Autonomous Argo Float Maps Warm Water Intrusion Beneath East Antarctic Glacier Denman

The autonomous Argo oceanographic float has successfully completed a pioneering transect beneath the ice shelf of East Antarctica. This mission gathered crucial temperature and salinity data that was previously inaccessible to direct measurement. Operating robotically, the instrument drifted for two and a half years, compiling nearly 200 ocean profiles across approximately 300 kilometers under the ice shelves of Denman and Shackleton. The findings from this data collection were formally presented in a study dated December 6, 2025.

The analysis derived from this mission painted a nuanced picture of the state of the ice shelves in the context of ongoing global climate shifts. The data clearly indicates that while the Shackleton Ice Shelf currently remains shielded from incursions of warmer water masses, the base of the Denman Glacier has already been reached by such warmer waters. This glacier is a significant concern because its potential destabilization could ultimately contribute 1.5 meters to the global sea level rise.

Denman Glacier is a formidable feature, measuring between 13 and 19 kilometers wide and extending 139 kilometers in length. Intriguingly, a canyon measuring 3,500 meters below sea level was discovered beneath it, establishing it as the deepest known land-based depression on Earth. Scientists previously documented that Denman Glacier lost approximately 268 billion tons of ice between 1979 and 2017, a rate that surpasses the average loss observed for other ice shelves in East Antarctica.

The intelligence gathered regarding subglacial ocean dynamics is vital, especially given widespread apprehension about the stability of the Antarctic ice sheet as a whole. The disintegration of ice shelves, which function as natural buttresses, can accelerate the flow of grounded continental ice, leading directly to a rise in global ocean levels. Although East Antarctica has long been viewed as comparatively more stable than its western counterpart, focusing attention on features like Denman underscores the latent instability present in this region.

The Argo mission, which globally maintains a fleet of about 3,800 floats, has brought about substantial advancements in climate change monitoring. The specific data collected during this transect allows for the refinement of models linking localized sea-level increases with changes in glacier thickness. Furthermore, in the broader context of Antarctic change, the slowing of the Antarctic Circumpolar Current—the world's most powerful current—is also associated with ice melt. Consequently, the data secured by this float serves as an essential component for calibrating global climate and oceanographic models.