Arctic Changes: The Big Picture - Enhanced Transcript
Table of Contents
The Arctic is Changing
- Dr. Ben Strauss (Narrator): The Arctic is a frozen place where ice covers an ocean as wide as a continent, and smothers Greenland under an ice sheet reaching two miles thick. But the Arctic is not frozen still.
This is the story of how it is changing Ã¢Â€Â” as seen from above Ã¢Â€Â” and from below.
From above, satellites began tracking Arctic sea ice cover routinely by 1979. The red line traces the minimum ice extent that year. Since then, with each passing decade, the area covered by ice has declined.
- Ben Strauss: Over the same years, something hidden has been taking place below the surface. Sea ice has been getting thinner, both in fall months, and the cold Arctic winter.
- Ben Strauss: We know this from submarine readings Ã¢Â€Â” declassified from the Cold War Ã¢Â€Â” along with more recent satellite measurements accurate to one inch. Scientists worry that this thinning makes sea ice vulnerable to a faster retreat.
But does sea ice loss really matter? After all, floating ice doesnÃ¢Â€Â™t raise the sea level when it melts, just like ice cubes donÃ¢Â€Â™t overflow your glass when they melt.
- Ben Strauss: But sea ice is like a bright white heat shield for the planet, reflecting solar energy back into space. As the shield shrinks, the exposed dark ocean absorbs more heat. That means a warmer Arctic; and a warmer Arctic could mean trouble for GreenlandÃ¢Â€Â™s great ice sheet and AlaskaÃ¢Â€Â™s glaciers.
Unlike sea ice, this ice sits on land Ã¢Â€Â” so when it melts or crumbles into the ocean, it does raise global sea level, affecting us all. To monitor, NASA satellites have been watching closely, measuring changes in ice sheet elevation, and even in the gravitational pull of ice masses, with satellites like giant scales in the sky.
- Ben Strauss: TheyÃ¢Â€Â™ve found that Greenland has been losing large amounts of ice Ã¢Â€Â” so much from 2004 to 2007 that you could build a fleet of state-sized rafts three feet thick, a big shift compared to the 1990s.
- Ben Strauss: Alaska has been shedding ice, too, averaging enough to fill a train of ice cars around the world, every day.
- Ben Strauss: On land, then, as at sea, the ice is retreating. In other wordsÃ¢Â€Â”far from being frozen still Ã¢Â€Â” the Arctic is moving with all the force of a freight train.