Rahul Somvanshi
The colossal Antarctic iceberg A23a, measuring 4,000 km² (twice the size of Greater London) and weighing nearly 1 trillion tonnes, has run aground approximately 90 km from South Georgia Island. This development marks the latest chapter in the iceberg’s remarkable 39-year journey since calving from Antarctica’s Filchner Ice Shelf in 1986.
Current Status and Location
After remaining grounded in the Weddell Sea for over 30 years, A23a began drifting northward in 2020. Satellite imagery confirms that as of March 1, 2025, the iceberg has come to a standstill near South Georgia, where it appears to be grounded on the continental shelf in waters approximately 200-300 meters deep.
“The iceberg is grounded on the continental shelf of the sub-Antarctic island of South Georgia, about 90 km from land,” explains Dr. Andrew Meijers, an oceanographer at British Antarctic Survey (BAS).
The 400-meter-thick ice mass has been closely tracked via satellite, with its journey marked by an unusual period in late 2024 when it became temporarily trapped in a Taylor Column—an oceanographic phenomenon where rotating water above a seamount delays drift.
“It’s probably going to stay more or less where it is, until chunks break off,” says Meijers, who encountered A23a in person during a December 2023 expedition aboard the RRS Sir David Attenborough.
Physical Characteristics and Transformation
Originally 3,900 km² when it calved, A23a has gradually shrunk to an estimated 3,234 km² through melting and fragmentation. Despite this reduction, it remains remarkably intact after nearly four decades.
“The future of all icebergs is that they will die. It’s very surprising to see that A23a has lasted this long and only lost about a quarter of its area,” notes Professor Huw Griffiths, who observed the iceberg from the RRS Sir David Attenborough.
Recent observations reveal accelerating decay: “Instead of a big, sheer pristine box of ice, you can see caverns under the edges,” Meijers describes. A 19 km-long chunk broke off in January 2025, and satellite imagery from April 2025 shows a 10 km fissure on its surface, suggesting further fragmentation is imminent.
Ecological Impacts
Potential Risks
The grounding poses both challenges and opportunities for local ecosystems. Where the iceberg scrapes the seabed, it causes immediate ecological disruption.
“Their entire universe is being bulldozed by a massive slab of ice scraping along the sea floor,” says Professor Griffiths, describing the impact on benthic organisms like coral, sea slugs, and sponges.
Some wildlife populations could face temporary feeding disruptions. WWF warned in May 2025 that macaroni penguins might need to take 800 km detours to feeding grounds, potentially reducing chick survival rates by 40%.
Nutrient Enrichment
However, BAS scientists note that A23a could deliver substantial ecological benefits through nutrient release.
“It’s like dropping a nutrient bomb into the middle of an empty desert,” explains Professor Nadine Johnston from BAS. “Nutrients stirred up by the grounding and from its melt may boost food availability for the whole regional ecosystem, including for charismatic penguins and seals,” adds Meijers.
The melting process releases particles and micronutrients like iron trapped in the ice, potentially triggering phytoplankton blooms visible as a “green halo” around the iceberg in satellite imagery. BAS documented a 20% increase in phytoplankton biomass near A23a during their December 2023 research expedition.
“Without ice, we wouldn’t have these ecosystems. They are some of the most productive in the world, and support huge numbers of species and individual animals, and feed the biggest animals in the world like the blue whale,” Griffiths notes.
BAS estimates suggest A23a-induced phytoplankton blooms could sequester approximately 2 million tonnes of CO₂—equivalent to removing 500,000 cars from the road for a year.
Economic Implications
A23a’s presence and eventual breakup will affect commercial activities around South Georgia, particularly fisheries.
“If it breaks up, the resulting icebergs are likely to present a hazard to vessels as they move in the local currents and could restrict vessels’ access to local fishing grounds,” warns ecologist Mark Belchier, who advises the South Georgia government.
Previous cases in 2021 showed icebergs near South Georgia caused a 30% decline in Patagonian toothfish catches. Insurance premiums for vessels operating in the region have increased by approximately 15% according to a 2023 Lloyds of London report.
Fishing industry representatives acknowledge these challenges: “This will be the most ice from an iceberg we will have ever dealt with in a fishing season, but we are well-prepared and resourced,” says Andrew Newman from Argos Froyanes, a fishing operator in the region.
Scientific Research and Monitoring
A23a represents a valuable natural laboratory for scientists studying ocean dynamics, biogeochemistry, and climate change impacts.
The BAS-led OCEAN:ICE project is actively investigating how “megabergs” like A23a influence ocean circulation, chemistry, and ecosystems. Researchers deployed robotic ocean gliders to measure sub-ice melt rates (approximately 0.5 meters/day) and nutrient distribution patterns.
“From a scientific perspective we are keen to see how the iceberg will affect the local ecosystem,” Meijers explains. “We have several ongoing studies looking at exactly how ‘megabergs’ influence the ocean circulation, its chemistry, and the ecosystems they support.”
During their December 2023 expedition, BAS scientists collected water samples around A23a to analyze its biogeochemical impact, measuring nutrient concentrations and phytoplankton community composition.
Climate Change Context
While icebergs like A23a are natural occurrences, their frequency and behavior offer insights into broader climate trends.
“Icebergs, including megabergs like this one, are a completely normal part of the lifecycle of the Antarctic ice sheets,” Meijers explains. “However, observations show that the ice shelves have lost around 6000 giga (billion) tonnes of their mass since the year 2000.”
This accelerated ice loss coincides with measured warming of circumpolar deep water eroding ice shelves from below. Natural calving cycles now occur approximately three times faster than pre-industrial rates, according to IPCC data from 2023.
The freshwater input from melting icebergs—A23a alone contains an estimated 1.1 billion tonnes—could potentially influence ocean circulation patterns. NASA researchers suggest iceberg melt could slow the Atlantic Meridional Overturning Circulation by up to 2% by 2100, with potential global climate implications.
Interesting Stories
Technological Tracking Advances
A23a’s journey has been documented using increasingly sophisticated remote sensing technologies. The European Space Agency’s Copernicus Sentinel-1 satellite provides regular imagery, while NASA’s Worldview tool enables public tracking of the iceberg’s movements.
BAS has deployed autonomous underwater gliders equipped with sonar to map underwater melt patterns and detect hidden channels forming beneath the ice. These technologies reveal that after emerging from the Weddell Sea in 2023, A23a accelerated to approximately 50 km/day, making it one of the fastest-moving icebergs on record.
Conclusion and Future Outlook
A23a’s grounding represents a pivotal moment in its decades-long existence. Scientists predict it will likely remain in place while gradually breaking into smaller fragments that will eventually melt completely.
The iceberg’s presence near South Georgia creates a complex mix of ecological, economic, and scientific impacts. While disrupting some marine habitats and potentially affecting wildlife feeding patterns and commercial fisheries, it simultaneously delivers vital nutrients that may enhance biological productivity and carbon sequestration.
BAS continues monitoring A23a via satellite imagery and oceanographic measurements, with particular interest in how its eventual breakup patterns might inform understanding of ice sheet dynamics in a warming climate.
“It will be interesting to see what will happen now,” concludes Meijers, highlighting the ongoing scientific value of this Antarctic giant in its final stage of existence.
