National Geographic News  [Printer-friendly version]
August 20, 2007


[Rachel's introduction: Arctic sea ice is disappearing at an
unprecedented rate. Just last year the National Snow and Ice Data
Center said that the Arctic was "right on schedule" to be completely
free of ice by 2070 at the soonest. Now they say that day may arrive
by 2030.]

By John Roach for National Geographic News

There is less sea ice in the Arctic than ever before recorded, thanks
in part to a warm, sunny summer, a climate scientist said today. And
the melting season isn't even over.

On Sunday the sea ice extent was measured at 1.93 million square miles
(5.01 million square kilometers).

"It's continuing to go down at a rapid pace," said Mark Serreze, a
senior scientist at the National Snow and Ice Data Center in Boulder,

The previous minimum record -- set on September 21, 2005 -- was 2.05
million square miles (5.32 million square kilometers).

By the end of this summer, scientists at the center say, Arctic sea
ice may drop below 1.74 million square miles (4.5 million square

Bruno Tremblay is an assistant professor of ocean and atmospheric
sciences at McGill University in Montreal, Canada, who is planning a
research cruise to the Russian Arctic in September.

In preparation for the trip, he has been observing updated maps of the
sea ice extent, which show the quickly melting ice.

"I never thought it would go that low that fast," Tremblay said.
"There's still a month of melting in front of us, and we're already
past the record of 2005."

Tipping Point?

Sea ice -- frozen, floating seawater -- melts and refreezes with the
seasons, but some of the ice persists year-round in the Arctic.

The current rate of sea ice melt is much faster than predicted by
computer models of the global climate system.

Just last year the National Snow and Ice Data Center's Serreze said
that the Arctic was "right on schedule" to be completely free of ice
by 2070 at the soonest. He now thinks that day may arrive by 2030.

"There's talk of a tipping point, where we thin the ice down
sufficiently so that at some point large parts of it can't survive the
summer melt season anymore, so we see this very rapid decline in ice
cover," he said.

"It's quite conceivable that that tipping point we talk about has
already been reached."

Particularly warm and sunny weather in the Arctic this summer has
helped speed up the pace of the melt, Serreze said. But the sea ice
decline is part of a decades' long trend.

In the dark days of the winter, some sea ice grows back. Overall,
however, the ice pack has thinned.

"It's really a reflection of what's been happening over the past 30
years -- this general pattern of warming, this general pattern of
thinner and thinner ice, which makes it more vulnerable," he said.

Climate Surprise

The loss of sea ice is already having well documented impacts on the
Arctic environment, such as shrinking polar bear habitat.

In addition, the melting sea ice will affect atmospheric circulation
and precipitation patterns, Serreze said.

"Think of the Arctic as sort of the refrigerator of the Northern
Hemisphere climate system. By losing that sea ice, we are greatly
altering the efficiency of that refrigerator," he said.

Since different parts of the climate system are integrated, what
happens in the Arctic will affect what happens elsewhere on the

However, the climate models disagree on the nature of the potential

"That's the concern. It's the things that we don't know, it's the
climate surprises in store," Serreze said.

If "we lose that sea ice, could we get a climate surprise because of
that -- a climate surprise that is difficult to deal with, like shifts
in precipitation?"

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