Showing posts with label Jay Zwally. Show all posts

Written by fatih al-farahat in ,


Greenland meltwater can drain faster than Niagara Falls

Dear Readers,

Another article from 2008. However, this year, the results will be way beyond what happened in 2008.

Greenland meltwater can drain faster than Niagara Falls

by John Roach for National Geographic News, April 17, 2008

Giant lakes of meltwater pooled on top of Greenland's ice sheets can suddenly drain to the bedrock, allowing the sheet to more easily slip forward, according to new research.

One lake that covered 2.2 square miles (5.6 km²) and held 11.6 billion gallons (43.9 billion liters) of fresh water drained completely in about 90 minutes, scientists observed recently.

The maximum drainage rate was faster than the average flow rate over Niagara Falls.

"It's a lot of water flowing onto the ice pretty quickly," said study lead author Ian Joughin, a glaciologist at the University of Washington in Seattle.

The same phenomenon repeats itself over and over throughout the summer months in Greenland as long, warm days melt the ice on the surface. (See a Greenland map.)

The contribution of Greenland's rapidly melting ice sheet to sea-level rise is one of the biggest unknowns highlighted in the UN Intergovernmental Panel on Climate Change's most recent report.

No Catastrophic Floods

During the recent rapid release of meltwater, water funneled through a 3,200-foot-long (980-meter-long) crack in the ice.

The deluge caused the ice sheet to rise by 3.9 feet (1.2 meters) in one location like a blister, Joughin said.

"As it rose, it got to the point where it couldn't support that anymore, and then this big block fractured out of there and lifted up," he added.

The drained water creates a lubricating effect that accelerates ice flow by 50-100% in the broad, slow-moving areas of the ice sheet, Joughin and colleagues found.

Joughin and Sarah Das of the Woods Hole Oceanographic Institution in Massachusetts, lead author of a separate study on the phenomenon, describe their findings in papers published online today in the journal Science.

Ice-Sheet Flow

Meltwater draining to the bedrock speeds up the flow of the entire ice sheet, including outlet glaciers—streams of ice that flow outward—by about 160-330 feet (50-100 m) a year, Joughin said.

During the summer, this speedup accounts for half to all of the movement of the broad ice sheet.

The outlet glaciers are moving much faster, and the lubrication effect of the meltwater is contributing only fractionally to their movement.

But the added slippage has only a minor effect on the pace of Greenland's outlet glaciers, which have been galloping toward the ocean in recent years.

Jay Zwally is a glaciologist at the NASA Goddard Space Flight Center in Greenbelt, Maryland, who first described the lubricating effect of water on Greenland's ice in a 2002 Science paper.

He was not involved in the current research, which he said confirms the effect occurs along much of the ice-sheet margins but may underestimate the effect on the outlet glaciers.

The new research, he said, primarily focuses on a single large outlet glacier that has unique characteristics. Other outlet glaciers show more of a speedup.

"So the question is still open," Zwally said.

(See a map of the world's disappearing ice sheets.)

Ice Sheet Dynamics

Richard Alley is a glaciologist at Pennsylvania State University in University Park who was not involved in the new research.

He said the findings are a vital clue to understanding how much ice could melt from Greenland, pushing global sea levels higher over the course of the next century.

The recent IPCC report, on which Alley was an author, noted that scientists need to determine the physics that control ice flow in Greenland and then plug that data in a computer model.

"They're finding out what happens," Alley said of the new work. "And [they're doing it] really well."

Zwally of NASA said the research is breaking new ground, but that more questions remain—for instance, how far inland does the lubrication extend?

"We may be looking at a couple of feet of sea-level contribution during this century," he said.

"But as this builds up, it is headed towards a point where it will continue to speed up."

Link: http://news.nationalgeographic.com/news/2008/04/080417-greenland-lakes.html

Written by fatih al-farahat in , ,


The Sermilik fjord in Greenland: a chilling view of a warming world

The Sermilik fjord in Greenland: a chilling view of a warming world

'We all live on the Greenland ice sheet now. Its fate is our fate'

The Sermilik fjord

The Sermilik fjord, where hundreds of icebergs are calving from Greenland's vast ice sheets. Photograph: Philippe Roy/Getty

It is calving season in the Arctic. A flotilla of icebergs, some as jagged as fairytale castles and others as smooth as dinosaur eggs, calve from the ice sheet that smothers Greenland and sail down the fjords. The journey of these sculptures of ice from glaciers to ocean is eerily beautiful and utterly terrifying.

