The world’s most enormous iceberg, A23a, has broken free from its long-standing position and is now navigating the icy waters of Antarctica. The trillion-metric-tonne behemoth had been grounded since it calved from the Filchner-Ronne Ice Shelf in West Antarctica in 1986, but recent satellite images have captured it kicking off on its new journey.
The berg’s unexpected voyage was first noticed by British Antarctic Survey remote sensing expert Dr Andrew Fleming on January 25. He says the iceberg was expected to start moving once it had melted enough to lose its grip on the Weddell Sea floor, but this happened much sooner than expected.
He notes the iceberg’s newfound freedom was likely brought on by the same factors that led to its decades-long dormancy: warming ocean temperatures and changes in wind patterns. “These icebergs are very vulnerable to melt and retreat,” Fleming explains. “They get stuck, and when they don’t move, they can quickly break into smaller pieces.”
A23a is now on a course to maneuver into the Antarctic Circumpolar Current, pushing it toward a path known as Iceberg Alley, where other large tabular icebergs often end up. This could lead it to drift towards the wildlife-rich island of South Georgia, home to millions of seals, penguins, and seabirds, Live Science reports. However, if it comes close to the land, it’s unlikely to cause severe damage.
Scientists don’t know precisely why the iceberg, one of the oldest on the planet, decided to start its odyssey after so many years, but they’re watching its trajectory closely. “It’s rare to see an iceberg of this size on the move,” British Antarctic Survey glaciologist Oliver Marsh says. “We will be monitoring its progress very carefully.”
What’s likely to happen now is that A23a will continue to drift until it enters the warmer Southern Ocean waters around South Africa, where it could disrupt shipping routes. Marsh says A23a may be able to survive in these warmer waters for quite some time, even though that’s only sometimes the case with older icebergs like this one.
This iceberg’s trip could also help scientists understand more about the processes that create and destroy icebergs of this type. For example, A23a’s dormancy was likely due to the dense berg, which caused it to weigh down on the ocean floor and be propelled by water currents. Over time, the iceberg may have thinned slightly, giving it that extra buoyancy needed to lift off the ocean floor and be pushed along by currents. This is how other icebergs of this kind usually break free from their moorings, Marsh adds. It’s also likely that the iceberg will eventually splinter into smaller pieces as it moves further north into warmer waters, creating an even more dangerous situation. But for now, experts are just happy to have A23a safely on the move.