Arctic Sea Ice Bottoms Out For 2007, Shatters All Time Record Low





The minimum low Arctic sea ice extent for 2007 is about 460,000 square miles less than the previous minimum record, set in 2005. The area of lost sea ice is roughly the equivalent of the area of Texas and California combined.
The minimum low Arctic sea ice extent for 2007 is about 460,000 square miles less than the previous minimum record, set in 2005. The area of lost sea ice is roughly the equivalent of the area of Texas and California combined.

Scientists from the University of Colorado at Boulder’s National Snow and Ice Data Center said today that the extent of Arctic sea ice appears to have reached its minimum for 2007 on Sept. 16, shattering all previous lows since satellite record-keeping began nearly 30 years ago.



The Arctic sea ice extent on Sept. 16 stood at 1.59 million square miles, or 4.13 million square kilometers, as calculated using a five-day running average, according to the team. Compared to the long-term minimum average from 1979 to 2000, the new minimum extent was lower by about 1 million square miles — an area about the size of Alaska and Texas combined, or 10 United Kingdoms, they reported.



The minimum also breaks the previous minimum set on Sept. 20 and Sept. 21 of 2005 by about 460,000 square miles, an area roughly the size of Texas and California combined, or five United Kingdoms, they found. The sea ice extent is the total area of all Arctic regions where ice covers at least 15 percent of the ocean surface.



Scientists blame the declining Arctic sea ice on rising concentrations of greenhouse gases that have elevated temperatures from 2 degrees F to 7 degrees F across the arctic and strong natural variability in Arctic sea ice, said the researchers.


The CU-Boulder research group said determining the annual minimum sea ice is difficult until the melt season has decisively ended. But the team has recorded five days of little change, and even slight gains in Arctic sea ice extent this September, so reaching a lower minimum for 2007 seems unlikely, they reported.



Arctic sea ice generally reaches its minimum extent in September and its maximum extent in March. The researchers used satellite data from NASA, the National Oceanic and Atmospheric Administration and the U.S. Department of Defense, as well as data from Canadian satellites and weather observatories for the study.



The CU-Boulder research group is reporting the news on its ongoing blog, along with images and discussion, which can be found on the Web at: nsidc.org/news/press/2007_seaiceminimum/20070810_index.html.



“The amount of ice loss this year absolutely stunned us because it didn’t just beat all previous records, it completely shattered them,” said CU-Boulder senior scientist Mark Serreze of NSIDC.

Scientist tracks greenland meltwater





Many glaciologists believe that snow/ice melt in Greenland could equate to a 1 meter increase in ocean levels, something that would be devastating to a major portion of the human population
Many glaciologists believe that snow/ice melt in Greenland could equate to a 1 meter increase in ocean levels, something that would be devastating to a major portion of the human population

World oceans would rise 23 feet and flood many coastal areas if climate change melted the entire Greenland ice cap. And satellite images from 1980 onward reveal the surface of this vast ice sheet is warming, getting soggy and staying wet for longer periods every year.



However, preliminary research by The University of Montana and its partners suggests some of this meltwater does not reach the ocean to contribute to sea-level rise. Instead it infiltrates downward into colder snow and refreezes into ice layers that can be more than a foot thick. These layers are fragmented, so water can’t flow atop them for long before draining downward again and freezing in place.



“We are still working up our results, but so far this is good news concerning worries about Greenland’s role in the sea level rise we see happening today,” said UM glaciologist Joel Harper. “Since many of the ice layers that form during a year of heavy melt are discontinuous, the next year’s melt can’t travel along the ice layers as a means of escaping the ice sheet.”



He said it’s so dark and cold during Greenland winters that even with some winter warming the snowpack is still extremely cold going into summer, “and summer melting always will have a hard time warming a snowpack laden with cold dense ice layers.”



Harper was part of a six-person scientific expedition that ventured onto the Greenland ice sheet for a month during June and July. They lived in tents high atop the ice cap at about 6,600 feet in a white, featureless landscape swept by endless wind. To do its work, the group made 60- to 70-mile journeys down into the melt zone closer to Greenland’s west coast, using snowmobiles to pull scientific gear and expedition members on skis.



