In 1986, a massive iceberg named A23a calved from an Arctic ice shelf that remained lodged for over three decades before beginning to drift northward in 2020. Now there’s the potential for A23a to collide with South Georgia, with cascading consequences for the remote island’s wildlife. Here, we discuss how this iceberg collision will impact the island and any other effects it might have on marine and terrestrial life.
The Birth of a Behemoth
In Antarctica’s vast, icy expanse, giant icebergs are born, each with a story to tell. One such giant iceberg is A23a, which was calved from the Filchner Ice Shelf in the 80s. With a mass of nearly a trillion tons and a size greater than twice the area of Greater London, it was wedged in the Weddell Sea for over three decades until it eventually began to gradually melt, shifted by winds and ocean currents, with chunks of ice tumbling into the water. In 2020, the iceberg finally dislodged and began its journey north.
The Great Escape
After years of being wedged in the Weddell Sea, A23a broke from the shelf and began to slowly move northward in 2020. This break is a result of the iceberg being shifted about by the Antarctic Circumpolar Current. Satellite imagery shows that it is moving toward the sub-Antarctic Island of South Georgia, a remote British overseas territory renowned for its extreme biodiversity.
The Collision Course
By early 2025, satellite imagery indicated that A23a was on a trajectory toward South Georgia Island. The outcome of the iceberg’s trajectory is uncertain as it is currently moving along with the Antarctic Circumpolar Current, the world’s strongest ocean current, and is set to reach a sharp turn in the current. However, given its size, this movement is slow, making the possibility of accurately predicting its grounding nearly impossible.
The Unpredictable Journey
Icebergs are notoriously unreliable because the ocean currents and winds define their path, and the sea floor’s topography can deflect them. Scientists are closely monitoring A23a, and they are unsure whether it will run aground off South Georgia’s shoreline or drift by unharmed. The Antarctic Circumpolar Current has played a significant role in A23a’s journey as its powerful flow influenced the iceberg’s path, guiding it toward South Georgia and contributing to its eventual grounding.
Grounding Near South Georgia
Thus far, the iceberg threatens to run aground 50 miles from South Georgia’s continental shelf, clogging access to valuable penguin and seal feeding grounds and putting these populations at risk. With the turn in the current, the iceberg will not directly crash into the island’s critical breeding areas, alleviating immediate concerns for the island’s wildlife, such as penguins, seals, and seabirds.
Potential Ecological Impacts
Past events have shown that such obstructions, such as A23a’s grounding, can have devastating effects on local wildlife populations. If A23a grounded off South Georgia, the effects would be enormous. It could obstruct access to feeding areas for penguins and seals, leading to increased mortality rates among chicks and pups as they venture out further in search of food. Further, it could disrupt ocean currents, redistribute nutrients, and potentially crush seafloor organisms under its enormous weight.
The Krill Stock Market Crash
South Georgia’s waters are rich in krill, which sustain 95% of the global fur seal population and 50% of Antarctic penguins. A23a’s collision could reduce krill availability by 40% during breeding seasons, collapsing marine food chains in the region. This highlights a natural systemic fragility in which wildlife relies on a single resource, such as krill. The iceberg’s disruption, therefore, poses devastating effects on multiple species and exposes how climate change can wreak havoc on ecological monocultures.
Melting and Nutrient Release
While the immediate consequences of a grounded iceberg are frightening, there are positive implications in the long term. For example, as A23a melts, it will release freshwater rich in nutrients, such as iron, into the surrounding ocean, stimulating phytoplankton blooms, which form the base of the marine food chain and potentially benefit the local ecosystem.
Lessons from Past Icebergs
Historical instances of large icebergs grounding near South Georgia have provided valuable insights. In 2004, iceberg A38 ran aground off the island, resulting in the starvation of thousands of penguin chicks and seal pups as adults were unable to reach feeding grounds. These events highlight the delicate balance between ice shelves and marine ecosystems, emphasizing the need for ongoing vigilance.
Climate Change and Iceberg Calving
Although A23a’s calving happened before significant climate change impacts, the increasing frequency of giant icebergs is related to warming temperatures and ice shelf destabilization. The regularity of these events highlights the broader relevance of global climate patterns on increasing ocean and atmospheric temperatures, which trigger ice shelf destabilization and frequent iceberg calvings.
Future Projections
The fate of A23a remains uncertain. It may continue to break apart, gradually melting and releasing nutrients, or it could remain grounded for a long time. However, scientists will continue to monitor A23a’s status using satellite imagery and field observations to better understand its impact on ocean circulation, nutrient distribution, and local wildlife. This is crucial for predicting future ecological outcomes.
Navigating the Icy Future
A23a shows the delicate balance of our earth’s ecological systems. While climate change continues to remake our world, the iceberg’s journey stresses the significance of monitoring large icebergs and their interactions with marine environments. Continued research is needed to anticipate the potential ecological impacts and inform conservation strategies for vulnerable wildlife habitats.
