The world's largest iceberg, known as A23a, has become lodged 73 kilometers from the remote Antarctic island of South Georgia. Measuring an impressive 3,300 square kilometers and weighing nearly one trillion tonnes, this colossal mass of ice has been drifting north from Antarctica since 2020. After being stuck for over three decades, the iceberg finally broke free, only to find itself grounded once more. This event has brought both ecological opportunities and concerns to the forefront, as scientists closely monitor its impact.
A23a's journey began in 1986 when it calved from the Antarctic shelf, embarking on a slow northward drift. During its migration, the iceberg encountered frequent delays caused by ocean forces that kept it spinning in place. Despite these challenges, it continued its trek until its recent grounding near South Georgia. The iceberg's movement is considered a "completely normal part of the lifecycle" of the Antarctic ice sheets, yet its size and age make it a subject of particular interest.
“In the last few decades, the many icebergs that end up taking this route through the Southern Ocean soon break up, disperse and melt,” – Andrew Meijers
Since late 2023, satellites have tracked A23a's path, offering valuable insights into its behavior. In January, a significant 19-kilometer-long chunk broke off from the iceberg, further altering its dynamics. Researchers have noted that the grounding of A23a could potentially boost food availability for the regional ecosystem, which includes penguins and seals. However, these same populations have already suffered due to a bird flu outbreak, resulting in a challenging season for both seals and penguins on the island.
“Nutrients stirred up by the grounding [of the iceberg] and from its melt may boost food availability for the whole regional ecosystem, including for charismatic penguins and seals,” – Andrew Meijers
The presence of A23a may also have economic implications, as its grounding could render some areas off-limits to commercial fishing ships. This restriction could impact local fisheries, affecting both their operations and the broader economy. Furthermore, as global temperatures continue to rise—now between 1.5 to 2.0 degrees Celsius above preindustrial levels—the mass loss of ice shelves has accelerated. Since 2000, ice shelves have lost an estimated 6,000 billion tonnes of mass, a trend largely attributed to climate change.
“This could reduce the amount of food coming back to pups and chicks on the island, and so increase mortality,” – Andrew Meijers