Image: Map showing variation in Arctic sea ice thickness.
NASA Goddard's Scientific Visualization Studio
This map shows Arctic sea ice thickness on average last winter. White areas are the thickest, and dark blue the thinnest.
updated 4/6/2009 4:51:12 PM ET 2009-04-06T20:51:12

As spring begins, more than 90 percent of the sea ice in the Arctic is only 1 or 2 years old, making it thinner and more vulnerable than at anytime in the past three decades, researchers with NASA and the National Snow and Ice Data Center in Colorado reported Monday.

"We're not set up well for summertime," ice data center scientist Walt Meier said at a news briefing. "We're in a very precarious situation."

Young sea ice in the Arctic often melts in the spring and summer. If it survives for two years, then it becomes the type of thick sea ice that is key. But the past two years were warm, and there's more young, thin ice at the top of the world.

In normal winters, thick sea ice — often about 10 feet thick or more — extends from the northern boundaries of Greenland and Canada almost to Russia. This year, the thick ice cap barely penetrates the bull's-eye of the Arctic Circle.

The amount of thick sea ice hit a record wintertime low of just 378,000 square miles this year, down 43 percent from last year, Meier said. The amount of older sea ice that was lost is larger than the state of Texas.

"Heading into the 2009 summer melt season, the potential continues for extensive ice retreat due to the trend toward younger, thinner ice that has accelerated in recent years," said University of Colorado professor James Maslanik. "A key question will be whether this second year ice is thick enough to survive summer melt."

"If it does, this might start a trend toward recovery of the perennial sea ice pack," Maslanik said. "If it doesn't, then this would be further evidence of the difficulty of re-establishing the ice conditions that were typical of 20 or 30 years ago."

'State of balance is likely to change'
Sea ice is important because the whiteness reflects sunlight away from Earth. The more it melts, the more heat is absorbed by the dark ocean, heating up the planet even more, said NASA polar regions program manager Tom Wagner. That warming also can change weather patterns worldwide and it alters the ecosystems for animals such as polar bears.

"That thick ice really traps ocean heat; it keeps the planet in its current state of balance," added Waleed Abdalati, director of the Center for the Study of Earth from Space at the University of Colorado and NASA's former chief ice scientist. "When we start to diminish that, the state of balance is likely to change, tip one way or another."

The Arctic essentially acts as a refrigerator for the rest of the globe. And the amount of sea covered by ice — thick or thin — has been shrinking at a rate of about 3 percent a decade in the Arctic.

This year, the maximum ice cover of 5.85 million square miles — reached on Feb. 28 — was higher than four of the previous five years. But it was still the fifth lowest since record-keeping began in 1979.

Usually, younger, thin ice accounts for about 70 percent of the ice cover. This year it reached 90 percent, Meier said.

USGS cites Antarctic concerns
And the problems of global warming caused melt is being seen at the other pole, too.

The U.S. Geological Survey last week released a detailed map of the Antarctic coastline and found dwindling and even disappearing ice shelves.

The map itself was finished in the middle of last year, but the previous Interior Department didn't want to release it and other Antarctic maps, said map co-author Richard Williams Jr., a glaciologist for the USGS. The report with the map bears the 2008 date and the previous interior secretary's name on it.

The map found for the first time that an entire ice shelf — the Wordie Ice Shelf on the western end of the Antarctic peninsula — has essentially disappeared. In 1966, it was 772 square miles. In addition, about 4,500 square miles of the Larsen Ice Shelf is gone.

"The map portrays one of the most rapidly changing areas on Earth, and the changes in the map are widely regarded as among the most profound, unambiguous examples of the effects of global warming on Earth," the USGS report concludes.

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Video: Satellites show Arctic literally on thin ice


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