Scientists Map 39,619 Grounded Icebergs Around Antarctica Using AI

Around Antarctica, thousands of icebergs are not drifting through the Southern Ocean. They are resting on the seafloor, anchored in shallow coastal waters and quietly influencing the movement of sea ice. For the first time, scientists have used artificial intelligence and satellite radar imagery to map this hidden population across the entire Antarctic coastline. The result is a continent wide dataset containing 39,619 grounded icebergs, most of them far smaller than the giant icebergs that dominate news photographs. About 93 percent measure less than 1 square kilometre, yet these small icebergs collectively help form what researchers call a “picket fence effect,” holding landfast sea ice in place. As reported by Phys.org, the discovery provides a new baseline for understanding Antarctic ice stability, marine ecosystems and the effects of a warming ocean.

Icebergs that do not drift

Most people imagine an iceberg as a floating block of ice carried by currents and wind. Grounded icebergs are different. They have become lodged on the seafloor, usually on shallow parts of the Antarctic continental shelf, and remain stationary for periods ranging from days to decades. Their immobility gives them an important physical role. A grounded iceberg can act like an anchor, helping sea ice remain attached to the coast. The ice around it may become more stable and resist breaking apart when winds, waves and ocean currents push against it. This stationary ice is known as landfast ice, or fast ice. It forms along the coast and around grounded icebergs during the polar winter. Unlike drifting sea ice, fast ice remains fixed in place for at least part of the year. It can protect ice shelves from ocean forces, provide habitat for seals and penguins, and support marine organisms living beneath and around the ice. The influence of each iceberg may be local, but thousands of grounded icebergs together can shape large sections of the coastal environment.

Why mapping them was difficult

Before this project, scientists did not have a complete, high resolution map of grounded icebergs around Antarctica. The coastline is enormous, the conditions are extreme and many icebergs are hidden within complex mixtures of sea ice, snow and shallow water. Manual mapping from satellite images is slow and demanding. Researchers must distinguish grounded icebergs from ordinary sea ice, ice shelf fragments and other bright or stationary features. A single image may not reveal whether an iceberg is genuinely resting on the seabed or temporarily held in place by surrounding fast ice. The new project used Sentinel 1 synthetic aperture radar imagery. Radar satellites can collect information in darkness and through cloud, making them particularly useful in polar regions where sunlight and clear skies are not guaranteed. Researchers trained an artificial intelligence system to recognise grounded iceberg features in the radar data. The method combined deep learning with information about bathymetry, sea ice concentration and changes across multiple images. These additional constraints helped reduce false identifications caused by confusing coastal conditions.

A continent wide count

The final dataset identified 39,619 stationary icebergs around Antarctica. Together, they covered about 13,430 square kilometres. They were distributed along roughly 57 percent of the Antarctic coastline, although their distribution was highly uneven. Just 14 percent of the coastline contained 80 percent of the grounded icebergs. The mapping was based on satellite observations from 2025, during a period when landfast sea ice was at a seasonal minimum. That timing helped researchers distinguish icebergs that were genuinely grounded from objects simply trapped in extensive surrounding sea ice. The project reduced the minimum detectable iceberg size to about 1.6 hectares, or four acres. That is far smaller than the enormous icebergs usually tracked by international monitoring agencies. Including these smaller features changed the overall picture of Antarctica’s grounded iceberg population. Rather than being dominated by a handful of giant icebergs, the dataset revealed a landscape filled with small, widely distributed anchors.

The importance of the smallest icebergs

Icebergs smaller than 1 square kilometre accounted for about 93 percent of all grounded icebergs. They also contributed roughly 54 percent of the total grounded iceberg area. That finding is significant because small icebergs are easy to overlook. Although they may not be prominent in the media, they are numerous enough to influence the coastal environment. Small, grounded icebergs can develop into chains of individual icebergs, spanning shallow waters and preventing sea ice from flowing freely or even causing it to build up and become more landlocked. “This configuration resembles a picket fence,” the scientists say. “While the individual pickets may be narrow, the series of pickets can impede or redirect movement. In the same way, small icebergs can act as physical barriers to sea ice and hold it in place.” Their collective impact may be greater than their individual size. The new map allows scientists to study these clusters as a system rather than treating each iceberg as an isolated object.

