World’s Largest Iceberg Disappears After Nearly 40 Years

The world’s largest iceberg, known as A23a, has almost completely disappeared after drifting in Antarctic and Southern Ocean waters for nearly 40 years. The iceberg broke away from Antarctica’s Filchner Ice Shelf in 1986. In 1991, it separated from a larger iceberg called A23 and was named A23a.

At its peak, A23a covered an area of around 2,000 square miles, roughly the size of the island of Bali.

According to National Geographic, the iceberg remained trapped in the Weddell Sea for several decades, with its bottom resting on the seabed. It eventually began moving in 2020 and drifted with ocean currents, reaching the open waters of the Southern Ocean in November 2023.

It was described as the largest drifting iceberg at the time. After reaching open water, A23a took an unexpected route. Instead of moving north, it became trapped in a powerful ocean current known as the Taylor Column in March 2024.

The iceberg continued spinning in the current for around eight months before breaking free in November 2024. As it entered warmer waters, its ice began melting rapidly. In March 2025, it became trapped again near South Georgia, around 70 miles from the island.

By June 2025, its area had fallen to less than 1,200 square miles, meaning it was no longer the world’s largest iceberg. Satellite images taken in January 2026 showed plumes of chlorophyll around the iceberg.

The US National Ice Center officially stopped monitoring A23a in March 2026 after its size fell below the required monitoring threshold. Satellite images from March and April showed the iceberg breaking into smaller pieces and spreading across the Southern Ocean.

Scientists later identified more fragments that they believed had once been part of A23a. Researchers continued to observe small remnants of the iceberg from space into May. After surviving for nearly four decades, most of A23a is now believed to have melted away.