Larsen C ice shelf breaks

As expected a huge iceberg has split off the Larsen C ice shelf on the Antarctica Peninsula.

The Larsen C Ice Shelf, which is between 200 and 600 metres thick, floats on the edge of The Antarctic Peninsula, holding back the flow of glaciers that feed into it.

Professor Adrian Luckman of Swansea University, lead investigator of the MIDAS project, said:

“We have been anticipating this event for months, and have been surprised how long it took for the rift to break through the final few kilometres of ice. We will continue to monitor both the impact of this calving event on the Larsen C Ice Shelf, and the fate of this huge iceberg.

The iceberg is one of the largest recorded and its future progress is difficult to predict. It may remain in one piece but is more likely to break into fragments. Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters.

Project Midas:  Larsen C calves trillion ton iceberg

A one trillion tonne iceberg – one of the biggest ever recorded – has calved away from the Larsen C Ice Shelf in Antarctica. The calving occurred sometime between Monday 10th July and Wednesday 12th July 2017, when a 5,800 square km section of Larsen C finally broke away. The iceberg, which is likely to be named A68, weighs more than a trillion tonnes.  Its volume is twice that of Lake Erie, one of the Great Lakes.

The final breakthrough was detected in data from NASA’s Aqua MODIS satellite instrument, which images in the thermal infrared at a resolution of 1km, and confirmed by NASA’s Suomi VIIRS instrument.

NASA Suomi VIIRS panchromatic image
from July 12 2017, confirming the calving

The development of the rift over the last year was monitored using data from the European Space Agency Sentinel-1 satellites – part of the European Copernicus Space Component. Sentinel-1 is a radar imaging system capable of acquiring images regardless of cloud cover, and throughout the current winter period of polar darkness.

The iceberg weighs more than a trillion tonnes (1,000,000,000,000 metric tonnes), but it was already floating before it calved away so has no immediate impact on sea level.

Although the remaining ice shelf will continue naturally to regrow, Swansea researchers have previously shown that the new configuration is potentially less stable than it was prior to the rift.  There is a risk that Larsen C may eventually follow the example of its neighbour, Larsen B, which disintegrated in 2002 following a similar rift-induced calving event in 1995.

Dr Martin O’Leary, a Swansea University glaciologist:

“Although this is a natural event, and we’re not aware of any link to human-induced climate change, this puts the ice shelf in a very vulnerable position. This is the furthest back that the ice front has been in recorded history. We’re going to be watching very carefully for signs that the rest of the shelf is becoming unstable.”

This is a huge iceberg and a big event. Calving of ice shelves is a natural occurrence, but they could be influenced by warming temperatures and they could influence the effects of climate change. These things are difficult to determine accurately.

Larsen C ice shelf crack splits

A crack separating the Larsen C ice shelf in Antarctica has been growing over the last decade, increasingly quickly since 2015.

Scientists have now detected a split in the crack, and think that it won’t be long before the ice shelf splits off altogether.

Previous splits:

https://nsidc.org/news/newsroom/larsen_B/index.html

Gizmodo: A Second Giant Crack Has Appeared On Antarctica’s Larsen C Ice Shelf

A 130km-long crack along Antarctica’s Larsen C Ice Shelf has remained stable since February, but scientists have now detected a new branch, one that’s extending about 10km from the main rift. It seems like only a matter of time before the 5000 square kilometre ice shelf plunges into the sea.

Geologists with Project MIDAS, a UK-based research project studying the effects of melting on the Larsen C ice shelf, have been monitoring the crack for several years now, but the rift experienced a sudden growth spurt this past December when it grew by 20km.

In January, the crack advanced another 10km over the course of two weeks. The Larsen C Ice Shelf is fully expected to collapse, or calve, at which time it will lose more than 10 per cent of its ice surface area (a region roughly the size of Delaware). The latest observations suggest this monumental event may happen sooner rather than later.

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The current location of the rift on Larsen C, as of 1 May 2017.

A report from Project MIDAS shows that, as of 1 May 2017, a new branch has appeared along the rift. The fissure emerged about 10km behind the tip of the main channel and is heading towards the ice-front. “This is the first significant change to the rift since February of this year,” write the geologists.

See also What Happens When That Enormous Antarctic Ice Shelf Finally Breaks?

Maybe some of the remnants will float up the coast of new Zealand again, as happened in 2006.

Larsen C ice shelf rift grows

It looks like the Larsen C ice shelf will break off in West Antarctica soon (in the next few months) after a sudden extension of the rift by 18 km in December, leaving just 20km holding 5000 square kilometre shelf on.

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Larsen A broke off in 1995, and Larsen B broke off in 2002.

This is what happens to ice shelves over time. There is no way of knowing if the process is being sped up by climate change or not.

RNZ: Huge iceberg poised to break off Antarctica

A long-running rift in the Larson C ice shelf grew suddenly in December and now just 20km of ice is keeping the 5000 sq km piece from floating away.

…in December the speed of the rift went into overdrive, growing by a further 18km in just a couple of weeks. What will become a massive iceberg now hangs on to the shelf by a thread just 20km long.

“If it doesn’t go in the next few months, I’ll be amazed,” project leader Prof Adrian Luckman, from Swansea University, told BBC News.

While very interesting this isn’t abnormal.

NZ Antarctic Research Institute director Gary Wilson said this was a fairly normal process for ice shelves to carve off when they came into enough interaction with storm swells.

He said the questions would be whether it would cause warmer water to get further under the ice shelf, and whether it would allow the storm swells to break up further back.

Larsen C is about 350m thick and floats on the seas at the edge of West Antarctica, holding back the flow of glaciers that feed into it.

As it floats on the sea, the resulting iceberg from the shelf will not raise sea levels. But if the shelf breaks up even more, it could result in glaciers that flow off the land behind it to speed up their passage towards the ocean. This non-floating ice would have an impact on sea levels.

According to estimates, if all the ice that the Larsen C shelf currently holds back entered the sea, global waters would rise by 10cm.

That’s likely to be a long term thing, if it happens. Sea levels have risen since the last ice age.

post-glacial_sea_level

What has changed recently is the huge increase in population and the establishment of settlements in low lying areas.