Amery Ice Shelf’s “Loose Tooth” Gets Looser

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The Amery Ice Shelf is an important dynamic system responsible for draining about 16 percent of the grounded East Antarctic ice sheet through only 2 percent of its coastline. Most of the mass input to the system occurs from the Lambert Glacier and several other glaciers. Mass loss from the system occurs through basal melting and iceberg calving. These images from the Multi-angle Imaging SpectroRadiometer (MISR) portray the ice shelf front on October 6, 2001 (top), and September 29, 2002 (bottom), and illustrate changes that took place over the year elapsed between the two views.

Amery Ice Shelf

Two longitudinal rifts, oriented roughly parallel to the direction of ice flow and measuring about 25 and 15 kilometers in length, are apparent near the seaward edge of the ice shelf. Between them, a transverse fracture extends eastward from the base of the western rift. This rift system is colloquially named the Amery “loose tooth.” Over the course of the one-year interval between these two MISR images, the ice front has advanced approximately 1.6 – 1.7 kilometers, and the transverse fracture and a three-way fissure at the juncture of the rifts have widened. When the transverse fracture eventually reaches the eastern rift, a large iceberg (25 kilometers x 25 kilometers) will be released. The Amery Ice Shelf is currently considered to be about two-thirds of the way through a calving cycle. The last major calving event occurred in the early 1960s, when a massive iceberg (measuring about 140 kilometers x 70 kilometers) was released. Image courtesy NASA/GSFC/LaRC/JPL, MISR Team Text by JPL and Institution of Oceanography.

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