Iceberg A23a

A23a is a large tabular iceberg which calved from the Filchner–Ronne Ice Shelf in 1986. It was then stuck on the sea bed for many years but then started moving in 2020. Its area is about 3900 sqkm, which made it one of the largest icebergs in the world until it was temporarily surpassed in size by A76.

In November 2023, A23a was tracked moving past the northern tip of the Antarctic Peninsula and headed toward the Southern Ocean. On 1 December 2023, the iceberg was intercepted by the polar research ship RRS Sir David Attenborough, off the tip of the Antarctic Peninsula. At 10 knots, it took the ship several hours to sail along two sides of the iceberg. The iceberg is expected to release a significant quantity of mineral dust as it melts and so the ship took water samples around its perimeter.

On 14 January 2024, dramatic archways caused by wave action on A23a were documented by a drone operated by Eyos Expeditions videographer Richard Sidey and expedition leader Ian Strachan. Their footage was published widely by the BBC and CNN.

The base Druzhnaya I was placed on the iceberg, until it calved. Subsequently, a rescue mission was started in 1987 and ultimately moved/renamed the base to Druzhnaya III.