The wall of ice that rises behind Sermilik fjord stretches for 1,500 miles (2,400 km) from north to south and smothers 80% of this country. It has been frozen for 3m years. Now it is melting, far faster than the climate models predicted and far more decisively than any political action to combat our changing climate. If the Greenland ice sheet disappeared sea levels around the world would rise by seven metres, as 10% of the world's fresh water is currently frozen here.

This is also the season for science in Greenland. Glaciologists, seismologists and climatologists from around the world are landing on the ice sheet in helicopters, taking ice-breakers up its inaccessible coastline and measuring glaciers in a race against time to discover why the ice in Greenland is vanishing so much faster than expected.

Gordon Hamilton, a Scottish-born glaciologist from the University of Maine's Climate Change Institute, is packing up equipment at his base camp in Tasiilaq, a tiny, remote east coast settlement only accessible by helicopter and where huskies howl all night.

With his spiky hair and ripped T-shirt, Hamilton could be a rugged glaciologist straight from central casting. Four years ago he hit upon the daring idea of landing on a moving glacier in a helicopter to measure its speed.

The glaciers of Greenland are the fat, restless fingers of its vast ice sheet, constantly moving, stretching down into fjords and pushing ice from the sheet into the ocean, in the form of melt water and icebergs.

Before their first expedition, Hamilton and his colleague Leigh Stearns, from the University of Kansas, used satellite data to plan exactly where they would land on a glacier.

"When we arrived there was no glacier to be seen. It was way up the fjord," he says. "We thought we'd made some stupid goof with the co-ordinates, but we were where we were supposed to be." It was the glacier that was in the wrong place. A vast expanse had melted away.

When Hamilton and Stearns processed their first measurements of the glacier's speed, they thought they had made another mistake. They found it was marching forwards at a greater pace than a glacier had ever been observed to flow before. "We were blown away because we realised that the glaciers had accelerated not just by a little bit but by a lot," he says. The three glaciers they studied had abruptly increased the speed by which they were transmitting ice from the ice sheet into the ocean.

Raw power

Standing before a glacier in Greenland as it calves icebergs into the dark waters of a cavernous fjord is to witness the raw power of a natural process we have accelerated but will now struggle to control.

Greenland's glaciers make those in the Alps look like toys. Grubby white and blue crystal towers, cliffs and crevasses soar up from the water, dispatching millenniums of compacted snow in the shape of seals, water lilies and bishops' mitres.

I take a small boat to see the calving with Dines Mikaelsen, an Inuit guide, who in the winter will cross the ice sheet in his five-metre sled pulled by 16 huskies.

It is not freezing, but even in summer the wind is bitingly cold and we can smell the bad breath of a humpback whale as it groans past our bows on Sermilik Fjord. Above its heavy breathing, all you can hear in this wilderness is the drip-drip of melting ice and a crash as icebergs cleave into even smaller lumps, called growlers.

Mikaelsen stops his boat beside Hann glacier and points out how it was twice as wide and stretched 300 metres further into the fjord just 10 years ago. He also shows off a spectacular electric blue iceberg.

Locals have nicknamed it "blue diamond"; its colour comes from being cleaved from centuries-old compressed ice at the ancient heart of the glacier. Bobbing in warming waters, this ancient ice fossil will be gone in a couple of weeks.

The blue diamond is one vivid pointer to the antiquity of the Greenland ice sheet. A relic of the last Ice Age, this is one of three great ice sheets in the world. Up to two miles thick, the other two lie in Antarctica.

While similar melting effects are being measured in the southern hemisphere, the Greenland sheet may be uniquely vulnerable, lying much further from the chill of the pole than Antarctica's sheets. The southern end of the Greenland sheet is almost on the same latitude as the Shetlands and stroked by the warm waters of the Gulf Stream.

