Scientists have discovered four giant lakes under the Antarctic ice.
Sub-glacial lakes can affect how quickly ice reaches the sea
Together the four are as big as Lake Vostok, the biggest body of water so far discovered in Antarctica.
Researchers say the newly found lakes appear to affect how rapidly ice is transported from the interior of the continent to the sea.
Writing in the journal Nature, they say that understanding the interaction of lakes and ice is crucial to forecasting the impacts of climate change.
The four lakes lie under the Recovery ice stream in Queen Maud Land (also known as Dronning Maud Land).
It brings ice from hundreds of kilometres inland into the Weddell Sea.
The lakes were found using a combination of radar data gathered by satellite, and records of an expedition mounted to the area in the 1960s on which scientists had used a pioneering ice-penetrating radar.
Sub-glacial lakes create tell-tale shapes in the surface of the ice above, while readings taken through the ice had detected, in the words of the 1960s expedition, "a possible melt layer at the bottom of the ice-cap".
About 150 lakes have been discovered under the frozen Antarctic surface.
In recent years there has been a lot of interest in water under the Antarctic ice, for various reasons.
Biologists have been intrigued by the possibility of finding new organisms in ecosystems which may have been cut off from the rest of the world for thousands of years.
Climate scientists have become increasingly keen to understand the process of "accelerated melting", where lubrication of ice flows by water and the disintegration of ice shelves could speed up the transfer of ice to the sea.
The research team found that the Recovery stream accelerates significantly as it passes over the lakes.
Upstream of the lakes, it flows at two to three metres per year; after passing them, at about 50 metres per year.
Whether there is a link to climate change is another question. The lakes lie in the eastern portion of Antarctica, where evidence suggests the icecap may be gaining mass rather than losing it.
Two of the new lakes are only exceeded in size by Lake Vostok
It is the west of the continent that primarily concerns climate researchers. Much of the Antarctic rock here lies below sea level, meaning that a warming of the oceans could lubricate ice flow on a significant scale.
But if sub-glacial lakes are affecting ice flow, that is something scientists will want to study further.
As this research team puts it: "The Recovery sub-glacial lakes and the associated Recovery ice stream tributaries have the potential greatly to affect the drainage of the East Antarctic ice sheet, and its influence on sea level rise in the near future."
Another expedition to the area, part of International Polar Year, is planned for 2008.