Scientists recognize that considerable ice cover already existed on Antarctica 35 million years ago, and the ice sheet has waxed and waned through glacial cycles ever since. Today, for example, there is little or no ice left. Even the Greenland ice sheet, which does still exist, is a comparative newcomer at seven million years old, and small in comparison to the Antarctic. Scientists say the waxing and waning of the northern hemisphere ice sheets changed sea level by about 110 meters. Ocean Drilling Program results show these ice sheets were very sensitive to climate change.
Mankind is on the edge of having the power to change global climate.
And because of its pivotal importance to world climate, we must try to understand the history of the Antarctic ice sheet. Most of the ice sheet is frozen to the rock beneath and cannot flow easily. The ice sheet drains by rapid ice flow, in narrow channels called ice streams. Here, the ice base is not frozen to the underlying rock, but is lubricated by unsorted wet sediment called till. The till is carried by the ice streams to the ice sheet edge.