Grounding line remote operated vehicle (GROV) exploration of the ice shelf cavity of Petermann Glacier, Greenland

The melting of ice by ocean waters along the periphery of ice sheets is a
major physical process driving their evolution in a warming climate. Using
the fiber-optic-tethered Grounding line Remote Operated Vehicle (GROV), we
explored the ice shelf cavity of Petermann Glacier, in Northwestern
Greenland, in May 2023, using a novel interferometric multibeam sonar
operating at 117 KHz with 360° viewing capability. The seafloor depth is
uniform at 820 m and 200 m deeper than anticipated. At the ice shelf base,
we find a succession of terraces interrupted by 20-40 m ice cliffs that
have no signature at the surface, but are consistent with double-diffusive
convection. The central melt channel deviates by ± 80 m from flotation, is
smoother than indicated by the surface, and reveals asymmetric melt. The
results demonstrate the fundamental importance of surveying the geometry
of ice shelf cavities to document ice-ocean interaction.