In the Southern Ocean, a thousand-year-old giant has just awakened. This colossal mass of ice is the A23a iceberg. It had remained relatively immobile for several decades, but this one has just started a new migrationa shift that the scientific community is carefully examining.
Why is A23a so important? Because the melting of icebergs contributes to the rise in sea levels and profoundly modifies ocean currents, with potentially serious consequences on the global climate.
A moving ice monument
The A23a iceberg, a titan of ice weighing nearly a trillion tons, has finally broken its moorings after decades of immobility. Detached in 1986 from the Filchner-Ronne ice shelf in West Antarctica, this 3,672 km behemoth2 – almost 35 times the surface area of Paris – was stuck in the seabed north of the South Orkney Islands (archipelago of the Antarctic continent)
Captive for several months of a Taylor column – a hydrodynamic phenomenon discovered by British meteorologist Geoffrey Taylor – the iceberg found itself trapped. These columns, real natural traps, are formed when ocean currents encounter underwater reliefs.
Above these submerged mountains, masses of water create vertical whirlpools, similar to rotating columns, that can hold even the largest objects in place. The A23a iceberg, despite its titanic mass, was only able to escape this liquid prison after several months of incessant rotation. He is now free from his aquatic prison.
DO YOU WANT TO BREAK FREE!?
Well, you’re not alone – Iceberg #A23athe world’s largest and oldest #icebergis on the move!
Learn how it escaped 👇 pic.twitter.com/G3J0U2KfFz
— British Antarctic Survey 🐧 (@BAS_News) December 13, 2024
A natural observatory
British Antarctic Survey researchers carefully follow this glacial mass. “ It is with enthusiasm that we observe A23a resuming its course after a long period of immobility. We are eager to see if its trajectory will align with that of other large icebergs and, more importantly, to assess the consequences of its movement on the local environment », Explains Andrew Meijers, oceanographer at the British institution.
Last year, during the BIOPOLE project, scientists photographed and studied this ice monster from the research vessel RRS Sir David Attenborough. Laura Taylor, biogeochemist, specifies: “ We know that these gigantic icebergs can bring nutrients to the waters they pass through, creating thriving ecosystems in normally less productive areas. What we don’t know is the specific impact that certain icebergs, their size and their origin may have on this process. We therefore took surface water samples before, during and after the passage of the iceberg. These data will allow us to understand what forms of life can develop around A23a and its influence on the oceanic and atmospheric carbon cycle. “.
Current projections suggest the iceberg will follow the Antarctic Circumpolar Current to the warmer waters of South Georgia Island. There, this glacial monument will gradually fragment, releasing its mineral wealth in the ocean. This planned dissolution could paradoxically instill a new life in marine areas that are usually not very productive, creating oases of biodiversity. However, let us not forget that such a phenomenon can also have negative consequences : imbalance of local ecosystems, disruption of food chains and, on a broader scale, rising sea levels. For coastal and island communities, this last point is extremely problematic.
- Point The giant A23a iceberg, stuck for decades, has resumed its drift in the Southern Ocean.
- As it melts, it will release nutrients which can revitalize marine areas, but also disrupt ecosystems.
- Its movement and melting will unfortunately contribute to sea level rise, a threat to coastal regions.
