Giant Iceberg A68A is no more

In July 2017, one of the world’s largest icebergs calved from the front of Larsen C, the result of a crack that had taken years to form. It was given the designation A68 - it was the 68th iceberg, originating in sector A, large enough to be registered by the US National Ice Center since records began in 1978 (see map). With a surface area of nearly 6,000 km2 and weighing approximately 1 billion tons, it was also the fourth largest iceberg ever recorded. 

So began the voyage of Iceberg A68, though slowly at first - for a year it barely moved, frequently grounding on the sea floor as it drifted along the coast of the Antarctic Peninsula. Then, with increasing speed, it drifted north driven by currents associated with the gyre of the Weddell Sea, along with katabatic winds that descend from the polar plateau. A68 became a social media star, with people around the world sharing satellite images that were freely available online. 

Finally, in 2020, it spun out of the Weddell Sea into the South Atlantic where many of the biggest icebergs go to die. Along the way, smaller chunks of ice calved off, some big enough to merit their own name, such as A68C. The mother berg, still largely intact, was redesignated A68A. Picked up by the powerful Antarctic Circumpolar Current, it moved in a north-easterly direction, bearing down on the island of South Georgia. 

In the end, the demise of Iceberg A68A was relatively swift. Over a period of four months from December 2020, A68A simply began shattering into smaller and smaller fragments, around the island of South Georgia. 

Professor Adrian Luckman of Swansea University said “Icebergs from the Peninsula normally break up around this location. A68’s demise was most likely due to a combination of factors such as air temperature (causing surface melt to drive hydro-fracture), sea temperature (which will have been gradually eroding the iceberg from below), and the long-period swell which doesn't normally make it through the pack ice further south. It is possible that the iceberg grounded, but I doubt that was a big factor in its break-up.”

By April, it was all over. The last major fragment of the berg adrift amidst the icy slush, still with the designation A68A, melted below the minimum threshold set by the USNIC: it was a mere 3 nautical miles long by 2 nautical miles wide. A68 was no more - the odyssey had come to its natural conclusion.