Mammoth iceberg breaks loose

25 April 2014 - 09:36 By Reuters
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MONITORED: The B-31 iceberg before separating from an Antarctic glacier on October 28 last year, top, and afterwards on November 13.
MONITORED: The B-31 iceberg before separating from an Antarctic glacier on October 28 last year, top, and afterwards on November 13.
Image: NASA EARTH OBSERVATORY/REUTERS

Scientists are monitoring an iceberg roughly six times the size of Manhattan - one of the largest now in existence - that broke off from an Antarctic glacier and is heading into the open ocean.

Nasa glaciologist Kelly Brunt said the iceberg covers about 660km² and is up to 500m thick.

Known as B31, the iceberg separated from Antarctica's Pine Island Glacier last November, Brunt said.

"It's one that's large enough that it warrants monitoring," she said in a telephone interview, noting that US government organisations, including the National Ice Centre, keep an eye on dozens of icebergs at any given time.

The iceberg's present location is not in an area heavily navigated by ships.

"There's not a lot of shipping traffic down there. We're not particularly concerned about shipping lanes. We know where all the big ones are," Brunt said.

Scientists are especially interested in this iceberg not only because of its size but because it originated in an unexpected location, she said.

"It's like a large sheet cake floating through the Southern Ocean."

The glacial crack that created the iceberg was first detected in 2011, according to Brunt, who is a scientist with Nasa Goddard Space Flight Centre and Morgan State University in Maryland.

Pine Island Glacier has been closely studied over the past two decades because it has been thinning and draining rapidly and may be an important contributor to sea level rise, scientists said.

They said the iceberg has floated across Pine Island Bay, a basin of the Amundsen Sea, and will likely be swept up soon in the swift currents of the Southern Ocean.

"We are doing some research on local ocean currents to try to explain the future motion properly," iceberg researcher Grant Bigg of the University of Sheffield in England said.

"It has been surprising how there have been periods of almost no motion, interspersed with rapid flow."

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