The world’s largest iceberg is on the move for the first time in over three decades, scientists said on Friday. At almost 4,000 square km, 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 berg — which once hosted a Soviet research station — has been stranded after its base became stuck to the floor of Weddell Sea. Scientists say A23a, among the world’s oldest icebergs, could become grounded again or break into smaller chunks, or ever make its way farther up towards South Africa.