Autonomous Argo Float Delivers Crucial Data From Beneath Denman and Shackleton Glaciers

In a significant achievement for polar science, an autonomous Argo drifting float, deployed by researchers from the Commonwealth Scientific and Industrial Research Organisation (CSIRO), successfully transmitted crucial transect data in early December 2025. This information was gathered directly from beneath the ice shelves of the Denman and Shackleton Glaciers in East Antarctica. The robotic instrument proved remarkably resilient, operating autonomously for two and a half years. During this extended mission, it recorded approximately 200 profiles detailing temperature and salinity measurements spanning from the seafloor up to the base of the ice cover.

Remarkably, the float spent eight full months submerged beneath the massive ice sheet, completely cut off from any possibility of satellite communication. This period of isolation highlights the instrument's robust engineering. The mission’s primary value lies in obtaining direct oceanographic readings from regions of East Antarctica that were previously inaccessible to direct measurement. This data provides an unprecedented look into the processes occurring at the ice-ocean interface.

Dr. Steve Rintoul of CSIRO emphasized that these observations are vital for developing a deeper understanding of the vulnerability of these ice shelves. The data was collected specifically within the boundary layer of water situated immediately below the ice base. Since the float could not surface to transmit data or recalibrate its position, researchers had to employ an ingenious method to reconstruct its path. They correlated the recorded ice thickness measurements at various contact points with existing, known satellite maps to piece together the robot’s trajectory under the ice.

Over the course of its operational lifespan beneath the ice, the robot managed to traverse a distance of roughly 300 kilometers under the glaciers. This extensive movement allowed for a broad spatial sampling of the sub-ice ocean conditions, which is critical for accurate modeling.

The subsequent analysis of the collected data revealed a stark divergence between the two glacial systems. The Shackleton Ice Shelf, situated geographically between 95° and 105° east longitude, appears relatively stable for the time being. Measurements indicate that warmer ocean water, which typically drives melting, is currently not infiltrating the area beneath its base. This shelf, first charted in 1840 by Charles Wilkes’s expedition, spans an area of approximately 37,400 square kilometers.

Conversely, the findings concerning the Denman Glacier confirmed existing scientific anxieties. This glacier is demonstrably being impacted by warmer water masses. The Denman Glacier, which was discovered in November 1912 by Sir Douglas Mawson’s expedition, is a major source of concern because its complete disintegration could potentially contribute 1.5 meters to the global sea level rise. Earlier investigations, such as the BedMachine Antarctica project conducted by the University of California, Irvine, had already identified a deep canyon beneath this glacier, plunging 3,500 meters below sea level, signaling inherent instability.

These newly acquired results significantly enhance the scientific community's grasp of the complex dynamics between the ocean and ice in this crucial Antarctic sector. Although the Argo float was initially launched with the specific goal of studying the Totten Glacier, the CSIRO researchers stress the immense value of this unexpected data for refining future sea-level rise projections. The mission has been deemed an overwhelming success, paving the way for more sophisticated monitoring techniques in the planet's polar regions.