For the most part, an ice sheet moves down slope slowly because the ice is in direct contact with underlying bedrock. In some places, however, ice races along much faster than the rest of the sheet. These areas of fast-moving flow, called ice streams, are believed to be caused by a thin, lubricating layer of water and mud between the ice and the land. In this video segment adapted from NOVA, a team of scientists seeks evidence to support their hypothesis that atmospheric warming—either now or in the past—may explain why water has formed beneath the ice sheet.
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