Tag Archives: arctic

Significant ozone hole remains over Antarctica

Significant ozone hole remains over Antarctica.

Ozone levels in the atmosphere above the South Pole dropped to a seasonal low of 102 Dobson Units Oct. 9, tied for the 10th lowest in the 26-year record. The ozone layer helps protect the planet's surface from harmful ultraviolet radiation. Every year, an ozone hole forms above the Antarctic for several weeks, because of environmental conditions and the presence of ozone-depleting chemicals. (Credit: NOAA)

ScienceDaily (Oct. 20, 2011) — The Antarctic ozone hole, which yawns wide every Southern Hemisphere spring, reached its annual peak on September 12, stretching 10.05 million square miles, the ninth largest on record. Above the South Pole, the ozone hole reached its deepest point of the season on October 9 when total ozone readings dropped to 102 Dobson units, tied for the 10th lowest in the 26-year record.

The ozone layer helps protect the planet’s surface from harmful ultraviolet radiation. NOAA and NASA use balloon-borne instruments, ground instruments, and satellites to monitor the annual South Pole ozone hole, global levels of ozone in the stratosphere, and the humanmade chemicals that contribute to ozone depletion.Watch movie online The Transporter Refueled (2015)

“The upper part of the atmosphere over the South Pole was colder than average this season and that cold air is one of the key ingredients for ozone destruction,” said James Butler, director of NOAA’s Global Monitoring Division in Boulder, Colo. Other key ingredients are ozone-depleting chemicals that remain in the atmosphere and ice crystals on which ozone-depleting chemical reactions take place.

“Even though it was relatively large, the size of this year’s ozone hole was within the range we’d expect given the levels of manmade, ozone-depleting chemicals that continue to persist,” said Paul Newman, chief atmospheric scientist at NASA’s Goddard Space Flight Center.

Levels of most ozone-depleting chemicals are slowly declining due to international action, but many have long lifetimes, remaining in the atmosphere for decades. Scientists around the world are looking for evidence that the ozone layer is beginning to heal, but this year’s data from Antarctica do not hint at a turnaround.

In August and September (spring in Antarctica), the sun begins rising again after several months of darkness. Circumpolar winds keep cold air trapped above the continent, and sunlight-sparked reactions involving ice clouds and humanmade chemicals begin eating away at the ozone. Most years, the conditions for ozone depletion ease by early December, and the seasonal hole closes.

Levels of most ozone-depleting chemicals in the atmosphere have been gradually declining since an international treaty to protect the ozone layer, the 1987 Montreal Protocol, was signed. That international treaty caused the phase out of ozone-depleting chemicals, then used widely in refrigeration, as solvents and in aerosol spray cans.

Global atmospheric models predict that stratospheric ozone could recover by the middle of this century, but the ozone hole in the Antarctic will likely persist one to two decades beyond that, according to the latest analysis by the World Meteorological Organization, the 2010 Ozone Assessment, with co-authors from NOAA and NASA.

Researchers do not expect a smooth, steady recovery of Antarctic ozone, because of natural ups and downs in temperatures and other factors that affect depletion, noted NOAA ESRL scientist Bryan Johnson. Johnson helped co-author a recent NOAA paper that concluded it could take another decade to begin discerning changes in the rates of ozone depletion.

Johnson is part of the NOAA team tracks ozone depletion around the globe and at the South Pole with measurements made from the ground, in the atmosphere itself and by satellite. Johnson’s “ozonesonde” group has been using balloons to loft instruments 18 miles into the atmosphere for 26 years to collect detailed profiles of ozone levels from the surface up. The team also measures ozone with satellite and ground-based instruments.

This November marks the 50th anniversary of the start of total ozone column measurements by the NOAA Dobson spectrophotometer instrument at South Pole station. Ground-based ozone column measurements started nearly two decades before the yearly Antarctic ozone hole began forming, therefore helping researchers to recognize this unusual change of the ozone layer.

NASA measures ozone in the stratosphere with the Ozone Monitoring Instrument (OMI) aboard the Aura satellite. OMI continues a NASA legacy of monitoring the ozone layer from space that dates back to 1972 and the launch of the Nimbus-4 satellite.

The vanishing Arctic lakes

Strange case of the vanishing Arctic lakes – environment – 17 October 2011 – New Scientist.



