Basal crevasses on the Larsen C Ice Shelf, Antarctica: Implications for meltwater ponding and hydrofracture

Abstract

A key mechanism for the rapid collapse of both the Larsen A and B Ice Shelves was meltwater‐driven crevasse propagation. Basal crevasses, large‐scale structural features within ice shelves, may have contributed to this mechanism in three important ways: i) the shelf surface deforms due to modified buoyancy and gravitational forces above the basal crevasse, creating >10 m deep compressional surface depressions where meltwater can collect, ii) bending stresses from the modified shape drive surface crevassing, with crevasses reaching 40 m in width, on the flanks of the basal‐crevasse‐induced trough and iii) the ice thickness is substantially reduced, thereby minimizing the propagation distance before a full‐thickness rift is created. We examine a basal crevasse (4.5 km in length, ∼230 m in height), and the corresponding surface features, in the Cabinet Inlet sector of the Larsen C Ice Shelf using a combination of high‐resolution (0.5 m) satellite imagery, kinematic GPS and in situ ground penetrating radar. We discuss how basal crevasses may have contributed to the breakup of the Larsen B Ice Shelf by directly controlling the location of meltwater ponding and highlight the presence of similar features on the Amery and Getz Ice Shelves with high‐resolution imagery.