The Link Between Receding Glaciers and Natural Disasters
Uploaded on Sep 17, 2010 Episode: 1392, Air Date: 7 July 2010
http://SupremeMasterTV.com
PLANET EARTH: OUR LOVING HOME
With climatologist Veli Albert Kallio
Showing posts with label Greenland. Show all posts
Showing posts with label Greenland. Show all posts
Monday, June 9, 2014
The Link Between Receding Glaciers and Natural Disasters
The Link Between Receding Glaciers and Natural Disasters
Uploaded on Sep 17, 2010 Episode: 1392, Air Date: 7 July 2010
http://SupremeMasterTV.com
Thursday, June 5, 2014
Thursday, May 22, 2014
Greenland Ice Sheet & Northern Polar Jet Stream - Peter Sinclair
Climate Change 2013: Greenland Ice Sheet & Northern Polar Jet Stream - Peter Sinclair
Published on Jul 23, 2013
New climate change science explained by Peter Sinclair, just back from a scientific expedition to the Greenland Ice Sheet. Sinclair explains the feedback effects of melting ice, and the impacts on the northern polar jet stream and mean sea level.
Sinclair leads educators on climate science and created the Climate Denial Crock of the Week video series, which tackles myths about global warming, the greenhouse effect, and carbon dioxide pollution.
Sinclair proposes moving towards wind and solar as the key to jobs and future energy needs.
Tuesday, May 20, 2014
Deep Valleys Under Greenland Mean Higher Sea-Level Rise
Deep Valleys Under Greenland Mean Higher Sea-Level Rise
The deep grooves under the massive ice sheet could facilitate flow into the ocean, which suggests sea level rise estimates for this century need to be revised upwards
May 19, 2014 Christa Marshall and ClimateWire
In a finding offering another sea-level rise warning, scientists yesterday reported the existence of deep, canyon-like valleys in the bedrock underneath the Greenland ice sheet that could facilitate the extensive flow of ice into the ocean.
The analysis of Greenland's topography from NASA and University of California, Irvine, scientists suggests that estimates of Greenland's contribution to sea-level rise may have to be revised upward for this century and beyond. It also follows on the heels of earlier studies this year indicating that parts of Greenland and Antarctica may be far more vulnerable to warming ocean temperatures than previously believed.
"For sure, this will have a strong impact on future modeling of sea-level rise. We just don't know how much yet," said Mathieu Morlighem, associate project scientist at the University of California, Irvine, and lead author of the study, published in Nature Geoscience.
Many older models of Greenland assumed that its massive ice sheet sat on bedrock that was relatively flat, even though scientists did not know the full thickness of the ice. There also was an assumption that many melting glaciers on the ice sheet's periphery eventually would retreat to higher ground on this flat bedrock, cutting off contact with warm ocean waters and slowing down the ice sheet's shedding.
The discovery of the valleys—which stretch more than 100 kilometers (62.1 miles) into Greenland's interior in some cases—suggests instead that some of Greenland's most vulnerable outlet glaciers will just keep retreating and retreating along deep canyons. About 100 of the valleys sit far below sea level and are attached to glaciers on Greenland's periphery that already are shedding ice, like Jakobshavn Isbræ glacier, said Morlighem.
That means that as these glaciers retreat, their fronts will remain in contact with warm ocean water that melts ice, rather than hitting higher ground anytime soon. "As long as the vertical face of the glaciers remains in contact with the ocean, they are vulnerable," said Morlighem.
Models will need to be recalibrated
"We once thought it would be decades for some of the glaciers to reach higher ground, and now it's maybe a thousand years for the longest troughs," he added. Previous mapping often did not capture the depth of the valleys, when their existence was known at all, he said.
The bed underneath Jakobshavn Isbræ glacier, for instance, is "several hundreds of meters deeper than in previous reconstructions," the paper states. Many of the discovered valleys also stretch farther into the interior of the ice sheet than previous measurements.
The paper reports that 107 marine-terminating glaciers are underlain by fjords extending on average 67 kilometers (41.6 miles) inland below sea level, a number 300 percent greater than one previous assessment. If these glaciers retreat at a similar rate to what they did in the past decade, 30 of them would disconnect from warm ocean waters by the end of the century with that kind of travel distance, it says.
"The beds at the margins of the ice sheet ... are probably one of the least explored parts of Earth's surface," said Ian Howat, a glaciologist at Ohio State University who did not participate in the research. He called the paper a "major breakthrough" culminating years of careful work that would give scientists much more data for assessing Greenland's changes.
