Scientists announced Wednesday that a much anticipated break at the Larsen C ice shelf in Antarctica has occurred, unleashing a massive iceberg that is more than 2,200 square miles in area and weighs a trillion tons.
In other words, the iceberg — one of the largest in recorded history to splinter off the Antarctic — is close to the size of Delaware and consists of almost four times as much ice as the fast melting island of Greenland loses in a year. It is expected to be given the name “A68″ soon, scientists said.
“Its volume is twice that of Lake Erie, one of the Great Lakes,” wrote researchers with Project MIDAS, a research group at Swansea and Aberystwyth Universities in Wales that has been monitoring the situation closely by satellite.
The break was detected by one NASA satellite, Aqua MODIS, and confirmed by a second, they said. The European Space Agency also has confirmed the break.
The iceberg contains so much mass that if all of it were added anew to the ocean, it would drive almost 3 millimeters of global sea level rise (it takes 360 billion tons of ice to produce 1 millimeter of ocean rise). In this case though, the iceberg is already afloat so there won’t be a substantial sea level change.
The Project MIDAS group said Wednesday that the effect of the break is to shrink the size of the floating Larsen C ice shelf by 12 percent. While they can’t be certain, they’re concerned that this could have a destabilizing effect on the shelf, which is among Antarctica’s largest.
“The iceberg is one of the largest recorded and its future progress is difficult to predict,” Adrian Luckman, the lead MIDAS researcher and an Antarctic scientist at Swansea University, said in a statement. “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.”
There is no expected immediate effect on shipping, Luckman said by email.
“Icebergs from this region occasionally make it out beyond the tip of the Antarctic Peninsula, but it will take a while for that to happen to this iceberg or its fragments, and there is not a lot of shipping in the area that I am aware of,” he explained.
Before the break, a rift across the Larsen C ice shelf had extended more than 100 miles in length, and just a few miles of remaining ice connected the nascent iceberg to the shelf. The break began years ago but had quickened its pace in the last year, increasingly convincing scientists that the iceberg detachment was inevitable, despite the fact that it is actually winter in Antarctica right now.
There is a debate over whether this event can be attributed in any way to climate change. Scientists don’t have all the data to show what is happening in the environment of the floating Larsen C ice shelf, which is affected not only by air temperatures above it but also ocean temperatures below it.
Antarctica’s ice shelves do calve large pieces regularly, a natural process. But at the same time, Larsen C is the next ice shelf in line in a southward progression that has previously seen the collapse of the Larsen A and Larsen B ice shelves, making this occurrence at least suspicious.
“I think we’re all scratching our heads as to just what combination of changes in the ice, air, and ocean caused this,” Ted Scambos, an Antarctic expert and senior research scientist with the National Snow and Ice Data Center, said by email. “It’s unclear if this is a new trend for this area of Antarctica. The case for a climate-related cause is not nearly as good as for other areas of Antarctica.”
The Antarctic continent is ringed by ice shelves, which are large, thick, floating extensions of glaciers that have extended from the land, where they have built up due to snowfall over vast time periods, into the sea. These shelves are now vulnerable to warming ocean waters, which can cause them to thin, break off pieces at an unusual rate, and even collapse. And when they do so, the ice behind them is liberated to flow more rapidly into the ocean, raising seas.
Scientists stress, however, that because the trillion ton iceberg is already afloat in the Weddell Sea, its detachment does not raise the globe’s sea level. Their fear, however, is that its loss could speed up the outward ice flow of the remainder of the Larsen C ice shelf, which would indeed increase sea level — but those glaciers only have the potential to raise seas by about a centimeter in this region.
The greater fear is the loss of ice shelves, and glaciers, farther southward in Antarctica, where the sea level rise potential begins to be measured in feet.