In the Amundsen Sea (West Antarctica), a Kongsberg Hugin autonomous underwater vehicle, operated by an international team with participation from the University of Gothenburg, ventured 17 kilometers under the Dotson ice shelf. There, it created six high-resolution maps of the icy “ceiling” and measured currents, temperature, salinity, and melting in Antarctica.
The result, published in Science Advances, describes an underwater landscape that challenges the idea of uniform melting: the ice erodes in different ways depending on the water’s speed, heat content, and the presence of fractures.
Features of the Underwater Landscape
The maps reveal three key elements:
- Terraces: flat surfaces between 200 and 2,000 meters wide, bordered by walls up to 5 meters high. In some areas, they stack in several levels, like steps carved from below.
- “Teardrops”: cavities sculpted upwards, between 20 and 300 meters long, with a typical relief of 14 meters. They are not visible on the surface, as the internal stresses of the ice prevent the basal relief from translating into external signals.
- Full-thickness fractures: some modified by basal melting, with eroded bases and associated marks. A Landsat analysis indicates that several originated in the 1990s and have widened over time, evidencing decades of progressive erosion.
Two Oceanographic Regimes
The study shows that Dotson does not melt uniformly:
- Eastern part: receives relatively warm and saline water (mCDW) through a deep channel. The ice is thicker (300–400 m) and the basal melting is around 1 meter per year.
- Western part: dominated by a colder, shallower, but faster flow, which favors channels and an average melting of 15 meters per year, with thinner ice (250 m).
The difference is not only thermal: in the west, shear-induced turbulence mixes heat towards the ice-ocean interface, accelerating the melting.
Hypotheses on the Shapes
- The “teardrops” could originate from turbulent plumes linked to Ekman dynamics, triggered by fractures or rocks released in the ice, propagating asymmetrically due to the Earth’s rotation.
- The terraces would be traces of episodic intrusions of warm water at the ice base, like those recorded between 2014 and 2016 by nearby oceanographic moorings.
Logistical Challenges
Operating under an ice shelf involves extreme limitations: without GPS or radio communication, the vehicle follows its route and can only transmit data upon surfacing.
In February 2024, during a final mission under Dotson, the robot did not return. The International Thwaites Glacier Collaboration reported that it likely remains under the shelf.
Continuity of Research
The loss of the vehicle does not halt the project. Kongsberg announced that the University of Gothenburg will replace it with a new Hugin, thanks to insurance funds and a private donation, to resume expeditions in Antarctica.
The obtained maps show that basal melting is organized into specific features —terraces, channels, fractures, and “teardrops”— that concentrate heat transfer and damage. The study warns that this diversity of processes must be incorporated into models to improve future melting projections, key to understanding the impact of climate change on the stability of Antarctic ice shelves.