THE lake-spotted landscape of Canada is home to a watery mystery. According to a painstaking satellite survey of 1.3 million lakes stretching from coast to coast, the country lost 6700 square kilometres – or 1.2 per cent – of its water surface area between 2000 and 2009. Yet what we know about the physical processes at play suggests the lakes should be growing, not shrinking.

Whatever the cause, the loss could impact local wildlife and human populations. “It’s an important finding. We need to find out what’s driving it,” says Larry Hinzman, director of the International Arctic Research Center in Fairbanks, Alaska. The comprehensiveness of the study makes it significant, he says.

Ten years is long enough that this could be a sign of climate change, Hinzman says, “and it’s over a large enough area that it’s bound to have ecosystem and climate impacts”. Migratory water fowl, aquatic life, and indigenous people who rely on the lakes for food and water may all face challenges if the drying continues.

Shrinking Arctic lakes have been observed before, but only in the southern-most part of the Arctic, where warming trends have melted permafrost and allowed lakes to drain into the soil. The new survey, carried out by Mark Carroll at the University of Maryland in College Park, finds just the reverse: northern lakes appear to be shrinking, while southern ones are not (Geophysical Research Letters, DOI: 10.1029/2011GL049427).

This is surprising, says Hinzman, not least because evidence suggests that the northern region received higher-than-average amounts of rain during the study period. “You would expect more precipitation to lead to higher lake levels,” says atmospheric scientist Stephen Dery at the University of Northern British Columbia in Prince George. “But here, it doesn’t.”

Much of the lake water comes from the seasonal snow pack melt. In theory, warmer temperatures across the region should be decreasing the snow pack – which should also boost the lakes. Another factor at play could be the delicate balance between precipitation and evaporation which Arctic lake levels depend on: warmer temperatures and higher winds could cause more evaporation. Hinzman and Dery say melting permafrost may also be involved. That would allow lake water to soak into thawed soil, but Carroll is not aware of any evidence that the permafrost in the far north is melting yet.

The water loss could affect the amount of greenhouse gases emitted by the region’s ecosystems. When lakes dry up, the sediment in the newly exposed soil can release carbon dioxide. But standing water can also release methane, so the lake shrinkage could lower methane levels. It remains to be seen whether the net result is to boost global warming or if the impacts offset each other.

2011 Sea Ice Minimum at near-record level

2011 Sea Ice Minimum : Image of the Day.

2011 Sea Ice Minimum

acquired September 9, 2011
Color bar for 2011 Sea Ice Minimum
acquired September 1, 2010 – September 30, 2011 download animation (8 MB, QuickTime)

In September 2011, sea ice covering the Arctic Ocean declined to the second-lowest extent on record. Satellite data from NASA and the National Snow and Ice Data Center (NSIDC) showed that the summertime ice cover narrowly avoided a new record low.

The image above was made from observations collected by the Advanced Microwave Scanning Radiometer (AMSR-E) on NASA’s Aqua satellite. The map—which looks down on the North Pole—depicts sea ice extent on September 9, 2011, the date of minimum extent for the year. The animation (link below the image) shows the growth and decline of sea ice from September 2010 to September 2011.

Ice-covered areas range in color from white (highest concentration) to light blue (lowest concentration). Open water is dark blue, and land masses are gray. The yellow outline shows the median minimum ice extent for 1979–2000; that is, areas that were at least 15 percent ice-covered in at least half the years between 1979 and 2000.

Melt season in 2011 brought higher-than-average summer temperatures, but not the unusual weather conditions that contributed to the extreme melt of 2007, the record low. “Atmospheric and oceanic conditions were not as conducive to ice loss this year, but the melt still neared 2007 levels,” said Walt Meier of NSIDC. “This probably reflects loss of multi-year ice in the Beaufort and Chukchi seas, as well as other factors that are making the ice more vulnerable.”

The low sea ice level in 2011 fits the pattern of decline over the past three decades, said Joey Comiso of NASA’s Goddard Space Flight Center. Since 1979, September Arctic sea ice extent has declined by 12 percent per decade.

“The sea ice is not only declining; the pace of the decline is becoming more drastic,” he noted. “The older, thicker ice is declining faster than the rest, making for a more vulnerable perennial ice cover.”

While the sea ice extent did not dip below the record, the area did drop slightly lower than 2007 levels for about ten days in early September 2011. Sea ice “area” differs from “extent” in that it equals the actual surface area covered by ice, while extent includes any area where ice covers at least 15 percent of the ocean.

