A23a Iceberg from Antarctica Nears Final Collapse After Four-Decade Journey

Feature image: The breakup and melt of iceberg A‑23A in the South Atlantic Ocean between 3 May 2025 (left) and 22 January 2026 (right). The right panel highlights melt ponds forming on the iceberg as it fragments, illustrating rapid ice loss and the dynamic changes in iceberg structure over time. Credit: European Union, Copernicus Sentinel-3 imagery. 

A23a, once the largest iceberg in the world, is now expected to disappear within weeks after nearly four decades at sea. It broke away from Antarctica’s Filchner Ice Shelf in 1986 but remained stuck for over 30 years before finally drifting north in 2020.  

Over the past year (2025-2026), the iceberg has rapidly melted, fractured, and shrunk as it moved into warmer waters of the South Atlantic. At its peak, A23a covered around 4,000 km², more than twice the size of Greater London and during its journey, it travelled thousands of kilometers across the South Atlantic, at times covering over 700 km in just 11 days.  

Scientists have closely followed its journey, using it as a real-world example to understand how Antarctic ice may respond to a warming climate. 

Key Highlights 

• A23a has shrunk from about 4,000 km² to ~180 km² 

• It was grounded for over 30 years before moving again in 2020 

• Its journey included being trapped and spinning in ocean currents 

• Rapid breakup occurred during 2025–2026 

• Meltwater caused cracks and fragmentation (hydrofracturing) 

• Now in warmer waters, it is expected to fully melt within weeks 

Link to Climate Change 

• Icebergs naturally melt, but warmer oceans are speeding up the process 

• A23a shows how ice weakens faster in rising temperatures 

• Similar processes are affecting Antarctic ice shelves 

• Ice shelf loss can contribute to long-term sea-level rise, impacting coastal communities worldwide. 

Global and Regional Implications 

• Wildlife impacts: Icebergs can disrupt feeding routes for marine species 

• Ocean changes: Melting ice affects ocean nutrients and ecosystems 

• Shipping risks: Smaller ice fragments can be hazardous 

• Warning signal: Rapid collapse highlights growing instability in polar regions 

Urgent Response Needed 

• Improve monitoring of Antarctic ice and ocean conditions 

• Reduce global emissions to slow ocean warming 

• Strengthen polar research and collaboration 

• Integrate polar risks into climate policy and planning 

Read our earlier alert here: Colossal Antarctic Iceberg Breaks Free and Drifts Away 

Read more: Extreme weather events | Climate Risks Daily