VOA慢速英語：科學(xué)家表示：巨大的南極冰山脫落

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A huge iceberg, seven times the size of New York City, broke off of Antarctica, scientists said Wednesday.

The iceberg that broke away is 5,800-square-kilometers large. It is described as weighing 1 trillion tons. That is about the same volume as the great Lake Erie between Canada and the U.S.

Scientists at the University of Swansea in Britain described the iceberg as one of the largest ever recorded. It broke off from the Larsen C ice shelf over the last few days.

The Larsen ice shelf is located off the coast of northwestern Antarctica. The area is connected to land, but floats on seawater instead of sitting on top of the continent.

The process of the ice breaking away and moving into the ocean is known as calving.

Researchers are watching closely to see whether climate change is affecting the calving process. For months they have kept their eyes-- and satellites -- on a large crack, or break, in this section of the Larsen ice shelf. While its breaking off into the water was not a surprise, the timing was.

“We have been anticipating this event for months, and have been surprised how long it took for the rift to break through the final few kilometers of ice,” said Adrian Luckman of Swansea University and MIDAS. “We will continue to monitor both the impact of this calving event on the Larsen C ice shelf, and the fate of this huge iceberg.”

The U.S. space agency NASA, and European Space Agency satellites have been watching the shelf. So have many people around the world who saw pictures of the large crack in the ice. The final break was first seen in an image from NASA’s Aqua MODIS satellite instrument.

This is not the first time parts of the Larsen ice shelf have broken off the frozen continent. The Larsen A shelf broke off in 1995 and the Larsen B fell in 2002. For years now, researchers from the British-based Antarctic project, MIDAS, have been monitoring the rift in Larsen C.

The researchers said because it was already floating before it broke off, “there is no immediate impact on sea level.” This event leaves the Larsen C ice shelf smaller by more than 12%, and “the landscape of the Antarctic Peninsula changed forever.”

The project is investigating the effects of a warming climate. They use a combination of fieldwork, satellite observation and computer models.

So, now what is going to happen to the iceberg?

The researchers suggest it is likely to break into pieces. They say that some of the ice may stay nearby for decades. Other parts may drift, or slowly move north into warmer waters.

Martin O’Leary is a glacier expert at Swansea University and a member of the MIDAS project team. He said, “Although this is a natural event, and we’re not aware of any link to human-induced climate change, this puts the ice shelf in a very vulnerable position.”

Anna Hogg, with the Centre for Polar Observation and Modelling at the University of Leeds, says there is not the evidence yet to say it is caused by climate change. “At this point it would be premature to say that this was caused by global warming,” she said.

Scientists will be watching the rest of the shelf for any signs of it becoming unstable. Adrian Luckman added that the ice shelf could regrow slowly or more calving could lead to its breaking off. Luckman said scientists have different opinions on what will happen next.

“Our models say it will be less stable, but any future collapse remains years or decades away,” he said.

I’m Anne Ball.

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Words in This Story

iceberg – n. a very large piece of ice floating in the ocean

calving – v. the breaking off of ice in big pieces from the edge of a glacier

anticipate – v. to think about something that will or may happen in the future

rift – n. a deep crack or opening in the ground

fate – n. the things that will happen to a person or a thing

vunerable – adj. easily hurt or harmed physically, mentally or emotionally