Tide-corrected flow velocity and mass balance of Campbell Glacier Tongue, East Antarctica, derived from interferometric SAR

Han, Hyangsun; Lee, Hoonyol

doi:10.1016/j.rse.2015.01.014

Cited by 19 publications

(10 citation statements)

References 49 publications

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“…where ∆e is the change in freeboard, ∆δ is the change in snow depth and firn densification, ρ i is the ice density, ρ w is the sea water density, and ρ s is the snow/firn density, respectively [25,34]. The density of ice and sea water has been assumed as 917 kg/m 3 and 1027-1030 kg/m 3 , respectively, in many studies on thickness estimation of the Antarctic ice shelves from the freeboard measurements by satellite altimetry [25,[35][36][37][38]. We used 917 kg/m 3 and 1027 kg/m 3 as the density of ice and water.…”

Section: Methodsmentioning

confidence: 99%

Changes in a Giant Iceberg Created from the Collapse of the Larsen C Ice Shelf, Antarctic Peninsula, Derived from Sentinel-1 and CryoSat-2 Data

et al. 2019

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The giant tabular iceberg A68 broke away from the Larsen C Ice Shelf, Antarctic Peninsula, in July 2017. The evolution of A68 would have been affected by both the Larsen C Ice Shelf, the surrounding sea ice, and the nearby shallow seafloor. In this study, we analyze the initial evolution of iceberg A68A—the largest originating from A68—in terms of changes in its area, drift speed, rotation, and freeboard using Sentinel-1 synthetic aperture radar (SAR) images and CryoSat-2 SAR/Interferometric Radar Altimeter observations. The area of iceberg A68A sharply decreased in mid-August 2017 and mid-May 2018 via large calving events. In September 2018, its surface area increased, possibly due to its longitudinal stretching by melting of surrounding sea ice. The decrease in the area of A68A was only 2% over 1.5 years. A68A was relatively stationary until mid-July 2018, while it was surrounded by the Larsen C Ice Shelf front and a high concentration of sea ice, and when its movement was interrupted by the shallow seabed. The iceberg passed through a bay-shaped region in front of the Larsen C Ice Shelf after July 2018, showing a nearly circular motion with higher speed and greater rotation. Drift was mainly inherited from its rotation, because it was still located near the Bawden Ice Rise and could not pass through by the shallow seabed. The freeboard of iceberg A68A decreased at an average rate of −0.80 ± 0.29 m/year during February–November 2018, which could have been due to basal melting by warm seawater in the Antarctic summer and increasing relative velocity of iceberg and ocean currents in the winter of that year. The freeboard of the iceberg measured using CryoSat-2 could represent the returned signal from the snow surface on the iceberg. Based on this, the average rate of thickness change was estimated at −12.89 ± 3.34 m/year during the study period considering an average rate of snow accumulation of 0.82 ± 0.06 m/year predicted by reanalysis data from the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2). The results of this study reveal the initial evolution mechanism of iceberg A68A, which cannot yet drift freely due to the surrounding terrain and sea ice.

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Section: Methodsmentioning

confidence: 99%

Changes in a Giant Iceberg Created from the Collapse of the Larsen C Ice Shelf, Antarctic Peninsula, Derived from Sentinel-1 and CryoSat-2 Data

et al. 2019

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“…Two-pass interferometry (InSAR) can be used to determine surface motion with sub-centimetre accuracy over vast remote areas. Therefore, InSAR has been applied to measure Antarctic-wide ice velocity (Mouginot et al, 2019) and to observe tidal strain of landfast sea ice (Han and Lee, 2018). In grounding-zone areas, where an ice sheet comes into contact with the ocean for the first time and forms floating glaciers and ice shelves, InSAR has become the state-of-the-art practice for measuring the flux divergence of ice-flow velocity (Mouginot et al, 2014;Han and Lee, 2015) and thus the mass balance of many ice shelves around Antarctica (Rignot et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Differential interferometric synthetic aperture radar for tide modelling in Antarctic ice-shelf grounding zones

