Trillion-Ton Iceberg Breaks Off Antarctica

Jul 12, 2017

By Jeanna Bryner

One of the largest icebergs ever recorded, packing about a trillion tons of ice or enough to fill up two Lake Eries, has just split off from Antarctica, in a much anticipated, though not celebrated, calving event.

A section of the Larsen C ice shelf with an area of 2,240 square miles (5,800 square kilometers) finally broke away some time between July 10 and today (July 12), scientists with the U.K.-based MIDAS Project, an Antarctic research group, reported today.

Scientists discovered the birth of this iceberg in data collected by an instrument aboard NASA’s Aqua satellite, called MODIS, which takes thermal infrared images.

The iceberg was expected, though scientists didn’t know when the crack in the ice sheet would finally release the floating chunk. The rift in the Larsen C ice shelf — the fourth-largest shelf in Antarctica — first showed itself in 2014, but it wasn’t until November 2016 that satellite measurements revealed it had grown to more than 300 feet (91 m) in width and 70 miles (112 km) in length. The most recent measurements from this summer put the rift at 124 miles (200 km) long, with the now-calved iceberg hanging on by a thread; just 3 miles (5 km) of ice connected it with the rest of the ice shelf.

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3 comments on “Trillion-Ton Iceberg Breaks Off Antarctica

  • As the ice is melting from the bottom-up, as warmer seawater reaches further under it, the very melting of these huge blocks of ices raises the sea level and causes the remaining ice to float up, letting more warmed seawater flow under it to previously inaccessible areas!

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    The giant berg A-68 looks finally to be on the move.

    Recent weeks have seen it shuffle back and forth next to the Antarctic ice shelf from which it broke away.

    But the latest satellite imagery now indicates the near-6,000 sq km block is swinging out into the Weddell Sea.

    A wide stretch of clear water has opened up between the berg’s southern end and the remaining Larsen shelf structure, suggesting A-68 is set to swing around and head north.

    This is the direction the Weddell currents should take the iceberg.

    Polar experts expect the trillion-tonne block to essentially bump along the shelf edge until it reaches the great eastward movement of ocean water known as the Antarctic Circumpolar Current.

    This would then export what is one of the largest bergs ever recorded out into the South Atlantic.

    How far A-68 actually gets along this predicted path is anyone’s guess, however. The berg already shows evidence of fragmentation at its edges.

    These bits – they carry the designation A-68b, A-68c, etc – all still float close to their parent. But in time they will get separated, and it is entirely possible that big segments with deep keels could get anchored in shallow waters and become semi-permanent “ice islands”.

    A-68 calved during mid-winter and it required radar satellites – such as Europe’s Sentinel-1 spacecraft – with their unique ability to pierce cloud and darkness to keep track of developments.

    With the return now to longer days in the Antarctic, opportunities are increasingly opening up for high-resolution optical satellites to take a close look at the state of the berg.

    And new imagery from the Spanish Deimos-2 spacecraft shows how the initial sharp edges of the block’s northern-western corner have been lost.

    So with European and other satellites monitoring these events, any interference from Trumpies at NASA will not cut off the climate information on Antarctic glaciers and ice shelves.

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