A huge area of the so-called Larsen C ice shelf — enough to cover the state of Delaware — has just broken off western Antarctica.
Project MIDAS — a UK-based Antarctica research project — confirmed the iceberg had detached on its Twitter account on Wednesday morning.
"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," a Project MIDAS blog post said shortly after the initial announcement.
Scientists first noticed a growing crack in Antarctica’s fourth-largest ice shelf in 2011. They’ve closely watched the crack spread at a faster rate in recent years, ultimately stretching more than 120 miles and carving out a chunk of ice covering more than 10% of the ice shelf’s area.
The iceberg broke off as a whole, but could eventually break up into smaller fragments.
"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," Prof. Adrian Luckman, the lead investigator of the MIDAS project, said in a statement on Wednesday. "Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters."
Experts don’t yet know whether the breaking, or “calving,” of this part of the ice shelf was triggered by man-made climate change.
“The calving event has the appearance of being a completely normal break of the ice shelf,” Ted Scambos, lead scientist at the Colorado-based National Snow and Ice Data Center, wrote in an email to BuzzFeed News.
“The only unusual thing is that it leaves the shelf smaller than it has been in the 125 years since it was first mapped,” Scambos said, adding that it has lost several icebergs in the past 30 years. “However, this kind of behavior is typical of ice shelves all across Antarctica.”
But what happens next could offer clues about possible climate change fingerprints.
“My guess is that it will simply grow back — the Larsen C is not close to the instability that we saw in the ice shelves to the north before they disintegrated,” Scambos said, referring to the melting and fracturing of two neighboring ice shelfs to the north, called Larsen A and Larsen B.
But if new cracks start forming in the Larsen C ice shelf, for example, that might suggest global warming is triggering bigger structural changes to this corner of Antarctica, Scambos explained.
Scientists will also be also be watching how fast different parts of the glacier are flowing and whether new features appear, such as water pooling on the surface of the glacier due to melting, that may point to climate change, according to Christopher Shuman, a research scientist at NASA Goddard Space Flight Center.
“It is not inconceivable this is a sign of changes to come. It’s hard to predict,” Shuman said. “But we’ll be watching though.”
Dr. Martin O'Leary — a glaciologist who is a member of the Project MIDAS team — conceded the calving leaves the ice shelf in a vulnerable position in a statement on Wednesday.
“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," O'Leary said.
"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.”
O'Leary's Project MIDAS colleague Prof. Luckman added that it was unclear whether or not the ice shelf would calve further and eventually collapse, or whether it would gradually regrow. However, he said that any potential collapse would be "years or decades" away.
Scientists’ main worry about a melting Antarctica is that the water frozen in its many grounded glaciers, which currently rest on bedrock, could cause global sea levels to rise by several feet. The new iceberg, however, won’t contribute to this rise. Similar to when ice cubes melt in a glass of water and the water level doesn’t rise, the amount of ocean currently displaced by the floating iceberg remains unchanged as it melts.
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Zahra Hirji is a science reporter for BuzzFeed News and is based in San Francisco
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