Serious consequences

Cracks in the Greenland ice sheet are getting bigger and bigger

(Bild: stock.adobe.com/Néstor Rodan)

The crevasses in the Greenland ice sheet are widening ever faster - with serious consequences. A team of scientists has now warned that this process can subsequently accelerate ice loss and have a massive impact on sea levels.

The cracks in the ice sheet have widened significantly in just five years. This is the conclusion of a study by an international research group reported in the journal "Nature Geoscience".

The team led by Tom Chudley from Durham University in the UK analyzed more than 8,000 3D surface maps of the ice sheet, which were created from high-resolution satellite images. The data shows that the crevasses on the fast-flowing edges of the ice sheet have become larger and deeper between 2016 and 2021. According to the study, this development is happening faster than previously observed.

Crevasses

Crevasses are wedge-shaped cracks that form when a glacier moves unevenly. The ice flows at different speeds: often faster at the surface and in the middle than at the edges or in deeper layers. This creates tensions that cause the ice to break up.

Climate change is leading to a shift in these dynamics, according to the research group. Higher temperatures cause the ice to flow faster, causing the cracks to widen and penetrate deeper into the ice. The study shows that at the edges of the ice sheet, where large glaciers meet the sea, the glacier flow rate has increased.

Time of equilibrium now over
The increase was offset by a decrease in crevasses on Sermeq Kujalleq ("Southern Glacier"), the fastest flowing glacier in Greenland, whose movement had temporarily slowed down during the study period. However, the flow rate of Sermeq Kujalleq has since increased again, indicating that the period of equilibrium between the growth and closure of crevasses on the ice sheet is now over.

"In a warming world, we would expect more crevasses to form. That's because glaciers are speeding up in response to warming oceans, and the meltwater filling the crevasses is pushing the cracks deeper into the ice," lead author Chudley is quoted as saying in a statement.

The study now allows for the first time to detect a significant increase in the size and depth of crevasses on fast-flowing glaciers at the edges of the Greenland ice sheet, over periods of five years or less, Chudley added.

As crevasses grow, they feed the mechanisms that cause the ice sheet's glaciers to move faster, driving water and heat into the ice sheet's interior and accelerating the calving of icebergs into the ocean.

Mitautor Ian Howat von der Ohio State University

Dangerous domino effect
Co-author Ian Howat, Director of the Byrd Polar & Climate Research Center at Ohio State University, adds: "As crevasses grow, they feed the mechanisms that cause the ice sheet's glaciers to move faster, driving water and heat into the interior of the ice sheet and accelerating the calving of icebergs into the ocean." These processes could in turn accelerate the flow of ice and lead to the formation of more and deeper crevasses - "a domino effect that could accelerate the loss of ice in Greenland," says Howat.

If the entire Greenland ice sheet melts, sea levels will rise by 7 meters
According to the study, Greenland has already contributed to a rise in sea level of around 14 millimetres since 1992. If the trend continues, the meltwater from the ice sheet could raise global sea levels by up to 30 centimetres by 2100. If all of Greenland's ice were to melt, sea levels could rise by as much as seven meters.