Melting and refreezing at the base of the Greenland ice sheet has created massive, complex structures the height of skyscrapers and the width of Manhattan, according to research published in Nature Geoscience.
The hidden formations more than a mile below the surface stand in stark contrast to the nearly flat, smooth exterior of the ice sheet and may accelerate its flow toward the sea, researchers say. Scientists had previously interpreted the irregular topography at the base of the ice as hills or mountains, but ice-penetrating radar revealed that the structures were made of ice rather than rock.
Scientists from Columbia University explained that as meltwater at the bottom refreezes over hundreds or 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.
Greenland’s glaciers appear to be moving more rapidly toward the sea as climate warms, but it remains unclear how the refreezing process will influence this trend, the researchers said. “We see more of these features where the ice sheet starts to go fast,” said the study’s lead author. “We think the refreezing process uplifts, distorts and warms the ice above, making it softer and easier to flow.”