Arctic sea ice extent on September 9, 2011, was 4.33 million square kilometers (1.67 million square miles). Averaged over the month of September, ice extent was 4.61 million square kilometers (1.78 million square miles). This places 2011 as the second lowest ice extent for both the daily minimum and the monthly average. Ice extent was 2.43 million square kilometers (938,000 square miles) below the 1979 to 2000 average.

Climate models have suggested that the Arctic could lose almost all of its summer ice cover by 2100, but in recent years, ice extent has declined faster than the models predicted.

  1. Further Reading

  2. NASA (2011, October 4) Arctic Sea Ice Continues Decline, Hits 2nd-Lowest Level. Accessed October 4, 2011.
  3. NASA Earth Observatory (n.d.) World of Change: Arctic Sea Ice.
  4. NOAA Climate Watch (2011, October 4) Old Ice Becoming Rare in Arctic. Accessed October 4, 2011.

NASA Earth Observatory images created by Jesse Allen, using AMSR-E sea ice concentration data provided courtesy of the National Snow and Ice Data Center. Caption based on text from Patrick Lynch (NASA) and Katherine Leitzell (NSIDC), edited by Michael Carlowicz.

Aqua – AMSR-E

Arctic ozone loss at record level

BBC News – Arctic ozone loss at record level.


The Arctic ozone hole lay over over populated regions for parts of winter and spring

Ozone loss over the Arctic this year was so severe that for the first time it could be called an “ozone hole” like the Antarctic one, scientists report.

About 20km (13 miles) above the ground, 80% of the ozone was lost, they say.

The cause was an unusually long spell of cold weather at altitude. In cold conditions, the chlorine chemicals that destroy ozone are at their most active.

It is currently impossible to predict if such losses will occur again, the team writes in the journal Nature.

Early data on the scale of Arctic ozone destruction were released in April, but the Nature paper is the first that has fully analysed the data.

“Winter in the Arctic stratosphere is highly variable – some are warm, some are cold,” said Michelle Santee from Nasa’s Jet Propulsion Laboratory (JPL).

“But over the last few decades, the winters that are cold have been getting colder.

Start Quote

Why [all this] occurred will take years of detailed study”

Michelle Santee JPL

“So given that trend and the high variability, we’d anticipate that we’ll have other cold ones, and if that happens while chlorine levels are high, we’d anticipate that we’d have severe ozone loss.”

Ozone-destroying chemicals originate in substances such as chlorofluorocarbons (CFCs) that came into use late last century in appliances including refrigerators and fire extinguishers.

Their destructive effects were first documented in the Antarctic, which now sees severe ozone depletion in each of its winters.

Their use was progressively restricted and then eliminated by the 1987 Montreal Protocol and its successors.

The ozone layer blocks ultraviolet-B rays from the Sun, which can cause skin cancer and other medical conditions.

Longer, not colder

Winter temperatures in the Arctic stratosphere do not generally fall as low as at the southern end of the world.

Polar stratospheric clouds Ozone destruction takes place within polar stratospheric clouds, with chlorine the main culprit

No records for low temperature were set this year, but the air remained at its coldest for an unusually long period of time, and covered an unusually large area.

In addition, the polar vortex was stronger than usual. Here, winds circulate around the edge of the Arctic region, somewhat isolating it from the main world weather systems.

“Why [all this] occurred will take years of detailed study,” said Dr Santee.

“It was continuously cold from December through April, and that has never happened before in the Arctic in the instrumental record.”

The size and position of the ozone hole changed over time, as the vortex moved northwards or southwards over different regions.

Some monitoring stations in northern Europe and Russia recorded enhanced levels of ultraviolet-B penetration, though it is not clear that this posed any risk to human health.

While the Arctic was setting records, the Antarctic ozone hole is relatively stable from year to year.

This year has seen ozone-depleting conditions extending a little later into the southern hemisphere spring than usual – again, as a result of unusual weather conditions.

Chlorine compounds persist for decades in the upper atmosphere, meaning that it will probably be mid-century before the ozone layer is restored to its pre-industrial health.

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Giant red crabs invade the Antarctic abyss

Giant red crabs invade the Antarctic abyss – environment – 07 September 2011 – New Scientist.




Huge crabs more than a metre across have invaded the Antarctic abyss, wiped out the local wildlife and now threaten to ruin ecosystems that have evolved over 14 million years.

