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  • 1
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    Monitoring permafrost and thermokarst processes with TanDEM-X DEM time series: Opportunities and limitations (2016)
    IEEE
    In:  EPIC336th IEEE International Geoscience and Remote Sensing Symposium, IGARSS 2016, IEEE, pp. 332-335
    Details
    Publication Date: 2017-01-21
    Description: Permafrost soils have been shown to respond rapidly to warming temperatures. When ice-rich permafrost soils thaw, the melting ground ice reduces the volume and stability of the soils, inducing changes in the topography. We monitor surface elevation changes in three test sites in Northern Eurasia using single-pass TanDEM-X Science Phase data with submetre vertical precision. The results indicate the suitability of single-pass InSAR data for monitoring thaw-induced topographic changes (e.g. coastal erosion) but they also reveal the spurious impact of late-lying snow packs and water bodies, both of which are common in lowland permafrost areas. Furthermore, the coherence and hence the precision with which elevation changes can be estimated is found to be limited by the noise level in certain cases. As some of these influences could be mitigated using appropriate mission and acquisition designs, we conclude that single-pass interferometry has considerable potential for monitoring thaw-induced surface elevation changes in permafrost areas, which in turn could contribute to assessing their vulnerability, fate, and climate system feedback in a warming climate.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev , info:eu-repo/semantics/article
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  • 2
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    A Statistical Test of Phase Closure to Detect Influences on DInSAR Deformation Estimates Besides Displacements and Decorrelation Noise: Two Case Studies in High-Latitude Regions (2016)
    IEEE
    In:  EPIC3IEEE Transactions on Geoscience and Remote Sensing, IEEE, 54(9), pp. 5588-5601, ISSN: 0196-2892
    Details
    Publication Date: 2021-08-16
    Description: Displacements of the Earth's surface can be estimated using differential interferometric synthetic aperture radar. The estimates are derived from the phase difference between two radar acquisitions. When at least three such acquisitions are available, one can compute the displacement between the first and the third acquisition and compare it with the sum of the two intermediate displacements. These two are expected to be equal for a piston-like spatially uniform deformation. However, this is not necessarily the case in measured data. Such lack of phase closure can be due to decorrelation noise alone. It has also been attributed to complex scattering processes such as soil moisture changes or multiple scattering sources. However, the nature of these nonrandom effects is only poorly understood in cold regions, as the role of snow and freeze/thaw processes has not been studied to date. To distinguish the noise-like and the systematic effects, an asymptotic Wald significance test is proposed. It detects situations when the observed closure error cannot solely be explained by noise. Such situations with p 〈; 0.05 are observed at the Ku-band during snow metamorphism and melt and following a summer precipitation event in Sodankylä, Finland. They can also be prevalent (〉 25%) in the X-band observations of ice-rich permafrost regions in the Lena Delta, Russia, indicating the presence of processes that can have systematic and deleterious impacts on the estimation of surface movements. Satellite-based monitoring of these displacements is thus possibly subject to complex error sources in high-latitude regions.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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