A KILDARE SCIENTIST studying the Antarctic says a huge crack in an ice shelf is about to create an iceberg the size of Mayo.
Earlier this week, Dr Martin O’Leary and his team at the UK’s Project Midas received data showing a deepening and widening of a large fissure in the Larsen C ice shelf on the Antarctic Peninsula.
The ice shelf is the most northerly outlying feature of the Antarctic ice sheet, which has seen record low levels of sea ice this winter.
An ice shelf is a floating sheet of ice permanently attached to a land mass – in this case the continent of Antarctica.
Over the past five decades, temperatures there have risen 2.5 degrees Celsius, weakening massive glaciers and leading to the formation of thousands of meltwater lakes.
O’Leary, a Cambridge graduate based at at the University of Swansea, says a huge crack in the Larsen C ice shelf will soon create a 5,000-square-kilometre iceberg.
When that happens, an entire ice shelf roughly the size of Ireland could also collapse into the ocean, raising sea levels by 10 centimetres worldwide.
Rare
“There is a very rare event, the last time something like this happened was in 1986 – a large iceberg broke off,” O’Leary told TheJournal.ie.
It’s now stretching across a big area, so it looks like there is going to be a very large breakoff.
Now, this is ice, so there are cracks, and we’ve been tracking a particularly big one of these cracks since about 2010.
O’Leary said he would be “very surprised” if the massive iceberg doesn’t float away in the next few months.
“The iceberg is going to be breaking off although it’s very hard to predict exactly when these things will happen,” he said.
Last year (2016) is expected to be confirmed to be the warmest year on record globally.
And the Antarctic Peninsula is one of the fastest warming places on Earth.
Propagating
The crack has grown progressively larger, starting in 2014, lengthening last summer – and progressing in the second half of December, when it grow by a further 18km in the space of two weeks.
A mega-iceberg twice the size of Wicklow is now connected to the mainland of Antarctica by just 20km of solid ice.
“We saw the satellite data on 2 January, just this week – which was brilliant timing,” O’Leary said.
He nevertheless cautioned about linking the imminent super-iceberg directly with global warming.
“In terms of cause, these cracks open up and then they start to fill with snow, and icy rubble and so on, and the pressure of that drives the icebergs out,” the 33-year-old, from Ardclough, in Co Kildare, added.
But when this breaks off, it means the ice shelf is going to be in a less stable position than it was beforehand. And then other processes, like glacier melts, can have an effect.
It’s possible that the entire Larsen C shelf could then collapse.
The front of any ice shelf acts as an arch across the front of the bay, holding all the ice in place, O’Leary explained.
In 2002, the nearby Larsen B ice shelf fell apart over the course of a couple of days after a similar iceberg broke away, breaking the arch which holds the ice shelf across the bay in the process.
The Larsen A ice shelf had previously collapsed in 1995.
Sea levels
“It’s possible that melting ice when the Mayo-sized iceberg leaves might break that arch – and the entire ice shelf could collapse,” O’Leary said.
It’s 60,000 square kilometres, so that’s getting on to the size of the Ireland.
The Republic of Ireland covers 70,000 square kilometres.
“If the Larsen C ice shelf collapses, all the glaciers that are being held at bay by the ice shelf will flow faster into the sea, and sea levels will rise by around 10cm. It’s a lot in one go,” O’Leary said.
Global warming
“From our point of view, it’s an exciting thing, it’s rare to see one of these things happen, but obviously there are concerns too with ongoing melt in the area.
“We’re seeing large amounts of melt in the Antarctic particularly towards the back of the ice shelf. That’s actually the main focus of our project.
We’ve been looking at melt ponds forming in the back of the area, and it looks like there’s been melts going on there that we didn’t know about.
“Temperatures in Antarctica are certainly a lot higher than they used to be, particularly the Antarctic Peninsula.”
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