Fracture In Larsen C Ice Shelf Results In Third Largest Iceberg Ever

It has been some time coming but the enormous chunk of ice that has been slowly breaking away from the side of the Larsen C ice shelf has, now, broken free. The resultant iceberg is about 5800 sq km in size and weighs in in the region of a trillion tons. That means 2 quadrillion bottles of water are now free to float away from Antarctica, where they were locked away as ice, and head north into warmer waters where they will eventually melt, over several years, and raise our sea levels.

Depending on how you like to measure these things the berg is either twice the size of Luxembourg, a quarter the size of Wales or the same size as Delaware; either way it’s bad news. When a similar event occurred on the Larsen B ice shelf in 2002 it resulted in the total collapse of that shelf. It isn’t certain if that will happen at Larsen C, mainly because we simply don’t know enough about how these calving events affect shelf stability, so all eyes will be focussed on Larsen C over the coming years to see if it stabilises or not.

The crack that separated the berg from the shelf was first noticed in satellite data in 2014 and it was known for sometime that this calving event was imminent. Ice at the free end of the iceberg was moving at 20 metres per day relative to the end still attached, this put enormous stress on the fracture that sped up its inevitable break away.

Like with hurricanes, storms and other specific weather events, it isn’t possible to say whether or not global warming caused this major calving event. But what we can say is that as the world has warmed in recent decades the ice shelves of Antarctica have become more unstable and they have not replenished themselves at the same rate as they have shed ice. This means there has been a net movement of water from its solid to liquid form.

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In just a couple of weeks one end of the berg had begun moving at 20 metres per day. Image credit: Adrian Luckman

In the weeks since President Trump decided to abdicate the United State’s role as a world leader and marshal them down the path of isolation and ridicule there has been a G20 meeting. It was heartening to see the rest of the worlds richest nations reaffirm their commitment to long term, lasting emissions cuts and leave Trump to wallow in a pit of his ill-founded smugness. Maybe he, and the wider American populace, will change his mind once Mar-a-Lago is underwater; until then, as Joseph de Maistre said: every nation gets the government it deserves.

 

Cover image courtesy of NASA.
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