Technology & Science

Antarctic ice shelf break offers scientists a 'natural experiment' to observe

Less than a month after a massive iceberg broke off the Larsen C ice shelf in Antarctica, scientists have gathered data on its changes, movement and whether climate change played a role in the break.

Iceberg has moved away from Larsen C ice shelf and spawned 11 smaller icebergs

A satellite image taken July 30 shows the size of the iceberg that broke from the Larsen C ice shelf and its distance from the Antarctic ice shelf. (A. Fleming/British Antarctic Survey)

Less than a month after a massive iceberg broke off the Larsen C ice shelf in Antarctica, scientists have gathered data on its changes, movement and whether climate change played a role in the break.

Since the iceberg the size of P.E.I. broke off the ice shelf, a process called calving, on July 12, it has moved roughly five kilometres and started to spawn several smaller icebergs, researcher Anna Hogg, from the University of Leeds, told CBC News.

The overall distance of the iceberg from Larsen C depends on where the measurement is taken, because the iceberg is so large.

"But it is moving. It is floating and not grounded in one place," she said.  

Not all icebergs move away from where they break off, Hogg said. One iceberg was stuck in Antarctica for more than 20 years, she said.

"The ocean temperatures are so cold they can get stuck and not move," she said.

About 11 smaller icebergs have broken off, the largest of which is more than 10 kilometres long.

Although a lot of attention is focused on the icebergs, there's still plenty to watch on the Larsen C ice shelf, Hogg said.

Cracks on the ice shelf, similar to the ones that led to this large iceberg calving, continue to grow, she said, with one crack 40 kilometres away from the Bawden Ice Rise, which gives structural support to the ice shelf.

"It's quite a long distance," Hogg said, but it will be worth watching.

'Natural experiment'

In this week's paper published in Nature Climate Change, the researchers say the iceberg's calving isn't necessarily the result of climate change.

"An event like this is to be expected. It is part of the natural life cycle of ice shelves and doesn't require any special explanation," Hilmar Gudmundsson, from the British Antarctic Survey, told CBC News.

Scientists will have to look at the larger picture of ice shelves over several decades to see if the calving off Larsen C is part of a trend.

"A single event like this is going to be very helpful, but with a single event we can't make any statement about whether this is related to climate change or not," Gudmundsson said.

Gudmundsson said improvements in satellite technology allow researchers the opportunity to watch this "natural experiment" and also to "test our models and understanding of how ice shelves affect the flow of glaciers."