The world's largest iceberg breaks off and drifts: what will be the consequences ?

© Simon Berger/Pexels

In the Southern Ocean, a thousand-year-old giant has just awakened. This colossal mass of ice is iceberg A23a. It had been relatively still for several decades, but this one has just begun a new migration, a movement that the scientific community is scrutinizing closely.

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 for the global climate.

A monument of ice in motion

The iceberg A23a, a titan of ice weighing nearly a trillion tons, has finally broken free after decades of immobility. Detached in 1986 from the Filchner-Ronne ice shelf in West Antarctica, this 3,672 km2 behemoth – almost 35 times the surface area of ​​Paris– had become stuck in the seabed north of the South Orkney Islands (an archipelago of the Antarctic continent)

Captive for several months in a Taylor column – a hydrodynamic phenomenon discovered by the British meteorologist Geoffrey Taylor – the iceberg found itself trapped. These columns, real natural traps, are formed when ocean currents meet underwater reliefs.

Above these submerged mountains, the masses of water create vertical vortices, similar to rotating columns, which can hold even the largest objects in place. The iceberg A23a, despite its titanic mass, was only able to escape this liquid prison after several months of incessant rotation. It is now freed from its aquatic prison.

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A natural observatory

Researchers from the British Antarctic Survey are closely monitoring this glacial mass. ” We are watching with excitement as A23a resumes its course after a long period of immobility. We are keen to see if its trajectory will align with that of other large icebergs and, more importantly, to assess the impact of its movement on the local environment ,” explains Andrew Meijers, an oceanographer at the British institution.

Last year, during the BIOPOLE project, scientists photographed and studied this ice monsterfrom the RRS Sir David Attenborough research vessel. Biogeochemist Laura Taylor explains: “ We know that these gigantic icebergs can bring nutrients to the waters they pass through, creating thriving ecosystems in areas that would normally be less productive. What we don't know is the specific impact that individual icebergs, their size and origin, can have on this process. So we took surface water samples before, during and after the iceberg's passage. 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 that the iceberg will follow the Antarctic Circumpolar Currentto the warmer waters of South Georgia Island. There, this glacial monument will gradually fragment, releasing its mineral wealth into the ocean. This programmed dissolution could paradoxically breathe new life into normally unproductive marine areas, 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 iceberg A23a, stuck for decades, has resumed its drift in the Southern Ocean.
• As it melts, it will release nutrients that could revitalize marine areas, but also disrupt ecosystems.
• Its movement and melting will unfortunately contribute to rising sea levels, a threat to coastal regions.

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