In 2022, an international team of scientists sent a 20-foot-long autonomous underwater vehicle (AUV) named “Ran” to explore the never-before-charted region beneath the Dotson Ice Shelf in West Antarctica. This mission aimed to uncover the complex dynamics responsible for the differing melting rates between the ice shelf’s western and eastern portions.
The International Thwaites Glacier Collaboration (ITGC) programmed the AUV “Ran” to dive into the cavity of the Dotson Ice Shelf, located near the Thwaites Glacier. Over the course of 27 days, the submersible traveled more than 600 miles, including a 10-mile journey directly into the cavity itself. The goal was to understand how glaciers melt faster near strong underwater currents and to map the topography of this critical ice shelf.
What the researchers discovered was striking: the western part of the Dotson Ice Shelf had vastly different characteristics compared to the thicker, slower-melting eastern portion. Using advanced multibeam sonar, “Ran” produced high-resolution maps of the ice’s underside, revealing unusual tear-drop-shaped features, icy plateaus, and detailed erosion patterns. These findings provided unprecedented insight into the ice shelf’s complex structure.
The results of this groundbreaking study were published in the journal *Science Advances*. Anna Wåhlin, the lead author, explained, “We have previously used satellite data and ice cores to observe how glaciers change over time. 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.”
Unlike glaciers, which rest on land, ice shelves float on the ocean and act as a crucial buttress that prevents ice on land from flowing into the sea, which would otherwise raise global sea levels. Because ice shelves rest on the ocean, it is possible—though challenging—to explore beneath them.
The “Ran” AUV was equipped to face these harsh subantarctic conditions. It used pulsed sound waves to map the ice shelf’s features but, due to its remote location, could not be tracked by GPS or communicated with during missions. Over 14 dives, some lasting a few hours and others over a full day, “Ran” mapped approximately 50 square miles of ice. The complexity of the structures uncovered exceeded all prior expectations.
Wåhlin remarked, “The mapping has given us a lot of new data that we need to analyze more closely. It’s clear that many previous assumptions about glacier underside melting fall short. Current models cannot explain the complex patterns we see. But with this method, we have a better chance of finding the answers.”
One key discovery linked the varying melt rates between the ice shelf’s east and west parts to a phenomenon called modified Circumpolar Deep Water (mCDW). This occurs when Pacific and Indian Ocean waters mix with local water masses, influencing the ice base. Ran’s measurements of underwater currents and the high melting rates along fractures within the glacier helped shed light on this process.
Originally, the team intended to study the nearby Thwaites Glacier, but its environment proved too difficult to access. Instead, the Dotson Ice Shelf served as an ideal testing ground for their equipment and methodology.
Surveys conducted in 2022 laid the groundwork for a return mission in early 2024 to assess changes in the ice shelf. Unfortunately, during this follow-up expedition, “Ran” failed to return to the designated rendezvous point. The team fears that the AUV may have either run aground or fallen victim to curious seals—representing a significant setback for research in this climate change-critical region.
Despite this loss, the data collected so far offers valuable new perspectives on how Antarctic ice shelves respond to ocean currents and environmental changes. Continued exploration and innovation remain vital as scientists strive to better understand—and ultimately protect—these fragile polar ecosystems.
https://www.popularmechanics.com/science/environment/a69220154/dotson-ice-shelf-discovery-secrets/
