Giant structures found underneath Antarctic ice

 Giant structures almost 400-meter-long discovered underneath Antarctic ice     

The world's climate is in crisis, and it is important to monitor potential tipping points like critical thresholds which, when breached, can lead to snowballing and potentially irreversible changes. As part of an attempt to understand how the ocean melts Antarctica’s ice shelves, researchers sent a remotely operated vehicle (ROV) called Ran underneath the Dotson ice shelf in West Antarctica, to map the region using sonar. These missions have now peeled back an astonishing layer of the Antarctic mystery, revealing formations nearly 400 meters in length hidden beneath the ancient ice. The features resemble teardrops, or claw marks. The results of the survey include some interesting finds like strange patterns of peaks and valleys at the glacier's base, where underwater currents are slowly eroding it and moving further into the cracks. What was especially odd was that coming out of these rougher-than-expected peaks and valleys were features resembling sand dunes, stretching up to 400 meters (1,300 feet) long. Analysing the features, the team believes that they are the result of the movement of water on the underside of the glacier due to the Earth's rotation.

In 2022, a team from the University of Gothenburg deployed the autonomous submersible Ran under the Dotson Ice Shelf, mapping more than 1,000 km's of submerged terrain and capturing detailed contours of a realm untouched by human eyes¹. One engineer described watching Ran’s descent as “like venturing into another planet,” underscoring the mission’s unprecedented scope. “We have previously used satellite data and ice cores to observe how glaciers change over time," lead author Anna Wåhlin, Professor of Oceanography at the University of Gothenburg, said. "By navigating the submersible into the cavity, we were able to get high resolution maps of the ice underside. It's a bit like seeing the back of the moon." During the expedition, the ROV travelled over 1,000 km's (621 miles) back and forth under the glacier, reaching 17 km's (10.5 miles) into a cavity within the ice. “Better models are needed to predict how fast the ice shelves will melt in the future. It is exciting when oceanographers and glaciologists work together, combining remote sensing with oceanographic field data," Wåhlin said. "This is needed to understand the glaciological changes taking place, the driving force is in the ocean."

Ran wasn’t your average underwater vehicle. Equipped with cutting-edge multi-beam sonar and advanced inertial navigation, it painted a high-resolution portrait of the glacial foundation. Engineers even accounted for Coriolis-induced currents, swirling flows driven by Earth’s rotation which NASA’s Jet Propulsion Laboratory highlights as crucial for accurate under-ice mapping. The expedition was conducted in the drift ice regions of West Antarctica. On the return visit in 2024, Ran disappeared without a trace beneath the ice. "If you look closely at the shapes they are not symmetrical, they are bent a bit like blue mussels, and the reason for that asymmetry is Earth's rotation," Wåhlin said. "Water moving on Earth is subject to something called the Coriolis force, which is acting to the left of the direction of motion in the Southern Hemisphere. If we are correct, there is a force balance in the layer closest to the ice where friction is balanced by the Coriolis force." The pattern of water which appears to have created this pattern is known as an Ekman Spiral.

What the data unveiled stunned the team: elongated, tear-shaped structures stretching nearly 400 meters, comparable to four football fields laid end to end. These features appear sculpted by complex hydraulic processes, possibly driven by subglacial melt water currents carving channels beneath the ice shelf. Subglacial channels can transport melt water at speeds exceeding one km per year, reshaping the ice base from below. "When surface water molecules move by the force of the wind, they, in turn, drag deeper layers of water molecules below them. Each layer of water molecules is moved by friction from the shallower layer, and each deeper layer moves more slowly than the layer above it, until the movement ceases at a depth of about 100 meters (330 feet)," the National Oceanic and Atmospheric Administration (NOAA) explains. Each sonar echo provides climate scientists with critical input for glacier-flow models. According to the National Snow and Ice Data Centre, understanding where melt water channels form and how they evolve is essential for predicting ice-shelf stability and projecting future sea-level rise.

The deeper water is affected by the Coriolis effect, with plumes spreading asymmetrically according to which hemisphere you are in. In the northern hemisphere, the plume spreads to the right; in the southern hemisphere, to the left. "As a result, each successively deeper layer of water moves more slowly to the right or left, creating a spiral effect. Because the deeper layers of water move more slowly than the shallower layers, they tend to 'twist around' and flow opposite to the surface current," NOAA says. The Dotson Ice Shelf acts as a natural buttress, slowing inland ice’s journey to the sea. If warming currents continue to erode its underbelly, we could see up to half a meter of global sea-level rise by 2100, imperilling coastal communities worldwide. Those hidden caverns beneath the ice may hold the key to our planet’s watery future. The team notes that the older "teardrop" shapes had tails more parallel to the flow, as expected using Ekman theory, but adds that more observations are needed. Unfortunately, since this expedition, the submersible has gone missing underneath the Doomsday Glacier. During dives, the submersible does not have constant contact with the researchers operating it. Instead, the AUV follows a pre-programmed route and uses an advanced navigation system to find its way back from underneath the ice to open water. 

However, after several successful dives underneath the ice, during one trip in January of 2024, Ran failed to appear at the rendezvous point. Despite searches with acoustic equipment, drones and helicopters, the team has been unable to locate Ran since. Plans are underway for a next-generation submersible with improved tracking and extended-range sensors. As researchers gear up for another descent, one can’t help but wonder what other marvels, and enigmas, lie dormant under Antarctica’s frozen veil. “It’s a bit like looking for a needle in a haystack, but without even knowing where the haystack is," Wåhlin said. "At this point, Ran’s batteries are dead. All we know is that something unexpected happened under the ice. We suspect it ran into trouble, and then something prevented it from getting out." The team believes this is likely sadly the end for Ran, though they note it is a better end for the submersible than aging and gathering dust in a garage. They now plan on replacing the submersible and continuing its important research in future ahead.