Harper said their research was funded by a $524,000 National Science Foundation grant. His project collaborators are Tad Pfeffer of the University of Colorado and Neil Humphrey of the University of Wyoming. Each scientist brought one graduate student to complete the team.



The researchers drilled 21 35-foot-long ice cores during the course of their work. They also dug many snow pits and did numerous experiments with colored dye to track meltwater flow. In addition, they installed two meteorological stations and used radar to map ice layers beneath the snow.



In five boreholes located in sequentially lower elevations across a 25-mile span, the team also installed vertical strings of temperature sensors to note melting and freezing events in the snow up to 35 feet deep. (When water freezes it releases heat – a thermal signature that can be detected.) Harper said the sensors – called thermisters – have their own power source and will record data until researchers retrieve them next year.



He compared the Greenland ice cap to pancake batter. In its middle at higher elevations there is more snowfall than melting. As more snow is poured on, it compresses the vast sheet, which flows outward toward the warmer coasts where there is more melting.



The team had two snowmobiles to haul six people and their gear down to the melt zones to do their research. The landscape is utterly devoid of landmarks, so they used global positioning systems to navigate during the three-hour traverses. Two scientists drove, while the rest were towed behind the snowmobiles on skis.



“While skiing, we put on every bit of clothing we had and an iPod because you were standing behind these snowmobiles for three hours or more,” Harper said. “We would use a bike tire as a harness clipped to the rope. So we would just stand there and try not to fall asleep as we were pulled along.”


Harper, who was a competitive skier as a youth in Colorado, also tried using a sail to kite ski across the ice cap. His power source was Greenland’s endless katabatic winds, which are caused by dense cold air atop the ice sheet flowing downward toward the warmer coasts.



“A lot of times it was too windy – you could get up to 30 mph no problem,” he said. “I could get screaming along – and I’m used to speed – but this was on the edge. I found it was too hard to navigate long distances with GPS when you are trying to fly the kite and not crash. It just wasn’t compatible with the whole group, so in the end it was more for fun.”



He said some of the melt zone contained barely wet snow, while others areas were a “slush swamp” of super-saturated snow that a person without skis could sink into like quicksand. The expedition had to make the long traverses from base camp because members didn’t dare camp in the melt zone. Too much thawing could bog down their snowmobiles and leave the researchers stranded in an area where ski planes can’t land. They might be stranded in the soggy snow until the next freeze.



“And if the snow machines would break, you couldn’t possibly ski back in a day,” he said. “It’s too far.”



Harper said his group will return next year to study another 75-mile stretch of the ice cap. They will start at the lowest elevation examined last summer and continue downward toward the coastal melt zone. The expedition will begin earlier in the year so the snow won’t be as treacherous at lower elevations.



“This is one reason why our results are preliminary,” he said. “We only have half the story. I suspect things might really be moving down below, but so far in the upper part of the ice sheet, we have thrown that out. In that area we found the melt is increasing every year, but it isn’t going anywhere.”



Harper said they decided to study the west side of the ice cap because it is accessible from the town of Kangerlussuaq, which is the logistics headquarters for science in Greenland. The ice they studied also is the headwaters of Jakobshavn, one of Greenland’s big calving glaciers that has increased speed in recent years. Their base camp was a three-hour plane ride from Kangerlussuaq.



“There was nothing special about our camp,” he said. “It was just some GPS coordinates we selected in the middle of nowhere. We got nailed by a big storm right after we arrived, but after that temperatures stayed between about 10 and 35 degrees Fahrenheit.”



Harper said their work might partially explain why Greenland isn’t a larger player in current sea-level rises despite its enormous ice cap. A 2007 article in the journal Science contends Greenland contributes about 0.5 millimeter to ocean level rise annually, while smaller glaciers scattered around the globe contribute 1.1 millimeter to sea-level rise.