Driven by the loss of ice, Arctic temperatures are warming more quickly than other parts of the world: last autumn air temperatures in the Arctic stood at a record 5 C above normal. For centuries, the ice sheets maintained an equilibrium: glaciers calved off icebergs and sent melt water into the oceans every summer; in winter, the ice sheet was then replenished with more frozen snow. Scientists believe the world's great ice sheets will not completely disappear for many more centuries, but the Greenland ice sheet is now shedding more ice than it is accumulating.

The melting has been recorded since 1979; scientists put the annual net loss of ice and water from the ice sheet at 300-400 gigatonnes (equivalent to a billion elephants being dropped in the ocean), which could hasten a sea level rise of catastrophic proportions.

As Hamilton has found, Greenland's glaciers have increased the speed at which they shift ice from the sheet into the ocean. Helheim, an enormous tower of ice that calves into Sermilik Fjord, used to move at 7 km (4.4 miles) a year. In 2005, in less than a year, it speeded up to nearly 12 km a year. Kangerdlugssuaq, another glacier that Hamilton measured, tripled its speed between 1988 and 2005. Its movement – an inch every minute – could be seen with the naked eye.

The three glaciers that Hamilton and Stearns measured account for about a fifth of the discharge from the entire Greenland ice sheet. The implications of their acceleration are profound: "If they all start to speed up, you could have quite a large rise in sea level in the near term, much larger than the official estimate by the Intergovernmental Panel on Climate Change (IPCC) would project," says Hamilton.

The scientific labours in the chill winds and high seas of the Arctic summer seem wrapped in an unusual sense of urgency this year. The scientists working in Greenland are keen to communicate their new, emerging understanding of the dynamics of the declining ice sheet to the wider world. Several point out that any international agreement forged at the UN climate change conference in Copenhagen in December will be based on the IPCC's fourth assessment report from 2007. Its estimates of climate change and sea-level rise were based on scientific research submitted up to 2005; the scientists say this is already significantly out of date.

The 2007 report predicted a sea level rise of 30-60 cm by 2100, but did not account for the impact of glaciers breaking into the sea from areas such as the Greenland ice sheet. Most scientists working at the poles predict a 1-m rise by 2100. The US Geological Survey has predicted a 1.5-m rise. As Hamilton points out: "It is only the first metre that matters".

Record temperatures

A 1-m rise – with the risk of higher storm surges – would require new defences for New York, London, Mumbai and Shanghai, and imperil swaths of low-lying land from Bangladesh to Florida. Vulnerable areas accommodate 10% of the world's population – 600 million.

The Greenland ice sheet is not merely being melted from above by warmer air temperatures. As the oceans of the Arctic waters reach record high temperatures, the role of warmer water lapping against these great glaciers is one of several factors shaping the loss of the ice sheet that has been overlooked until recently.

Fiamma Straneo, an Italian-born oceanographer, is laboriously winding recording equipment the size of a fire extinguisher from the deck of a small Greenpeace icebreaker caught in huge swells at the mouth of Sermilik fjord.

In previous decades, the Arctic Sunrise has been used in taking direct action against whalers; now it offers itself as a floating research station for independent scientists to reach remote parts of the ice sheet. It is tough work for the multinational crew of 30 in this rough-and-ready little boat, prettified below deck with posters of orang-utans and sunflowers painted in the toilets.

Before I succumb to vomiting below deck – another journalist is so seasick they are airlifted off the boat – I examine the navigational charts used by the captain, Pete Willcox, a survivor of the sinking of the Rainbow Warrior in 1985. He shows how they are dotted with measurements showing the depth of the ocean but here, close to the east coast of Greenland, the map is blank: this part of the North Atlantic was once covered by sea ice for so much of the year that its waters are still uncharted.

Earlier in the expedition, the crew believe, they became the first boat to travel through the Nares Strait west of Greenland to the Arctic Ocean in June, once impassable because of sea ice at that time of year. The predicted year when summers in the Arctic would be free of sea ice has fallen from 2100 to 2050 to 2030 in a couple of years.

