Cause of long potentially damaging channels on Antarctic Ice Shelves found

Large rocky hills deep under glaciers can create huge channels on the surface of the ice, even if the hills are buried under two kilometers of ice.

The Antarctic glaciers are remote and difficult to study, which means that their behavior is unknown. These knowledge gaps mean that scientists do not know exactly how they will respond to climate change.

However, thanks to new technologies, researchers are able to study them in more detail than ever before, even looking through glaciers several kilometers thick to observe the processes taking place at their bases.

The team, including researchers from British and American universities, used radar penetrating the ice on aircraft to scan the glacier and determine what is happening at its base.

In a study published today in Nature Communications, researchers led by Imperial College London have connected a huge 130-kilometer canal (distance between London and Birmingham) to the surface of an Antarctic ice floe to the landscape located two kilometers under the ice cap in upstream.

The channel and associated features on the ice surface are thought to be a point of instability on the ice floe. If the surface ice melts, the water will preferentially flow on these features, digging a deeper channel and creating other weaknesses.

Identify instabilities

Surface channels of pack ice are observed across Antarctica, so the process uncovered by the research is likely to be trivial. Now that the cause has been identified, researchers can look for similar signs of instability in other Antarctic channels, particularly in areas known to be vulnerable to change.

Professor Martin Siegert, Project Leader at the Grantham Institute – Climate Change and Environment at the Imperial, said: "This discovery will help us identify potential areas of the Antarctic that may pose an increased risk of change. Because of the ice channeling, we can not ignore the underground processes, even if they are below two kilometers of ice in some of the most remote places on the planet. "

He added: "The melting of surfaces on Antarctic ice has been observed in recent years and an increase in atmospheric conditions would increase levels, which would reinforce the need to limit global warming to 1.5 ° C above sea level. above pre-industrial levels ".

Hold the ice

The study area – centered on the Ice Stream Foundation – is one of the poorest regions of Antarctica, located near the pack ice "ground", resting on land rather than water. The ice cap on the ground supplies ice in the ocean and thus contributes to sea level change.

Floating ice shelves hold the ice sheet and provide a "backward force" to reduce the speed of ice on the ground. Floe pack ice weakness can therefore lead to an accelerated flow of melted ice and a rise in sea level.

The Ice Stream Foundation is also the type of glacier that can have water at its base, flowing between the bottom of the glacier and the underlying rock. The team found that when the base of the glacier encountered a large isolated hill at the same point as it began to float, a cleft formed under the ice below the hill.

This hole was filled with water from the base of the glacier, which made a hole in the ice. This gouge reached 800 meters high in some places and led to the vast channel that is seen on the surface of the ice.

"Hard rock formations form 130-km ice canals crossing water concentrating in basal ripples" by Hafeez Jeofry, Neil Ross, Anne Le Brocq, Graham Alastair, Jilu Li, Prasad Gogineni, Mathieu Jordan and Martin J Siegert is published in Nature Communications.

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More information:
Hafeez Jeofry et al. The hard rock formations create 130 km ice channels through the concentration of water in the basal ripples, Nature Communications (2018). DOI: 10.1038 / s41467-018-06679-z