“Other recent work shows that ice loss from small glaciers and ice caps like those in Montana dominate current sea-level rise and will likely continue to dominate sea-level increases for at least the next 50 years,” he said. “Since there are several hundred thousand small glaciers around the world, the sea-level rise we expect from them is still very significant.



“I don’t know of any glaciologist who thinks anything like a 6-meter (19.8 foot) sea-level rise is in the cards by the end of the century,” Harper said, “but even 1 meter – which is at the upper end of what we currently think might be possible – would be a very big deal.”

Rising Surface Temperatures Drive Back Winter Ice in Barents Sea


Rising sea-surface temperatures in the Barents Sea, northeast of Scandinavia, are the prime cause of the retreating winter ice edge over the past 26 years, according to research by Jennifer Francis, associate research professor at Rutgers’ Institute of Marine and Coastal Sciences (IMCS). The recent decreases in winter ice cover is clear evidence that Arctic pack ice will continue on its trajectory of rapid decline, Francis said.



In a paper published in Geophysical Review Letters, Francis and Elias Hunter, a research specialist in Francis’ laboratory, found that the rising average winter-time sea-surface temperature of the Barents Sea – up 3 degrees Celsius since 1980 – is likely driven by increasing greenhouse gases, which in turn are melting more ice. Francis and Hunter used satellite information dating back 26 years to perform their study.



Scientists have known for some time that the extent of perpetual, summer ice cover in the Arctic has been shrinking, but until the past few years, the average amount of winter ice has been relatively steady. The winter ice amount is important because if it begins to decrease, scientists believe it is an indicator that enough extra heat from the sun is being absorbed in summer in new open water areas so that the ice grows less in winter and is more easily melted the following summer, leading to even less summer ice. The record-breaking ice loss this year is further, dramatic evidence that this process is underway. While satellites can see the recent winter ice retreat, no one knew until now what was driving the ice back. Francis said she and Hunter were surprised when they discovered that warming ocean temperatures – and not atmospheric effects – were the main source of winter ice retreat, and that the warming is linked to general rising temperatures of the Atlantic Ocean via the Gulf Stream, which brings Atlantic water into the Barents Sea. “In the Barents Sea, I expected more influence from atmospheric heating; but it [the retreat of the ice edge] seems to be governed almost entirely by warming from the ocean,” Francis said.


Should the warming trend continue — and all indications are that it will — there would be considerable economic and political implications. “Fishing, shipping, oil exploration will all be easier to do in the Arctic if there is less ice around for a shorter time,” Francis said.



Francis and Hunter were in for another surprise in the Bering Sea, between Alaska and Siberia. That sea is virtually cut off from the Pacific Ocean by the Aleutian Islands. The researchers expected the ice edge there to be pushed around by northerly and southerly winds, but that wasn’t the case. Instead, it was the strength or weakness of the Aleutian Low – a semi-permanent storm with predominantly easterly winds in much of the Bering Sea – that determined the ice edge. In years when the low was weak – when the east wind didn’t blow as hard – the ice edge crept farther south. In years when the east winds blew hard, the ice edge retreated northward. The strength of the Aleutian Low oscillates in cycles lasting 10 to 20 years, Francis said, and right now, appears to be in a weak cycle. That means that the ice edge in the Bering Sea, not exposed to the world’s ocean system like its Barents Sea counterpart, has not retreated as much. Computer models predict, however, that the Aleutian Low will strengthen as the global climate system adapts to increasing greenhouse gases.

Strong Evidence Points to Earth’s Proximity to Sun as Ice Age Trigger





The Dome Fuji deep ice core, Antarctica, with drill. This ice was retrieved from a depth of 1,332 meters (4,370 feet), which was deposited about 89,000 years ago. - Photo: Dr. Hideaki Motoyama, National Institute of Polar Research, Japan
The Dome Fuji deep ice core, Antarctica, with drill. This ice was retrieved from a depth of 1,332 meters (4,370 feet), which was deposited about 89,000 years ago. – Photo: Dr. Hideaki Motoyama, National Institute of Polar Research, Japan

When do ice ages begin? In June, of course.



