The Guardian (
The Arctic ice cap has collapsed at an unprecedented rate this summer and levels of sea ice in the region now stand at record lows, scientists have announced.
Experts say they are "stunned" by the loss of ice, with an area almost twice as big as the
So much ice has melted this summer that the Northwest passage across the top of
If the increased rate of melting continues, the summertime
Mark Serreze, an Arctic specialist at the US National Snow and Ice Data Centre at
Dr Serreze said: "If you asked me a couple of years ago when the
The new figures show that sea ice extent is currently down to 4.4m square kilometres (1.7m square miles) and still falling.
The previous record low was 5.3m square kilometres in September 2005. From 1979 to 2000 the average sea ice extent was 7.7m square kilometres.
The sea ice usually melts in the Arctic summer and freezes again in the winter. But Dr Serreze said that would be difficult this year.
"This summer we've got all this open water and added heat going into the ocean. That is going to make it much harder for the ice to grow back."
Changes in wind and ocean circulation patterns can help reduce sea ice extent, but Dr Serreze said the main culprit was man-made global warming.
"The rules are starting to change and what's changing the rules is the input of greenhouse gases."
Ice withdrawal 'shatters record'
BBCNews.com, Sept. 22, 2007
Arctic sea ice shrank to the smallest area on record this year, US scientists have confirmed.
The National Snow and Ice Data Center (NSIDC) said the minimum extent of 4.13 million sq km (1.59 million sq miles) was reached on 16 September.
The figure shatters all previous satellite surveys, including the previous record low of 5.32 million sq km measured in 2005.
Earlier this month, it was reported that the
The fabled Arctic shipping route from the
Arctic sea ice loses area in summer months and regrows in the winter cold.
The researchers at NSIDC judge the ice extent on a five-day mean. The minimum for 2007 falls below the minimum set on 20-21 September 2005 by an area roughly the size of
Speaking to BBC News on Monday this week, Mark Serreze, a senior research scientist at the NSIDC, said: "2005 was the previous record and what happened then had really astounded us; we had never seen anything like that, having so little sea ice at the end of summer. Then along comes 2007 and it has completely shattered that old record."
He added: "We're on a strong spiral of decline; some would say a death spiral. I wouldn't go that far but we're certainly on a fast track. We know there is natural variability but the magnitude of change is too great to be caused by natural variability alone."
The team will now follow the progress of recovery over the winter months.
In December 2006, a study by US researchers forecast that the
A team of scientists from the
Sea ice has a bright surface which reflects 80% of the sunlight that strikes it back into space. However, as the ice melts during the summer, more of the dark ocean surface becomes exposed.
Rather than reflecting sunlight, the ocean absorbs 90% of it, causing the waters to warm and increase the rate of melting.
Scientists fear that this feedback mechanism will have major consequences for wildlife in the region, not least polar bears, which traverse ice floes in search of food.
On a global scale, the Earth would lose a major reflective surface and so absorb more solar energy, potentially accelerating climatic change across the world.
Story from BBC NEWS:
The minimum ice area for this year, 1.59 million square miles, appeared to be reached Sunday. The ice is now spreading again under the influence of the deep Arctic chill that settles in as the sun drops below the horizon at the North Pole for six months, starting Friday.
The findings were reported by the National Snow and
While satellite tracking of polar sea ice has been done only since 1979, several ice experts who have studied Russian and Alaskan records going back many decades said the ice retreat this year was probably unmatched in the 20th century, including during a warm period in the 1930s. I do not think that there was anything like we observe today in the 1930s or 1940s, said Igor Polyakov, an ice expert at the
The ice retreat has been particularly striking this year. The Alaskan side of the Arctic Ocean has stretches of thousands of square miles of open water; the fabled Northwest Passage through the islands of northern Canada was free of ice for weeks; and the sea route between the Atlantic and Pacific Oceans north of Russia was nearly clear a week ago, with one small clot of ice around a group of Siberian islands.
Mark Serreze, a senior researcher at the snow and ice center, said it was increasingly clear that climate change from the buildup of greenhouse gases was playing a role in the Arctic warming, which is seen not only in the floating ice but also in melting terrestrial ice sheets, thawing tundra and warming seawater.
We understand the physics behind whats going on, Dr. Serreze said. You can always find some aspect of natural variability that can explain some things. But now it seems patterns that used to help you dont help as much anymore, and the ones that hurt you hurt you more.
