However, Iceberg A23a is now in its final weeks of existence, a landmark that represents the end of one of the most monitored voyages of a glacier throughout the history of science. Once the holder of the record for the largest iceberg in the world, this massive piece of ice, originating from the Antarctic Ice Shelf, has been drifting for almost four decades. However, NASA images, along with data from the British Antarctic Survey, have revealed that it is now turning blue due to melting, a process that may lead to the complete disappearance of the iceberg in the coming weeks.
To the scientists who have been monitoring the journey of Iceberg A23a since it first broke away from the Ice Shelf of Antarctica in 1986, the end of this massive iceberg is a landmark that has sparked curiosity, as some of the scientists were born the same year the iceberg first broke away.
How a 4,000 km² Iceberg Spent Nearly 40 Years at Sea
When en A23a finally broke off from Antarctica, it measured about 4,000 square kilometers, an area greater than Greater London twice over. Immediately after, the berg came to rest on the sea bed of the Weddell Sea, where it stayed for over 30 years. A Soviet research station was evacuated from the top of the berg when it calved.
It was not until 2020 that satellite imagery recorded signs of the berg moving again. It moved northwards, got stuck rotating in a Taylor column—a rotating vortex formed by the impact of ocean currents on a seamount, and at one time threatened penguin and seal colonies off the coast of South Georgia Island before narrowly missing the coastline.
In early 2025, A23a still covered an area of 3,600 square kilometres. However, the ice berg’s condition continued to deteriorate throughout the year. As South Atlantic Ocean temperatures rose to almost 10 degrees centigrade, A23a began disintegrating from all sides. By September 2025, the British Antarctic survey confirmed that A23a was disintegrating into large pieces, each large enough to be monitored individually. The title of the “world’s largest ice berg” rested with D15a, which is located near the Australian Davis base in Antarctica.
NASA Images Show Blue Meltwater — A Sign of Structural Collapse
In the last days of December 2025, NASA’s MODIS device on the Terra satellite spotted something remarkable: large patches of deep blue water on the surface of what was left of A23a. A day later, an astronaut on the International Space Station took a photograph of the berg from space and found an even larger body of water.
Scientists attributed the blue color to the effect of sunlight passing through deep water. This indicated that the water had reached depths of several meters. Water on an iceberg causes existing cracks to open up by hydrofracture, where the weight of water causes the ice to crack from the inside out. This can cause the water to drain suddenly as the crack reaches the waterline.
Scientists also found a “rampart-moat” effect at the waterline as they studied the berg. This is caused by differential melting at the waterline. It also “sprang a leak,” with scientists at NASA observing evidence of a freshwater “plume” where the water had forced its way through the ice and into the water.
By January 2026, the US National Ice Center estimated A23a’s remaining area at around 1,182 square kilometres — still larger than New York City, but a fraction of its original size. Scientists say once it shrinks below approximately 70 square kilometres, it will no longer be tracked.
Disclaimer: This article is based on publicly available information from reputable sources including NASA Earth Observatory, the British Antarctic Survey (BAS), the US National Ice Center, and peer-reviewed researchers quoted in major science publications. All scientific claims reflect publicly available data as of the date of publication. This article does not represent the views of any government or research institution.