Jay Zwally, a NASA scientist, recently suggested it could be virtually ice-free by late summer 2012. Between 2004 and 2008, the area of "multiyear" Arctic sea ice (ice that has formed over more than one winter and survived the summer melt) shrank by 595,000 sq miles, an area larger than France, Germany and the United Kingdom combined.

Undaunted by the sickening swell of the ocean and wrapped up against the chilly wind, Straneo, of Woods Hole Oceanographic Institution, one of the world's leading oceanographic research centres, continues to take measurements from the waters as the long Arctic dusk falls.

According to Straneo, the rapid changes to the ice sheet have taken glaciologists by surprise. "One of the possible mechanisms which we think may have triggered these changes is melting driven by changing ocean temperatures and currents at the margins of the ice sheet."

She has been surprised by early results measuring sea water close to the melting glaciers: one probe recovered from last year recorded a relatively balmy 2 C at 60 metres in the fjord in the middle of winter. Straneo said: "This warm and salty water is of subtropical origin – it's carried by the Gulf Stream. In recent years a lot more of this warm water has been found around the coastal region of Greenland. We think this is one of the mechanisms that has caused these glaciers to accelerate and shed more ice."

Straneo's research is looking at what scientists call the "dynamic effects" of the Greenland ice sheet. It is not simply that the ice sheet is melting steadily as global temperatures rise. Rather, the melting triggers dynamic new effects, which in turn accelerate the melt.

"It's quite likely that these dynamic effects are more important in generating a near-term rapid rise in sea level than the traditional melt," says Hamilton. Another example of these dynamic effects is when the ice sheet melts to expose dirty layers of old snow laced with black carbon from forest fires and even cosmic dust. These dark particles absorb more heat and so further speed up the melt.

After Straneo gathers her final measurements, the Arctic Sunrise heads for the tranquillity of the sole berth at Tasiilaq, which has a population of fewer than 3,000 but is still the largest settlement on Greenland's vast east coast. Here another scientist is gathering her final provisions before taking her team camping on a remote glacier.

Invisible earthquakes

Several years ago Meredith Nettles, a seismologist from Colombia University, and two colleagues made a remarkable discovery: they identified a new kind of earthquake. These quakes were substantial – measuring magnitude five – but had been invisible because they did not show up on seismographs. (While orthodox tremors registered for a couple of seconds, these occurred rather more slowly, over a minute.)

The new earthquakes were traced almost exclusively to Greenland, where they were found to be specifically associated with large, fast-flowing outlet glaciers. There have been 200 of them in the last dozen years; in 2005 there were six times as many as in 1993.

Nettles nimbly explains the science as she heaves bags of equipment on to a helicopter, which will fly her to study Kangerdlugssuaq glacier. "It's quite a dramatic increase, and that increase happened at the same time as we were seeing dramatic retreats in the location of the calving fronts of the glaciers, and an increase in their flow speed," she says. "The earthquakes are very closely associated with large-scale ice loss events."

In other words, the huge chunks of ice breaking off from the glaciers and entering the oceans are large enough to generate a seismic signal that is sent through the Earth. They are happening more regularly and, when they occur, it appears that the glacier speeds up even more.

The scientists rightly wrap their latest observations in caution. Their studies are still in their infancy. Some of the effects they are observing may be short-term.

The Greenland ice sheet has survived natural warmer periods in history, the last about 120,000 years ago, although it was much smaller then than it is now. Those still sceptical of the scientific consensus over climate change should perhaps listen to the voices of those who could not be accused of having anything to gain from talking up climate change.

Inuit warnings

Arne Sorensen, a specialist ice navigator on Arctic Sunrise, began sailing the Arctic in the 1970s. Journeys around Greenland's coast that would take three weeks in the 1970s because of sea ice now take a day. He pays heed to the observations of the Inuit. "If you talk to people who live close to nature and they tell you this is unusual and this is not something they have noticed before, then I really put emphasis on that," he says. Paakkanna Ignatiussen, 52, has been hunting seals since he was 13. His grandparents travelled less than a mile to hunt; he must go more than 60 miles because the sea ice disappears earlier – and with it the seals. "It's hard to see the ice go back. In the old days when we got ice it was only ice. Today it is more like slush," he says. "In 10 years there will be no traditional hunting. The weather is the reason."

