The world's largest and oldest iceberg is drifting through the Southern Ocean, as scientists had predicted. It is called A23a and after being practically stuck on the seabed for years and having been spinning in recent months, it has freed itself from its previous location, north of the South Orkney Islands. It is now circulating in the ocean surrounding Antarctica, as reported by scientists from the British Antarctic Survey in a press release.
Weighing almost one trillion tons and with a size estimated at 3,900 square kilometers in February 2024, the mega-iceberg A23a is a true ice giant whose evolution has been monitored by scientists since it broke off from the Filchner Ice Shelf in Antarctica in 1986. Shortly after forming, it got trapped off the coast and for three decades barely moved, remaining stranded on the seabed of the Weddell Sea before starting its slow journey north in 2020. The depth of the iceberg favored its stagnation for years, turning it into a kind of ice island.
Since then, the iceberg's journey has been marked by several events that have intrigued scientists. Last spring, the iceberg got trapped in what scientists call a Taylor column. This is a fluid dynamics phenomenon that also occurs in the ocean: water rotating over an underwater mountain traps objects in place. This dynamic kept A23a spinning in the area for months, delaying its expected drift northward.
Another image of the iceberg during the British Antarctic Survey expeditionRoseanne Smith
Exactly a year ago, researchers from the British Antarctic Survey embarked on an expedition to the Weddell Sea aboard the research vessel RRS Sir David Attenborough, named in honor of the famous British naturalist and broadcaster, during which they observed and studied the iceberg as part of the BIOPOLE project.
During this scientific mission, they took the first photographs of the iceberg in motion while investigating how Antarctic ecosystems and sea ice influence global carbon cycles.
The team also collected samples of the ocean surface waters surrounding this ice mass. Through their analysis, they aim to determine what life could form around A23a and how it affects carbon in the ocean and its balance with the atmosphere. "We know that these giant icebergs can provide nutrients to the waters they pass through, creating thriving ecosystems in areas that would otherwise be less productive," explained biochemist Laura Taylor from the BIOPOLE project in a statement.
The ship 'RRS Sir David Attenborough', last year alongside iceberg A23aTheresa Gossman, Matthew Gascoyne, Christopher Grey
"It is exciting to see A23a moving again after periods of stagnation. We are interested to see if it will take the same route as other large icebergs that have broken off from Antarctica. And more importantly, what impact this will have on the local ecosystem," explained oceanographer Andrew Meijers from the same British scientific institution.
A23a is expected to continue its journey through the Southern Ocean following the Antarctic Circumpolar Current, which is likely to push it towards the South Georgia Islands, according to the trajectory calculated by oceanographers. The presence of this iceberg could have a negative impact on the fauna in the area, disrupting the reproduction and food search of seals, penguins, or seabirds that breed in this archipelago located in the southern Atlantic Ocean.
On the other hand, in that region, it will encounter slightly warmer water, so it is expected that this ice mass will fragment into smaller icebergs and gradually melt.
Effects of Climate Change in Antarctica
The latest report from the British Antarctic Survey on the state of sea ice in Antarctica, published last May, documented historically low levels in 2023. Specifically, the study published in the journal Geophysical Research Letters noted that two million square kilometers less ice were measured than in a normal winter.
This drastic reduction surprised scientists, as it occurred after decades of constant sea ice growth until 2015. According to their analysis, "it was extremely unlikely" to have such a low sea ice record "without the influence of climate change."
Regarding the latest assessment from the European Copernicus service for November 2024, published last week, "the extent of sea ice in Antarctica reached its lowest monthly value for November, 10% below average, slightly lower than the values in 2016 and 2023, continuing a streak of historically large negative anomalies observed throughout 2023 and 2024." Sea ice concentration anomalies in the Southern Ocean were above average in the Weddell Sea and in a large sector of western Antarctica, and below average in sectors of the South Atlantic, the Indian Ocean, and the Ross Sea.