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Projects

Measuring Antarctic uplift due to ice loss, from space

This exciting project will use measurements of ground movement made from space, to constrain the response of the ground to current, and past, ice mass change in the Antarctic. This in turn will improve estimates of ongoing ice loss. The student will be based in Leeds and optional fieldwork in the Antarctic will be involved.

Ice loss from the West Antarctic Ice Sheet already accounts for around 10% of present-day global sea-level rise and is accelerating. As the mass of the ice changes, the ground beneath responds to the change in surface loading both immediately, and with a delayed response lasting up to thousands of years, an effect known as glacial isostatic adjustment (GIA). Understanding the GIA response is key to constraining ongoing ice loss, as it also affects the main measurement methods used to constrain ongoing ice loss: satellite gravimetry and altimetry.

The GIA response depends on the flow characteristics (rheology) of the mantle, which are vertically and laterally variable, and poorly known. Those constraints we do have come from seismic studies and also from viscoelastic modelling of ground motion measurements made by GNSS (e.g. Nield et al, 2014; Samrat et al, 2020). However, the logistical challenge of running GNSS instruments in such a hostile and remote location means that the measurements are spatially sparse, and are not able to capture the full variability of ground displacements, as individual glaciers respond differently to changing conditions.

Radar Interferometry (InSAR), on the other hand, is a technique that can provide spatially dense measurements of surface displacement from space (Hooper et al, 2012). Making these measurements in the Antarctic is challenging, due to snow coverage in winter and with large regions covered by ice, but our preliminary efforts have shown it to be possible (Figure 1).

InSAR velocities on rocky outcrops
Figure 1. Average velocities measured by InSAR over four years on rocky outcrops between glaciers. Velocities are relative to the reference point ‘R’.

InSAR is commonly used in the natural hazards community for earthquake analysis and monitoring of volcanoes, and at the University of Leeds we have developed algorithms for mass processing of data, and the reduction of measurement errors introduced by variable atmospheric conditions. InSAR is also used for commercial applications, such as monitoring of infrastructure, and SatSense Ltd have developed their own state-of-the-art approach to InSAR processing and interpretation.

The aim of this project is to use the combined expertise from Leeds and SatSense to make InSAR measurements over the whole Antarctic Peninsula and, working with experts in BAS and Durham, to use these data to better constrain the rheological properties of the region through modelling. The project will also involve fieldwork to install radar reflectors at key locations on the Antarctic Peninsula, subject to a successful application for support from BAS. This will enable the InSAR results, which are relative measurements, to be tied to a global reference frame.

Specific objectives are:

  • Process InSAR data for the whole Antarctic Peninsula and extract time series for individual rocky outcrops;
  • Apply the latest atmospheric correction techniques to the InSAR data;
  • Install radar reflectors on the peninsula to provide absolute constraints on velocity;
  • Use the InSAR measurements combined with GNSS data to constrain viscoelastic models.

 

References

Hooper, A., Bekaert, D., Spaans, K. and Arıkan, M., 2012. Recent advances in SAR interferometry time series analysis for measuring crustal deformation. Tectonophysics, 514, pp.1-13.

Nield, G. A., et al. 2014. Rapid bedrock uplift in the Antarctic Peninsula explained by viscoelastic response to recent ice unloading. Earth and Planetary Science Letters, 397, 32-41.

Samrat, Nahidul Hoque, et al. “Reduced ice mass loss and three-dimensional viscoelastic deformation in northern Antarctic Peninsula inferred from GPS.” Geophysical Journal International 222.2 (2020): 1013-1022.