The Thwaites Glacier in Antarctica is one of the most studied ice masses in the world. But recent research by a team using underwater robots is providing new insight into the mystery of glaciers thinning from below.
Quoted from NBC News, the Thwaites Glacier is called the 'Doomsday Glacier' because it is shrinking very quickly amidst the Earth's increasingly warm conditions. This glacier has both intrigued and worried scientists because its melt can raise sea level levels significantly.
Previous studies have found that these glaciers could collapse within 100 years, and meltwater from an ice mass the size of a province could raise global sea levels by up to 0.6 meters.
Scientists are eager to understand where and how Thwaites lost ice because glaciers are often considered a determinant of planetary change.
By looking down at the bottom of Thwaites Glacier, researchers can study how warm water funnels into cracks and crevices and make important measurements of where the ice meets the ocean.
The findings, reported in two separate papers published in the journal Nature, will help scientists better estimate what may happen as glaciers thin and paint a more detailed picture of how Thwaites changed as a whole.
"None of this changes the trends we've observed about rapid ice sheet disintegration," said Britney Schmidt, a professor of Earth and atmospheric sciences at Cornell University and lead author of one of the studies.
"These findings also tell not only how much melting is occurring but where and how it is occurring beneath Thwaites in a very important part of the system," he said.
Schmidt and colleagues from Cornell University, Pennsylvania State University and the British Antarctic Survey operated an underwater robot dubbed Icefin through boreholes almost 600 meters deep in the ice sheet.
The cylindrical drone spied fissures in the ice floor where warm water penetrated and caused rapid melting. These gaps are cracks that are usually formed by pressure on the ice when the glacier moves above the ground or juts out into the sea and weakens. The researchers observed crevices filled with warm water even at the base line of the glacier, where the ice first meets the ocean.
"These crevices are essentially flowing warm water faster than any other part of the glacier system. So they're not just flaws in the cracks in the ice, they're also a feature of these giants, and that process starts right at the runway line." he explained.
Icefin also discovered long ladder-shaped features known as terraces on the ice floor where significant melting occurred at different angles, he added. These features, along with the widening of the crevasses, hollow out the ice shelves from below and weaken the glaciers at points that are already prone to collapse.
In a separate study led by Peter Davis of the British Antarctic Survey, researchers found that a layer of fresh water between the ice floor and the ocean actually helps stabilize the flat part of the ice sheet. Disbursement in this region was found to be slower than previously estimated using computer models.
"Glaciers are still changing very quickly, but it helps us understand why some parts of a glacier move one way and other parts act in another," said Schmidt.
While Davis and his colleagues calculated slower rates of melting under the ice, the findings still add to a worrying outlook on the health of the glaciers. Thwaites' runway zone, where it meets the seafloor, has retreated nearly 14 km since the late 1990s.
"Our results were surprising but the glaciers are still a problem. If the ice shelves and glaciers were in balance, the ice escaping from the continents would equal the amount of ice lost through melting and iceberg building. What we found was that even with little melting, there was still rapid retreat of glaciers." "It doesn't appear to take much melting to push the glaciers out of this balance."