The Grand Chasms, Filchner Ice Shelf, Antarctica.
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Ice shelves are marine based extensions of ice caps and sheets.
Since ice shelves float on water they have very little drag associated
with them, this leads to very high flow velocities. The pulling force
on the ice increases as the square of the floating ice thickness.
Grounded ice is the only thing that resists the pulling force. At
areas of grounded ice the surface can melt due to extensive surface crevassing.
The melted water can penetrate to the base through crevasses and lubricate
the grounded ice. The lubrication reduces drag at the bottom of the
glacier which increases glacier velocity. The faster the ice shelf is moving,
extensive crevassing will result. This positive feedback loop can
cause ice shelves to rapidly increase their velocities. |
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