  We recently reported on the radio-frequency attenuation length of cold polar
ice at Summit Station, Greenland, based on bistatic radar measurements of
radio-frequency bedrock echo strengths taken during the summer of 2021. Those
data also include echoes attributed to stratified impurities or dielectric
discontinuities within the ice sheet (layers), which allow studies of a)
estimation of the relative contribution of coherent (discrete layers, e.g.) vs.
incoherent (bulk volumetric, e.g.) scattering, b) the magnitude of internal
layer reflection coefficients, c) limits on the azimuthal asymmetry of
reflections (birefringence), and d) limits on signal dispersion in-ice over a
bandwidth of ~100 MHz. We find that i) after averaging 10000 echo triggers,
reflected signal observable over the thermal floor (to depths of approximately
1500 m) are consistent with being entirely coherent, ii) internal layer
reflection coefficients are measured at approximately -60 to -70 dB, iii)
birefringent effects for vertically propagating signals are smaller by an order
of magnitude relative to comparable studies performed at South Pole, and iv)
within our experimental limits, glacial ice is non-dispersive over the
frequency band relevant for neutrino detection experiments.