The stench of rotting seal flesh wafts from a bag in the porch of his house in Tasiilaq as Ignatiussen's wife, Ane, remarks that, "the seasons are upside down."

Local people are acutely aware of how the weather is changing animal behaviour. Browsing the guns for sale in the supermarket in Tasiilaq (you don't need a licence for a gun here), Axel Hansen says more hungry polar bears prowl around the town these days. Like the hunters, the bears can't find seals when there is so little sea ice. And the fjords are filled with so many icebergs that local people find it hard to hunt whales there.

Westerners may shrug at the decline of traditional hunting but, in a sense, we all live on the Greenland ice sheet now. Its fate is our fate. The scientists swarming over this ancient mass of ice, trying to understand how it will be transformed in a warming world, and how it will transform us, are wary of making political comments about how our leaders should plan for one metre of sea level rise, and what drastic steps must be taken to cut carbon emissions. But some scientists are so astounded by the changes they are recording that they are moved to speak out.

What, I ask Hamilton, would he say to Barack Obama if he could spend 10 minutes with the US president standing on Helheim glacier?

"Without knowing anything about what is going on, you just have to look at the glacier to know something huge is happening here," says the glaciologist. "We can't as a scientific community keep up with the pace of changes, let alone explain why they are happening.

"If I was, God forbid, the leader of the free world, I would implement some changes to deal with the maximum risk that we might reasonably expect to encounter, rather than always planning for the minimum. We won't know the consequences of not doing that until it's way too late. Even as a politician on a four-year elected cycle, you can't morally leave someone with that problem."

Link: http://www.guardian.co.uk/environment/2009/sep/01/sermilik-fjord-greenland-global-warming

Written by fatih al-farahat in , , ,


R. Kwok et al., J. Geophys. Res., 114 (2009): Thinning and volume loss of the Arctic Ocean sea ice cover: 2003–2008

Journal of Geophysical Research - Oceans, 114 (2009) C07005; doi: 10.1029/2009JC005312.

Thinning and volume loss of the Arctic Ocean sea ice cover: 2003–2008

R. Kwok, G. F. Cunningham (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, U.S.A.), M. Wensnahan (Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, U.S.A.), I. Rigor (Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, U.S.A.), H. J. Zwally (Cryospheric Sciences Branch, NASA Goddard Space Flight Center, Greenbelt, MD, U.S.A.), and D. Yi (SGT, Inc., NASA Goddard Space Flight Center, Greenbelt, MD, U.S.A.)

Abstract

We present our best estimate of the thickness and volume of the Arctic Ocean ice cover from 10 Ice, Cloud, and land Elevation Satellite (ICESat) campaigns that span a 5-year period between 2003 and 2008. Derived ice drafts are consistently within 0.5 m of those from a submarine cruise in mid-November of 2005 and 4 years of ice draft profiles from moorings in the Chukchi and Beaufort seas. Along with a more than 42% decrease in multi-year (MY) ice coverage since 2005, there was a remarkable thinning of ∼0.6 m in MY ice thickness over 4 years. In contrast, the average thickness of the seasonal ice in midwinter (∼2 m), which covered more than two-thirds of the Arctic Ocean in 2007, exhibited a negligible trend. Average winter sea ice volume over the period, weighted by a loss of ∼3000 km3 between 2007 and 2008, was ∼14,000 km3. The total MY ice volume in the winter has experienced a net loss of 6300 km3 (>40%) in the 4 years since 2005, while the first-year ice cover gained volume owing to increased overall area coverage. The overall decline in volume and thickness are explained almost entirely by changes in the MY ice cover. Combined with a large decline in MY ice coverage over this short record, there is a reversal in the volumetric and areal contributions of the two ice types to the total volume and area of the Arctic Ocean ice cover. Seasonal ice, having surpassed that of MY ice in winter area coverage and volume, became the dominant ice type. It seems that the near-zero replenishment of the MY ice cover after the summers of 2005 and 2007, an imbalance in the cycle of replenishment and ice export, has played a significant role in the loss of Arctic sea ice volume over the ICESat record.

