One of biggest icebergs ever
It’s among the largest in recorded history to splinter off the Antarctic continent
Scientists confirmed that a much anticipated break at the Larsen C ice shelf in Antarctica has occurred, unleashing a massive iceberg that is more than 5700 sq km in area and weighs a trillion tonnes.
In other words, the iceberg — among the largest in recorded history to splinter off the Antarctic continent — consists of almost four times as much ice as the fast melting ice sheet 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 re- search 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 instrument, MODIS on the Aqua satellite, and confirmed by a second, they said. The European Space Agency has also confirmed the break.
The iceberg contains so much mass that if all of it were added anew to the ocean, it would drive almost 3mm of global sea level rise. In this case though, the ice was already afloat so there won’t be a substantial sea level change.
The Project Midas group said that the effect of the break is to shrink the size of the floating Larsen C ice shelf by 12 per cent. While they can’t be certain, they’re concerned that this could have a destabilising effect on the remainder of the shelf, which is among Antarctica’s largest. “The iceberg is one of the largest recorded and its future progress is difficult to predict,” said Adrian Luckman, the lead Midas researcher and an Antarctic scientist at Swansea. “It may remain in one piece but is more likely to break into fragments. Some . . . may remain in the area for decades, while parts . . . may drift north.”
There is no expected immediate effect on shipping, Luckman said. “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.”
The change is large enough that it will trigger a redrawing of the Antarctic coastline, according to Ted Scambos, a scientist with the National Snow and Ice Data Centre.
Even larger icebergs than this have broken off of Antarctica in the past, including one over 10,360 sq km, famously dubbed B15, in 2000 off the Ross Ice Shelf. It was the biggest iceberg ever recorded.
Larsen C also lost an even larger piece in 1986, Scambos said, but that occurred in different circumstances. It came after the shelf had grown considerably and extended much farther out into the Weddell Sea than it does now.
Indeed, the front of Larsen C ice shelf has retracted back farther than ever previously observed, according to Eric Rignot, a glaciologist with Nasa and the University of California, Irvine. “The ice front is now almost 40km farther back. A similar evolution was seen on Larsen A and B before they collapsed in 1995 and 2002 respectively.”
If you add together all the ice lost from the various Larsen ice shelves since the 1970s, it is around 19,035 sq km, according to figures from Rignot.
Scientists will now proceed to track the iceberg using satellite imagery, and should be able to get a chance at regular glimpses even in Antarctic night, due to the use of radar and thermal imaging. The iceberg’s progress is expected to be northward in the direction of South America. First, it will be swept up in the Weddell Sea Gyre, an elongated circuit of ocean flow, and then should pass to the west of South Georgia and the South Sandwich Islands, according to Helen Amanda Fricker, an Antarctic expert at the Scripps Institution of Oceanography. Then the iceberg, or its pieces, will become swept up in the Antarctic Circumpolar Current, which encircles the entire continent, flowing in a west-toeast direction.
Before the break, a rift across the