Cause of long, potentially damaging channels on Antarctic ice shelves found

Large rock hills deep below glaciers can cause huge channels on the ice surface – even if the hills are buried under two kilometres of ice.

Crevassing on the Foundation Ice Stream
Crevassing on the Foundation Ice Stream

Glaciers in Antarctica are remote and difficult to review, which suggests a lot of regarding their behavior is unknown. These data gaps mean scientists cannot be certain however they’re going to answer global climate change.

However, with new technology researchers are able to study them in bigger detail than ever before, even searching through kilometers-thick glaciers to look at processes occurring at their bases. For the study, scientists used ice-penetrating measuring device mounted on planes to see through the ice mass and determine what’s happening at its base.

Scientists have connected an enormous 130-km-long channel on the surface of an Antarctic floating shelf ice to the landscape 2 kilometers below the ice sheet upstream. The channel is thought to be a point of instability on the ice shelf. If the surface ice melts, water will preferentially run down these features, carving out a deeper channel and creating further weaknesses.

As the ice, flowing from upper-left to lower-right, encounters a hill beneath the ice (light grey shape), a cavity is created under the ice shelf. Water (red and blue arrows) feeds into the cavity, melting a channel that is reflected on the ice surface (dark grey channel)
As the ice, flowing from upper-left to lower-right, encounters a hill beneath the ice (light grey shape), a cavity is created under the ice shelf. Water (red and blue arrows) feeds into the cavity, melting a channel that is reflected on the ice surface (dark grey channel)

According to scientists, the study will help pinpoint potential regions of Antarctica that may be of enhanced risk of change because of ice shelf channeling.

Project lead Professor Martin Siegert, from the Grantham Institute – Climate Change and the Environment at Imperial, said, “It also reminds us that we can’t ignore subsurface processes – even if they are below two kilometers of ice in some of the most remote places on Earth.”

“Surface melting on Antarctic ice shelves has been noticed in the last few years, and further warming of atmospheric conditions would lead to increased levels – adding to the need to restrain global warming to 1.5C above pre-industrial levels.”

The region that scientists studied, is known as one of the poorest known parts of Antarctica, near the edge of the ‘grounded’ ice sheet, resting on land rather than water.

The grounded ice sheet feeds ice into the ocean, then contributes to water level modification. Holding the ice sheet back are the floating ice shelves, which offer a ‘back force’ to scale back the speed of the grounded ice. Weakness within the floating ice will so result in an accelerated flow of the grounded ice, and water level rise.

The team found that when the base of the glacier encountered a large solitary hill at the same point it starts to float, a gap emerged under the ice downstream of the hill. This gap was crammed by water from around the base of the ice mass, that sliced a gouge upwards into the ice. This gouge was 800 meters high in some places and LED to the intensive channel seen on the surface of the ice.

The study is published in the journal Nature Communications.