2019

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Abstract. Differential interferometric synthetic aperture radar (DInSAR) is an essential tool for detecting ice-sheet motion near Antarctica's oceanic margin. These space-borne measurements have been used extensively in the past to map the location and retreat of ice-shelf grounding lines as an indicator for the onset of marine ice-sheet instability and to calculate the mass balance of ice sheets and individual catchments. The main difficulty in interpreting DInSAR is that images originate from a combination of several SAR images and do not indicate instantaneous ice deflection at the times of satellite data acquisitions. Here, we combine the sub-centimetre accuracy and spatial benefits of DInSAR with the temporal benefits of tide models to infer the spatio-temporal dynamics of ice–ocean interaction during the times of satellite overpasses. We demonstrate the potential of this synergy with TerraSAR-X data from the almost-stagnant southern McMurdo Ice Shelf (SMIS). We then validate our algorithm with GPS data from the fast-flowing Darwin Glacier, draining the Antarctic Plateau through the Transantarctic Mountains into the Ross Sea. We are able to reconstruct DInSAR-derived vertical displacements to 7 mm mean absolute residual error and generally improve traditional tide-model output by up to 39 % from 10.8 to 6.7 cm RMSE against GPS data from areas where ice is in local hydrostatic equilibrium with the ocean and by up to 74 % from 21.4 to 5.6 cm RMSE against GPS data in feature-rich coastal areas where tide models have not been applicable before. Numerical modelling then reveals Young's modulus of E=1.0±0.56 GPa and an ice viscosity of ν=10±3.65 TPa s when finite-element simulations of tidal flexure are matched to 16 d of tiltmeter data, supporting the hypothesis that strain-dependent anisotropy may significantly decrease effective viscosity compared to isotropic polycrystalline ice on large spatial scales. Applications of our method include the following: refining coarsely gridded tide models to resolve small-scale features at the spatial resolution and vertical accuracy of SAR imagery, separating elastic and viscoelastic contributions in the satellite-derived flexure measurement, and gaining information about large-scale ice heterogeneity in Antarctic ice-shelf grounding zones, the missing key to improving current ice-sheet flow models. The reconstruction of the individual components forming DInSAR images has the potential to become a standard remote-sensing method in polar tide modelling. Unlocking the algorithm's full potential to answer multi-disciplinary research questions is desired and demands collaboration within the scientific community.

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“…where an ice-sheet comes in contact with the ocean for the first time and forms floating glaciers and ice-shelves, InSAR has become the state-of-the-art practice to measure the flux divergence of ice-flow velocity (Mouginot et al, 2014;Han and Lee, 2015) and thus the mass balance of many ice-shelves around Antarctica (Rignot et al, 2013). InSAR can also be used to identify vertical deflection due to ocean tides.…”

Section: Introductionmentioning

confidence: 99%

Differential InSAR for tide modelling in Antarctic ice-shelf grounding zones

Wild

Marsh

Rack

2019

Preprint

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Abstract. Differential interferometric synthetic aperture radar (DInSAR) is an essential tool for detecting ice-sheet motion near Antarctica's oceanic margin. These space-borne measurements have been used extensively in the past to map the location and retreat of ice-shelf grounding lines as an indicator for the onset of marine ice-sheet instability and to calculate the mass balance of ice-sheets and individual catchments. The main difficulty in interpreting DInSAR is that images originate from a combination of several SAR images and do not indicate instantaneous ice deflection at the time of satellite data acquisition. Here, we combine the sub-centimetre accuracy and spatial benefits of DInSAR with the temporal benefits of tide models to infer the spatiotemporal dynamics of ice-ocean interaction during the times of satellite overpasses. We demonstrate the potential of this synergy with TerraSAR-X data from the almost stagnant Southern McMurdo Ice Shelf. We then validate our algorithm with GPS data from the fast-flowing Darwin Glacier, draining the Antarctic Plateau through the Transantarctic Mountains into the Ross Sea. We are able to match DInSAR to 0.84 mm; generally improve traditional tide models by up to −39 % from 10.8 cm to 6.7 cm RMSE against GPS data from areas where ice is in local hydrostatic equilibrium with the ocean; and up to −74 % from 21.4 cm to 5.6 cm RMSE against GPS data in feature-rich coastal areas where contemporary tide-models are most inaccurate. Numerical modelling then reveals a Young’s modulus of E = 1.0 GPa and an ice viscosity of 10 TPa s when finite-element simulations of tidal flexure are matched to 16 days of tiltmeter data; supporting the theory that strain dependent anisotropy may significantly decrease effective viscosity compared to isotropic polycrystalline ice on large spatial scales. Applications of our method range from (i) refining coarsly-gridded tide models to resolve small-scale features at the spatial resolution and vertical accuracy of SAR imagery, to (ii) separating elastic and viscoelastic contributions in the satellite derived flexure measurement and (iii) gaining information about large-scale ice heterogenity in Antarctic ice-shelf grounding zones, the missing key to improve current ice-sheet flow models. The reconstruction of the individual components forming DInSAR images has the potential to become a standard remote-sensing method in polar tide modelling. Unlocking the algorithm's full potential to answer multi-disciplinary research questions is desired and demands collaboration within the scientific community.

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Tide-corrected flow velocity and mass balance of Campbell Glacier Tongue, East Antarctica, derived from interferometric SAR

Cited by 19 publications

References 49 publications

Changes in a Giant Iceberg Created from the Collapse of the Larsen C Ice Shelf, Antarctic Peninsula, Derived from Sentinel-1 and CryoSat-2 Data

Changes in a Giant Iceberg Created from the Collapse of the Larsen C Ice Shelf, Antarctic Peninsula, Derived from Sentinel-1 and CryoSat-2 Data

Differential interferometric synthetic aperture radar for tide modelling in Antarctic ice-shelf grounding zones

Differential InSAR for tide modelling in Antarctic ice-shelf grounding zones

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