World’s largest iceberg on the move after breaking free from a vortex

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World’s largest iceberg on the move after breaking free from a vortex

The largest and oldest iceberg in the world, named A23a, is on the move again after being stuck in a votex for months near the South Orkney Islands. It is now drifting in the Southern Ocean.

The colossal iceberg weighing nearly a trillion tonnes and twice the size of Greater London, calved from Antarctica’s Filchner Ice Shelf in 1986. It remained grounded on the seabed in the Weddell Sea for over 30 years before starting its slow drift north in 2020.

Journey marked by intriguing events

The journey of the iceberg has been characterized by several intriguing scientific events. For months,

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was trapped in a Taylor Column—an oceanographic phenomenon where rotating water above a seamount holds objects in place. This dynamic kept the iceberg spinning in one spot, delaying its anticipated rapid drift north.

The iceberg is now is expected to continue drifting into the Southern Ocean, guided by the Antarctic Circumpolar Current, which will likely carry it towards the sub-Antarctic island of South Georgia. There, it will encounter warmer water, causing it to break up into smaller icebergs and eventually melt.

According to Andrew Meijers, an oceanographer at the British Antarctic Survey who co-leads the OCEAN:ICE project, it is “exciting to see A23a on the move again after being stuck for periods”. The team is

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to study whether it will take the same route as other large icebergs that have calved off Antarctica, and more importantly, what impact this will have on the local ecosystem.

Scientists are also closely monitoring the impact of A23a as it drifts through different environments. They are examining how the iceberg is

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the local ecosystem, particularly in terms of nutrient supply and carbon cycling.

A23a’s influence on Antarctic ecosystems

A year ago, researchers aboard the British Antarctic Survey’s state-of-the-art research vessel, the RRS Sir David Attenborough, observed and studied the iceberg as part of a science mission in the Weddell Sea for the BIOPOLE project. Scientists captured the first photos of the moving iceberg while analyzing how Antarctic ecosystems and sea ice affect global ocean cycles of carbon and nutrients. They also collected data alongside the vast iceberg.

For Laura Taylor, a biogeochemist on the BIOPOLE cruise, the close encounter with A23a underscored the significance of these giant icebergs.

“We know that these icebergs can bring nutrients to the waters they pass through, fostering thriving ecosystems in otherwise less productive areas. What we don’t yet understand is the specific impact that particular icebergs, their size, and their origins have on this process,” Taylor said.

She further explained that researchers took samples of ocean surface waters behind, immediately adjacent to, and ahead of A23a’s route. These samples will help them understand the impact of the iceberg on the carbon levels in the ocean and how it affects the balance with the atmosphere, allowing scientists to better comprehend the life that could thrive around the iceberg.

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