Giant iceberg A68a shatters into large fragments

A68a: The section that looks like a "finger" is torn
The huge iceberg drifting through the South Atlantic seems to have seen a great split.
Tuesday's latest satellite imagery shows large cracks in tabular mountain A68a, with huge blocks of ice beginning to separate and move away from each other.
The A68a, which calved from Antarctica in 2017, swam off the coast of the island of South Georgia.
Experts have observed whether it could land in shallow water.
If that were the case - and parts of the mountain still might - it could cause problems for the penguins and seals of the British Overseas Territory as they forage for fish and krill.
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The picture at the top of this page is from the EU's Sentinel-1 radar spaceship. It was acquired on Tuesday at 07:17 GMT.
Although the cracks were very pronounced on Monday, they had not yet cut through A68a by then.
"Almost three and a half years since it moved away from the Larsen C Ice Shelf, the A68a iceberg - the fourth largest on record - is beginning to disintegrate," noted Adrian Luckman of Swansea University, UK.
"A68 ​​is not only one of the largest icebergs ever recorded, but also one of the most viewed.
"With such a massive increase in the volume of satellite data in recent times and a tremendous improvement in the speed at which it can be made available, this ability has been well put to good use in monitoring this giant iceberg on its way from birth to destruction." he told BBC News.
The US National Ice Center operates the iceberg naming system.
How the mountain looked on Monday. Deep cracks, but not yet fully fragmented
The Bergs are given a prefix letter depending on which quadrant of the Antarctic they calve from, as well as a number to determine their position in the sequence of large outliers. Fragmentations are then given a suffix letter.
Just last week a large chunk of A68a broke off and this was called A68d. You can see "d" behind the main mountain in another Sentinel-1 image from Monday processed by Pierre Markuse.
Two of the largest fragments identified by Sentinel-1 on Tuesday have already been named A68e and A68f.
British Antarctic Survey GIS and mapping specialist Laura Gerrish roughly calculates the areas of the various fragments:
A68a - 2,600 km²
A68d - 144 km²
A68e - 655 km²
A68f - 225 km²
(Fragments A68b and A68c broke up a long time ago and are not in close proximity.)
Laura Gerrish is tracking the mountain in South Georgia
Although now greatly reduced in size, A68a is still imposing and could still be a significant hindrance to foraging in South Georgia.
Right now, all of the mountain fragments are being carried away in a fast-moving stream of water known as the Southern Antarctic Circumpolar Current Front. This will likely sweep the chunks around the island and then throw them north.
Satellites will monitor their progress as they bypass the flat continental shelf. There are a number of places where the fragments could catch and anchor in place.
When the A68 first calved out of Antarctica, it was nearly 6,000 square kilometers - about a quarter the size of the whale.
To put the rest of Tuesday's A68a into context: 2,600 km² is still larger than Greater London, which comprises around 1,500 km² of land.
Why A68a has little to do with climate change
The iceberg came from a part of Antarctica where it is still very cold - the Larsen C Ice Shelf. This is a mass of floating ice formed by glaciers that flowed into the ocean from the east side of the Antarctic Peninsula. Upon entering the water, the floating fronts of the glaciers rise and merge into a single protrusion. The calving of Bergs on the front edge of this shelf is a very natural behavior. The shelf maintains a balance, and the throwing out of bergs is one way of offsetting the accumulation of mass from snowfall and the influx of more ice from the eating glaciers ashore. Larsen C calves large icebergs like A68 on decadal time scales.
This very high-resolution image from Planet shows the crumbling edge of the A68d
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos

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