After 30 years of being ‘stuck’ on the spot, the world’s biggest iceberg is on the move.
Called A23a, the block of ice is around 1,540 sq miles in area – more than twice the size of Greater London (607 sq miles) – and a whopping 1,312 feet thick.
A23a – which is shaped like a ‘tooth’ – is now being carried northwards by wind and ocean currents ‘at speed’ after 30 years of being grounded by the ocean floor.
It’s drifting past the Antarctic Peninsula (which sticks out from the mainland like a tail) and should break down due to rougher waters once it reaches the open ocean.
Objects as big as A23a have to be constantly tracked after the break off as they could pose a threat to ships, as well as wildlife.
Called A23a, the block of ice is around 1,540 sq miles in area – more than twice the size of Greater London (607 sq miles) – and a whopping 1,312 feet thick
A23a is now being carried northwards by wind and ocean currents ‘at speed’ after 30 years of being ‘stuck’ to the ocean floor. The tooth-shaped berg can be seen in the right of this November 15 2023 image with the tip of the Antarctic Peninsula to the left
Unlike many of the large icebergs that detach from Antarctica and float away, A23a had only moved a couple of hundred miles since it broke off from the Filchner Ice Shelf in August 1986.
Its lack of movement was because it was ‘grounded’ (or stuck) on the sea floor and, as a result, is less vulnerable to fragmenting.
However, the huge iceberg has now broken free.
Icebergs ‘ground’ on the ocean floor when their keel – the bit below the water’s surface – is deeper than the water’s depth.
Dr Andrew Fleming, a remote sensing expert from the British Antarctic Survey, told the BBC that he spotted the first signs of movement from A23a back in 2020.
‘It was grounded since 1986 but eventually it was going to decrease in size sufficiently to lose grip and start moving,’ he said.
‘[We were] wondering if there was any possible change in shelf water temperatures that might have provoked it, but the consensus is the time had just come.’
American planetary scientist Lindy Elkins-Tanton is part of a voyage on the way to visit A23a, according to her recent X post.
Antarctica is home to a number of ice shelves marked out in this map, including Filchner, Shackleton and Ross. Filchner is to the east of the Antarctic Peninsula (the bit that sticks out from the Antarctic mainland like a little tail)
A23a calved from the Filchner Ice Shelf in Sep 1986 and grounded in the southern Weddell Sea in Nov 1991. Around three decades later it has started to move north
The former record holder was A76, which detached from an ice shelf in the Weddell Sea in May 2021 , but it has since fragmented into three pieces.
Iceberg A23a is expected to be reach the Antarctic Circumpolar Current – a 13,000 mile loop of ocean water that flows around Antarctica.
It could become grounded again near South Georgia, an island further north in the southern Atlantic Ocean and a hotspot for seals and seabirds.
If that happens, experts fear that it could disrupt the feeding routines of the creatures – for example, if it parked in an area where foraging usually happens.
But if it melts, minerals released from the ice could provide nutrients for organisms at the bottom of ocean food chains.
‘In many ways these icebergs are life-giving; they are the origin point for a lot of biological activity,’ said Dr Catherine Walker at the Woods Hole Oceanographic Institution in Massachusetts.
The record for the largest current iceberg changes most years, as new icebergs are calved off the Antarctic continent and subsequently break into smaller fragments.
Rising waters and air temperatures caused by global warming are triggering instabilities along the coasts of Antarctica and Greenland, accelerating melting and increasing the rates of calving.
Pictured is the Antarctic Circumpolar Current – the 13,000 mile loop of ocean water that flows around Antarctica
The former record holder was A76, which detached from an ice shelf in the Weddell Sea in May 2021, but it has since fragmented into three pieces.
Ice shelves are large floating platforms of ice that connect to a landmass, such as Antarctica, although they’re also found in other polar locations such as Greenland.
According to the Guinness World Records, the largest iceberg ever was in excess of 12,000 sq miles (31,000 sq km) – larger than Belgium.
This whopper was sighted 150 miles west of Scott Island, in the Southern Ocean by the USS Glacier on 12 November 1956.
