The world’s biggest iceberg is on the move after more than 30 years being stuck to the ocean floor.
A23a, as it’s called, calved from the Antarctic coastline in 1986, but almost immediately grounded in the Weddell Sea to become, essentially, an ice island.
At almost 4,000 sq km (1,500 sq miles) in area, it’s more than twice the size of Greater London.
The past year has seen it drifting at speed, and the berg is now about to spill beyond Antarctic waters.
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“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,” said Dr Andrew Fleming, a remote sensing expert from the British Antarctic Survey.
A23a has put on a spurt in recent months, driven by winds and currents, and is now passing the northern tip of the Antarctic Peninsula.
This is the same movement of water - and accompanying westerlies - that the famous explorer Sir Ernest Shackleton exploited in 1916 to make his escape from Antarctica following the loss of his ship, the Endurance, in crushing sea-ice.
Shackleton aimed his lifeboat for South Georgia, and it’s at this island that you will frequently see the big tabular bergs sitting offshore.
As these big bergs melt, they release the mineral dust that was incorporated into their ice when they were part of glaciers scraping along the rock bed of Antarctica.
“In many ways these icebergs are life-giving; they are the origin point for a lot of biological activity,” said Dr Catherine Walker, from the Woods Hole Oceanographic Institution, who was born in the same year as A23a.
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