A68, an iceberg covering an area of nearly 6 000 sq km when it broke away from Antarctica in 2017, is virtually gone, broken into countless pieces that the US National Ice Center says are no longer worth tracking.
What is Happening?
- In 2017, A68 calved from the Larson C Ice Shelf on the edge of the Antarctic Peninsula, where it hardly moved for a year. Then it started to drift north with increasing speed, riding on strong currents and winds.
- The iceberg, weighing one billion tonnes, took a familiar route, spinning out into the South Atlantic towards South Georgia, the small island where many of the biggest icebergs go to melt away when they get caught in the current shallows. However, A68 escaped this fate.
- Instead, the waves, warm water and higher air temperatures in the Atlantic caused A68 to melt away, shattering into smaller and smaller pieces.
- The USNIC is the body recognised internationally for naming icebergs and tracking those that might pose a threat to shipping. For an iceberg to make it on the USNIC list of concern, it must either have a long-axis of greater than 18.5km or an area of at least 68.5 sq km. None of A68’s fragments now qualify. The last major piece, known as A68a, was measured on Friday to be just 5.5 km by 3.7km.
Adrian Luckman from Swansea University, told BBC News, “It’s amazing that A68 lasted as long as it did. If you think about the thickness ratio – it’s like four pieces of A4 paper stacked up on top of one another. So this thing is incredibly flexible and fragile as it moved around the ocean. It lasted for years like that. But it eventually broke into four-to-five pieces and then those broke up as well.”
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Lessons Learnt from A68
- A68 will inform researchers on both how ice shelves are constructed and how they break apart to produce icebergs.
Christopher Shuman from the University of Maryland, Baltimore County (UMBC) and Nasa-Goddard, says, “The one thing that is probably worth mentioning as a scientific result was how much was learned about the fracture toughness of the suture zones where inland glaciers joined together to form the floating shelf ice. Because we had new sensors seeing the rift evolution more frequently, I’m sure useful insights were gleaned that could not have been ‘seen’ in the decade before. This is a real testament to the investments being made in Earth observation.”
- A68 is the product of a natural process, according to many glaciologists. Ice shelves will maintain an equilibrium, and the ejection of icebergs is one way they balance the accumulation of mass from snowfall and the input of more ice from the feeding glaciers on land.
- While the A68 iceberg shouldn’t be used as a shining example of human-caused climate change in Antarctica and beyond, it did showcase the processes through which warming can destroy ice structures. One of these is called hydrofracturing, whereby warming produces a lot of surface meltwater that then fills fissures and cracks, driving these openings through to the base of the ice.
Featured image by: Flickr