An enormous iceberg that split off from the Antarctic ice sheet decades ago has turned an alarmingly bright shade of vivid blue — an alarming indication that it’s about to undergo complete disintegration before the much warmer summer months are over.
When it first detached in 1986, the ice giant known as A-23A was twice the size of Rhode Island, becoming one of the largest and oldest bergs to be tracked by scientists, according to NASA. In January 2025, it measured around 1,410 square miles, earning it the Guinness world record for the largest existing iceberg.
It has since shrunk to a mere 456 square miles, roughly the size of Manhattan, by early January following several major pieces breaking off over the last year. According to data by the US National Ice Center, several other icebergs have now overtaken A-23A in terms of total square miles.
While the berg’s birth 40 years ago isn’t believed to have been the result of human-induced climate change, it’s yet another pertinent reminder that we will continue seeing massive icebergs, or “megabergs,” calving from the melting Antarctic ice shelf as global temperatures continue to climb and warm ocean waters.
A satellite image highlighted by NASA on its website last week shows the enormous iceberg “sopping with blue meltwater” as it drifts off the coast of the southern tip of South America — a “giant swimming pool, as New Scientist put it. The image, which was taken on December 26 by NASA’s Terra satellite, shows pools of deep blue water visible on its surface, which, according to experts are clear signs of “ongoing disintegration events.”
“You have the weight of the water sitting inside cracks in the ice and forcing them open,” explained University of Colorado Boulder senior research scientist Ted Scambos in a statement to NASA.
The blue diagonal stripes visible in the satellite image are of particular interest. Experts believe they’re scour marks that date back to a time when A-23A was dragged across Antarctic bedrock hundreds of years ago.
“The striations formed parallel to the direction of flow, which ultimately created subtle ridges and valleys on the top of the iceberg that now direct the flow of meltwater,” added National Snow & Ice Data Center senior research scientist Walt Meier told NASA. “It’s impressive that these striations still show up after so much time has passed, massive amounts of snow have fallen, and a great deal of melting has occurred from below.”
The situation is dire enough that scientists believe A-23A could be months, if not weeks, away from disintegrating completely.
“I certainly don’t expect A-23A to last through the austral summer,” retired University of Maryland Baltimore County scientist Chris Shuman told NASA.
At the current rate, temperatures are already around three degrees Celsius warmer than expected — such a disintegration could accelerate.
A-23A left the relatively shallow waters near the Antarctic ice shelf in 2020, and spent several years drifting and spinning. It almost collided with South Georgia island last year.
NASA described its deathwatch as a “bittersweet moment.”
“I’m incredibly grateful that we’ve had the satellite resources in place that have allowed us to track it and document its evolution so closely,” Shuman said. “A-23A faces the same fate as other Antarctic bergs, but its path has been remarkably long and eventful. It’s hard to believe it won’t be with us much longer.”
Meanwhile, scientists race to better understand how icebergs behave and how shrinking glaciers due to global warming affect their famously unpredictable behavior.
More on icebergs: Doomsday Glacier Bombarded by Earthquakes
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