The scientific organization British Antarctic Survey (BAS) has reported that the world’s largest and oldest iceberg is on the move again. The colossus had remained north of the South Orkney Islands for the last few months, rotating on its own axis. Now it is drifting through the Southern Ocean.
The large frozen mass is known as A23a. It weighs almost a billion tons and covers an area of more than 3,670 square kilometers, which is equivalent to twice the size of London. In 1986, it broke off from the Filchner Ice Shelf in Antarctica. It remained stranded on the seabed of the Weddell Sea for more than three decades. Four years ago it shrank enough to break free from the bottom and move slowly northward.
The megaiceberg was dragged by ocean currents until it became trapped in a Taylor column, a circular current that originates over seamounts and keeps objects inside. A23a broke free from the vortex in recent days and scientists expect it to transition to warmer waters. It is expected to reach the subantarctic island of South Georgia where it will break up and melt.
“It’s exciting to see the A23a moving again after periods where it was stagnant. We are interested to see if it will follow the same path as other large icebergs that have broken off from Antarctica and, more importantly, what impact this will have on the local environment,” says Andrew Meijers, oceanographer at BAS.
Researchers have for years studied the erosion and influence of this block of ice on Antarctic ecosystems and global carbon and nutrient cycles. A group of scientists, participating in the BAS BIOPOLE project, captured the first images of the moving iceberg and documented how its presence modified the biogeochemical processes of the Southern Ocean and marine polar habitats.
Antarctica is changing
Laura Taylor, biogeochemist at BIOPOLE, explains that “these giant frozen mountains can provide nutrients to the waters they pass through, creating thriving ecosystems in areas that would otherwise be less productive.” He recognizes that there is still no certainty about the difference that certain icebergs can make in this process depending on their size and origin.
BAS experts have taken samples of surface water adjacent to A23a. Taylor says that laboratory analysis of these liquids “should help us determine what life could form around the iceberg and how carbon impacts the ocean and its balance with the atmosphere.”
The first speculations indicate that the iceberg calving was caused by the natural growth cycle of the shelf. Specialists rule out that this contributes to the rise in sea level. Despite this, they warn that climate change is causing drastic changes in the Antarctic continent with the potential to affect various coastal areas around the world.
The World Meteorological Organization estimates that more than 90% of the world’s oceans experienced heat waves at some point in 2023. Various vital habitats and food systems were damaged. The effects were especially visible in the global set of reference glaciers. The group suffered the largest ice loss ever certified since 1950. “Antarctic sea ice extent was the lowest ever recorded, with a peak late-winter extent of one million square kilometers below the previous year’s record.” , points out the organization.
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