A-23A, a 'megaberg' that weighed nearly a trillion tonnes and measured 1,540 square miles at its peak, originally calved from Antarctica's Filchner Ice Shelf in 1986. It remained grounded on the seabed for over 30 years, almost unchanged in the shallow waters of the Weddell Sea, before finally setting off on its journey in 2020. This long grounding period contributed to its remarkable longevity, as noted by NASA in a blog post that ranked it among the giants known to have calved from Antarctica.
After freeing itself in 2020, A-23A drifted more than 2,000 miles northward, spending several months spinning in an ocean vortex known as the Taylor column. In December 2024, satellite images confirmed it was drifting north in the Southern Ocean, an event that scientists described as exciting. According to Daily Mail - Science & Tech, Dr Andrew Meijers, an oceanographer with the British Antarctic Survey, described the movement as intriguing, noting interest in whether it would follow routes taken by other large icebergs.
I noticed in recent weeks how Mother Nature seemed to keep a veil of clouds over the dying iceberg as if trying to give it some privacy at this stage.
Dr Jan Lieser of Australia's Bureau of Meteorology has been tracking A-23A using remote sensing, and according to Daily Mail - Science & Tech, he described how recent weeks saw clouds obscuring the dying iceberg as if providing privacy. NASA wrote that A-23A's journey ended in the South Atlantic Ocean, highlighting its significance for scientific study due to its size and durability. The exact date of its final disintegration remains unknown, as do the specific causes of the extensive melt and breakage in its final months, which reduced it to just over 66 square miles before fragmentation.
Alarm bells started to ring when A-23A appeared to be on a collision course with South Georgia, a remote British island and wildlife haven. At that time, it measured around 1,351 square miles, roughly the size of Cornwall, and was once just 173 miles off the coast. Simon Wallace, captain of the South Georgia government vessel Pharos, warned that A-23A was dangerously close to grounding and smashing into pieces. Whether it ever actually collided with or grounded on South Georgia is unclear, and the environmental impacts of its disintegration on the South Atlantic Ocean, including how many fragments it broke into, have not been confirmed.
Iceberg A-23A ranks among the giants known to have broken, or 'calved', from Antarctica. Though several other icebergs in the satellite era have been larger, A-23A was remarkable for its longevity. After spending its early days in the Weddell Sea, its journey came to an end in the South Atlantic Ocean, months shy of its 40th birthday. These images show the iceberg at the start and end of its lifespan.
Scientists expressed excitement about A-23A's movement in December 2024, but many unknowns persist about its final stages. The disintegration marks the end of a landmark event in polar science, with ongoing research likely to shed light on iceberg dynamics and climate interactions in the region.
It's exciting to see A-23A on the move again after periods of being stuck. We are interested to see if it will take the same route the other large icebergs that have calved off Antarctica have taken.