associated with a sharp decrease in the ice surface and bottom elevation so that ice volumetric cross-section narrows down and the crevasses are being created on the ice surface. The local maxima in standard deviation of ice velocity, S1 and S2, showed random temporal fluctuation due to the rotational ice swirls causing error in offset tracking method. It is suggested that more robust offset tracking method is necessary to incorporate rotational motion.

• Korean Journal of Remote Sensing
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• v.35 no.6_1
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• pp.933-944
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• 2019

This study analyzes the tide deformation of land boundary regions on the east (Region A) and west (Region B) sides of the Ross Ice Shelf in Antarctica using Double-Differential Interferometric Synthetic Aperture Radar (DDInSAR). A total of seven Sentinel-1A SAR images acquired in 2015-2016 were used to estimate the accuracy of tide prediction model and Young's modulus of ice shelf. First, we compared the Ross Sea Height-based Tidal Inverse (Ross_Inv) model, which is a representative tide prediction model for the Antarctic Ross Sea, with the tide deformation of the ice shelf extracted from the DDInSAR image. The accuracy was analyzed as 3.86 cm in the east region of Ross Ice Shelf and it was confirmed that the inverse barometric pressure effect must be corrected in the tide model. However, in the east, it is confirmed that the tide model may be inaccurate because a large error occurs even after correction of the atmospheric effect. In addition, the Young's modulus of the ice was calculated on the basis of the one-dimensional elastic beam model showing the correlation between the width of the hinge zone where the tide strain occurs and the ice thickness. For this purpose, the grounding line is defined as the line where the displacement caused by the tide appears in the DDInSAR image, and the hinge line is defined as the line to have the local maximum/minimum deformation, and the hinge zone as the area between the two lines. According to the one-dimensional elastic beam model assuming a semi-infinite plane, the width of the hinge region is directly proportional to the 0.75 power of the ice thickness. The width of the hinge zone was measured in the area where the ground line and the hinge line were close to the straight line shown in DDInSAR. The linear regression analysis with the 0.75 power of BEDMAP2 ice thickness estimated the Young's modulus of 1.77±0.73 GPa in the east and west of the Ross Ice Shelf. In this way, more accurate Young's modulus can be estimated by accumulating Sentinel-1 images in the future.

• Korean Journal of Remote Sensing
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• v.34 no.3
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• pp.545-552
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• 2018

Grounding line is used as evidence of the mass balance showing the vulnerability of Antarctic glaciers and ice shelves. In this research, we utilized a high resolution digital elevation model of glacier surface derived by recently launched satellites to estimate the position of grounding line of Campbell Glacier in East Antarctica. TanDEM-X and TerraSAR-X data in single-pass interferometry mode were acquired on June 21, 2013 and September 10, 2016 and CryoSat-2 radar altimeter data were acquired within 15 days from the acquisition date of TanDEM-X. The datasets were combined to generate a high resolution digital elevation model which was used to estimate the grounding line position. During the 3 years of observation, there weren't any significant changes in grounding line position. Since the average density of ice used in estimating grounding line is not accurately known, the variations of the grounding line was analyzed with respect to the density of ice. There was a spatial difference from the grounding line estimated by DDInSAR whereas the estimated grounding line using the characteristics of the surface of the optical satellite images agreed well when the ice column density was about $880kg/m^3$. Although the reliability of the results depends on the vertical accuracy of the bathymetry in this study, the hydrostatic ice thickness has greater influence on the grounding line estimation.