Measurements of broadband backscattering from the terminus of a tidewater glacier

The submerged termini of tidewater glaciers are a critical, yet poorly characterized component of high latitude regions. While traditional oceanographic measurement techniques are limited by iceberg calving dangers, remote measurements made by active acoustic systems represent a useful, if underutilized, tool. This manuscript investigates the potential connections between ice face geometry, internal ice properties, and backscattering through broadband (170-250 kHz) split-beam echosounder observations collected over a range of grazing angles at Hans glacier in Svalbard. The ice face position and local slope were derived from split-aperture processing methods. Spectral trends in backscattering over a frequency band of 80 kHz were measured at grazing angles between 48° and 74°. Overall, backscattering showed a weak frequency dependence across grazing angles, following power law trends ranging from 10log10f0.27 to 10log10f-0.35. The broadband spectral trend results could be attributed to several scattering mechanisms associated with the ice-ocean interface (e.g., surface roughness, gas bubbles, thermohaline structure), which are discussed, along with the need for the collection of additional observational datasets, including in situ measurements of submerged termini properties.