(Received 2 February 2009, accepted 22 April 2009, published 7 July 2009.)

Kwok, R., G. F. Cunningham, M. Wensnahan, I. Rigor, H. J. Zwally, & D. Yi (2009), Thinning and volume loss of the Arctic Ocean sea ice cover: 2003–2008, Journal of Geophysical Research, 114 (2009) C07005; doi:10.1029/2009JC005312.

Link to abstract: http://www.agu.org/pubs/crossref/2009/2009JC005312.shtml

Written by fatih al-farahat in , ,


NASA's JPL: New NASA ICESat Satellite Survey Reveals Dramatic Arctic Sea Ice Thinning

NEWS RELEASE: 2009-107 July 7, 2009

New NASA Satellite Survey Reveals Dramatic Arctic Sea Ice Thinning

PASADENA, Calif. – Arctic sea ice thinned dramatically between the winters of 2004 and 2008, with thin seasonal ice replacing thick older ice as the dominant type for the first time on record. The new results, based on data from a NASA Earth-orbiting spacecraft, provide further evidence for the rapid, ongoing transformation of the Arctic's ice cover.

Scientists from NASA and the University of Washington in Seattle conducted the most comprehensive survey to date using observations from NASA's Ice, Cloud and land Elevation Satellite, known as ICESat, to make the first basin-wide estimate of the thickness and volume of the Arctic Ocean's ice cover. Ron Kwok of NASA's Jet Propulsion Laboratory in Pasadena, Calif., led the research team, which published its findings July 7 in the Journal of Geophysical Research-Oceans.

The Arctic ice cap grows each winter as the sun sets for several months and intense cold ensues. In the summer, wind and ocean currents cause some of the ice naturally to flow out of the Arctic, while much of it melts in place. But not all of the Arctic ice melts each summer; the thicker, older ice is more likely to survive. Seasonal sea ice usually reaches about 2 m (6 ft.) in thickness, while multi-year ice averages 3 m (9 ft.).

Using ICESat measurements, scientists found that overall Arctic sea ice thinned about 0.17 m (7 in.) a year, for a total of 0.68 m (2.2 ft.) over four winters. The total area covered by the thicker, older "multi-year" ice that has survived one or more summers shrank by 42%.

Previously, scientists relied only on measurements of area to determine how much of the Arctic Ocean is covered in ice, but ICESat makes it possible to monitor ice thickness and volume changes over the entire Arctic Ocean for the first time. The results give scientists a better understanding of the regional distribution of ice and provide better insight into what is happening in the Arctic.

"Ice volume allows us to calculate annual ice production and gives us an inventory of the freshwater and total ice mass stored in Arctic sea ice," said Kwok. "Even in years when the overall extent of sea ice remains stable or grows slightly, the thickness and volume of the ice cover is continuing to decline, making the ice more vulnerable to continued shrinkage. Our data will help scientists better understand how fast the volume of Arctic ice is decreasing and how soon we might see a nearly ice-free Arctic in the summer."

In recent years, the amount of ice replaced in the winter has not been sufficient to offset summer ice losses. The result is more open water in summer, which then absorbs more heat, warming the ocean and further melting the ice. Between 2004 and 2008, multi-year ice cover shrank 1.54 million km² (595,000 sq. miles) -- nearly the size of Alaska's land area.

During the study period, the relative contributions of the two ice types to the total volume of the Arctic's ice cover were reversed. In 2003, 62% of the Arctic's total ice volume was stored in multi-year ice, with 38% stored in first-year seasonal ice. By 2008, 68% of the total ice volume was first-year ice, with 32% multi-year ice.

"One of the main things that has been missing from information about what is happening with sea ice is comprehensive data about ice thickness," said Jay Zwally, study co-author and ICESat project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "U.S. Navy submarines provide a long-term, high-resolution record of ice thickness over only parts of the Arctic. The submarine data agree with the ICESat measurements, giving us great confidence in satellites as a way of monitoring thickness across the whole Arctic Basin."

