Newly Discovered Frozen Underworld Beneath Greenland Speeding its Flow to the Sea

Beneath the barren whiteness of Greenland, there lies a mysterious frozen underworld, which through its melting and refreezing process, may be speeding its ice flow to the sea.

Using ice-penetrating radar, researchers have discovered ragged blocks of ice as tall as city skyscrapers and as wide as the island of Manhattan at the very bottom of the ice sheet.

Scientists said the findings, published in the journal Nature Geoscience, could deepen their understanding of how the ice sheets of Greenland and Antarctica respond to climate change.

"We see more of these features where the ice sheet starts to go fast," Robin Bell, the study's lead author and a geophysicist at Columbia University's Lamont Doherty Earth Observatory, said in a statement. "We think the refreezing process uplifts, distorts and warms the ice above, making it softer and easier to flow."

Until recently, scientists studying the Greenland ice sheet for evidence of global warming-induced changes had thought the shapes they discerned beneath the ice sheet were mountain ranges, The Guardian reported. New gravity-sensing and radar operating from NASA's airborne surveys revealed otherwise.

The structures - some one-kilometer thick - cover about a tenth of northern Greenland, researchers estimate. They become bigger and more common as the ice sheet narrows into ice streams, or glaciers, headed for the sea. Researchers believe that as the meltwater at the bottom refreezes - a process that has been underway for thousands of years - it radiates heat into the surrounding ice sheet, making it pick up its pace as the ice becomes softer and flows more easily.

In fact, the Petermann Glacier in the north of Greenland, which shed a 100-square-mile chunk of ice in 2010, is sweeping about a dozen large features with it toward the coast as it funnels off the ice sheet. Accelerating ice flows such as this are worrying scientists, especially as our climate continues to warm.

"Overall, these observations suggest that basal freeze-on is a key control on the large-scale flow of Petermann Glacier, a possibility that has not been explored previously," said University of Texas researcher Joseph MacGregor.

Researchers expected to find such warped formations at Greenland's interior, but not at its edges where lakes form and rivers flow over the surface, they said. Water from these features fall through crevasses in the ice to reach the base of the ice sheet, where some of it refreezes. This refreezing and deformation may actually contribute to faster melting, and be more widespread than previously thought.