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The trajectory of one of the largest icebergs ever monitored reveals how currents, warmer waters, and decades of satellite observation help explain changes in giant icebergs from Antarctica.
The A23a, Antarctic iceberg known as the “queen of icebergs”, ceased to be the largest in the world after losing large blocks of ice during its movement through the South Atlantic.
The fragmentation gained momentum in 2025, when the ice mass passed through the region of South Georgia, an area where ocean currents and waters further north favor the breakup of icebergs coming from Antarctica, according to researchers monitoring the phenomenon.
NASA recorded in April 2026 that the trajectory of A23a ended in fragmentation in the South Atlantic.
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The case was monitored by satellites for nearly four decades, from the detachment from the Filchner-Ronne ice shelf in 1986 to the reduction of the block to smaller fragments.
The origin of iceberg A23a in Antarctica
The A23a detached from the Filchner-Ronne ice shelf in Antarctica in 1986.
At the time, it had an area close to 4,000 square kilometers, according to data released by NASA, a size that placed it among the largest icebergs ever monitored by satellite.
After detaching, the block did not immediately follow through the ocean.
It remained grounded on the Weddell Sea floor for more than three decades, a behavior considered unusual by researchers studying large icebergs.
This prolonged stay meant that A23a was observed by different generations of satellites and scientific teams.
While other large icebergs formed and disappeared in shorter intervals, A23a remained practically stationary for much of its existence.
Only later did it start moving more intensely, on a route that took it to the more northern waters of the Antarctic Ocean.
The British Antarctic Survey reported in December 2024 that the iceberg had freed itself from an area north of the South Orkney Islands, after spending a period rotating almost in the same spot.
In March 2025, the British agency reported that A23a appeared to have run aground near the sub-Antarctic island of South Georgia, another monitored segment of its trajectory.
Ocean currents accelerated the breakup of A23a
The loss of mass intensified when A23a began to be influenced by currents around South Georgia.
Polar oceanographer Andrew Meijers, from the British Antarctic Survey, told CNN that the iceberg was following a strong current known as the Southern Antarctic Circumpolar Current Front.
According to Meijers, the A23a was “breaking up rapidly” and releasing large blocks big enough to be classified and tracked separately by the U.S. National Ice Center.
The assessment attributes the fragmentation to the combined action of currents, waves, and ocean conditions less favorable to ice preservation.
The process occurred in stages.
In July, August, and September 2025, the U.S. National Ice Center confirmed that parts of the A23a separated and began receiving new designations, such as A-23D, A-23E, A-23F, A-23G, A-23H, and A-23I.
The division indicated that the former megaberg no longer behaved as a single dominant plate.
The breakup of blocks of this type involves different physical forces.
Long waves, tides, and relatively warmer water act on cracks and structurally weakened regions of the ice.
Scientist Ted Scambos, from the University of Colorado, explained to the Associated Press that the iceberg was still thick but thinner than when it left the continent, a condition that favored breaks at vulnerable points.
D15A assumed the position of the largest iceberg in the world
With the reduction of the A23a, the position of the current largest iceberg passed to the D15A.
According to the Guinness World Records, the D15A measured about 3,050 square kilometers in April 2026 and had assumed the record at the end of 2025, after the decline of the A23a.
The D15A broke off from the West Ice Shelf in East Antarctica in January 2016.
Unlike the A23a in its last months of movement, this iceberg remained in an area close to Australia’s Davis research station, according to records cited by institutions monitoring Antarctica.
Even after losing the title of the largest in the world, the A23a still maintained significant dimensions.
In January 2026, estimates from the U.S. National Ice Center cited by NASA indicated that the remaining area was 1,182 square kilometers.
Satellite images from that period showed bluish meltwater on the surface of the block.
For scientists studying polar ice, this type of record may indicate changes in the iceberg’s structure and an increase in areas susceptible to fractures, especially when the mass moves to warmer latitudes.
Satellites recorded almost 40 years of the A23a
NASA reported that on April 3, 2026, images from the NOAA-21 satellite showed what was left of the A23a near the end of its trajectory.
The iceberg had drifted to warmer waters north of South Georgia and the South Sandwich Islands, more than 2,300 kilometers from the point where it originally broke off.
By March 27, 2026, researchers tracking the movement via remote sensing estimated that the A23a had shrunk to just over 170 square kilometers.
The reduction represented a significant drop from the dimensions recorded when the block was still classified as the largest iceberg on the planet.
The trajectory of the A23a also highlights the role of satellite monitoring in polar science.
The iceberg was recorded from Landsat 5 images in November 1986 to recent observations made by sensors like the VIIRS aboard NOAA-21.
This sequence allowed for documenting the detachment, periods of immobility, drift, rotations, mass loss, and fragmentation.
For researchers, icebergs of this size serve as study objects to understand oceanic and glaciological processes.
As they melt, they release fresh water, sediments, and nutrients into the ocean, temporarily altering local conditions.
When they fragment, they may also require attention from maritime monitoring agencies, as smaller parts can still pose a navigation risk.
What the A23a Reveals About Antarctica
The formation and breakup of large icebergs are part of the natural dynamics of Antarctica’s ice shelves.
However, scientists differentiate this process from the broader loss of continental ice and the reduction of shelves that act as barriers for land-supported glaciers.
Since icebergs are already floating, their direct melting does not significantly raise sea levels.
The most observed impact by researchers occurs when ice shelves weaken and no longer contain land glaciers, allowing more ice to advance into the ocean.
In the case of the A23a, scientific interest is associated with the combination of size, duration, and route.
The South Georgia region frequently appears in the movement of large icebergs from Antarctica because ocean currents can carry these masses to areas where water and wave action accelerate fragmentation.
The designation of “queen of the icebergs” reflected the period when the A23a held, for long intervals, the position of the largest known iceberg.
With the reduction and fragmentation recorded by scientific bodies, the block ceased to hold this position but remained one of the most closely monitored cases in modern Antarctic observation.
The story of the A23a also helps to show how phenomena distant from everyday life can be tracked on a global scale.
From satellite images, researchers can measure, compare, and record changes in remote areas of the planet with increasing precision.
After nearly 40 years of monitoring, the “queen of the icebergs” ceased to be a single dominant mass and became a set of fragments in the South Atlantic.
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