Three years ago, researchers predicted that as the deep waters of the Southern Ocean warmed, king crabs would invade Antarctica within 100 years.

But video taken by a remotely operated submersible shows that more than a million Neolithodes yaldwyni?have already colonised Palmer Deep, a basin that forms a hollow in the Antarctic Peninsula continental shelf.

They are laying waste to the landscape. Video footage taken by the submersible shows how the crabs prod, probe, gash and puncture delicate sediments with the tips of their long legs. “This is likely to alter sediment processes, such as the rate at which organic matter is buried, which will affect the diversity of animal communities living in the sediments,” says Craig Smith of the University of Hawaii at Manoa, whose team discovered the scarlet invaders.

Hungry invaders

The crabs also appear to have a voracious appetite. Echinoderms – sea urchins, sea lilies, sea cucumbers, starfish and brittle stars – have vanished from occupied areas, and the number of species in colonised areas is just a quarter of that in areas that have escaped the invasion.

“[Echinoderms] constitute a significant proportion of the large animals on the seafloor in many Antarctic shelf habitats,” says Smith.

The crabs come from further north and moved in as Antarctic waters have warmed, probably swept into Palmer Deep as larvae in warm ocean currents. They now occupy the deepest regions of Palmer Deep, between 1400 and 950 metres. In 1982, the minimum temperature there was 1.2 °C – too cold for king crabs – but by last year it had risen to a balmier 1.47 °C.

Melting ice sheets tend to make shallower waters in Antarctica cooler than deeper ones. There were no king crabs at depths of 850 metres or less, suggesting that these waters are still too cold for them. But with waters warming so rapidly, they could spread to regions as shallow as 400 metres within as little as 20 years, says Smith.


“Several years ago, my colleagues and I predicted that warming sea temperatures off the west Antarctic Peninsula would allow predatory sea crabs to invade and disrupt the completely unique marine bottom fauna,” says Richard Aronson of the Florida Institute of Technology in Melbourne.

“Craig Smith and his team have now discovered a population in a deep basin gouged into the continental shelf off the western peninsula,” says Aronson. “What’s exciting, new and a bit scary about their find is that somehow, the crabs had to get from the deep sea over part of the continental shelf and then into the basin that is the Palmer Deep.”

“That means they’re close to being able to invade habitats on the continental shelf proper, and if they do the crabs will probably have a radical impact on the bottom communities.”

The best long-term solution? To slow the rate of global warming, says Smith.

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2011.1496

Arctic Ice Loss at near-record levels & Several Other Reuters Updates










World Atlas ice loss claim exaggerated: scientists | Reuters.

LONDON | Mon Sep 19, 2011 3:27pm EDT

(Reuters) – The Times Atlas of the World exaggerated the rate of Greenland’s ice loss in its thirteenth edition last week, scientists said on Monday.

The atlas, published by HarperCollins, showed that Greenland lost 15 percent of its ice cover over the past 12 years, based on information from the National Snow and Ice Data Center in Colorado in the United States.

The Greenland ice sheet is the second biggest in the world and significant shrinking could lead to a global rise in sea levels.

“While global warming has played a role in this reduction, it is also as a result of the much more accurate data and in-depth research that is now available,” HarperCollins said on its website on Monday.

However, a number of scientists disputed the claim.

“We believe that the figure of a 15 percent decrease in permanent ice cover since the publication of the previous atlas 12 years (ago) is both incorrect and misleading,” said Poul Christoffersen, glaciologist at the Scott Polar Research Institute (SPRI) at the University of Cambridge.

“We concluded that a sizable portion of the area mapped as ice-free in the Atlas is clearly still ice-covered.”

Other scientists agreed.

“These new maps are ridiculously off base, way exaggerated relative to the reality of rapid change in Greenland,” said Jeffrey S. Kargel, senior research scientist at the University of Arizona.

The Times Atlas suggested the Greenland ice sheet has lost 300,000 square kilometers in the past 12 years, at a rate of 1.5 percent per year.

However, measurements suggest this rate is at least 10 times faster than in reality, added J. Graham Cogley, Professor of Geography at Trent University, Ontario, Canada.

“It could easily be 20 times too fast and might well be 50 times too fast,” he added.

Last year, a U.N. committee of climate scientists came under fire for bungling a forecast of when Himalayan glaciers would thaw.

The panel’s 2007 report, the main guide for governments in fighting climate change, included an incorrect projection that all Himalayan glaciers could vanish by 2035, hundreds of years earlier than scientists’ projections.


