A stunning new animation has revealed the journey of an iceberg four times the size of Manhattan that broke off the West Antarctic ice shelf in September.
Satellite images show behaviour that is ‘both interesting and of concern,’ as the 100-square-mile iceberg is seen getting stuck on its way into the Southern Ocean, before disintegrating into smaller icebergs.
While the calving event at Antarctica’s Pine Island Glacier – the fastest melting glacier on the continent – wasn’t all that surprising, scientists say the behaviour suggests the patterns of ice flow are changing as the area thins.
A stunning new animation has revealed the journey of an iceberg four times the size of Manhattan that broke off the West Antarctic ice shelf in September. Researchers say its behaviour is both ‘interesting and of concern’
The Pine Island Glacier (PIG) is responsible for the loss of roughly 45 billion tons of ice in Antarctica each year.
The recent calving event, in which the 100-square-mile chunk of ice split off, has ‘troubling’ implications for future sea level rise, according to researchers with the British Antarctic Survey.
‘What we’re witnessing on Pine Island Glacier is worrying,’ Dr Robert Larter, a marine geophysicist at British Antarctic Survey.
‘We’re now seeing changes in the calving behaviour of the ice shelf, when for 68 years we saw a pattern of advance and retreat resulting in the calving of a single large iceberg which left the ice front to approximately the same place.
‘The calving of icebergs in 2001, 2007, and 2013 are well-documented. Each calving event returned the ice front to more or less the same position and the ice shelf flowed into the sea again.
‘But with continuing thinning it was clear that sooner or later there would have to be a change to this pattern – and this is what we are witnessing now.’
The huge iceberg broke off from the Pine Island Glacier in late September, roughly two months after another significant calving event elsewhere in Antarctica, when an iceberg the size of Delaware broke off the Larsen C ice shelf.
While the ice shelf has been thinning for decades, the researchers say there has been no systematic retreat of the ice front since it was first observed in 1947 – until two years ago.
A huge iceberg four times the size of Manhattan (pictured) has broken off of an Antarctic glacier. The calving is the second time in just two years that a massive iceberg has separated from the continent’s Pine Island Glacier
The Pine Island Glacier, found in western Antarctica, has been losing ice at an accelerating rate over the past four decades
‘What’s both interesting and of concern is the lines along which the iceberg has broken follow the pattern of crevasses develop in the ice shelf that it calved from,’ Larter said.
‘This change of behaviour might reflect the crevasses within the ice shelf having an increasing influence on the spacing and pattern of iceberg calving as a result of the thinning that has taken place over the past few decades.’
Most of the time, icebergs break free from glaciers around the edges, but this most recent departure from western Antarctica’s Pine Island Glacier has stemmed from an interior section.
This is unusual, and is not the first time the glacier has exhibited this behaviour in recent years, with a 224-square-mile (580 sq km) interior segment breaking off in 2015.
Experts have warned it could be the result of warming ocean waters melting the ice from below, destabilizing it.
‘If the ice shelf continues to thin and the ice front continues to retreat, its buttressing effect on PIC will diminish, which is likely to lead to further dynamic thinning and retreat of the glacier,’ Dr Larter said.
‘PIG already makes the largest contribution to sea-level rise of any single Antarctic glacier and the fact that its bed increases in depth upstream for more than 200 km means there is the possibility of runway retreat that would result in an even bigger contribution to sea level.’