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article imageEvidence shows Antarctic's Brunt Ice Shelf is about to break off

By Karen Graham     Apr 8, 2019 in Science
Glaciology experts have issued evidence that a large section of the Brunt Ice Shelf in Antarctica, which is home to the British Antarctic Survey's Halley Research Station, is about break off.
The iceberg, measuring over 1,500 square kilometers — which is twice the size of New York City — is expected to break away from the Brunt Ice Shelf within the next few months, reports New Atlas.
The resulting iceberg will be about 1,500 square kilometers (580 square miles) in size and be between 150 and 250 meters (492 and 820 feet) thick.
Scientists have been following closely the progression of the two cracks in the ice shelf — especially after the second crack, the "Halloween Crack," as it came to be known, was spotted to the north of the crack discovered in 2012. Previously stable for about 35 years, this crack has started spreading northward at an accelerated rate of about 4 kilometers (2.5 miles) a year.
Image taken January 23  2019.
Image taken January 23, 2019.
NASA Earth Observatory
The Halloween crack is also lengthening by nearly 4 kilometers a year. The fracture moving in a northward direction has only about three miles to go before reaching the Halloween crack.
Calving of the iceberg not related to climate change
Researchers from Northumbria University, in Newcastle upon Tyne, UK, in collaboration with scientists from ENVEO, a remote sensing company in Austria, have submitted research for publication in the journal the Cryosphere this month that shows how the break-off of part of the Brunt Ice Shelf is part of its natural life cycle.
Professor Hilmar Gudmundsson of Northumbria explains: "I have been carrying out research in this area for more than 15 years and have been monitoring the growth of the cracks since they first emerged in 2012."
Gudmundsson goes on to say that there has been a great deal of speculation over the cause of the movement seen in the ice shelf and this has, in turn, led to even more questions of what the impact of the calving event will have when it breaks away.
"However," says Gudmundsson, "what many people do not realize is that this is a natural process and something which has happened time and again. We recognize that climate change is a serious problem which is having an impact around the world and particularly in the Antarctic. However, there is no indication from our research that this particular event is related to climate change."
Halley VI research station will be relocating to a safer site on the Brunt Ice Shelf in Antarctica. ...
Halley VI research station will be relocating to a safer site on the Brunt Ice Shelf in Antarctica. Image from 2016.
British Antarctic Survey
What is causing the break-off?
Actually, little is known about the processes that drive rift formation on the ice sheets prior to calving, or what controls the timing of these events, according to the research paper.
Using data from observations made by the British Antarctic Survey (BAS) and data from the Copernicus Sentinel-1 and Sentinel-2 satellites, Jan De Rydt and Hilmar Gudmundsson have built a model to describe the behavior of the floating ice platform. The team was able to reveal how stresses across the ice shelf are distributed, reports Science Daily.
"It all fits together; it's a very compelling piece of work," says Gudmundsson, reports the BBC. "It shows that the chasm started to grow because of the stresses building up, and they built up because of the natural growth of the ice shelf. The ice shelf itself created this chasm."
"There is no indication from oceanographic or atmospheric data that the climate is changing in the Brunt area," Dr. De Rydt told the BBC. "Our ocean observations are limited but whatever we have doesn't indicate anything unusual, and our model shows that what we are seeing can be perfectly explained by natural changes in the geometry of the ice shelf."
“The near-term future of Brunt Ice Shelf likely depends on where the existing rifts merge relative...
“The near-term future of Brunt Ice Shelf likely depends on where the existing rifts merge relative to the McDonald Ice Rumples,” said Joe MacGregor, a glaciologist at NASA’s Goddard Space Flight Center.
NASA Earth Observatory
According to the researchers, this also means that the loss of the Brunt Ice Shelf isn't expected to contribute to sea level rise. They base this claim on historical evidence.
"Maps drawn by Shackleton and Wordie during their expedition to the Brunt Ice Shelf in 1915 show that, at that time, the ice shelf was quite extended," says Gudmundsson.
"However, by the time the Halley Research Station was established in the 1950s the reach of the ice shelf was much shorter, indicating that a large iceberg must have broken away at some point after 1915."
More about brunt ice shelf, natural growth, internal feedbacks, mechanical tension, Science
 
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