The Deepest Point of All Earth's Continents Has Been Discovered in Antarctica

The deepest point on any of Earth's continents has been discovered by scientists.

The trench, which stretches two miles below sea level, is found beneath the Antarctic ice in what is known as the Denman trough.

Researchers discovered the trough as part of a project to make the most detailed map of the land beneath Antarctica to date. BedMachine is a topography map of Antarctica, showing the ridges, trenches and slopes that make up the landscape. The international team of researchers, led by glaciologists from the University of California, Irvine, created the map using data from 19 research institutions going back over 40 years. It used radar and satellite images to work out the thickness of the ice and the land below, covering an enormous area.

The map and findings related to it have been published in the journal Nature Geoscience. Mathieu Morlighem, lead author of the study, told Newsweek that he started working on BedMachine almost by accident. He had been creating models of ice sheets with colleagues from NASA's Jet Propulsion Laboratory and when they ran these models on two glaciers, they realized something was wrong. "Some glaciers that we know are currently losing mass were gaining mass, for example," he said. "We started investigating the problem: was it the model resolution, inaccurate physics, bad forcings? We realized that it was because the shape of the bed was not right."

Morlighem said the scientists realized that if they wanted better ice sheet models, they needed better maps of the bed beneath. Morlighem then came up with a new technique to see the ground under the ice—satellite data of changes to the surface, snow accumulation, and lines of radar data that can be applied to areas where radar is currently unavailable.

"The biggest challenge was that Antarctica is huge—bigger than the US and Mexico combined—and so applying this method to the entire coast was very time-consuming: it took about five years to get to BedMachine," he said.

Once completed, however, the researchers were able to find previously unknown features of the land below the ice. They discovered pronounced ridges across the troughs that feed the Ross ice shelf. This is the largest ice shelf in Antarctica and has been a point of concern to climate scientists, with research suggesting it could be at risk of collapse under projected global warming.

"These ridges were unknown and make this sector of the ice sheet extremely resilient to increase in ocean-induced melting," Morlighem said. "Working on climate change, we don't have good news frequently ... that being said, we found other sectors that we did not know would be more vulnerable to climate change."

He continued: "The other big surprise was, of course, the incredible trough of Denman Glacier."

BedMachine
BedMachine Antarctica. Map showing the land under Antarctica's ice. Mathieu Morlighem / UCI

Scientists knew this large glacier in East Antarctica had a trough beneath it, but they had no idea how deep it was. Morlighem said there had been several attempts to work this out using airborne radar, but as soon as they flew over, the echo would mask the bed.

With the new technique, the team was able to deduce the Denman trough reached 3.5 kilometers (2.17 miles, or 11,482 feet) below sea level—the deepest point on land.

"Denman Glacier flows through a deep canyon more than 3,500m below sea level ... BedMachine reveals that the bed beneath this ice stream is the deepest continental point on Earth," the team wrote.

The trough, Morlighem added, is about 62 miles long and 12.4 miles wide. "Troughs and fjords are typical of glacial landscape: as glaciers flow, advance and retreat, they carve the bed and so over tens of thousands of years, we can have very deep valleys depending on the rates of erosion," he said.

The deepest known point on Earth—not just its continents—is the Challenger Deep in the Mariana Trench, which stretches to a depth of around 36,200 feet, or almost seven miles.

BedMachine should help scientists better forecast how Antarctica will respond to climate change in the coming years. By knowing the landscape beneath, they can create more accurate models for future warming.

"I am an ice sheet modeler, so I [want] to see how this map affects the projections of sea level rise," Morlighem said. "It is also—and will always be—a work in progress: it will get better as we get more data, so I plan on maintaining it over the foreseeable future."