The B-31 Iceberg is seen before, (top) on October 28, 2013 and after separating on November 13, 2013, from a rift in Antarctica's Pine Island Glacier in this NASA Earth Observatory handout image. Scientists are monitoring an unusually large iceberg -
The B-31 Iceberg is seen before, (top) on October 28, 2013 and after separating on November 13, 2013, from a rift in Antarctica's Pine Island Glacier in this NASA Earth Observatory handout image. Scientists are monitoring an unusually large iceberg - roughly six times the size of Manhattan - that broke off from an Antarctic glacier and is heading into the open ocean, although not in an area heavily navigated by ships. REUTERS/NASA Earth Observatory/Holli Riebeek/Handout via Reuters. REUTERS/NASA Earth Observatory

A breakaway iceberg from Antartica which is six times larger than Manhattan, has the NASA's Earth Observatory worried. Scientists believed the rogue iceberg could drift to populated shipping lanes which could disrupt the industry.

Categorized as B31, the iceberg spans 35 kilometres by 20 kilometres (21 by 12 miles), roughly the size of Singapore, and is a mile (500 metres) thick. NASA glaciologist Kelly Brunt said the iceberg separated from Antarctica's Pine Island Glacier in November 2013.

The iceberg is currently in a location not heavily navigated by ships.

"However, it is hard to predict with certainty where and when these things will drift. Icebergs move pretty slowly, and watching this iceberg will be a waiting game," Brunt said.

If caught in the coastal counter-current, the breakaway B31 could go around the frozen continent heading west, or eastward if the iceberg enters the wider circumpolar current.

It could pose a hazard in the coming months if it drifts to populated shipping lanes, scientists said.

Pine Island Glacier, from where the iceberg originated, was first detected in 2011. It's been closely studied over the past two decades because it has been thinning and draining rapidly. Scientists said these development could be an important contributor to the rising sea level.

Tom Wagner, NASA's cryosphere program manager, said the shelf of Pine Island Glacier has been moving forward at roughly 4 kilometres per year, so the calving of this iceberg is not necessarily a surprise.