"This is going to prompt a flurry of rerunning of models" projecting future sea-level rise, he said.
Andrew Shepherd, a professor of Earth observation and Greenland expert at the University of Leeds, said the new data are "robust and will be trusted by the wider scientific community." Like Howat, he said the findings could have major implications for predictions of how the Greenland ice sheet evolves.
"This could lead to an upwards revision of predicted ice losses," he said.
Ice thickness is deceptively hard to measure, Howat said. In many locations, the ice is deep and wet, and the surface is crevassed and rough, making it difficult to fully assess with radar, he noted. It's taken decades to determine "basic things" like where the interface between underlying rock and ice is.
How high? An ongoing debate
Since the 1970s, there have been measurements of Greenland's ice thickness via radar pinging of the interface between ice and underlying foundation. The problem with those measurements, Morlighem said, is that they were scattered, and the data were limited to areas where there were flights over the ice sheet.
There had been some previous detections of the depths underneath the ice, but there was little understanding whether it was a limited depression or part of a much more extensive canyon, he said. The researchers used a range of data of other ice sheet dynamics, like snowfall and surface velocity of ice, to create a more detailed overview of Greenland's topography.
Greenland's ultimate contribution to sea-level rise is a subject of ongoing debate among scientists. A report from the Intergovernmental Panel on Climate Change last year found that between 1993 and 2010, the Greenland ice sheet contributed less than 10 percent to global sea-level rise. Thermal ocean expansion of the ocean and glaciers contributed the most.
Six or seven years ago, some initial projections suggested that sea levels could rise quite high by 2100, said Howart. Subsequent papers from multiple scientists pulled initial numbers far back and reported figures closer to 3 feet, he said. Now the trend may be going in the other direction with new data about ice sheets, although a lot more research is needed, he said.
Last week, scientists reported that glaciers in West Antarctica may be on a pathway of irreversible decline, although it could take centuries for their collapse (ClimateWire, May 13). In March, another paper reported that northeast Greenland—long considered relatively stable—was shedding significant amounts of ice (ClimateWire, March 17).
Shepherd said, though, that there still is still a lot of uncertainty about how much additional melt in some locations of the Greenland ice sheet will actually be lost to the ocean.
Inland, the surface of Greenland is made up of low-density firn, something halfway between snow and solid ice, he noted. In these places, meltwater can percolate through the firn and refreeze.
"It's not easy to measure or model how much additional meltwater refreezes rather than runs off into the ocean," he said.
The analysis of Greenland's topography from NASA and University of California, Irvine, scientists suggests that estimates of Greenland's contribution to sea-level rise may have to be revised upward for this century and beyond. It also follows on the heels of earlier studies this year indicating that parts of Greenland and Antarctica may be far more vulnerable to warming ocean temperatures than previously believed.
"For sure, this will have a strong impact on future modeling of sea-level rise. We just don't know how much yet," said Mathieu Morlighem, associate project scientist at the University of California, Irvine, and lead author of the study, published in Nature Geoscience.
Many older models of Greenland assumed that its massive ice sheet sat on bedrock that was relatively flat, even though scientists did not know the full thickness of the ice. There also was an assumption that many melting glaciers on the ice sheet's periphery eventually would retreat to higher ground on this flat bedrock, cutting off contact with warm ocean waters and slowing down the ice sheet's shedding.
The discovery of the valleys—which stretch more than 100 kilometers (62.1 miles) into Greenland's interior in some cases—suggests instead that some of Greenland's most vulnerable outlet glaciers will just keep retreating and retreating along deep canyons. About 100 of the valleys sit far below sea level and are attached to glaciers on Greenland's periphery that already are shedding ice, like Jakobshavn Isbræ glacier, said Morlighem.
That means that as these glaciers retreat, their fronts will remain in contact with warm ocean water that melts ice, rather than hitting higher ground anytime soon. "As long as the vertical face of the glaciers remains in contact with the ocean, they are vulnerable," said Morlighem.
Models will need to be recalibrated
"We once thought it would be decades for some of the glaciers to reach higher ground, and now it's maybe a thousand years for the longest troughs," he added. Previous mapping often did not capture the depth of the valleys, when their existence was known at all, he said.
The bed underneath Jakobshavn Isbræ glacier, for instance, is "several hundreds of meters deeper than in previous reconstructions," the paper states. Many of the discovered valleys also stretch farther into the interior of the ice sheet than previous measurements.
