In 2022, a bright orange autonomous submarine named Ran was deployed beneath West Antarctica’s Dotson Ice Shelf by scientists from the International Thwaites Glacier Collaboration. Equipped with upward-looking sonar, Ran surveyed 54 square miles of previously uncharted terrain under the floating ice, revealing a complex landscape of terraces, channels, and teardrop-shaped pits — none of which were visible from satellite imagery. These formations provided new insight into how melting occurs beneath ice shelves, driven by the Circumpolar Deep Water current, a relatively warm and salty flow from the Southern Ocean.

When researchers returned in early 2024 to track changes, Ran was redeployed but failed to resurface. Despite extensive search efforts using acoustic equipment, drones, and helicopters, no trace of the submarine was found. Possible causes include mechanical failure, collision with an ice ridge, or interference from marine life like seals. The extreme pressures of deep-sea environments also pose risks to robotic explorers.

Before its loss, Ran transmitted detailed maps that are now published in Science Advances. These maps show that melting is not uniform — the western side of Dotson melts faster due to stronger currents delivering more heat, while the eastern side remains relatively stable. This uneven erosion matters because ice shelves act like doorstops, holding back land-based glaciers. As they thin, glaciers accelerate into the ocean, contributing to global sea-level rise.

Since 1979, Antarctic melt has already raised global sea levels by about half an inch. Ran’s final data helps improve the accuracy of climate models and sea-level projections, offering a clearer picture of how vulnerable ice shelves respond to warming oceans. The mission highlights both the promise and peril of robotic exploration in Earth’s most remote environments.