Antarctica's A-68: Is the world's biggest iceberg
about to break up?
By Jonathan
Amos
Science
correspondent
23 April
2020
A-68 has
now dropped a large chunk of ice itself. The main berg is about 150km long
The world's
biggest iceberg, A-68, just got a little smaller.
At around
5,100 sq km, the behemoth has been the largest free-floating block of ice in
Antarctica since it broke away from the continent in July 2017.
But on
Thursday, it dropped a sizeable chunk measuring about 175 sq km.
The iceberg
is currently moving north from the Antarctic Peninsula. Having entered rougher,
warmer waters - it is now riding currents that should take it towards the South
Atlantic.
Prof Adrian
Luckman, who's been following A-68's progress, said the new fracture could mark
the beginning of the end of this icy giant.
"I am
continually amazed that something so thin and fragile has lasted so long on the
open sea," the Swansea University researcher told BBC News.
"I
suspect that the final break-up is now starting, but the ensuing fragments will
probably be with us for years."
Evidence of
Thursday's split came via a radar image acquired by the European Union's
Sentinel-1 satellite.
Wide but
thin: A-68 has a profile akin to a few sheets of A4 paper stacked on top of
each other
A-68's name
comes from a classification system run by the US National Ice Center, which
divides the Antarctic into quadrants. Because the berg broke from the Larsen C
Ice Shelf in the Weddell Sea, it got an "A" designation.
"68" was the latest number in the series of large calvings in that
sector.
Properly,
we should refer to the berg as A-68A - that's because subsequent breakages also
get their own related name. A-68B was dropped early in the life of the main
berg. This new chunk will almost certainly get the designation A-68C.
Were there
indications that this particular corner would come off? "Not that I have
seen. I've been keeping an eye on progress, but mostly it's been attrition of
small flakes from all around," said Prof Luckman.
For months
it appeared to catch on the seafloor and didn't move very far. But eventually
it spun around and picked up pace as it drifted northwards. This past austral
summer saw the giant break free of the persistent sea-ice that clogs the
Weddell Sea - a significant development because it has exposed A-68 to much
greater swells. Its structure is now under more stress and further splits
should be expected.
It's
currently travelling past the South Orkney Islands which form the far tip of
the Antarctic Peninsula. Currents should then throw it in the general direction
of South Georgia and the South Sandwich Islands.
How much
longer A-68 can maintain its present integrity is anyone's guess. But even if
it does suffer a major fragmentation event, the individual icy blocks could
persist well into the 2020s before melting away.
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