Summer Arctic sea ice melt at or near record

(Reuters) – Arctic sea ice this summer melted to a record low extent or will come a close second, two different research institutes said on Tuesday, confirming a trend which could yield an ice-free summer within a decade.

The five biggest melts in a 32-year satellite record have all happened in the past five years, likely a result of both manmade climate change and natural weather patterns.

One impact of an ice-free summer may be disrupted world weather, with hints already as some scientists blame recent chill winters in Europe and North America on warmer, open Arctic seas diverting polar winds south.

Researchers at the University of Bremen in Germany say that this year has already toppled 2007 after sea ice retreated to a record low on September 8.

The U.S.-based National Snow and Ice Data Center (NSIDC) says this year is number two with the melt season all but over before winter returns to the high Arctic.

“I’m increasingly confident it will remain number two,” said Mark Serreze, head of the NSIDC. But the result may be close enough to declare a tie, he added.

Most important than the record was the trend, said University of Bremen’s Georg Heygsterall, referring to how the years since 2007 had all since bigger summer melts than those before.

A tie would echo the World Meteorological Organization’s view on recent rising global temperatures, after it declared 2010 a tie with 1998 and 2005 for the hottest year since such records began about a century and a half ago.

Bremen and NSIDC use satellites to measure microwave radiation from the ice pack, but with slightly different methods: NSIDC can achieve a sharper image, but Bremen to a higher resolution of 6 kilometers compared with 25 km.


Researchers agree that summer sea ice is disappearing faster than expected.

“An ‘ice-free’ summer Arctic is rapidly on its way. Most data indicate that the models are underestimating the rate of ice-loss,” said Kim Holmen, research director at the Norwegian Polar Institute.

“That means that we see more rapid change than the model scenarios have suggested. It also means that there are processes out there that influence ice that we have yet to understand.”

The summer ice retreat has already reached levels which were forecast three decades from now in models used in the U.N. climate panel’s flagship report four years ago.

The Intergovernmental Panel on Climate Change (IPCC) used models which forecasted an ice-free summer at the end of this century.

But that could happen as early as 2013, according to one of the most aggressive estimates. Other experts predict an ice-free Arctic Ocean in summer anywhere from 2020-2050.

“I still see a high likelihood of a near ice-free Arctic Ocean during summer around 2016, plus or minus three years,” said Wieslaw Maslowski at the California-based Naval Postgraduate School.

More difficult to measure than area is ice thickness, which is also diminishing, most scientists agree.

Researchers at the University of Washington in Seattle calculated ice volume, combining area and thickness, reached a record low last year and would do so again this year.

(Reporting by Gerard Wynn)


More on Sea-Ice loss:

Thu Sep 15, 2011 3:49pm EDT

<span class="articleLocation”>(Reuters) – Sea ice on the Arctic Ocean shrank to its second-smallest extent since modern records began, in keeping with a long-term trend, the U.S. National Snow and Ice Data Center reported on Thursday.

The annual sea ice minimum was reached on September 9, the center said on its website here in a preliminary finding.

“Changing winds could still push ice flows together reducing ice extend further,” the researchers said. A full analysis will be available in October, when monthly data are available for all of September, which is usually the month when the annual minimum is reached.

Arctic Sea ice is an important sign of a changing climate, and what happens in the Arctic has a major influence on global weather patterns.

At its apparent minimum, sea ice around the North Pole covered 1.67 million square miles (4.33 million square km). That measurement is 61,800 square miles (160,000 square km) above the all-time record low reached in 2007, the center said.

However, it is far below the average minimum for the period 1979 through 2000, according to NSIDC. The satellite record began in 1979.

These figures differ from those reported by the University of Bremen in German, which issued a statement that the Arctic ice reached a record low minimum on September 8.


Both the University of Bremen and NSIDC use microwave sensors to observe Arctic ice, but these sensors are on different satellites. The Bremen report uses images with higher spatial resolution, according to Walter Meier of NSIDC.

“They can see in more detail, they can see these little patches of water, whereas we see these areas as just ice covered,” Meier said by telephone. He said there can be higher potential for error with these high-resolution images, though there is no evidence of error in this case.

NSIDC’s records go back to 1979; the records used by Bremen go back to 2003. Both indicate the last five years were the least icy in the Arctic sea ice satellite record.

It’s not surprising that this year has not eclipsed the record year of 2007, Meier said.