How the “picket fence” works

When sea ice forms along the Antarctic coast, wind and ocean movement can push it away from land. Grounded icebergs interrupt that movement. They provide points around which ice can accumulate and freeze together, creating a broader field of fast ice. The resulting ice can stabilise the edge of nearby ice shelves by reducing the reach of waves and ocean swells. Ice shelves are floating extensions of glaciers, and their collapse or thinning can allow more land ice to flow into the ocean. Grounded icebergs are not a complete defence against warming, but they may affect the conditions that determine how stable coastal ice remains. The picket fence effect is not uniform. It depends on the depth of the seafloor, iceberg distribution, sea ice conditions and ocean forces. Some clusters may strengthen fast ice, while others may have a smaller or temporary influence. The new dataset gives climate and ice researchers the information needed to incorporate these features into models. Without knowing where the grounded icebergs are, it is difficult to estimate their role in regional ice stability.

A risk from warming oceans

Small grounded icebergs may also be particularly sensitive to climate change. Because they have less ice mass, they can melt more quickly than larger grounded icebergs. But if they lose enough ice, they could become ungrounded and float away. This could weaken the picket fence effect where small icebergs are important anchors. Loss of individual icebergs may not be significant but loss of dense clusters may change the stability of nearby fast ice. More warmth in the ocean can speed up melting from below, especially in coastal regions where currents bring heat under sea ice and around grounded icebergs. Changes in snowfall, sea ice formation and ocean circulation could also affect the duration of the icebergs’ fixed position. The new map provides a baseline against which future changes can be measured. Scientists can return to the same regions in later years and determine whether icebergs have melted, shifted, grown through snowfall or become ungrounded.

More than an ice stability story

Grounded icebergs also influence marine ecosystems. Their presence affects seabed scouring, where shifting ice can scrape the seafloor and disturb organisms living there. Although grounded icebergs are stationary for a time, changes in their position can leave physical marks and redistribute sediment. The surrounding sea ice supports algae and other organisms that form the base of polar food webs. These communities feed krill and other small animals, which in turn support fish, penguins, seals and whales. A change in fast ice conditions can therefore influence food availability and habitat across several levels of the ecosystem. The icebergs may also contribute nutrients to coastal waters as they melt. Nutrients released from ice can support marine productivity, particularly in regions where sunlight and nutrient availability interact to create seasonal blooms. Mapping the icebergs helps researchers study these ecological relationships at a continental scale. It gives them a way to ask not only where grounded icebergs are located, but what kinds of communities develop around them.

Why artificial intelligence matters

The project demonstrates a practical use of AI in Earth science. The technology did not replace field observations or scientific judgement. It made it possible to analyse vast amounts of satellite data consistently and identify patterns that would have been difficult to map manually. Deep learning systems are especially useful for recognising shapes and textures in large image collections. But they can also make mistakes. That is why the researchers combined AI predictions with physical constraints and multi temporal observations. A feature had to fit the expected characteristics of a grounded iceberg across different conditions. The resulting dataset was published in Earth System Science Data under the title Grounded Icebergs around Antarctica: A High-Resolution Dataset Derived from Deep Learning and Sentinel-1 Synthetic Aperture Radar. The dataset is intended to support future research into coastal ice stability, marine productivity and the response of Antarctic environments to climate change.

A new view of Antarctica’s coast

The first Antarctic wide map changes the way scientists see the continent’s coastal zone. The important features are not only enormous ice shelves and famous drifting icebergs. Thousands of smaller icebergs, often overlooked in earlier surveys, are helping organise the movement of sea ice. The discovery also shows how much detail can remain hidden in an environment that has been observed by satellites for decades. Better algorithms and higher resolution data can reveal patterns that previous mapping methods could not capture. As Antarctica warms, the position and stability of grounded icebergs may change. Some may remain fixed for years, while others melt or drift away. Tracking those changes will help scientists understand how the relationships between seafloor, iceberg, fast ice and ice shelves evolve. For now, the 39,619 icebergs form a new reference point. Together, they reveal a frozen coastal system that behaves less like open water and more like a field of anchors, holding pieces of Antarctica in place.