The research team attributes the changes in the overall thickness and volume of Arctic Ocean sea ice to the recent warming and anomalies in patterns of sea ice circulation.

"The near-zero replenishment of the multi-year ice cover, combined with unusual exports of ice out of the Arctic after the summers of 2005 and 2007, have both played significant roles in the loss of Arctic sea ice volume over the ICESat record," said Kwok.

For images of the Arctic sea ice decline, visit: http://www.nasa.gov/topics/earth/features/icesat-20090707.html .

For more information about ICESat, visit: http://icesat.gsfc.nasa.gov .

For more information about NASA and agency programs, visit: http://www.nasa.gov .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

Alan Buis (818) 354-0474, Jet Propulsion Laboratory, Pasadena, CA. Alan.buis@jpl.nasa.gov

Steve Cole (202) 358-0918, NASA Headquarters, Washington. Stephen.e.cole@nasa.gov

-end-

Written by fatih al-farahat in , , ,


Arctic Ice Melting at Alarming Pace

Arctic Ice Melting at Alarming Pace

by Thomas Omestad – Wed Dec 17, 2:11 pm ET

New studies being released this week indicate that climate change is exerting massive and worrying change on the Arctic region--reducing the volume of ice, releasing methane gas into the atmosphere, and dramatically raising air temperatures in some parts of the Arctic.

The findings will give fresh urgency to international deliberations on the next global climate change pact planned for December 2009 in Copenhagen. The studies also will likely intensify international pressure on the incoming Obama administration to embrace major cuts in the emission of greenhouse gases in an effort to help stabilize global temperatures.

NASA scientists will reveal that more than 2 trillion tons of land ice on Greenland and Alaska, along with in Antarctica, have melted since 2003. Satellite measurements suggest half of the loss has come from Greenland. Melting of land ice slowly raises sea levels.

The World Meteorological Organization, a United Nations agency, is also reporting that ice volume in the Arctic this year fell to its lowest recorded level to date.

Experts from the National Snow and Ice Data Center in Colorado will further reveal that temperatures this fall in some Arctic areas north of Alaska were 9 or 10 degrees Fahrenheit above average. The long-predicted phenomenon is known as "Arctic amplification." As global air temperatures increase, the Arctic tends to show greater changes because the ice pack that once reflected solar heat is reduced in scope. More heat is therefore absorbed. The study is being discussed at a meeting of the American Geophysical Union in San Francisco.

Says NASA climate scientist H. Jay Zwally, "We may be going through a tipping point [in climate change] right now." He adds, "Once the ice goes away, you're absorbing much more heat." The Arctic, he says, is showing two to three times the overall global rate of temperature increase.

The Arctic, adds Mark Serreze of the National Snow and Ice Data Center, plays a key role in global weather. "You're starting to fundamentally change the Arctic refrigerator," he says. "You're fiddling with the dials on that refrigerator--maybe changing weather patterns well beyond the Arctic."

The changes in the Arctic, analysts predict, will launch an unprecedented era of oil and gas exploration, mineral exploitation, shipping, fishing, and tourism--all placing a fragile ecosystem at risk. One result of the new opportunities could begeopolitical competition among the five countries with Arctic Ocean frontage: Russia, the United States, Canada, Denmark (through Greenland), and Norway.

The changes are also being documented by visitors to the Arctic. Minnesota polar explorer Will Steger this June encountered high, jagged blocks of ice near Canada's Ellesmere Island that ultimately forced his team to change its plans. The ice blocks were apparently from ice shelves that had broken off.

"We were traveling over the ruins of the Arctic Ocean," Steger said. "Five, 10, 20 years from now, when we see this picture clearly, we won't believe what we've done."

