Rifting and calving of the Amery Ice Shelf
Rifts in floating ice shelves that surround Antarctica are the largest crevasses seen in the glaciological world.
Understanding the mechanisms of rifting and their formation/evolution is critical to quantifying the overall mass balance and stability of the ice shelf. Calving happens when large sections of the floating ice shelf break off and subsequently melt and break up into smaller icebergs. The nature and frequency of calving events is of interest to understand if any link exists with global climate change, ie whether the oceans are warming and causing increased calving and melting of the ice shelves.
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| Figure 1. The rifting zone at the front of the Amery Ice Shelf – termed the 'loose tooth'. Image copyright NASA/GSFC/LARC/JPL, MISR Team |
Our region of study is the Amery Ice Shelf, which is the largest ice shelf in East Antarctica. The last major calving event on the Amery occurred in 1962-63 and we are studying a section at the front of the ice shelf, affectionately termed the 'loose tooth'. The 'loose tooth' is an area of about 30 by 30 km, and currently an approximately east-to-west (transverse) fracture of this section is moving at approximately 10-14 m/day (see figure 1 above and photo below). In other words, over one year, the transverse fracture will extend further eastwards by about 4-5 km and it will widen as it breaks off from the main ice shelf. The ice shelf itself is moving forwards in a northerly direction at about 1300 m/yr.
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| Helicopter view of the 'loose tooth' fracture on Amery Ice Shelf. Photo R. Coleman |
The main objective of the project for this summer season (2002-2003) is to monitor the propagation (widening, elongation and vertical displacement) of the 'loose tooth' by measuring the horizontal and vertical movements across the tip of the fracture area with Global Positioning System (GPS) units.
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| A GPS site near the 'loose tooth' showing the solar panel, equipment box, GPS antenna and pole and the seismometer located near the flag. Photo R. Coleman. |
An array of seismometers has also been deployed to 'listen' to the cracking and snapping of the fracture. The GPS array consists of 6 sites (see photo above), positioned around the tip of the fracture (within 300 m to 2 km away), that will continuously record data for about 7-8 weeks.
This project is being done collaboratively with researchers from the University of Tasmania (Associate Professor Richard Coleman), Scripps Institution of Oceanography, USA (Dr Helen F. and Jeremy B.), the Antarctic Cooperative Research Centre (Neal Y.) and the University of Canberra (Associate Professor Peter M.). This season Richard Coleman and Jeremy B. (a PhD student at Scripps) are part of the field party undertaking the measurement program.
Article written by Associate Professor Richard Coleman
