The calving – and melting – of the largest icebergs like A23a is a natural phenomenon and not necessarily the result of climate change, although parts of Antarctica are now shedding icebergs faster than the ice can be replaced.
Scientists have been closely watching A23a’s disintegration for hints as to how Antarctica might respond to rising temperatures – specifically its ice shelves, the floating tongues of glaciers that extend into the ocean.
Ice shelves play an important role in the stability of much of the Antarctic ice sheet. But it’s by no means clear how quickly they might collapse in a warming climate and what that could mean for sea-level rise.
While not an exact match, icebergs can act as “travelling natural laboratories” for how some of these processes could unfold, explains Walker.
“We can learn a lot from how these big icebergs evolve in warmer conditions, and then try to map that onto what we expect ice shelves will do,” she says.
In the 11 days up to 22 February, the now smaller, lighter berg travelled more than 700km (435 miles) north-east across the South Atlantic, hurtling along at an average of about 2.7km/h (1.7mph).
That journey exposed A23a to warmer waters, close to 10C at the surface – bad news for an iceberg.
“Every day, all day, it’s in warmer and warmer water,” says Shuman. “It’s just like ice in your drink. It doesn’t take all that long to disappear.”
