Since calving off Antarctica’s Filchner–Ronne Ice Shelf in 1986, the colossal iceberg A23a remained grounded for decades. Now, exposed to increasingly warm waters and ocean turbulence, this once mighty megaberg is rapidly falling apart and may disappear entirely within weeks.
Imprisoned in the Weddell Sea for over 30 years, A23a only began drifting freely around 2020. For most of its existence, it stood undisturbed—until now.
Once weighing nearly a trillion metric tons and stretching across roughly 1,400 square miles (comparable to Rhode Island), A23a has shrunk to approximately 1,700 square kilometers—about half its original size—roughly matching Greater London.
In recent weeks, enormous chunks—some as large as 400 km²—have broken off the iceberg, creating floating hazards for maritime navigation. Smaller fragments litter the surrounding ocean, rendering tracking increasingly difficult.
Scientists, including Andrew Meijers (British Antarctic Survey) and Ted Scambos (University of Colorado), warn the iceberg may disintegrate completely by the end of spring—or even in a sudden collapse akin to an ice avalanche.
With A23a’s breakup, the title of the world’s largest iceberg now belongs to D15a, located off Antarctica near Australia’s Davis Station, covering about 3,000 km².
Climate Significance
While iceberg disintegration is a natural phenomenon, the speed at which A23a is collapsing reflects accelerating changes in Antarctica. Increasing ocean temperatures and wave energy—both intensified by climate change—are forcing the rapid disintegration of massive ice bodies.
Though melting icebergs don’t directly raise sea levels, their loss permits glacial ice from land to flow into the ocean, contributing to sea-level rise. Additionally, the breakup presents navigational hazards and could disrupt ecosystems—particularly near South Georgia Island, once threatened by A23a’s presence.
