Towards Coherent Change Detection for Ice Sheet Near-Surface Process Studies with Airborne Ice-Penetrating Radar

Meltwater percolation and refreezing in porous firn is difficult to observe, but plays a key role in controlling the rate of melt-water runoff from the Greenland Ice Sheet. Coherent change detection (CCD) with repeated airborne ice-penetrating radar acquisitions is a promising method for resolving these processes. However, existing surveys were not designed for interferometric processing, and CCD has not yet been applied to near-surface ice-penetrating radar data. Here, we develop a workflow for estimating the coherence between repeat acquisitions by the Operation IceBridge Accumulation Radar. We demonstrate that stratigraphic structures such as ice slabs and ice layers maintain good coherence even over a temporal baseline of one year. However, porous firn with heterogeneous ice lensing has poor coherence, suggesting that tighter baseline control and improved co-registration and motion compensation methods would be required to reliably observe subsurface change in the percolation zone.