The world’s largest iceberg, A23a, is once again on the move after being trapped in a rotating water column for much of 2024. Measuring 3,800 square kilometers (1,500 square miles)—more than twice the size of Greater London—and 400 meters (1,312 feet) thick, A23a is an enormous mass of ice that detached from the Antarctic continent in 1986. Initially, it broke free from the ice shelf, only to become lodged on the floor of the Weddell Sea, a part of the Southern Ocean, where it remained for over three decades.
In 2020, A23a began to drift slowly northward, but in the spring of 2024, it became ensnared in a rotating column of water near the South Orkney Islands. This “vortex” caused the iceberg to spin in place for several months, hindering its movement. However, recent observations by the British Antarctic Survey (BAS) reveal that the iceberg is now moving northward once more, marking an exciting new phase in its journey.
Dr. Andrew Meijers, an oceanographer at BAS, expressed his enthusiasm for A23a’s movement, saying, “It’s exciting to see A23a on the move again after periods of being stuck.” He highlighted that the research team is particularly interested in understanding whether A23a will follow the same trajectory as other large icebergs that have calved off Antarctica in the past. The iceberg’s northward path is significant, as it is expected to eventually leave the Southern Ocean and enter the Atlantic, where warmer waters will likely cause it to break up into smaller fragments and melt. The iceberg’s interaction with the Southern Ocean and its eventual journey into the Atlantic presents an important opportunity for scientists to study the effects of such large ice masses on the global climate.
The iceberg’s movement is of particular interest to oceanographers and climate scientists because of its potential impact on local ecosystems. As it moves through the Southern Ocean, A23a is known to provide nutrients to the surrounding waters, fostering thriving ecosystems in regions that might otherwise be nutrient-poor. According to Laura Taylor, a biogeochemist who was part of the team aboard the RRS Sir David Attenborough, “Giant icebergs can create thriving ecosystems in otherwise less productive areas,” but scientists are still researching how specific icebergs—especially those of enormous scale like A23a—affect these processes.
The British Antarctic Survey’s research into icebergs’ influence on ecosystems began last year when scientists aboard the RRS Sir David Attenborough collected detailed data on the waters surrounding A23a. The researchers are particularly focused on understanding the iceberg’s role in providing crucial nutrients to the marine environment, which can lead to bursts of productivity in the ocean’s food chain. This interaction between the iceberg and the ocean is critical, as it can affect everything from plankton blooms to the behavior of larger marine species.
The study of A23a and other massive icebergs also holds climate significance. As icebergs like A23a move from the Antarctic region into warmer waters, they contribute to the overall melting of polar ice, which has implications for global sea levels. Researchers continue to monitor these icebergs’ paths to better understand how climate change is influencing the movement and breakdown of ice shelves in Antarctica.
A23a’s journey northward provides valuable scientific data on the long-term behavior of large icebergs and their influence on both marine ecosystems and global climate systems. As scientists track its movement, they continue to explore how icebergs like A23a will shape the future of oceanic environments and contribute to our understanding of climate dynamics. The iceberg’s eventual disintegration will likely provide further insight into the effects of ice melt and the broader consequences for Earth’s oceans and atmosphere.
