Abstract
Abstract. We report on the recent reactivation of a large rift in the Brunt Ice Shelf, East Antarctica, in December 2012 and the formation of a 50 km long new rift in October 2016. Observations from a suite of ground-based and remote sensing instruments between January 2000 and July 2017 were used to track progress of both rifts in unprecedented detail. Results reveal a steady accelerating trend in their width, in combination with alternating episodes of fast ( > 600 m day−1) and slow propagation of the rift tip, controlled by the heterogeneous structure of the ice shelf. A numerical ice flow model and a simple propagation algorithm based on the stress distribution in the ice shelf were successfully used to hindcast the observed trajectories and to simulate future rift progression under different assumptions. Results show a high likelihood of ice loss at the McDonald Ice Rumples, the only pinning point of the ice shelf. The nascent iceberg calving and associated reduction in pinning of the Brunt Ice Shelf may provide a uniquely monitored natural experiment of ice shelf variability and provoke a deeper understanding of similar processes elsewhere in Antarctica.
Highlights
The formation of the rift coincided with a period of accelerating ice flow, which started in the 1970s (Gudmundsson et al, 2017) and was likely related to wide-spread dynamical changes to the ice shelf triggered by a calving event to the north of the McDonald Ice Rumples (MIR) (Thomas, 1973)
The sudden fracture of the ice shelf and the abrupt formation of the Halloween Crack (HC) suggests a period of critical crack growth, which typically occurs in materials that are subjected to high tensile stresses or stresses that are applied for long enough such that initial fractures grow to a critical length, after which catastrophic failure happens (Lawn, 1993; Rist et al, 2002)
The reactivation of Chasm 1 in December 2012 and the formation of the Halloween Crack in October 2016 have been documented in great detail and have provided an unprecedented view on the dynamics of such rifts, commonly found in Antarctica
Summary
Episodic observations of the configuration of the BIS since 1915 and effectively continuous observations since the 1990s suggest that, at present, the ice front is in its most advanced position since the start of measurements, and Anderson et al (2014) hypothesized that a new calving cycle is likely to happen before 2020
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