Nearly 40,000 grounded icebergs on the seafloor were identified along the entire Antarctic coast in a first high-resolution map that reveals the distribution of these features and their role in the stability of coastal sea ice.
The survey, conducted by researchers from the Australian Antarctic Program Partnership, the Institute for Marine and Antarctic Studies, the Australian Antarctic Division and Geoscience Australia, used radar imagery from the Sentinel-1 satellite and an artificial intelligence tool trained to automatically identify icebergs that remain fixed on the seafloor.
The study, published in the journal Earth System Science Data, identified 39,619 grounded icebergs in 2025. Collectively, these structures occupy an area of about 13,430 square kilometres and are distributed along 57% of the Antarctic coast. However, their presence is quite uneven: only 14% of the coast accounts for 80% of all identified icebergs.
One of the main conclusions concerns the size of these structures. Contrary to what the attention usually given to large icebergs might suggest, it is the smaller ones that dominate the ensemble. Icebergs smaller than one square kilometre account for 93% of the total and correspond to 54% of the area occupied by grounded icebergs.
The use of Sentinel-1 images and an automated system allowed the identification of structures as small as 1.6 hectares, significantly reducing the minimum size that could be detected by previous methods.
The “picket fence” effect
The researchers consider that the high concentration of these small icebergs in shallow waters contributes to the so-called picket fence effect. Like posts of a fence, grounded icebergs act as anchor points that help keep coastal sea ice in place, known as landfast ice.
This ice, in turn, plays an important role in protecting Antarctic ice shelves by helping to reduce their exposure to the action of the Southern Ocean. Grounded icebergs also provide habitat and nutrients for marine ecosystems.
The distribution now identified could help to better understand how these coastal zones respond to climate change. The researchers warn that the smaller icebergs may be particularly vulnerable to ocean warming, melting more quickly and no longer being anchored to the seafloor.
This loss of anchor points could trigger relatively rapid changes in the stability of coastal sea ice and, consequently, in the dynamics of Antarctica’s coastal zones.
The new dataset is intended to serve as a reference for future models of coastal ice stability and to monitor environmental changes on the Antarctic continent.
