Robot deployed underneath 'Doomsday Glacier' delivers surprising views

Cutting-edge research, which required the deployment of a robot named Icefin into a 600-meter-deep borehole, delivered a never-before-seen perspective on the changes occurring beneath the Thwaites glacier in western Antarctica. Nicknamed the 'Doomsday Glacier,' it is the size of Great Britain or the state of Florida in the U.S.

Researchers concluded that although melting beneath the floating ice shelf has increased, it's currently at a rate lower than many computer models predict, according to two papers published in Nature (February 15). 

The findings boost our understanding of one of the fastest-changing ice-ocean systems in Antarctica and, significantly, the glacier's role in future sea level rise.

How will Thwaites Glacier raise sea levels?

Thwaites Glacier has had one of the quickest rates of change of any glacier in Antarctica, with a 14-kilometer retreat in the grounding line (the point where it meets the seafloor) since the late 1990s. 

Since a significant portion of its ice sheet is submerged, it is vulnerable to rapid, irreversible ice loss. Melt from this loss could cause the sea level to rise by more than 50 centimeters within centuries.

Dr. Peter Davis of the British Antarctic Survey (BAS) made measurements of the ocean as part of the MELT project using a 600-meter-deep borehole drilled around two kilometers from the grounding line. His measurements were then compared with melt rate observations made at five additional sites below the ice shelf. 

Over nine months, Davis found that the ocean surface along the grounding line warmed and salted. However, the ice base melted on an average of 2 to 5 meters - a rate slower than in previous models.

Icefin: what is the underwater robot?

In a second paper, a group of scientists and engineers led by Dr. Britney Schmidt of Cornell University in the U.S. deployed a robot named Icefin through the 600-meter-deep borehole. Icefin was designed with grounding zones in mind - especially those previously impossible to survey.

The team discovered that the melting rate along the flat areas of the ice shelf is slowed by a layer of fresher water between the bottom and the ocean underneath the ice shelf. 

To their surprise, the bottom of the ice shelf had developed stair-like topography due to melting: rapid melting occurs in these locations and ice cracks.

"These new ways of observing the glacier allow us to understand that it's not just how much melting is happening, but how and where it is happening that matters in these hot parts of Antarctica, said Dr. Britney Schmidt in a press release, who's an Associate Professor at Cornell University and lead author of the second study.