A giant iceberg that snapped off Antarctica’s Larsen-C ice shelf some three and a half years ago shrank towards the end of its drift across the Southern Ocean, but released 152 billion tonnes of freshwater.
The European Space Agency (ESA) says scientists have charted the fate of A-68A, which had a surface area of more than twice the size of Luxemburg – one of the largest icebergs on record.
Antarctic icebergs are named from the Antarctic quadrant in which they were originally sighted, then a sequential number, and then if the iceberg breaks, a sequential letter is added.
For the first two years of its life, A-68A stayed in the cold waters of the Weddell Sea close to its parent ice shelf, where it experienced little in the way of melting, according to the ESA.
However, once the berg began its northward journey across the Drake Passage, it travelled through increasingly warm waters and began to melt.
To track how the area of A-68A changed, scientists drew on imagery from five satellites. The newly published study says that A-68A collided only briefly with the seafloor and broke apart shortly afterwards, making it less of a risk in terms of blockage.
By the time it reached the shallow waters around South Georgia, the iceberg’s keel had reduced to 141 metres below the ocean surface, shallow enough to just avoid the seabed which is around 150 metres deep.
“If an iceberg’s keel is too deep it can get stuck on the seafloor. This can be disruptive in many ways; the scour marks can destroy fauna, and the berg itself can block ocean currents and predator foraging routes,” the ESA says.
“However, a side effect of the melting was the release of a colossal 152 billion tonnes of freshwater close to the island – a disturbance that could have a profound impact on the island’s marine habitat,” it says.