Greenland Ice Sheet At Risk From Growing Network of Lakes

The future stability of Greenland’s ice sheet is at risk from a growing network of melting lakes that currently extends over 100 kilometers. Scientists discovered these fast-draining lakes have started a chain reaction, which could lead to the potential collapse of the Greenland ice sheet.

Every summer, warmer temperatures leads to the formation of lakes on the surface of the Greenland ice sheet. Although many of these lakes exist for weeks or months, they eventually drain through nearly 1 kilometer of ice in just a few hours, transferring massive amount of water and heat to the base of the ice sheet.

Although it was previously thought these drainage events were isolated, a new study suggests the lakes actually form a massive interconnected network. Researchers discovered the affected areas include sensitive regions of the interior of the ice sheet — the impact of ice flow on these regions is considered to be substantial.

How are these interconnected network of lakes being formed? According to the researchers, when one lake drains, the water spreads rapidly under the ice sheet and flows faster. The faster flow allows new fractures to open up on the surface of the ice sheet, which in turn act as the perfect pipeline for draining other lakes.

This process has the potential to start a chain reaction that can drain multiple lakes, some of which could be located as far as 80 kilometers away. In one such case, 124 lakes drained in just five days. Scientists said these events can temporarily accelerate ice flow by 400 percent, which in turn can also ramp up sea-level rise.

“Transfer of water and heat from surface to the bed can escalate extremely rapidly due to a chain reaction,” Poul Christoffersen, from Cambridge University’s Scott Polar Research Institute and lead author of the new study, said in a statement. “In one case we found all but one of 59 observed lakes drained in a single cascading event. Most of the melt lakes drain in this dynamic way.”

The new research highlights how forces under Greenland’s ice sheet can undergo sudden changes, leading to the formation of fractures of frozen ice. Researchers developed a 3D model to help demonstrate how even lakes formed in the stable area of the ice sheet can drain when fractures, caused by other rapidly-melting lakes, open up on the surface.

“We found clear evidence of these crevasses at 1,800 metres above sea level and as far 135 kilometres inland from the ice margin. This is much farther inland than previously considered possible,” Christoffersen added.

“The transformation of forces within the ice sheet when lakes drain is sudden and dramatic,” said co-author Marion Bougamont, also from the Scott Polar Research Institute. “Lakes that drain in one area produce fractures that cause more lakes to drain somewhere elsewhere. It all adds up when you look at the pathways of water underneath the ice.”

“This growing network of melt lakes, which currently extends more than 100 kilometers inland and reaches elevations as high a 2,000 meters above sea level, poses a threat for the long-term stability of the Greenland ice sheet,” said Christoffersen. “This ice sheet, which covers 1.7 million square kilometers, was relatively stable 25 years ago, but now loses one billion tons of ice every day. This causes one millimeter of global sea level rise per year, a rate which is much faster than what was predicted only a few years ago.”

Although a complete loss of all the ice in Greenland is very unlikely in this century, researchers warn the way the ice sheet is responding to climate change calls for a global effort in drastically reducing greenhouse gas emission levels.

The new research has been published in the journal Nature Communications.