You cant dismiss this as natural variability, he said. Were starting to see the system respond to global warming.
Still, he and other scientists acknowledged that both poles were extraordinarily complicated systems of ice, water and land, and that the mix of human and natural influences was not easy to clarify.
Sea ice around
Arctic sea ice at record low
Open waters in northern ocean highlight massive melting.
Nature.com, Sept. 19, 2007
Even for a society jaded by the continual breaking of climate records, the retreat of Arctic ice this year is stunning.
Sea-ice extent -- the total number of 25 x 25 kilometer square sections of ocean covered by at least 15% ice -- in the Arctic Ocean melts from about 16 million km2 every March to a minimum sometime in September or October, the exact date normally only being evident in retrospect. The US National Snow and Ice Data Center (NSIDC) says the previous record absolute minimum was 5.32 million km2, set in 2005. This year has already reached 4.14 million km2 -- the lowest since records began in the late 1970s.
This has opened the Northwest Passage -- the most direct shipping route between the Atlantic and
"I'm shocked daily, looking at the maps," said Marika Holland, sea-ice researcher at the US National Center for Atmospheric Research in
Some models suggest that if the current trends continue, we'll hit a first summer day entirely free of sea ice sometime between 2050 and 2100 1,2 - dates accepted by the Intergovernmental Panel on Climate Change. Other studies predict it could happen even earlier3.
"The observations and the climate models both point in the same direction, and that direction is we will reach a seasonal ice-free state. I wouldn't say it's inevitable; without some important changes I think that it's likely," says
Going, going, gone
As well as examining the area over which sea ice is prominent, scientists also look at the actual area of ice. Processing of NSIDC data by researchers at the
There are three ideas as to what could have caused such a dramatic drop this year, according to John Walsh, of the
Feedback effects may make recovery from this new low harder -- ice reflects sunlight whereas open sea absorbs it. So less ice this year will militate against lots of ice next year, as well as boosting global warming.
"This year does stand out as a jump downward," says Walsh. "I would say the odds favour an extreme year next year too."
Whether global warming should be blamed entirely for this year's low is not entirely clear. Variation in the factors mentioned by Walsh is not necessarily caused by climate change. But a warmer planet has resulted in thinner ice, which is more vulnerable to warm weather.
Initial results from a German survey that were revealed last week show that arctic ice is approximately 50% of its 2001 thickness.
As if to drive home how complex the sea-ice problem is, as the Northern Hemisphere hits record lows, at the other side of the world the sea-ice area is close to breaking the record for maximum area of 16.03 million km2.
As well as opening up trade routes, the reduction of sea ice in the north will have consequences on local wildlife too. The most visible example of this will be polar bear populations; newly released reports from the US Geological Survey (USGS) suggest that two-thirds of the bears could be lost within 50 years because of reduced sea ice. Polar bears rely on the ice as a hunting platform and the USGS models predict a 42% loss of habit in the key summer breeding months.
Arctic Ice Melt Gets Stark Reassessment
Discovery.com, Sept. 7, 2007
Sept. 6, 2007 -- Summertime sea ice in the
"This (is) a major change from the third IPCC report," said oceanographer James Overland of the National Oceanographic and Atmospheric Administration. "This is moving the threshold up."
When they ran the remaining models together, there was a stark shift in the predictions: the amount of ice loss expected by the IPCC by the year 2100, the new test showed, will occur by 2050. A report on the study appears in the Sept. 8 issue of Geophysical Research Letters.
What it means, said Overland, is that in places like the north coast of
"It's a huge effect on wildlife," said marine biologist Jacqueline Grebmeier of the
For animals like walruses, which feed on clams and other shallow seafloor organisms, moving the ice to deeper waters effectively moves their grocery store out of reach. Other species already moving north with the ice and running into trouble are diving ducks, ringed seals and polar bears.
Opening the Arctic waters in summer has another effect on the ecology, she said. It allows plankton on the surface to eat up nutrients in the water that would, under ice, drop to the bottom to feed life there. In other words, more open water also effectively cuts off supplies to the walrus's sea-bottom supermarket.
While the open waters may benefit shipping, Grebmeier is worried that vessels using a new Northwest Passage could bring more invasive species to the
"You'll have winners and losers," said Overland. A small bit of good news, he said, is the good chance that many of the channels in the Canadian archipelago will remain clogged with ice, leaving a refuge for Arctic species.
