Deriving melt rates at a complex ice shelf base using in-situ radar: application to Totten Ice Shelf

A phase‐sensitive radar (ApRES) was deployed on Totten Ice Shelf to provide the first in‐situ basal melt estimate at this dynamic East Antarctic ice shelf. Observations of internal ice dynamics at tidal timescales showed that early arrivals from off‐nadir reflectors obscure the true depth of the ice shelf base. Using the observed tidal deformation, the true base was was found to lie at 1910‐1950 m depth, at 350‐400 m greater range than the first reflection from an ice‐ocean interface. The robustness of the basal melt rate estimate was increased by using multiple basal reflections over the radar footprint, yielding a melt rate of 22 ± 2.1 m a⁻¹. The ApRES estimate is over 40% lower than the three existing satellite estimates covering Totten Ice Shelf. This difference in basal melt is dynamically significant and highlights the need for independent melt rate estimates using complementary instrumentation and techniques that rely on different sets of assumptions.