Measuring turbulent dissipation rates beneath an Antarctic ice shelf

Microstructure shear, temperature, and conductivity observations from a tethered profiler have been made beneath George VI Ice Shelf to examine processes driving vertical heat flux in the oceanic turbulent boundary layer. Such measurements at the ice-ocean interface within the cavity of an ice shelf are unprecedented, requiring the deployment of a profiler through 400-m deep access boreholes. We describe the drilling technique developed for this purpose, which involves using a brush to widen the deepest section of the borehole, and as evidence that this novel technique can be successful, we present shear and thermal variance spectra from the profiler. These spectra indicate that dissipation rates of turbulent kinetic energy, from which heat flux can be calculated, can be resolved beneath an ice shelf as well as they can be in open water.