Internal Structure and Formation Process of a Giant East Antarctic Grounding‐Zone Wedge

Abstract The marine‐based portions of the East Antarctic Ice Sheet are currently losing mass at an accelerating rate due to atmospheric and oceanic forcing. Assessing these changes requires understanding long‐term grounding‐zone dynamics preserved in glacial geomorphology, including understudied East Antarctic shelf sectors. We present geophysical evidence for the detailed internal architecture of a giant ∼260 m‐high grounding‐zone wedge (GZW) in Vincennes Bay just offshore the Aurora Subglacial Basin. A bed slope transition from retrograde to prograde likely slowed grounding‐zone retreat, culminating in a stillstand. Prograding internal foresets indicate a single major stabilization event tied to a ∼65 km grounding‐line readvance, probably after the Last Glacial Maximum. The new high‐resolution seismic data allow analyzing the nucleation and the evolution of a GZW in unprecedented detail, thus providing key constraints on grounding‐zone behavior and its sensitivity to local topography and associated subglacial geological variations along ice‐sheet beds.