The world's largest iceberg is on the move for the first time in more than three decades, scientists said Friday.

At almost 4,000 square kilometers (1,500 square miles), the Antarctic iceberg called A23a is roughly three times the size of New York City.

Since calving off West Antarctica's Filchner-Ronne Ice Shelf in 1986, the iceberg — which once hosted a Soviet research station — has largely been stranded after its base became stuck on the floor of the Weddell Sea.