Flying 1,500 feet above the Antarctic coast, NASA scientists recently passed over a bizarrely straight-edged rectangular iceberg and snapped a picture of the floating slab.
While an intriguing image for the many of us who don’t take aerial surveys of the changing, cracking, and melting Antarctic coast, these “tabular” icebergs are a common sight for scientists working in Antarctica.
“It’s not uncommon to see that in Antarctica — although that [the tabular iceberg spotted by NASA] is a fresh and sharp looking one,” Ted Scambos, a senior research scientist at the National Snow and Ice Data Center, said in an interview.
From yesterday’s #IceBridge flight: A tabular iceberg can be seen on the right, floating among sea ice just off of the Larsen C ice shelf. The iceberg’s sharp angles and flat surface indicate that it probably recently calved from the ice shelf. pic.twitter.com/XhgTrf642Z
— NASA ICE (@NASA_ICE) October 17, 2018
“The ice shelves that produce the icebergs are extremely flat and expansive, so we often see nearby tabular icebergs similar to the one seen in the photo,” Brooke Medley, NASA’s Operation IceBridge deputy project scientist, added over email.
For years, Antarctic scientists have documented the curiously straight-edged icebergs floating in the water after snapping off from ice shelves — the ends of massive glaciers that float over the ocean.
In 2008 the British Antarctic Survey flew over a whole collection of these freakishly perfect tabular icebergs, which had broken off of the Wilkins Ice Shelf on the Antarctic Peninsula.
The strange icebergs really become visible at about 8 seconds in:
“It’s just amazing,” said Scambos of the Wilkins tabular icebergs. “There are hundreds of them.”
“There’s a whole field of these impossibly square blocks,” he added.
Whether it’s the recent tabular iceberg captured by NASA off the Larson C Ice Shelf, or the Wilkins blocks above, the method of their creation is the same.
The expansive ice shelves that create the icebergs are hanging off of Antarctic land, somewhat similar to the flimsy tape extended out from a tape measure.
“After a while, a tape measure will bend from its own weight,” Catherine Walker, a NASA scientist who researches Antarctic glaciers, said in an interview.
“Usually, you get a certain point in which you pass its [the iceberg’s] ability to hold itself up,” said Walker. “Then you get a straight line where it calves.”
Generally, ice shelves are very uniform substances, added Scambos. “In general, if you just have a long, flat plate you can have long, straight cracks.”
This iceberg captured by NASA — akin to the Wilkins icebergs — was also pretty new and fresh, which certainly helped its profoundly sharp, almost unnatural appearance.
“That shape is not hugely surprising,” said Walker. “It’s relatively new and not rounded off by melting or anything like that — a new piece of broken glass is sharp.”
A month from now, however, waves and melting will likely eat away at the iceberg’s sharp, right-angled form. But for now, it’s in near-perfect shape — even if we can’t quite see the entire slab.
“The scale of icebergs is often hard to convey,” said Medley. “While I wasn’t on this flight, it’s important to remember that several of these icebergs cannot fit in the full camera frame due to their immensity.”