WORLD REPORT EDITION    TOP STORY

February 7, 2003

Thin Ice?

Scientists explore the causes of Antarctica's melting ice

Antarctica is a land of ice. The rocky continent at the bottom of the world is blanketed in ice up to three miles thick. Massive shelves of ice cling to its sides, a necklace of sea ice surrounds it, and colossal icebergs float near its shores.

The continent's ice holds 75% of the Earth's freshwater. If it all melted, global sea levels would rise 200 feet! So it's no wonder that scientists were alarmed last winter when a section of ice shelf about the size of Rhode Island crumbled into the sea in just one month. The Larsen Ice Shelf is on a peninsula where the average temperature has risen a worrisome 4.5 degrees in the last 50 years.

There have been other dramatic changes on the frozen continent. Over the past three years, a bunch of giant icebergs have broken off the Ross Ice Shelf in the south. Some of the bergs have trapped about 40 miles of floating ice near the U.S.'s main Antarctic research base, McMurdo Station. Few supply ships have been able to reach the station. Local Adelie penguins are now having a hard time getting through the ice to the open sea where they feed.

Nature or Nightmare?

Penguins in peril! Crumbling ice shelves! Icebergs as big as Massachusetts! Such dramatic events seem to signal a major disaster. In fact, some environmentalists worry that Antarctica's recent meltdowns are a sign that the whole planet is heating up. They blame this global warming on increasing air pollution. Factories, cars and trucks all release heat-trapping gases such as carbon dioxide. If the scientists are right about global warming, then the recent melts are just the tip of the iceberg - things could get much worse.

But many scientists who study Antarctica question whether global warming is to blame. In fact, recent observations show that Antarctica's interior is getting cooler, not warmer. "We don't even know if we're looking at changes that are just [in Antarctica]," says Ohio State University earth scientist Berry Lyons, "or if they are related to changes on a global scale."

The melting may be nothing new. A study published last month in the journal Science claimed that the West Antarctic Ice Sheet has been slowly melting for 10,000 years. Geologists studied rocks near the South Pole to determine how long ago ice had melted off of them. "There was a gradual and continuous melting," said John O. Stone, a geology professor at the University of Washington, Seattle, who wrote the report.

Stone and others believe that it may be normal for Antarctica to have long periods of cooling and warming. Radar images show that ice streams beneath the surface are pushing ice from the continent's center to its edges. Recent studies show that new snowfall replaces the ice at Antarctica's center, so overall, the amount of ice is not shrinking.

Getting the Cold, Hard Facts

Humans began studying Antarctica only 180 years ago. Harsh conditions, especially during its frigid, sunless winters, prevent researchers from doing work outside for half the year. But because the world's oceans and climate are so greatly influenced by Antarctica, scientists are checking it out like never before.

"Here we have a continent that is so important to our future," says earth scientist Peter Doran of the University of Illinois, "and we can't even agree on what's been going on there for the past few decades."

Doran leads a group that has just taken deep sections of earth, called core samples, from some of west Antarctica's lake bottoms. He believes that the samples will show weather data and melting patterns for the past 15,000 years.

On January 12, a NASA satellite called ICEsat went into orbit. The 661-pound space device is designed to measure changes in the ice sheets covering Antarctica and Greenland.

Antarctica's ice is a big clue to our planet's condition. Even a slight increase in sea level, no matter what the cause, would be a disaster for the nearly 2 billion people living in coastal areas. That's why scientists are keeping their eyes on the ice.

http://www.timeforkids.com/TFK/magazines/story/0,6277,418673,00.html