After nearly 40 years drifting across Antarctic waters, the world’s largest iceberg, A-23A has entered an active and accelerated breakup phase, with satellite imagery confirming widespread structural failure across its surface.
Scientists say the development signals the imminent end of one of the most closely monitored ice giants in modern polar research.
Surface water triggers structural collapse
High-resolution satellite images captured in late December revealed large pools of meltwater spreading across A-23A’s surface, along with fresh fractures along its outer edges. According to researchers, the accumulation of water intensified internal stress, weakening the iceberg’s margins and pushing it from slow erosion into rapid fragmentation.
Chris Shuman of the University of Maryland, Baltimore County linked the surface flooding to hydrofracture a process in which meltwater forces cracks deeper into the ice sheet. Once water penetrates structural weaknesses, fractures can widen dramatically, accelerating collapse.
“I certainly don’t expect A-23A to last through the austral summer,” Shuman said.
From Antarctic giant to shrinking remnant
A-23A first broke away from Antarctica in 1986, initially spanning about 1,544 square miles (3,999 square kilometers), ranking it among the largest icebergs ever tracked.
By early January 2026, its size had shrunk to roughly 456 square miles (1,181 square kilometers), following several major breakoffs in 2025. The latest satellite observations suggest that its remaining mass may fragment within days or weeks.
For more than 30 years, A-23A remained lodged in the Weddell Sea, pinned by shallow seafloor ridges east of the Antarctic Peninsula. This grounding shielded it from stronger ocean currents and wave erosion, significantly prolonging its lifespan.
When it finally broke free in 2020, it entered more dynamic waters, where warmer currents and storms began accelerating its deterioration.
Shortly after its release, the iceberg became caught in a Taylor column a rotating column of water formed by ocean currents interacting with underwater topography. The phenomenon caused A-23A to spin in place for months, exposing the same ice faces repeatedly to wave action.
Though the delay slowed its northward journey, it may also have contributed to surface instability by allowing meltwater to pool along elevated ridges.
Once it escaped the vortex, ocean currents carried it toward the South Atlantic.
As it drifted north, A-23A approached South Georgia Island, a remote island known for dense seabird and marine wildlife populations. The iceberg narrowly avoided collision before temporarily grounding in shallow coastal waters.
Grounding can scrape ice against the seabed, causing further fragmentation and dispersing smaller chunks into surrounding waters. After breaking free again in late 2025, visible cracking intensified across its surface.
Hydrofracture accelerates breakup
Scientists point to hydrofracture as the likely driver of the current rapid collapse. When surface meltwater collects and seeps into cracks, it exerts pressure that can split ice from within. Satellite imagery shows pale water plumes near the iceberg evidence of meltwater draining into the surrounding ocean.
Once internal drainage begins, structural integrity declines rapidly, often leading to swift fragmentation.
Impacts on ocean systems and shipping
Large Antarctic icebergs contribute significant volumes of freshwater to the Southern Ocean. Research has shown that such freshwater inputs can alter surface ocean mixing, influencing nutrient distribution and regional heat exchange.
As A-23A fragments, smaller ice pieces may drift into shipping routes, particularly under poor visibility or extended polar darkness. Fragmentation increases navigational hazards while redistributing freshwater across a broader area.
Satellites have tracked A-23A’s journey for decades, providing a rare long-term record of iceberg evolution. Continuous remote monitoring has allowed scientists to observe its grounding, drift, spin cycles, and now its final breakup.
“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.
These records will remain valuable long after the iceberg vanishes, offering researchers critical data for refining predictive models of iceberg movement and decay.
As A-23A enters its final days, its breakup underscores the complex interplay between ocean currents, atmospheric warming, and ice stability. Surface meltwater, shifting currents, and decades of satellite observation now converge in the closing chapter of one of Antarctica’s most enduring ice giants.
While A-23A’s disappearance will mark the end of a long-lived Antarctic landmark, scientists continue watching the southern continent for the next generation of massive icebergs beginning their own long drift northward.