Australia: The Land Where Time Began

A biography of the Australian continent 

Antarctica - East Antarctic Ice Sheet (EAIS)

This is a terrestrial ice sheet grounded mostly above sea level resting on several large basins in the interior, some of which reach a depth of more than 1 km. The average depth of this ice sheet is a bit more than 3 km, having a steep marginal profile corresponding to geologic models that are based on mass balance and plastic flow and basal sliding is absent (Hughes, 1973). The trajectories of the flow of the ice sheet are mainly downwards.

EAIS drainage is mainly divergent towards the coast, though there are important exceptions, such as in the region of the Amery Ice Shelf and portions of the ice sheet that drain into the Ross Ice Shelf and the Ronne-Filchner Ice Shelf through the TAM. Ice flow velocities decrease as the ice approaches the coast as a result of the divergent drainage pattern, the typical range being from a few m/yr to a few tens of m/yr, which indicates that if there is any basal meltwater it is not extensive or wide enough to enhance the flow of the ice sheet by basal sliding. Lake Vostok, near the centre East Antarctica, a freshwater lake with an area of about 14,000 km², about the size of Lake Ontario, is the most notable exception (Williams, 1996).

In coastal areas of East Antarctica there are ice cliffs that have ice fronts that advance slowly as a result of the erosion of the ice front by waves as rapidly as it advances. These ice cliffs may be grounded several hundred metres below sea level, though they are typically grounded at sea level. In areas where glacial drainage converges towards the coast ice streams are found, where they extend into the sea as either fringing ice shelves or smaller glacier tongues that are associated with large outer glaciers. These glacier tongues are relatively small but they accommodate significant glacial drainage.

Sources & Further reading

1. Anderson, John B., 1999, Antarctic Marine Geology, Cambridge University Press