Phase Center of L-Band Radar in Polar Snow and Ice

Backscatter from an aggregate of inhomogeneities combine to form an apparent surface reflection particularly in relation to interferometric synthetic aperture radar. The depth z_φ of this reflection can reside well below the true surface when the transmissivity at the interface between air and the aggregate is high. Snow and ice provide good examples, for which we calculate z_φ with different accumulation history and physical properties using a 0.5-3.0-GHz ground-penetrating radar. We acquired our data along transects in Antarctica and Svalbard. We find values of z_φ >; 40 in low-absorbing Antarctic firn and ≈10 meters in glaciers and ice shelves where melt-freeze cycles and lateral mass movement lead to an electrically more heterogeneous snow and ice column. The heterogeneity reduces dielectric contrast more rapidly with depth. Thus, z_φ is found at shallower depth, but still resides several meters beneath the snow surface.