Analysis of Antarctic ice cores led by Kenji Kawamura, a visiting scientist at Scripps Institution of Oceanography, UC San Diego, shows that the last four great ice age cycles began when Earth’s distance from the sun during its annual orbit became great enough to prevent summertime melts of glacial ice. The absence of those melts allowed buildups of the ice over periods of time that would become characterized as glacial periods.



Results of the study appear in the Aug. 23 edition of the journal Nature.



Jeff Severinghaus, a Scripps geoscientist and co-author of the paper, said the finding validates a theory formalized in the 1940s but first postulated in the 19th Century. The work also helps clarify the role of carbon dioxide in global warming and cooling episodes past and present, he said.



“This is a significant finding because people have been asking for 100 years the question of why are there ice ages,” Severinghaus said.



A premise advanced in the 1940s known as the Milankovitch theory, named after the Serbian geophysicist Milutin Milankovitch, proposed that ice ages start and end in connection with changes in summer insolation, or exposure to sunlight, in the high latitudes of the Northern Hemisphere. To test it, Kawamura used ice core samples taken thousands of miles to the south in Antarctica at a station known as Dome Fuji.


Scientists studying paleoclimate often use gases trapped in ice cores to reconstruct climatic conditions from hundreds of thousands of years in the past, digging thousands of meters deep into ice sheets. By measuring the ratio of oxygen and nitrogen in the cores, Kawamura’s team was able to show that the ice cores record how much sunlight fell on Antarctica in summers going back 360,000 years. The team’s method enabled the researchers to use precise astronomical calculations to compare the timing of climate change with sunshine intensity at any spot on the planet.



Kawamura, a former postdoctoral researcher at Scripps, used the oxygen-nitrogen ratio data to create a climate timeline that was used to validate the calculations Milankovitch had created decades earlier. The team found a correlation between ice age onsets and terminations, and variations in the season of Earth’s closest approach to the sun. Earth’s closest pass, or perihelion, happens to fall in June about every 23,000 years. When the shape of Earth’s orbit did not allow it to approach as closely to the sun in that month, the relatively cold summer on Earth encouraged the spread of ice sheets on the Northern Hemisphere’s land surface. Periods in which Earth passed relatively close in Northern Hemisphere summer accelerated melt and brought an end to ice ages.



“When we start to come to the point of closest approach in June, that’s when the big ice melts off,” said Severinghaus.



Kawamura said the new timeline will serve as a guide that will allow researchers to test climate forecast models of the effects of carbon dioxide levels in the atmosphere. The team found that the changes in Earth’s orbit that terminate ice ages amplify their own effect on climate through a series of steps that leads to more carbon dioxide being released from the oceans into the air. This secondary effect, or feedback, has accounted for as much as 30 percent of the warming seen as ice ages of the past have come to an end.



“An important point is that climate models should be validated with the past climate so that we can better predict what will happen in the future with rising CO2 levels,” said Kawamura. “For that, my new timescale can distinguish the contribution to past climate change from insolation change and CO2.”



In addition to Kawamura and Severinghaus, authors of the report included Takakiyo Nakazawa, Shuji Aoki, Koji Matsumoto, and Hisakazu Nakata of Tohoku University, Sendai, Japan; Frederic Parrenin of Laboratoire de Glaciologie et Geophysique de l’Environment in Grenoble, France; Lorraine Lisiecki and Maureen Raymo of Boston University; Ryu Uemura, Hideaki Motoyama, Shuji Fujita, Kumiko Goto-Azuma, Yoshiyuki Fujii, and Okitsugu Watanabe of the National Institute of Polar Research in Tokyo, Japan; Manuel Hutterli of the British Antarctic Survey in Cambridge, England; and Francoise Vimeux and Jean Jouzel of Laboratoire des Sciences du Climat et de l’Environment in Gif-sur-Yvette, France.



The research was supported by a Grant-in-Aid for Creative Scientific Research and a Grant-in-Aid for Young Scientists from the Ministry of Education, Science, Sports and Culture in Japan, the Gary Comer Science and Education Foundation and the National Science Foundation.