In a remarkable turn of events, scientists have observed the world’s largest iceberg, A23a, starting to move for the first time in over 30 years. This colossal Antarctic iceberg, boasting an impressive size of almost 4,000 square kilometres (1,500 square miles), approximately three times the area of New York City, has been adrift since its detachment from West Antarctica’s Filchner-Ronne Ice Shelf in 1986.
A once-stationary behemoth, A23a has been stranded in the Weddell Sea after its base became wedged on the ocean floor. However, recent satellite images indicate a change in its status, with the iceberg rapidly advancing past the northern tip of the Antarctic Peninsula. Strong winds and ocean currents are propelling this nearly trillion-metric-ton mass, making it an uncommon spectacle that has caught the attention of researchers, including glaciologist Oliver Marsh from the British Antarctic Survey.
The iceberg’s movement is a rare occurrence, prompting scientists to closely monitor its trajectory. As it gains momentum, A23a is expected to be carried into the Antarctic Circumpolar Current, directing it toward the Southern Ocean along a route famously known as “iceberg alley,” where similar large icebergs are often found drifting in the dark waters.
The motivation behind A23a’s sudden mobility remains uncertain. Marsh suggests that gradual thinning over time may have rendered the iceberg slightly more buoyant, enabling it to lift off the ocean floor and be propelled by ocean currents. Notably, A23a is one of the world’s oldest icebergs.
There is a possibility that A23a could once again become grounded, potentially at South Georgia Island. This scenario would pose a significant challenge to the island’s abundant wildlife, including millions of seals, penguins, and seabirds that breed on the island and depend on the surrounding waters for foraging. In 2020, a similar concern arose with another massive iceberg, A68, threatening to collide with South Georgia. Fortunately, A68 eventually broke into smaller pieces, averting a potential catastrophe. A similar fate could be in store for A23a.
However, Marsh emphasizes that an iceberg of this magnitude has the potential to persist in the Southern Ocean for an extended period, possibly making its way northward toward South Africa, where it could disrupt shipping routes. The unfolding journey of A23a continues to be a captivating and dynamic event that scientists are keenly observing.
