A giant ice shelf rift 'inevitable' in the frozen continent |
Gulf Times - 10 January, 2017
Ice shelves cracking up around northern parts of Antarctica has not been uncommon in recent years.
But, something major is about to happen in the frozen continent and that might add another four inches to sea levels over the years and decades.
A vast iceberg, expected to be one of the biggest ever recorded with an area of more than 5,000sq km and more than 1,100ft thick, is poised to break off Antarctica.
A rift, slowly developing across the Larsen C ice shelf on the Antarctic Peninsula in recent years, expanded abruptly last month, growing by about 18km.
It is now more than 80km long with just 20km left before it snaps, said scientists at Project Midas at the University of Swansea in Wales.
As one scientist observed, the rapid growth in giant rift between it and the southern continent means its break-off is “inevitable” in a few months’ time.
The giant ice block is part of the Larsen C Ice Shelf, which is the leading edge of one of the world’s largest glacier systems.
It is called an ice shelf because it is floating on the ocean.
Though it is normal for ice shelves to calve big icebergs, since snow accumulation gradually pushes old glacier ice out to sea, the destabilisation of this piece of floating ice is likely accelerated by rapid human-caused global warming.
Satellite images suggest the crack began opening up around 2010 and lengthened more than 29km by 2015.
By March 2016 it had grown nearly 23km longer.
Back in November, a team of scientists in Nasa’s Operation IceBridge survey flew over the rift to confirm it’s at least 129km long, 300ft wide, and 0.5km deep.
Another group of researchers, from Swansea University in the UK, say the entire Delaware-size block of ice is hanging on by just 20km of unfractured ice.
When the block does break off, it will be the third-largest in recorded history.
Computer modelling by some researchers suggests the calving of Larsen C’s big ice block might destabilise the entire ice shelf itself, which is about 50,000sq km via a kind of ripple effect.
However, a rapid ice shelf collapse would not be unprecedented.
In 2002, a large piece of the nearby Larsen B Ice Shelf snapped off, but within a month – and quite unexpectedly – an even larger swath of the 10,000-year-old feature behind it rapidly disintegrated.
The rest of Larsen B may splinter off by 2020.
If there is any good news about the rift in Larsen C, it’s that the ice shelf “is already floating in the ocean, so it has already displaced an equivalent water mass and minutely raised sea level as a result,” said Joe MacGregor, a glaciologist and geophysicist at Nasa’s Goddard Space Flight Center.
Whether climate sceptics admit it or not, lot of ice is melting in Antarctica, which, along with the surrounding Southern Ocean, are key drivers of Earth’s oceanic and atmospheric systems.
About 90% of Earth’s ice is found here, and 70% of all available fresh water is locked up in the Antarctic ice sheet – if melted, this would raise sea levels by nearly 60m.