STAGNATION OF ICE-STREAM-C, WEST ANTARCTICA BY WATER PIRACY

The dynamic behavior of the West Antarctic ice sheet is of interest be cause of the possibility that it may change and cause rapid sea-level rise. Attention is focused on the fast-moving and rapidly responding i ce streams that drain the ice sheet. One of these, ice stream C, large ly stopped about a century ago, and some models for this shutdown post ulate negative feedbacks that would tend to stabilize the ice-sheet. H ere, new data are presented indicating that the slowdown of the ice st ream is restricted to its lower part, and occurred because of loss of lubrication on localized ''sticky spots'' at the bed of the ice stream . The increased friction probably arises from a topographic accident o f the glacier bed that has directed lubricating water to the neighbori ng ice stream B, together with slow drawdown of the ice sheet, rather than from any general stabilizing feedbacks.