Satellite measurements of the icy surface of Antarctica have detected an active system of lakes under ice that is about one kilometer deep. As we hear from VOA's Art Chimes, scientists are still uncertain about the role that the underground water plays in the movement of the so-called ice streams that may contribute to a rise in sea level.

Very precise measurements from a research satellite called ICEsat identified changes on the surface as lakes underneath the ice filled and drained as much as two cubic kilometers of water during the three-year study.

The lakes are under moving sections of ice, called ice streams, that flow into the Ross Ice Shelf.

The existence of water under the ice streams has been known for some time, but what's surprising is how much water is involved and how fast it moves.

Helen Amanda Fricker

Lead author Helen Amanda Fricker says it's an important process to understand because of its potential impact on sea levels as ice flows off Antarctica and into the ocean. "Well, it's important because the ice streams are the mechanism whereby the ice is transported form the deep interior of Antarctica out to the Ocean, and so if you have changes in the amount of water which is underneath the ice, then you will change the speed at which the ice is transported," she said.

The water under the ice streams acts as a lubricant to ease the travel of the ice toward the sea. So you would think that more water under the ice would result in faster-moving ice. But that's not what's happening. NASA scientist Robert Bindschadler says it illustrates how much more they need to learn. "And there is this conundrum, the fact that this ice stream is slowing down, yet most of the water produced under these ice streams over these three years is not getting out. How do you reconcile those two," he said.

Although global warming could result in rising sea levels from melting ice, particularly ice covering Greenland, Bindschadler says global warming is not a factor in these lakes underneath the Antarctic ice sheet.

The research was published in the online edition of the journal Science. The authors spoke at the annual meeting of the American Association for the Advancement of Science.