40-year-old iceberg A-23a is turning blue and nearing final melt.

A-23a, a 40-year-old iceberg that calved from Antarctica's Filchner Ice Shelf in 1986, is drifting toward the South Atlantic near South Georgia and showing vivid blue meltwater patterns as it breaks up.

A-23a is a 40-year-old tabular iceberg that calved from Antarctica's Filchner Ice Shelf in 1986. It spent decades grounded in the Weddell Sea before beginning a northward drift in 2020. Recent NASA satellite images show vivid blue areas on its surface that scientists link to surface meltwater. The berg is now much reduced in size as it moves into the South Atlantic near South Georgia. Known details: - A-23a originally formed when about a 4,000 square-kilometre slab separated from the Filchner Ice Shelf in 1986. - The iceberg remained wedged in the Weddell Sea until 2020 and has since drifted northward along the Antarctic peninsula toward the Scotia Sea and Drake Passage, reaching waters near South Georgia about 2,800 kilometres from its origin. - The U.S. National Ice Centre reported A-23a had shrunk to about 781 square kilometres after recent calving events. - NASA imagery shows bright blue, mushy areas on the surface; researchers say these are likely meltwater pooling in cracks and flowing along striations in the ice. - Scientists told NASA it is unlikely A-23a will survive the upcoming Southern Hemisphere summer and that it is expected to continue breaking up in warmer waters. Summary: A-23a's long journey from the Filchner Ice Shelf has left it smaller and marked by visible meltwater patterns. It is currently near South Georgia and scientists report it is unlikely to persist through the Southern Hemisphere summer. The precise timing of its final breakup is not specified.