Posted on 7 October 2013
At 250 metres high, the channels are almost as tall as the Eiffel tower and stretch hundreds of kilometres along the ice shelf. The channels are likely to influence the stability of the ice shelf and their discovery will help researchers understand how the ice will respond to changing environmental conditions. The findings are published in Nature Geoscience.
Researchers from York joined colleagues from the University of Exeter, Newcastle University, the University of Bristol, the University of Edinburgh and the British Antarctic Survey in using 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 focussed 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.
Dr David Rippin, senior lecturer in the Environment Department at York said: “We know very little about the drainage of water beneath the Antarctic Ice Sheet. Here, ice up to several kilometres thick makes direct observation virtually impossible.
“However, seeing such large channels in one of the floating ice shelves that surround Antarctica and then seeing that these channels line up with locations where we predict water would outflow from under the Antarctic Ice Sheet, is strong evidence that channelized drainage exists beneath, at least parts of, this huge ice sheet. This has significant implications for Antarctica’s dynamic behaviour.”
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. Now, with the connection to the meltwater system established, readily obtainable observations from the channels have the potential to shed light on how meltwater flows at the base of an inaccessible kilometre-thick ice sheet.
The study received funding from Natural Environment Research Council (NERC) and the European Space Agency (ESA).