Arctic ice reaches historic seasonal low; “We are almost out of multiyear sea ice in the northern hemisphere.”
"Arctic ice reaches historic seasonal low; “We are almost out of multiyear sea ice in the northern hemisphere.”"
“I would argue that, from a practical perspective, we almost have a seasonally ice-free Arctic now, because multiyear sea ice is the barrier to the use and development of the Arctic,” said Barber [Canada’s Research Chair in Arctic System Science at the University of Manitoba].
The latest tracking of Arctic sea ice extent from the National Snow and Ice Data Center shows that we’ve hit the record low Arctic sea ice extent for this time of year. In a post last week, “Warm winds slow autumn ice growth,” NSIDC noted “October 2009 had the second-lowest ice extent for the month over the 1979 to 2009 period.”
As Reuters noted in their remarkable piece on Canadian cryosphere scientist David Barber, “Scientists link higher Arctic temperatures and melting sea ice to the greenhouse gas emissions blamed for global warming.”
Here’s more on what Barber found in a recent expedition:
“We are almost out of multiyear sea ice in the northern hemisphere,” he said in a presentation in Parliament. The little that remains is jammed up against Canada’s Arctic archipelago, far from potential shipping routes….
Barber spoke shortly after returning from an expedition that sought — and largely failed to find — a huge multiyear ice pack that should have been in the Beaufort Sea off the Canadian coastal town of Tuktoyaktuk.
Instead, his ice breaker found hundreds of miles of what he called “rotten ice” — 50-cm (20-inch) thin layers of fresh ice covering small chunks of older ice.
“I’ve never seen anything like this in my 30 years of working in the high Arctic … it was very dramatic,” he said.
“From a practical perspective, if you want to ship across the pole, you’re concerned about multiyear sea ice. You’re not concerned about this rotten stuff we were doing 13 knots through. It’s easy to navigate through.”
Rotten ice — good term. That’s what human emissions of greenhouse gases have done to the Arctic, covered it in rotten ice.
Reuters photo caption: “
Scientists have fretted for decades about the pace at which the Arctic ice sheets are shrinking. U.S. data shows the 2009 ice cover was the third-lowest on record, after 2007 and 2008.
An increasing number of experts feel the North Pole will be ice free in summer by 2030 at the latest, for the first time in a million years.
“I would argue that, from a practical perspective, we almost have a seasonally ice-free Arctic now, because multiyear sea ice is the barrier to the use and development of the Arctic,” said Barber.
Fresh first-year ice always forms in the Arctic in the winter, when temperatures plunge far below freezing and the North Pole is not exposed to the sun….
The Arctic is warming up three times more quickly than the rest of the Earth, in part because of the reflectivity, or the albedo feedback effect, of ice.
As more and more ice melts, larger expanses of darker sea water are exposed. These absorb more sunlight than the ice and cause the water to heat up more quickly, thereby melting more ice.
Barber said the ice was now being melted both by rays from the sun as well as from below by the warmer water.
For more on this well known positive feedback (see “What exactly is polar amplification and why does it matter?)
Scientists are also seeing more cyclones, which pick up force as they absorb heat from the warmer water. The cyclones help generate waves that break up ice sheets and also dump large amounts of snow, which has an insulating effect and prevents the ice sheets from thickening.
After a long search, Barber’s ice breaker finally found a 16-km (10-mile) wide floe of multiyear ice that was around 6 to 8 meters (20-26 feet) thick. But as the crew watched, the floe was hit by a series of waves, and disintegrated in five minutes.
“The Arctic is an early indicator of what we can expect at the global scale as we move through the next few decades … So we should be paying attention to this very carefully,” Barber said.
We should be paying close attention, since this positive feedback is linked to another, even more dangerous one (see “Tundra 4: Permafrost loss linked to Arctic sea ice loss“).
I asked NSIDC director’s Mark Serreze for a comment on this article, and he wrote me:
Dave Barber’s observations give the sort of on-the-ground confirmation of the situation that lends confidence to predictions that we’re headed towards a seasonally ice-free Arctic Ocean. Dave’s been up there looking at sea ice conditions for many years. He knows what he’s talking about.
NSIDC Research Scientist Walt Meier also replied:
This is an interesting article. To some extent Dave’s statement depends on how you define multiyear year. Certainly the older ice (e.g., >5 years) is virtually gone and there’s very little 3-4 year-old ice. However, the past couple years, each summer has retained a fair amount of first-year ice (which ages into second year, and now third year ice). So there is some build-up of what you would term “young” multiyear ice. In theory, that ice could eventually stabilize or even increase (for a time) the multiyear pack. On the other hand, multiyear is constantly moving out of the Arctic as part of the natural drift. So, much of the “young” multiyear ice may be gone before it can mature into older ice.
The most interesting thing in the article is that the old multiyear ice is so broken up now. Even if there is a considerable amount, it is all in broken (or even rotten) floes of ice and not a largely consolidated pack like it used to be. That is a significant change in the character of the ice cover beyond the basic changes in extent and age distribution.