Crack in Antarctic Ice Shelf is About to Launch a Delaware-Sized Iceberg

Scientists are watching intently as a titanic section of Larsen C, the fourth largest ice shelf in Antarctica, prepares to break off into the sea as an iceberg the size of Delaware. The question is, when?

ScienceAlert reports that satellite images began tracking the spread of an enormous crack in the ice shelf in 2010. As it reached 120 miles in length this spring, the fissure suddenly forked earlier this year. and the resultant rift will cause a 2,000 square mile section -- 10% of Larsen C's total area -- to break off into the ocean.

Though scientists cannot predict exactly when this will happen, it could be a matter of weeks, says Dan McGrath, a scientist with the U.S. Geologic Survey.

When the sudden fork occurred, one crack continued parallel toward the Southern Ocean, while the other continued north, creating the giant rift. Andrian Luckman and Martin O'Leary, scientists at Swansea University in the UK wrote on their blog that the crack has grown 11 miles between May 25 and May 31. Just eight miles remain before the rift reaches the sea, causing the block to plunge into the ocean.

Most importantly, computer modelling has shown that the remainder of Larsen C might become "less stable" after the iceberg breaks off and may fully disintegrate like a neighboring shelf, Larsen B, did in 2002 -- a disatrous acceleration that could raise sea levels by several inches.

Calving, as this process of shedding icebergs is called, is a natural process, especially when snow accumulations force old ice to be pushed out to sea. But the speed with which this calving incident is occuring in Antarctica and the relative size of the area in jeopardy are alarming to scientists.

Joe MacGregor, a glaciologist and geophysicist at NASA's Goddard Space Flight Center, says when the block breaks off, it will be the third largest such block to do so.

The scientists' latest update came just days before Trump announced the U.S. withdrawal from the Paris Agreement on Climate Change.