Giant 250-metre high channels of ice, almost the height of the Eiffel Tower, have been discovered beneath a floating ice shelf in Antarctica.
The channels, that stretch hundreds of kilometres along the ice shelf, will help predict future of Antarctic ice, researchers said.
Researchers from the University of Exeter, Newcastle University, the University of Bristol, the University of Edinburgh, the British Antarctic Survey and the University of York, used satellite images and airborne radar measurements to reveal the channels under the ice shelf.
The channels can be seen on the surface of the ice shelf, as well as underneath, because the ice floats at a different height depending on its thickness.
The researchers also predicted the path of meltwater flowing under the part of the ice in contact with the land - known as the ice sheet.
They discovered that the predicted flow paths lined up with the channels under the ice shelf at the point where the ice starts to float.
The match-up indicates that the water flow beneath the grounded ice sheet is responsible for the formation of the channels beneath the floating ice shelf.
When the meltwater flowing under the ice sheet enters the ocean beneath the ice shelf, it causes a plume of ocean water to form, which then melts out the vast channels under the ice shelf.
Previously, it was thought that water flowed in a thin layer beneath the ice sheet, but the evidence from this study suggests it flows in a more focused manner much like rivers of water.
The way in which water flows beneath the ice sheet strongly influences the speed of ice flow, however, the implications for the future of the ice sheet are yet to be determined.
"If we are to understand the behaviour of the ice sheet, and its contribution to changes in sea level, we need to fully understand the role of water at the base of the ice sheet," said Dr Anne Le Brocq from the University of Exeter.
"The information gained from these newly discovered channels will enable us to understand more fully how the water system works and, hence, how the ice sheet will behave in the future," Brocq said.
Channels of this magnitude have been observed before elsewhere, but their formation has been attributed to purely oceanic processes rather than meltwater exiting the grounded ice sheet.