That year was “a perfect storm” of ice-melting conditions in the Arctic, he said: warmer and sunnier than usual, with extremely warm ocean water and winds all acting in concert.

The fact that 2011 has seen the second-lowest ice extent without these extreme conditions shows a change in the character of the ice cover, Meier said.

Back in 2007, the ice was a consolidated mass which melted from the edges. This year, he said, the ice is more dispersed and the area is dominated by seasonal ice cover — less hardy than multi-year ice — which is more prone to melt.

“Now it doesn’t take as extreme of weather conditions to get to the 2007 ballpark,” Meier said.

(Reporting by Deborah Zabarenko in Washington, Editing by Cynthia Osterman)



Petermann Glacier break-up

BBC News – ‘Gob-smacking’ scale of Petermann Glacier break-up.

These photos of the Petermann Glacier were taken two years apart, in the summer of 2009 (top) and in July 2011 These photos of the Petermann Glacier were taken two years apart, the latest one in July 2011 (top) and in the summer of 2009

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New pictures have revealed the extent to which a huge glacier in northern Greenland has broken up in just two years, claims a glaciologist.

Dr Alun Hubbard of Aberystwyth University said he was “gob-smacked” by the scale of the Petermann Glacier’s break-up since he last visited in 2009.

The glacier is 186 miles (300km) long and 3,280ft (1000m) high – over three times the height of the Eiffel Tower.

Last year, it shed a piece of ice measuring 77 square miles (200 sq km).

Dr Hubbard has been researching the Greenland ice sheet for some years.

His team of researchers and scientists from Aberystwyth and Swansea universities have made several trips to the country.

Located in north west Greenland, the Petermann Glacier accounts for 6% of the area of the Greenland ice sheet, said Dr Hubbard.

Start Quote

It’s like looking into the Grand Canyon full of ice and coming back two years later to find it’s full of water”

Dr Alun Hubbard Aberystwyth University

It terminates as a floating tongue of ice, measuring around 43 miles (70km) long by 12 miles (20km) wide, the largest of its kind in the northern hemisphere.

“Although I knew what to expect in terms of ice loss from satellite imagery, I was still completely unprepared for the gob-smacking scale of the break-up, which rendered me speechless,” said Dr Hubbard.

“It was incredible to see. This glacier is huge, 20km across and 1000m high.

“It’s like looking into the Grand Canyon full of ice and coming back two years later to find it’s full of water.”

He said data recovered from global positioning system (GPS) sensors at the site was being analysed at Aberystwyth.

Cracks and rifts

With support from the US National Science Foundation and the Natural Environment Research Council in the UK, Dr Hubbard travelled by helicopter to the glacier to gather data from time lapse cameras and GPS sensors set up in July and August 2009, with the help of Greenpeace.

The GPS sensors were set in anticipation of a large break-up of ice that eventually occurred by on 3 August, 2010.

Dr Hubbard said this led to the formation of an ice island measuring more than 77 square miles (200 sq km).

He believes the cracks and rifts in what remains of the ice shelf means it is also likely to break up at some point in the near future.

Dr Hubbard visited the Petermann glacier at the end of July, and returns to Aberystwyth on Sunday.

His work is part of a wider project involving researchers from Bristol, Cambridge, Edinburgh, Denmark, Sweden, the Netherlands, Germany and the United States.

Antarctica rising as ice caps melt

Antarctica rising as ice caps melt – environment – 31 July 2011 – New Scientist.

ANTARCTICA is rising like a cheese soufflé: slowly but surely. Lost ice due to climate change and left-over momentum from the end of the last big ice age mean the buoyant continent is heaven-bound.

Donald Argus of NASA’s Jet Propulsion Laboratory in Pasadena, California, and colleagues used 15 years of GPS data to show that parts of the Ellsworth mountains in west Antarctica are rising by around 5 millimetres a year (Geophysical Research Letters, DOI: 10.1029/2011gl048025). Elsewhere on the continent, the rise is slower.

A faster rise has been seen in Greenland, which is thought to be popping up by 4 centimetres a year.

Ongoing climate change could be partly to blame: Antarctica is losing about 200 gigatonnes of ice per year, and for Greenland the figure is 300 gigatonnes. Earth’s continents sit on viscous magma, so the effect of this loss is like taking a load off a dense foam mattress.

