The dramatic loss of the block could trigger the rapid collapse of the whole shelf and cause sea levels to rise, experts said.
Scientists at the British Antarctic Survey (BAS) will now study the stability of Larsen C Ice Shelf and how its newly exposed ocean and seabed areas are populated with life.
A BAS spokesman said the iceberg had been “hanging by a thread” for months.
It formed more than 10% of the shelf at more than 6,000 km² in area and 30m of the 190m-thick block is now above sea-level.
Director of Science Professor David Vaughan said the collapse of nearby ice shelves had “resulted in the dramatic acceleration of the glaciers behind them, with larger volumes of ice entering the ocean and contributing to sea-level rise.
“If Larsen C now starts to retreat significantly and eventually collapses, then we will see another contribution to sea level rise.
“There is little doubt that climate change is causing ice shelves to disappear in some parts of Antarctica at the moment.
“We see no obvious signal that climate warming is causing the whole of Antarctica to break up. However, around the Antarctic Peninsula, where we saw several decades of warming through the latter half of the 20th century, we have seen these ice shelves collapsing and ice loss increasing.
“Larsen C itself might be a result of climate change, but, in other ice shelves we see cracks forming, which we don’t believe have any connection to climate change.”
Researchers from BAS and the University of Swansea, who used satellite imagery to monitor a 170km rift in the shelf on daily basis, reported the iceberg had fully detached at 8am yesterday (wed).
The newly exposed ocean and underlying seabed have been put forward to be made into a internationally-recognised Special Area for Scientific Research.
Dr Phil Trathan, Head of Conservation Biology said: “If designated, this would restrict commercial fishing activities and provide a valuable opportunity for studying the new habitats created, including how species colonize the area and new communities develop.”
Remote sensing analyst Andrew Fleming, said: “Our glaciologists will now be watching closely to see whether the remaining Larsen C Ice Shelf becomes less stable than before the iceberg broke free, and our biologists will be keen to understand how new habitats formed by the loss of the ice are colonised.”
Conservation biologists said the “calving event” followed the collapse of ice shelves Larsen A and Larsen B further north in the continent in 1995 and 2002.
A BAS spokesman said it “will provide unique scientific opportunities for understanding how new biological communities develop and how new species occupy the newly exposed area.”