One of world's largest icebergs A23a drifting beyond Antarctic waters after it was grounded for three decades

Iceberg A23a, 3x size of NYC and 2x size of London, has been drifting for a year after being grounded for 34 years. British Antarctic Survey's Andrew Fleming said it was just time for it to move and it's now heading to sub-Antarctic South Georgia via wind and ocean currents.

One of the world’s largest icebergs is drifting beyond Antarctic waters, after being grounded for more than three decades, according to the British Antarctic Survey.

The iceberg, known as A23a, split from the Antarctic’s Filchner Ice Shelf in 1986. But it became stuck to the ocean floor and had remained for many years in the Weddell Sea.

The iceberg is about three times the size of New York City and more than twice the size of Greater London, measuring around 4,000 square kilometres (1,500 square miles).

Andrew Fleming, a remote sensing expert from the British Antarctic Survey, told the BBC on November 24 that the iceberg has been drifting for the past year and now appears to be picking up speed and moving past the northern tip of the Antarctic Peninsula, helped by wind and ocean currents.

“I asked a couple of colleagues about this, wondering if there was any possible change in shelf water temperatures that might have provoked it, but the consensus is the time had just come,” Mr. Fleming told the BBC.

“It was grounded since 1986, but eventually it was going to decrease [in size] sufficiently was to lose grip and start moving,” he added.

Mr. Fleming said he first spotted movement from the iceberg in 2020. The British Antarctic Survey said it has now ungrounded and is moving along ocean currents to sub-Antarctic South Georgia.