2006年VOA标准英语-Satellites Show Dramatic Melting At Poles

By Paul Sisco
Washington, DC
24 May 2006
 
watch Melting Poles report

NASA scientists, working with 10 years of satellite data, find a dramatic thinning of ice around the edges of Greenland, and Antarctica too.   

satellite view of earth    
  
Using satellite technology and various measurements, NASA scientists confirm the earth is melting at both poles.  In the north, at the Arctic, the melting of Greenland's three-kilometer thick ice sheet had been expected, though not as dramatically as it is now happening.  But in the south, many believed the far more massive ice sheets covering Antarctica would increase in the 21st century. That's not so, according to the NASA observations and data.  Despite increasing snowfall, Antarctica's ice sheets are shrinking. 

Isabella Velicogna  
  
Research Scientist, Dr. Isabella Velicogna is with the University Of Colorado explains the evidence of melting. "What is unique about what we found is that for the first time, we are able to say, we are sure that the Antarctic ice sheet is losing mass, and at a significant rate."

 
Jaz Zwally
  
NASA Glaciologist, Dr. Jay Zwally. “The warmer ocean comes underneath 1 the ice shelves and melts them from the bottom, and warmer air from the top melts them from the top so they're thinning and eventually they get to a point they go poof?"

The findings come from, Grace, which stands for "Gravity Recovery and Climate Experiment ... twin satellites orbiting the earth in tandem 2 that are constantly measuring variations in the Earth's mass and gravitational field.  Dr. Isabella Velicogna, authored the study. "We studied the changing mass of the Antarctic ice sheet using the data from the gravity recovery and climate experiment, Grace, and we found Antarctica is losing mass and is losing a significant about of mass (at) about 152 cubic kilometer a year, which is equivalent to how much water the United Stares is using in three months.  So it's a lot of water." 

 
James Hansen
  
Combining data from the grace experiment with other research tools, scientists tracking Antarctica's melting ice sheet express concern.  NASA Earth Science Director, James Hansen. "If we pass a certain point of no return then we're going to get large sea level rise even though it would take a century or two or three to play out fully 3, we will have started a process we just can't stop."

Scientists say rising sea levels are a great danger to coastal 4 villages and cities.  While the new analysis shows fluctuations 5 in Antarctica's ice sheet and even some thickening in parts, melting over the last five years has contributed to a sea level rise of 1.2 millimeters.  This suggests a small but significant rise in sea levels of almost half a millimeter annually 6.