But there is another possible contributor. “The Earth has a very long memory,” says Argus. As a result, “there is also a viscous response to ice loss from around 5000 to 10,000 years ago going on”.

Despite this effect, the known ice loss at both poles suggests that embedded in the local rises is a signal of current climate change – researchers just have to tease it out.

Sea level rise more from Antarctica than from Greenland during last interglacial

Sea level rise less from Greenland, more from Antarctica, than expected during last interglacial.

Where did all that extra water come from? Mainly from melting ice sheets on Greenland and Antarctica, and many scientists, including University of Wisconsin-Madison geoscience assistant professor Anders Carlson, have expected that Greenland was the main culprit.

But Carlson’s new results, published July 29 in Science, are challenging that assertion, revealing surprising patterns of melting during the last interglacial period that suggest that Greenland’s ice may be more stable — and Antarctica’s less stable — than many thought.

“The Greenland Ice Sheet is melting faster and faster,” says Carlson, who is also a member of the Center for Climatic Research in the Nelson Institute for Environmental Studies. But despite clear observations of that fact, estimates of just how much the ice will melt and contribute to sea level rise by the end of this century are highly varied, ranging from a few centimeters to meters. “There’s a clear need to understand how it has behaved in the past, and how it has responded to warmer-than-present summers in the past.”

The ice-estimation business is rife with unknown variables and has few known physical constraints, Carlson explains, making ice sheet behavior — where they melt, how much, how quickly — the largest source of uncertainty in predicting sea level rises due to climate change.

His research team sought a way to constrain where ice remained on Greenland during the last interglacial period, around 125,000 years ago, to better define past ice sheet behavior and improve future projections.

The researchers analyzed silt from an ocean-floor core taken from a region off the southern tip of Greenland that receives sediments carried by meltwater streams off the ice sheet. They used different patterns of radiogenic isotopes to identify sources of the sediment, tracing the silt back to one of three “terranes” or regions, each with a distinct geochemical signature. The patterns of sedimentation show which terranes were still glaciated at that time.

“If the land deglaciates, you lose that sediment,” Carlson explains. But to their surprise, they found that all the terranes were still supplying sediment throughout the last interglacial period and thus still had some ice cover.

“The ice definitely retreated to smaller than present extent and definitely raised sea level to higher than present” and continued to melt throughout the warm period, he adds, but the sediment analysis indicates that “the ice sheet seems to be more stable than some of the greater retreat values that people have presented.”

The team used their results to evaluate several existing models of Greenland ice sheet melting during the last interglacial period. The models consistent with the new findings indicate that melting Greenland ice was responsible for a sea level rise of 1.6 to 2.2 meters — at most, roughly half of the minimum four-meter total increase.

Even after accounting for other Arctic ice and the thermal expansion of warmer water, most of the difference must have come from a melting Antarctic ice sheet, Carlson says.

“The implication of our results is that West Antarctica likely was much smaller than it is today,” and responsible for much more of the sea level rise than many scientists have thought, he says. “If West Antarctica collapsed, that means it’s more unstable than we expected, which is quite scary.”

Ultimately, Carlson says he hopes this line of research will improve the representation of ice sheet responses to a warming planet in future Intergovernmental Panel on Climate Change (IPCC) reports. Temperatures during the last interglacial period were similar to those expected by the end of this century, and present-day temps have already reached a point that Greenland’s glaciers are melting.

The Science paper was co-authored by UW-Madison colleagues Elizabeth Colville, Brian Beard, Alberto Reyes, and David Ullman and Oregon State University researchers Robert Hatfield and Joseph Stoner, and supported by UW-Madison and the National Science Foundation.

Warming Arctic releases frozen organic air pollutants

Warming Arctic releases frozen organic air pollutants – environment – 28 July 2011 – New Scientist.

  • 28 July 2011

Air pollutants emitted decades ago are coming back to haunt us. As the Arctic warms, persistent organic pollutants, or POPs, trapped in snow and ice are being re-released. This unwelcome return has been suspected for some time but is now confirmed by 16 years’ worth of data.

POPs travel around the globe on winds, build up in food and water supplies, and accumulate in animal body fat. They have also been linked to serious human health problems, including cancer, and can be passed from mother to fetus. They have been banned under the Stockholm convention since 2004.

The new study looked at air concentrations of POPs up to 2009 in Svalbard, Norway, and in Canada’s Nunavut province, and found an increase since 2000 (Nature Climate Change, DOI: 10.1038/nclimate1167).