The potential of InSAR for assessing meltwater lake dynamics on Antarctic ice shelves
Surface meltwater drains on several Antarctic ice shelves, resulting in surface and sub-surface lakes that are potentially critical for the ice shelf collapse. Yet, our understanding and assessment of the drainage or refreezing of these lakes is limited, mainly due to lack of field observations and...
| Main Authors: | , , |
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| Format: | Text |
| Language: | English |
| Published: |
2021
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/tc-2021-169 https://tc.copernicus.org/preprints/tc-2021-169/ |
| Summary: | Surface meltwater drains on several Antarctic ice shelves, resulting in surface and sub-surface lakes that are potentially critical for the ice shelf collapse. Yet, our understanding and assessment of the drainage or refreezing of these lakes is limited, mainly due to lack of field observations and to the limitations of optical satellite imagery. Therefore, this paper explores the potential of backscatter intensity and of interferometric coherence and phase from C-band synthetic aperture radar (SAR) imagery as an alternative to assess the dynamics of meltwater lakes. In two case studies over Amery and Roi Baudouin ice shelves, we analyse i) the spatial and ii) the temporal variations of SAR backscatter intensity with iii) coherence and iv) interferogram phase (InSAR) patterns detected by Sentinel-1 data over multiple meltwater lakes. Throughout the year the lakes are observed in completely frozen state, in partially frozen state with a floating ice lid, and as open water lakes. The analysis reveals that the meltwater lake delineation is challenging during the melting period when the contrast between melting snow and lakes is confounded. On the other hand, it shows that the lake dynamics can be effectively captured during the refreezing process and the winter season by combining backscatter and InSAR information. In particular, the InSAR coherence and interferogram phase information are deemed essential throughout this whole period to distinguish between refrozen ice and subsurface meltwater. Additionally, the results provide significant evidence on the potential of the interferogram fringe patterns to detect and characterise instant events, such as lake drainage events over ice shelves. The potential of this technique to monitor these meltwater change events is however strongly determined by the satellite revisit interval and potential changes in scattering properties due to snowfall or melt events. |
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