Permafrost-thaw and soil moisture

Enlarged view: Permafrost - Lena River Delta — Observations of a thaw slump in the Mackenzie River Delta, Canada. A: Aerial photo of a thaw slump (courtesy Simon Zwieback). B: Sentinel-2 L1C image of part of the area in the Mackenzie River Delta (Date: 21.08.2017), C: Result after DEM generation process for single-pass TanDEM-X observation in the Science Phase (01.06.2015). The heigt change shows the difference to a previous TanDEM-X DEM from 2013. The strong height change of up to -8m indicate that the thaw slump shown in A was increasing in size between the two observations.

We study how plant growth and changes in soil moisture affect space-borne radar measurements of deformations of the Earth's surface

Using a technique called Differential Interferometric SAR (DInSAR), scientists can measure deformations of the Earth’s surface from space. The centimetre accuracies that can be achieved have made this technique useful for characterizing many processes and movements, such as those related to volcanic activities, the movement of glaciers, or subsidence caused by permafrost-thaw. This measurement works by combining two radar acquisitions from different times. During this time gap, the moisture content of the soil can change and such changes can impact the DInSAR signals and thus the deformation estimates.

We want to characterize the properties and magnitudes of these effects. To this end, we analyse satellite and airborne measurements, and we also conduct dedicated experiments using the group's ground-based radar systems. Our goals are:

to model the effect of soil moisture changes in mineral and organic soils on DInSAR measurements
to elucidate the impact of vegetation dynamics on these measurements
to estimate soil moisture changes and vegetation parameters from radar data
to improve deformation estimates by correcting for these effects and quantifying the associated uncertainties

Enlarged view: DEM differencing to monitor permafrost thawing — TerraSAR-X DInSAR signal observed over the Lena River Delta (72°N, 126°E), which is underlain by permafrost, in late August 2014 with a time gap of 11 days. The water bodies such as the river branches are shown in black. The brightness of the image indicates the coherence, a measure of the quality with which deformations can be retrieved. The phase, from which the displacements are computed, is indicated by different colours. Spatial variatiations of this phase might not only be caused by deformations, but for instance also changes of the soil moisture content.