Australia: The Land Where Time Began

A biography of the Australian continent 

Antarctica - Pine Island Glacier, subglacial melt channels & Fracture in Floating Part

The authors¹ carried out a study using a dense grid of radar sections that penetrated the ice of the Pine Island Glacier in West Antarctica which revealed a network of sinuous channels beneath the glacier, typically with a width of 500 m-3 km, and reaching to 200 m high, in the base of the ice shelf, that develop while the ice is floating, as a result of basal melting of the ice shelf. Isolated reflections from within the ice shelf are shown by the radar to be above the apex of most channels. It was confirmed by comparing the radar data with acoustic data obtained from an autonomous submersible that these echoes arise from open basal crevasses 50-100 m wide that align with the subglacial channels, which penetrate up to 1/3 of the thickness of the ice. According to the authors¹ analogous surface crevasses are present on the ridges between the basal channels. It is suggested by the authors¹ that both sets of crevasses formed as the melting of the subglacial channels was occurring, being a response to vertical flexing of the ice shelf towards the hydrostatic condition. It was found from finite element modelling of the stresses produced after the formation of basal channels, that were idealised, indicate the stresses generated have the correct pattern, and providing the channels were formed rapidly enough would be of sufficient magnitude to explain the formation of the basal and surface sets of crevasses that were observed. The conclusion arrived at by the authors¹ is that basal melting of the ice shelf has a role in determining the patterns of surface and basal crevasses. Structural weakening of the ice shelf, possibly as a prelude to its complete collapse, may therefore result from more than a single cause, as increased delivery of warm ocean water to the cavity beneath the ice shelf may cause thinning as well as structurally weakening the ice shelf.

Sources & Further reading

1. Vaughan, David G., Hugh F. J. Corr, Robert A. Bindschadler, Pierre Dutrieux, G. Hilmar Gudmundsson, Adrian Jenkins, Thomas Newman, Patricia Vornberger, and Duncan J. Wingham. "Subglacial Melt Channels and Fracture in the Floating Part of Pine Island Glacier, Antarctica." Journal of Geophysical Research: Earth Surface 117, no. F3 (2012): F03012.