Link to article: http://news.yahoo.com/s/usnews/20081217/ts_usnews/arcticicemeltingatalarmingpace

Written by fatih al-farahat in , , ,


At top of Greenland, new worrisome cracks in ice

BLOGGER'S NOTE: SEE ALSO THESE POSTS WITH SATELLITE PHOTOS OF THE BREAKUP, CRACKS, AND JAKOBSHAVN GLACIER:

http://climatechangepsychology.blogspot.com/2008/08/northern-greenlands-petermann-glacier.html

http://climatechangepsychology.blogspot.com/2008/08/jakobshavn-glacier-retreats-to-new.html

by Seth Borenstein, AP Science Writer, 21 August 2008

WASHINGTON — In northern Greenland, a part of the Arctic that had seemed immune from global warming, new satellite images show a growing giant crack and an 11-square-mile chunk of ice hemorrhaging off a major glacier, scientists said Thursday.

And that's led the university professor who spotted the wounds in the massive Petermann glacier to predict disintegration of a major portion of the Northern Hemisphere's largest floating glacier within the year.

If it does worsen and other northern Greenland glaciers melt faster, then it could speed up sea level rise, already increasing because of melt in southern Greenland.

The crack is 7 miles long and about half a mile wide. It is about half the width of the 500 square mile floating part of the glacier. Other smaller fractures can be seen in images of the ice tongue, a long narrow sliver of the glacier.

"The pictures speak for themselves," said Jason Box, a glacier expert at the Byrd Polar Research Center at Ohio State University who spotted the changes while studying new satellite images. "This crack is moving, and moving closer and closer to the front. It's just a matter of time till a much larger piece is going to break off.... It is imminent."

The chunk that came off the glacier between July 10 and July 24 is about half the size of Manhattan and doesn't worry Box as much as the cracks. The Petermann glacier had a larger breakaway ice chunk in 2000. But the overall picture worries some scientists.

"As we see this phenomenon occurring further and further north — and Petermann is as far north as you can get — it certainly adds to the concern," said Waleed Abdalati, director of the Center for the Study of Earth from Space at the University of Colorado.

The question that now faces scientists is: Are the fractures part of normal glacier stress or are they the beginning of the effects of global warming?

"It certainly is a major event," said NASA ice scientist Jay Zwally in a telephone interview from a conference on glaciers in Ireland. "It's a signal but we don't know what it means."

It is too early to say it is clearly global warming, Zwally said. Scientists don't like to attribute single events to global warming, but often say such events fit a pattern.

University of Colorado professor Konrad Steffen, who returned from Greenland Wednesday and has studied the Petermann glacier in the past, said that what Box saw is not too different from what he saw in the 1990s: "The crack is not alarming... I would say it is normal."

However, scientists note that it fits with the trend of melting glacial ice they first saw in the southern part of the massive island and seems to be marching north with time. Big cracks and breakaway pieces are foreboding signs of what's ahead.

Further south in Greenland, Box's satellite images show that the Jakobshavn glacier, the fastest retreating glacier in the world, set new records for how far it has moved inland.

That concerns Colorado's Abdalati: "It could go back for miles and miles and there's no real mechanism to stop it."

Ohio State University images and data: http://bprc.osu.edu/MODIS/

Link to article: http://news.yahoo.com/s/ap/20080821/ap_on_sc/sci_greenland_glaciers



BLOGGER'S NOTE: rather than adding a new post, I am just pasting in a new bit here:

The scientists also said that the margin of the massive Jakobshavn glacier has retreated inland further than at any time in the past 150 years of observation.

They believe, moreover, that it has not retreated so far inland "in at least the last 4,000 to 6,000 years."

Jakobshavn's northern branch has broken up in the last several weeks and the glacier has lost at least 10 square kilometers (three square miles) since the end of the last melt season, the researchers said.

About one-tenth of Greenland's icebergs come from Jakobshavn, making it the island's most productive glacier.

The glacier lost 94 square kilometers (36 square miles) of ice field betwen 2001 and 2005, a phenomenon that drew international attention to the impact of global warming on glaciers, the scientists said.

Meanwhile, the roof of an ice tunnel in Argentina's gigantic Perito Morena glacier, 60 meters high and weighing thousands of tonnes, suddenly collapsed July 8, a phenomenon unheard of in the dead of the southern hemisphere winter.

Scientists blamed global warming for the collapse.

Link: http://news.yahoo.com/s/afp/20080821/sc_afp/usenvironmentclimategreenland_080821233046