A23A, the iceberg that would not leave

On 31 December 2020 the US National Ice Center added A23A to its weekly list of Antarctic icebergs. It stayed on the list for 273 weekly listings, until 20 March 2026. This post follows A23A through those listings only: where it was, how big the list said it was, and the path it took.

• First listing: 31 December 2020, at 75.87° S, 41.24° W.
• Last listing: 20 March 2026, at 48.95° S, 31.79° W.
• Largest area in the record: 3,840 km², on 19 April 2024.
• Area at the last listing: 141 km².

A year without moving

A23A is the largest remaining part of the iceberg A23. The first listing puts it in the Weddell Sea, and the list gave its size as 40 by 34 nautical miles, about 74 by 63 kilometres.

Through all of 2021 it hardly moved. The last listing of that year, on 31 December 2021, reads 75.87° S, 40.69° W, almost exactly where the first one began.

Setting off

In 2022 the weekly positions began to change. By 11 March 2022 the listed position was more than 100 kilometres from the starting point. By the last listing of the year it was at 72.35° S, 46.38° W.

The next year it kept moving, north and west. On 21 April 2023 it was at 71.68° S, 51.90° W, and on 3 November 2023 at 63.34° S, 51.68° W. The listing of 29 March 2024, at 59.65° S, was the first north of 60° S, the line that marks the edge of the Antarctic Treaty area.

Adding up the straight lines between the weekly points gives about 9,000 kilometres. That is a rough figure, since weekly points joined by straight lines cannot show every turn. The distance in a straight line between the first and the last listed position is about 3,000 kilometres.

A shrinking figure

Our record has no area for A23A before 19 April 2024, when the list gave 3,840 km². That is the largest figure in our record. During 2025 it fell steadily, from 3,643 km² on 2 January to 1,182 km² on 26 December.

The last months were faster. Between consecutive weekly listings the area went from 1,035 to 532 km² (16 January 2026), from 561 to 360 km² (26 February) and from 360 to 141 km² (6 March). The last listing, on 20 March 2026, gives A23A a length of 9 nautical miles and a width of 7.

What the list does not say

After 20 March 2026 A23A no longer appears on the list, and the list does not say why. An iceberg can break into pieces too small to track, melt away, or leave the list for another reason. We cannot tell which, so we say only what we know: it has not been listed since.

Under our farewell rule, an iceberg that stays off the list for eight weeks is marked as in farewell. A23A is now one of the icebergs in farewell in our registry. Its page keeps its record: the farewell page for A23A shows its last journey, and the full record has its logbook.