Preprints
https://doi.org/10.5194/egusphere-2024-2972
https://doi.org/10.5194/egusphere-2024-2972
25 Nov 2024
 | 25 Nov 2024
Status: this preprint is open for discussion.

InSAR sensitivity to active layer ground ice content in Adventdalen, Svalbard

Lotte Wendt, Line Rouyet, Hanne H. Christiansen, Tom Rune Lauknes, and Sebastian Westermann

Abstract. Interferometric Synthetic Aperture Radar (InSAR) remote sensing of surface displacement in permafrost environments has the potential to resolve ground ice dynamics and potentially active layer thickness, yet field validation is sparse. Here we present a comparison between in-situ ground ice contents and the seasonal InSAR displacements of the following thawing season at 12 coring sites in Adventdalen, Svalbard. The study is focused on the year 2023, where frozen sediment cores were collected at the end of spring from the active layer and the uppermost permafrost. The sediment cores were analyzed with high resolution for volumetric ground ice and excess ice contents. The active layer thickness was estimated by probing the thaw depth at the end of the thawing season 2023, allowing to estimate the amount of expected subsidence from seasonal ground ice melt. The InSAR vertical displacements for the thawing season were derived from Small Baseline Subset (SBAS) processing of Sentinel-1 imagery. The expected subsidence from ground ice melt within the measured active layer thickness aligned well with the seasonal InSAR maximum vertical displacement. Monte Carlo simulations were performed to include uncertainties in the expected and measured InSAR subsidence, leading to a mean coefficient of determination of 0.68 and a mean absolute error of 15 mm for the correlation between InSAR subsidence and expected subsidence from in-situ ground ice melt. Excess ice is highly variable and is the main source of the expected subsidence during this thawing season, which was exceptionally warm. The expected subsidence and active layer thickness show only a weak relationship due to the observed complex ice content distribution in the active layer and uppermost permafrost. Our results show the significant potential of InSAR for mapping ground ice variability; however, they also suggest that estimating active layer thickness using InSAR requires careful consideration of the complex occurrence of both pore and excess ice in the active layer and uppermost permafrost.

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Lotte Wendt, Line Rouyet, Hanne H. Christiansen, Tom Rune Lauknes, and Sebastian Westermann

Status: open (until 06 Jan 2025)

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Lotte Wendt, Line Rouyet, Hanne H. Christiansen, Tom Rune Lauknes, and Sebastian Westermann

Data sets

Ground ice contents and InSAR displacements from Adventdalen, Svalbard. Lotte Wendt https://zenodo.org/doi/10.5281/zenodo.11187359

Lotte Wendt, Line Rouyet, Hanne H. Christiansen, Tom Rune Lauknes, and Sebastian Westermann

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Short summary
In permafrost environments, the ground surface moves due to the formation and melt of ice in the ground. This study compares ground surface displacements measured from satellite images against field data of ground ice contents. We find good agreement between the detected seasonal subsidence and observed ground ice melt. Our results show the potential of satellite remote sensing for mapping ground ice variability, but also indicate that ice in excess of the pore space must be considered.