The world’s biggest iceberg that “refuses to die” is on the move after 30 years – but scientists cannot work out where it is headed.

Iceberg A23a first broke away from the Filchner Ice Shelf, in the southern Weddell Sea on Antarctica, back in 1986.

But almost immediately after that it became stuck in the sediment at the bottom of the Weddell Sea, kept in place by a 350-metre-deep ice keel anchor. It then remained there for more than 30 years.

It gradually melted until 2020, which enabled the berg to re-float and continue on its journey.

However, the current debate is where A23a will end up, as it continues to throw surprises at scientists and has been dubbed the iceberg “that refuses to die”.

It is incredibly hard to gauge just how massive iceberg A23a really is.

Satellite measurements at that time showed the frozen block has a total average thickness of just over 900ft and has a mass just below a trillion tonnes, the BBC reported. It is twice the size of Greater London.

After dislodging in the Weddell Sea, the berg moved slowly at first, before currents and winds then swept it north towards warmer air and waters.

A23a is now following a path that exports much of Antarctica’s floating ice – what scientists refer to as “Iceberg Alley” – that points in the direction of the British overseas territory of South Georgia.

It is, however, on a “path of destruction” according to the BBC – it will fragment and melt away. The process of decay is already evident in satellite imagery and close-up photos taken from visiting ships. Every day, large chunks are falling off into the sea, some the size of football pitches, others the size of lorries.

In December 2023, it had reached the tip of the Antarctic Peninsula, where there is a convergence of various streams of fast-moving water that turn clockwise around the continent. At this point, scientists could not predict where it would go next thanks to the dominant westerly winds that control the area.

By April this year it was drifting along the 60th Parallel, close to the South Orkney Islands, about 430 miles northeast of the tip of the Antarctic Peninsula. It was at this point many scientists expected the berg to head onwards into warmer waters, fragment and melt away.

However, by August it was revealed that A23a had been spinning on the spot for months, when it should have been racing along with Earth’s most powerful ocean current. Scientists believe it has been captured on top of a huge rotating cylinder of water – a Taylor Column – where it might remain stuck for years

“Usually you think of icebergs as being transient things; they fragment and melt away. But not this one,” observed polar expert Prof Mark Brandon.

“A23a is the iceberg that just refuses to die,” the Open University researcher told BBC News. Scientists are now closely watching to see what happens next.

One may immediately turn to point the blame at global warming for the berg’s breaking off from the Antarctic mainland. However, it is more complicated than that. A23a came from a part of the Antarctic that is still very cold. The shedding of large segments of ice at the forward edge of this shelf is a natural behaviour.

That being said, it is true that in other parts of the continent, we have seen warmer conditions trigger whole-shelf collapse, producing a large number of bergs.

Scientists now also believe that Iceberg Alley witnessed a great flux of bergs about 1.2m years ago, after drilling into the ocean floor and dating the muds there. It was evidence, scientists think, of a previously unrecognised warming phase that broke apart many of West Antarctica’s ice shelves.

There are positives to A23a’s melting, however. Like all big bergs, its progressive melt will be dispersing the mineral dust that was caught up in its ice when it was still part of a glacier. In the open ocean, this dust is a source of nutrients for the organisms that form the base of ocean food chains.