Constraining an Ocean Model Under Getz Ice Shelf, Antarctica, Using A Gravity‐Derived Bathymetry.

Getz Ice Shelf, the largest producer of ice shelf meltwater in Antarctica, buttresses glaciers that hold enough ice to raise sea level by 22 cm. We present a new bathymetry of its sub‐ice shelf cavity using a three‐dimensional inversion of airborne gravity data constrained by multibeam bathymetry at sea and a reconstruction of the bedrock from mass conservation on land. The new bathymetry is deeper than previously estimated with differences exceeding 500 m in a number of regions. When incorporated into an ocean model, it yields a better description of the spatial distribution of ice shelf melt, specifically along glacier grounding lines. While the melt intensity is overestimated because of a positive bias in ocean thermal forcing, the study reveals the main pathways along which warm oceanic water enters the cavity and corroborates the observed rapid retreat of Berry Glacier along a deep channel with a retrograde bed slope. Plain Language Summary: The Getz Ice Shelf is a major ice shelf in West Antarctica that is rapidly melting. Its exposure to warm oceanic water has made it the largest producer of ice shelf meltwater in Antarctica. To understand its evolution and the impact on sea level rise of the glaciers that flow into it, it is essential to obtain a better description of the bathymetry beneath its hundreds of meters of floating ice. We use a combination of airborne gravity and other data to infer the depth of the cavity. We find the seabed to be in several regions more than 500 m deeper than previously reported, hence revealing one of the deepest ice shelf cavities in West Antarctica. When used in combination with an ocean model, the bathymetry helps to better explain the spatial variability in melt observed from remote sensing data, the pathways for warm waters to reach the ice shelf, and the recent evolution of selected glaciers. Key Points: Sub‐ice shelf bathymetry reconstructed with a 3D inversion of gravity data reveals one of the deepest ice shelf cavities in West AntarcticaAn ocean model coupled with the new bathymetry indicates pathways where warm ocean water enters the cavityThe new bathymetry helps elucidate the recent evolution of Getz glaciers and explain why Getz is a large producer of meltwater [ABSTRACT FROM AUTHOR]