The newly calved berg, designated A-76 by scientists, was spotted in recent satellite images captured by the Copernicus Sentinel-1 mission, the space agency said in a statement posted on its website on Wednesday with a photo of the enormous, oblong ice sheet.

Its surface area spans 4320 square kilometres and measures 175km long by 25km wide.

By comparison, the ACT occupies 2358 sq km.

The enormity of A-76, which broke away from Antarctica's Ronne Ice Shelf, ranks as the largest existing iceberg on the planet, surpassing the now second-place A-23A - which is about 3380 sq km and also floating in the Weddell Sea.

Another massive Antarctic iceberg that had threatened a penguin-populated island off the southern tip of South America has since lost much of its mass and broken into pieces, scientists said earlier this year.

A-76 was first detected by the British Antarctic Survey and confirmed by the US National Ice Center based in Maryland using imagery from Copernicus Sentinel-1, consisting of two polar-orbiting satellites.

The Ronne Ice Shelf on the flank of the Antarctic Peninsula is one of the largest of several enormous floating sheets of ice that connect to the continent's landmass and extend out into the surrounding seas.

Periodic calving off of large chunks of those shelves is part of a natural cycle.

But some ice shelves along the Antarctic Peninsula have undergone rapid disintegration in recent years, a phenomenon scientists believe may be related to climate change, according to the US National Snow & Ice Data Center.

Australian Associated Press