British scientists discovered rivers flowing under the Antarctica ice shelf by examining small changes in elevation using data collected by a European Space Agency (ESA) satellite.
The team found anomalies in the surface elevation of the ice sheet, the oldest, thickest ice in the region,using ultra-precise measurements from ERS-2's radar altimetry and radar interferometry, according to an article published in Nature. Close inspection of one anomaly revealed an abrupt fall in ice-surface elevation with a corresponding abrupt rise some 290 kilometers away. The scientists state the only possible explanation for these changes is that a large flow of water was transferred beneath the ice from one sub-glacial lake into several others.
Duncan Wingham, of the University College London, who led the team said, "Previously, it was thought that water moves underneath the ice by very slow seepage. But this new data shows that, every so often, the lakes beneath the ice pop off like champagne corks, releasing floods that travel very long distances."
Sub-glacial lakes in Antarctica were first identified in the 1960s. Since then more than 150 have been discovered, but it is thought thousands may exist, as much of the bed of Antarctica remains unexamined. The team focused its study on the Dome Concordia region in East Antarctica, where more than 40 lakes are known to be.
"Hence we turned to ERS-2 SAR interferometry, which has excellent spatial resolution," Wingham said. "With it, we were able to image the area of at least part of one lake, which was enough to give us an idea of the volume, and with this we could get at the rate of the flow," he added.
The finding challenges the widely held assumption that sub-glacial lakes evolved in isolated conditions for several millions of years and raises the possibility that large floods of water from deep within the ice's interior may have generated huge floods that reached the ocean in the past and may do so again.