An autonomous underwater vehicle named Ran has provided the first high-resolution maps of the underside of West Antarctica’s Dotson Ice Shelf, revealing complex erosion patterns that indicate ice shelves are melting unevenly. According to researchers from the International Thwaites Glacier Collaboration, these findings—published in the journal Science Advances—demonstrate that warm, salty ocean currents are carving intricate channels and terraces into the ice, which acts as a critical buffer against rising sea levels.
How did the robot map the underside of the ice?
The 20-foot-long autonomous vehicle, Ran, navigated the cavity beneath the Dotson Ice Shelf in 2022 to conduct a survey of 54 square miles. Led by University of Gothenburg oceanographer Anna Wåhlin, the team utilized upward-looking sonar to capture data that satellites cannot detect. The resulting imagery revealed that the ice shelf is not a uniform sheet but is instead characterized by “frozen staircases” of terraces, deep grooves, and teardrop-shaped pits that reach up to 1,000 feet in length. Wåhlin described the experience as akin to viewing the far side of the Moon for the first time.
Antarctic melt has contributed to approximately half an inch of global sea-level rise since 1979. Mapping the underbelly of ice shelves is essential for scientists to create more accurate climate models and predict future coastal flooding risks.
Why is the ice melting into these specific shapes?
The varied erosion patterns are primarily driven by the speed and temperature of Circumpolar Deep Water, a relatively warm and salty current from the Southern Ocean. According to the research team, when this current moves slowly, it creates gradual, stepped terraces. Conversely, faster-moving currents carve out the smoother channels and elongated pits observed in the sonar data. The western region of the Dotson shelf experiences more rapid melting than the eastern side due to these stronger, heat-bearing current flows.
What happens to the ice shelf when it thins?
Ice shelves like Dotson function as natural “doorstops,” providing structural resistance that prevents land-based glaciers from sliding into the ocean. As the underside of the shelf thins due to oceanic heat, its ability to hold back these glaciers diminishes. This process accelerates the discharge of land ice into the sea, which is a primary driver of global sea-level rise. By identifying the specific areas where the shelf is most vulnerable, researchers can now provide more precise forecasts regarding the stability of the West Antarctic Ice Sheet.
What is the status of the Ran research vehicle?
During a follow-up expedition in early 2024 to monitor ice movement, the Ran vehicle disappeared during its mission. Despite extensive search efforts involving helicopters, drones, and acoustic detection equipment, the team recovered no debris. While the exact cause of the loss remains unconfirmed, researchers have suggested potential factors including mechanical failure, collisions with ice ridges, or interference from marine life in the high-pressure environment of the deep ocean.
Frequently Asked Questions
- Why can’t humans explore these depths instead? Humans are limited by the extreme pressure of the deep ocean, which makes direct exploration of sub-ice cavities dangerous and technically unfeasible.
- How do satellites compare to underwater mapping? Satellites monitor the surface of the ice, but they cannot “see” the structural erosion occurring on the underside of shelves, which is where the most critical melting happens.
- What is the next step for this research? With the baseline data provided by Ran, scientists aim to refine climate models to better predict how individual ice shelves will respond to changing ocean temperatures.
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