An unmanned submarine exploring Antarctica’s hidden underside has delivered one of the most detailed looks yet at how ice shelves melt from below, before disappearing without a trace. As reported by Earth.com, the autonomous vehicle known as Ran mapped unusual and complex structures beneath West Antarctica’s Dotson Ice Shelf and then lost contact roughly ten miles under the ice.
The mission was led by Anna Wåhlin of the University of Gothenburg, whose work focuses on how ocean currents erode ice shelves and destabilize glaciers. Ran, an autonomous underwater vehicle, spent nearly a month in 2022 navigating alone beneath the Dotson Ice Shelf, surveying an area of about 54 square miles that had never been directly observed.
What the submarine discovered challenged simple models of ice melt. Sonar maps revealed flat plateaus, stacked terraces, smooth channels, and large teardrop-shaped pits carved into the ice from below. Some of these pits were nearly 1,000 feet long and more than 160 feet deep. Because these features are invisible to satellites, they remained unknown until Ran’s mission.
The patterns point to uneven melting driven by ocean currents. Warm Circumpolar Deep Water flows into the cavity beneath Dotson, but Ran’s measurements showed that the heat focuses erosion on the western side of the shelf. There, faster currents create turbulence that scours the ice smooth and accelerates thinning. On the eastern side, slower flows leave behind terraced steps, likely formed as slightly warmer water peeled away layers of ice over many years.
Ran also imaged fractures cutting through the entire thickness of the ice shelf. Many of these cracks, some open since the 1990s, were widened and smoothed at their bases by melting. These fractures act as hidden channels, steering warm water deeper into the ice and concentrating damage in ways that large-scale computer models often miss.
Together with satellite data, the findings help explain why West Antarctica is losing ice so rapidly. Ice loss from the region has already contributed more than half an inch to global sea level rise since the late 1970s. When floating ice shelves thin or weaken, they lose their ability to brace inland glaciers, allowing those glaciers to speed up their flow into the ocean.
The mission ended abruptly when Ran failed to return from a later dive intended to extend the mapping. With no real-time communication possible beneath hundreds of feet of ice, the team could only wait. The submarine never resurfaced, and no signals or debris were detected. Possible causes range from mechanical failure to a collision with unseen ice ridges.
Despite the loss, Ran’s earlier missions transformed scientists’ understanding of how ice and ocean interact beneath Antarctica. The detailed maps reveal a hidden landscape of terraces, channels, and fractures that strongly influence melting. For researchers trying to predict future sea level rise, Ran’s final data provide a rare and invaluable window into processes that were once completely out of sight.
The study is published in Science Advances.
