The world’s largest iceberg, known as A23a, is once again on the move, drifting through the Southern Ocean after months of being stuck in one spot, according to scientists from the British Antarctic Survey (BAS).
Initially spanning 3,672 square kilometers (about 1,418 square miles) as of August 2023—making it slightly larger than Rhode Island—the A23a iceberg has been closely monitored since it first calved from the Filchner-Ronne Ice Shelf back in 1986. For more than 30 years, A23a remained grounded on the seafloor of Antarctica’s Weddell Sea, likely held in place by its immense weight and size.
Over time, the iceberg gradually eroded, which likely reduced its mass just enough to free it from its position on the seabed. Once released, it began drifting with ocean currents but soon became trapped again, this time in a Taylor column—a swirling water vortex created when currents encounter underwater obstacles, such as mountains.
Now, scientists report that A23a has managed to break free of the vortex and is expected to continue drifting toward warmer waters. Its current path suggests it may travel toward South Georgia, a remote island in the South Atlantic Ocean. If it reaches those warmer waters, A23a is likely to break apart and eventually melt.
A23a has held the title of “world’s largest current iceberg” multiple times since the 1980s, though it has occasionally been surpassed by larger icebergs such as A68, which calved in 2017, and A76 in 2021. However, those massive icebergs broke apart relatively quickly compared to A23a’s decades-long existence.
While this particular iceberg calved as part of the natural growth and retreat cycle of Antarctica’s ice shelves, scientists emphasize that climate change is significantly altering the continent’s ice dynamics. Melting ice in Antarctica could have far-reaching consequences, including contributing to rising global sea levels.
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Throughout A23a’s lengthy journey, researchers have studied its impact on the surrounding ocean, particularly its influence on carbon cycles and nutrient distribution. Icebergs of this size can provide essential nutrients to otherwise nutrient-poor waters, fostering rich ecosystems along their path.
Laura Taylor, a biogeochemist who analyzed water samples near A23a, highlighted the importance of studying these massive icebergs. “We know that giant icebergs deliver nutrients to the waters they drift through, supporting life in areas where productivity is typically low,” she explained in the BAS statement.
“What remains unclear is how specific icebergs—like A23a—affect this process based on their size, origin, and movement. By collecting water samples from different points along the iceberg’s route—behind it, alongside it, and ahead of it—we hope to better understand how these icebergs shape ocean ecosystems and impact carbon exchange between the ocean and the atmosphere,” Taylor added.
The ongoing research surrounding A23a could provide valuable insights into the role of icebergs in ocean health and global carbon cycles, while also shedding light on the larger-scale effects of a changing Antarctic environment.