Arctic Melt Unnerves the Experts
The New York Times, Andrew C. Revkin, Oct. 2, 2007
The Arctic ice cap shrank so much this summer that waves briefly lapped along two long-imagined Arctic shipping routes, the Northwest Passage over
Over all, the floating ice dwindled to an extent unparalleled in a century or more, by several estimates.
Now the six-month dark season has returned to the North Pole. In the deepening chill, new ice is already spreading over vast stretches of the
Scientists are also unnerved by the summers implications for the future, and their ability to predict it.
Complicating the picture, the striking Arctic change was as much a result of ice moving as melting, many say. A new study, led by Son Nghiem at NASAs Jet Propulsion Laboratory and appearing this week in Geophysical Research Letters, used satellites and buoys to show that winds since 2000 had pushed huge amounts of thick old ice out of the Arctic basin past Greenland. The thin floes that formed on the resulting open water melted quicker or could be shuffled together by winds and similarly expelled, the authors said.
The pace of change has far exceeded what had been estimated by almost all the simulations used to envision how the
The world is paying more attention than ever.
Proponents of cuts in greenhouse gases cited the meltdown as proof that human activities are propelling a slide toward climate calamity.
Arctic experts say things are not that simple. More than a dozen experts said in interviews that the extreme summer ice retreat had revealed at least as much about what remains unknown in the
For one thing, experts are having trouble finding any records from
Some scientists who have long doubted that a human influence could be clearly discerned in the
We used to argue that a lot of the variability up to the late 1990s was induced by changes in the winds, natural changes not obviously related to global warming, said John Michael Wallace, a scientist at the University of Washington. But changes in the last few years make you have to question that. Im much more open to the idea that we might have passed a point where its becoming essentially irreversible.
Experts say the ice retreat is likely to be even bigger next summer because this winters freeze is starting from such a huge ice deficit. At least one researcher, Wieslaw Maslowski of the
In essence, Arctic waters may be behaving more like those around
(Reflecting the different geography and dynamics at the two poles, there has been a slight increase in sea-ice area around
While open Arctic waters could be a boon for shipping, fishing and oil exploration, an annual seesawing between ice and no ice could be a particularly harsh jolt to polar bears.
Many Arctic researchers warned that it was still far too soon to
start sending container ships over the top of the world.
Natural variations could turn around and counteract the greenhouse-gas-forced change, perhaps stabilizing the ice for a bit, said Marika Holland, of the National Center for Atmospheric Research in
But, she added, that will not last. Eventually the natural variations would again reinforce the human-driven change, perhaps leading to even more rapid retreat, Dr. Holland said.
So I wouldnt sign any shipping contracts for the next 5 to 10 years, but maybe the next 20 to 30.
While experts debate details, many agree that the vanishing act of the sea ice this year was probably caused by superimposed forces including heat-trapping clouds and water vapor in the air, as well as the ocean-heating influence of unusually sunny skies in June and July. Other important factors were warm winds flowing from
But another factor was probably involved, one with roots going back to about 1989. At that time, a periodic flip in winds and pressure patterns over the Arctic Ocean, called the Arctic Oscillation, settled into a phase that tended to stop ice from drifting in a gyre for years, so it could thicken, and instead carried it out to the
The new NASA study of expelled old ice builds on previous measurements showing that the proportion of thick, durable floes that were at least 10 years old dropped to 2 percent this spring from 80 percent in the spring of 1987, said Ignatius G. Rigor, an ice expert at the University of Washington and an author of the new NASA-led study.
Without the thick ice, which can endure months of nonstop summer sunshine, more dark open water and thin ice absorbed solar energy, adding to melting and delaying the winter freeze.
The thinner fresh-formed ice was also more vulnerable to melting from heat held near the ocean surface by clouds and water vapor. This may be where the rising influence of humans on the global climate system could be exerting the biggest regional influence, said Jennifer A. Francis of Rutgers University.
Other Arctic experts, including Dr. Maslowski in Monterey and Igor V. Polyakov at the University of Alaska, Fairbanks, also see a role in rising flows of warm water entering the Arctic Ocean through the Bering Strait between Alaska and Russia, and in deep currents running north from the Atlantic Ocean near Scandinavia.
A host of Arctic scientists say it is too soon to know if the global greenhouse effect has already tipped the system to a condition in which sea ice in summers will be routinely limited to a few clotted passageways in northern
But at the university in