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Iceberg knocks the block off Drygalski Ice Tongue
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Iceberg knocks the block off Drygalski Ice Tongue

April 12, 2006
An enormous iceberg, C-16, rammed into the well-known Drygalski Ice Tongue, a large sheet of glacial ice and snow in the Central Ross Sea in Antarctica, on 30 March 2006, breaking off the tongue's easternmost tip and forming a new iceberg.

The collision on 30 March shows the ice tongue breaking off, and the final image on 1 April captures C-16 and the new iceberg swinging to the other side of the ice tongue. Mark Drinkwater of ESA's Ocean and Ice Unit said: “During its passage to the coastal foot of the Drygalski Ice Tongue, C-16, which measures 18.5 kilometers by 55 kilometers, looped into and around McMurdo Sound before being carried quickly to the north.

"The surface ocean currents appear to have predominantly steered the iceberg, not the winds, thus telling us about important aspects of the adjustment in the ocean circulation since the departure of large grounded icebergs off Ross Island."

The floating Drygalski Ice Tongue, which protrudes 80 kilometers into the ocean, is connected to the David Glacier. If it were to break loose, scientists fear it could alter ocean currents and change the region's climate.

C-16 was formed in 2000 when Iceberg B-15A, measuring 27 kilometers by 161 kilometers, bumped into the jutting edge of the Ross Ice Shelf and snapped a large piece off. The new iceberg, originally named B-20 and later changed to C-16, then ran aground north of Ross Island. Over the last three months it had escaped its perch and made its way north where it collided with the ice tongue last week.

The National Ice Center (NIC), located in Maryland, USA, names icebergs according to the quadrant in which they are originally sighted. There are four quadrants (A, B, C and D). A sequential number is then assigned to the iceberg. B-20 was first spotted in the B quadrant and was the twentieth iceberg to be logged in that area. When B-20 navigated to the C quadrant, it was renamed to C-16.

NIC named the new iceberg, the piece of the ice tongue which broke off as a result of the C-16 collision, C-25, which measures 13 kilometers by 11 kilometers.

Envisat's ASAR acquired these images in Wide Swath Mode (WSM), providing spatial resolution of 150 meters. ASAR can pierce through clouds and local darkness and is capable of differentiating between different types of ice.

(Image of the week published the 7 April 2006)

Technical Information:
  • Satellite: Envisat
  • Instrument: ASAR
  • Acquisition: 30-Mar-2006
  • Centre coordinates: lat. 75.50, lon. 165.30


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