A polar bear stands on a ice floe in Baffin Bay above the Arctic Circle, as seen from the Canadian Coast Guard icebreaker Louis S. St-Laurent in July 2008. (Jonathan Hayward/Canadian Press)

The giant mass of Arctic sea ice is getting thinner and not lasting as long, with scientists warning that such physical changes are cause for global concern.

Researchers with NASA and the National Snow and Ice Data Center in Colorado released new information Monday that shows the northern polar ice cap is continuing its decade-long trend of shrinking.

Thicker, older ice floating on the Arctic Ocean is not replenishing like it used to.

More recent, thinner seasonal ice now makes up about 70 per cent of the ice in winter — up from 50 per cent in the 1980s and 1990s.

"What we're finding is that the ice is now thinner than ever," said Thomas Wagner with the Cryospheric Sciences Program at NASA in Washington, D.C.

"It's receding a lot in the summer. And then, when it begins to grow back in the winter, it's not growing back to the size it once was."

Arctic ice is important for constraining the planet's heat, said Wagner. The ice works like an air conditioner for the world, naturally cooling air and water. It also acts like a mirror, reflecting solar radiation back into space.

"As that ice melts, it's replaced with darker sea water that absorbs a lot more light and begins to heat up."

Melting ice raises geopolitical pressures

The shrinking of the ice cap is also opening up new shipping routes and opportunities for exploring natural resources, said Wagner.

The different "geopolitical landscape" already has some countries laying claim to the Arctic and beefing up their security measures, he pointed out.

It's believed the Arctic contains as much as 25 per cent of the world's undiscovered oil and gas.

Canada, Russia, the United States and a number of Nordic countries are competing for jurisdiction over untapped natural resources. It's believed the Arctic contains as much as 25 per cent of the world's undiscovered oil and gas.

Shrinking ice also has an effect on Arctic wildlife such as polar bears and seals, as well as on people living in the region who rely on ice for transportation and hunting, said Walter Meier of the snow and ice data centre.

He said Arctic ice measured about 15 million square kilometres at the end of February — down about 720,000 square kilometres from the winter average and a decline that's roughly the size of Texas.

Ice-free Arctic in summer no longer a far-fetched notion

Ronald Kwok with the NASA jet propulsion laboratory in California described how the space agency first launched a satellite in 2003 to precisely measure differences in the Earth's surface elevations within a couple of centimetres. Prior to that, ice thickness had been measured by submarines.

"Now, we can do it almost over the entire Arctic Ocean from space," said Kwok.

He said researchers are still calculating the last five years worth of data to determine melting trends and predictions.

Summers in 2005 and 2007 were unusually warm and offered almost no replenishments of ice, he said.

"If the same melting and ice area is blown off the Arctic area this year, then we can expect a fairly low ice extent this coming summer."

Meier said the suggestion of an ice-free Arctic in the summer was laughable a few years ago, but some studies have predicted that scenario could happen within the next five to 30 years.

"That seems fairly unlikely, but it's not totally out of the realm of possibility," he said.