Deep beneath the frozen cover of the Greenland Ice Sheet, stretches for 1,600 kilometers a valley in which an underground river flows, carrying water from Central Greenland to the northern coast.
In the past, planes flying over Greenland have partially mapped a rocky subsoil valley beneath the ice, but their radar coverage of the region has left gaps, said Christopher Chambers, a researcher at Hokkaido University in Sapporo, Japan.
To build a clearer picture of what lies beneath Greenland's surface, Chambers and colleagues created a simulation to explore the valley at different depths and simulate how water could melt from the surface of a glacier deeper below - possibly creating a flowing river, Chambers told Live Science … He presented his findings at the annual meeting of the American Geophysical Union (AGU).
Radar maps showed that the valley floor was extremely flat at a depth of 300 meters and 500 meters below the surface, Chambers said. It could be an area with active erosion or sediment deposition, such as a river, he explained.
Since this river will flow in the dark for hundreds of kilometers under the ice, the researchers called it a "dark river".
The dark river probably doesn't have very strong or constant currents because the melting of the glacier is dissipating over a large area, Chambers said.
The river can sometimes be quite powerful "but only at certain times", when large reservoirs of melt water accumulate and then release into the valley, he added.