Grounding line of Denman Glacier, East Antarctica from satellite radar interferometry

Grounding line, elevation changes, and melt rates maps of Denman Glacier, East Antarctica.

Using satellite radar interferometry from the COSMO-SkyMed mission we map the grounding line of Denman Glacier, East Antarctica. We complement these data with some historical interferometric radar acquisition from the European satellite ERS-1/2. We present new maps of elevation changes on the grounded and floating portions of Denman Glacier obtained by temporally differencing TanDEM-X Digital Elevation Models.

Methods
To map the grounding line of Denman Glacier, we form SAR interferograms with a one day time interval by coherently combining SAR acquisitions from ERS-1/2 satellites in 1996 and from the Agenzia Spaziale Italiana (ASI) COSMO-SkyMed (CSK) mission between 2016 and 2018. We multi-look each interferogram with a 8x8 averaging window and remove the topographic signal affecting each interferometric acquisition with a TanDEM-X (TDX) at 30 m spacing. We form 29 CSK Differential Interferogram (DInSAR) (i.e. difference between two SAR interferograms) to reveal the vertical motion of ice in response to changes in oceanic tides.

We generate a time series of Digital Elevation Model at 12 m spacing and meter-scale vertical precision using SAR bistatic acquisition from the TDX mission. The processing chain includes: a) spaceborne monostatic TerraSAR-X processing; b) bistatic TDX processing; c) interferometric combination of images; d) phase unwrapping; e) phase-to-height conversion; f) geocoding to a latitude/longitude grid.

We differentiate temporally separated TDX DEMs to generate elevation changes map on grounded ice and ocean-induced melt rates maps on floating ice. We smooth elevation changes maps (dh/dt) using a 15x15 pixels moving average window to obatain dh/dt maps at 1.5 km spacing.

On floating ice, we differentiate TDX DEMs by tracking ice parcel with time and correcting for ice flow divergence. We use a chip size of 30x30 pixels with steps of 16 pixels in both horizontal and vertical directions and smooth the results with a 15x15 moving average window to obtain ocean-induced melt rate maps at 1.5 km spacing.