The paper reports that 107 marine-terminating glaciers are underlain by fjords extending on average 67 kilometers (41.6 miles) inland below sea level, a number 300 percent greater than one previous assessment. If these glaciers retreat at a similar rate to what they did in the past decade, 30 of them would disconnect from warm ocean waters by the end of the century with that kind of travel distance, it says.
"The beds at the margins of the ice sheet ... are probably one of the least explored parts of Earth's surface," said Ian Howat, a glaciologist at Ohio State University who did not participate in the research. He called the paper a "major breakthrough" culminating years of careful work that would give scientists much more data for assessing Greenland's changes.
"This is going to prompt a flurry of rerunning of models" projecting future sea-level rise, he said.
Andrew Shepherd, a professor of Earth observation and Greenland expert at the University of Leeds, said the new data are "robust and will be trusted by the wider scientific community." Like Howat, he said the findings could have major implications for predictions of how the Greenland ice sheet evolves.
"This could lead to an upwards revision of predicted ice losses," he said.
Ice thickness is deceptively hard to measure, Howat said. In many locations, the ice is deep and wet, and the surface is crevassed and rough, making it difficult to fully assess with radar, he noted. It's taken decades to determine "basic things" like where the interface between underlying rock and ice is.
How high? An ongoing debate
Since the 1970s, there have been measurements of Greenland's ice thickness via radar pinging of the interface between ice and underlying foundation. The problem with those measurements, Morlighem said, is that they were scattered, and the data were limited to areas where there were flights over the ice sheet.
There had been some previous detections of the depths underneath the ice, but there was little understanding whether it was a limited depression or part of a much more extensive canyon, he said. The researchers used a range of data of other ice sheet dynamics, like snowfall and surface velocity of ice, to create a more detailed overview of Greenland's topography.
Greenland's ultimate contribution to sea-level rise is a subject of ongoing debate among scientists. A report from the Intergovernmental Panel on Climate Change last year found that between 1993 and 2010, the Greenland ice sheet contributed less than 10 percent to global sea-level rise. Thermal ocean expansion of the ocean and glaciers contributed the most.
Six or seven years ago, some initial projections suggested that sea levels could rise quite high by 2100, said Howart. Subsequent papers from multiple scientists pulled initial numbers far back and reported figures closer to 3 feet, he said. Now the trend may be going in the other direction with new data about ice sheets, although a lot more research is needed, he said.
Last week, scientists reported that glaciers in West Antarctica may be on a pathway of irreversible decline, although it could take centuries for their collapse (ClimateWire, May 13). In March, another paper reported that northeast Greenland—long considered relatively stable—was shedding significant amounts of ice (ClimateWire, March 17).
Shepherd said, though, that there still is still a lot of uncertainty about how much additional melt in some locations of the Greenland ice sheet will actually be lost to the ocean.
Inland, the surface of Greenland is made up of low-density firn, something halfway between snow and solid ice, he noted. In these places, meltwater can percolate through the firn and refreeze.
"It's not easy to measure or model how much additional meltwater refreezes rather than runs off into the ocean," he said.
Saturday, April 26, 2014
BBC Earth The Power Of The Planet - Ice
BBC Earth The Power Of The Planet - Ice
Uploaded on Sep 18, 2011
Monday, March 24, 2014
Melting Point Greenland
Melting Point Greenland
Published on Dec 21, 2012
2013 National Headliners Award First Prize Environmental Reporting:
In the summer of 2012, one of the most vital ecosystems on earth, the Greenland ice sheet, experienced a meltdown that alarmed scientists the world over. Greenland is an island encased in ice and it's the world's second largest ice sheet after Antarctica. That summer, ninety-seven percent of the surface ice melted. "Melting Point" is a comprehensive examination of this event. Videographer Snorre Wik shot the footage under tough conditions—hauling around 1,000 pounds of gear by helicopter, by SUV (on Greenland's mostly dirt roads) and out on a thinning ice sheet made treacherous by the sun. Wik improvised to get the shots he needed—lying on helicopter floors to steady his camera without a gyro-stabilized mount, or holding his DSLR by hand on the dashboard of SUVs. His efforts were both breathtaking and disturbing.
Additionally, Jens Christiansson is responsible for filming the destruction of the Watson River bridge. Marco Tedesco and his team of researchers filmed the moulins and ice cap during the record meltoff.
Monday, March 17, 2014
Sea Levels To Rise More Than Expected Due To Warming-Driven Surge In Greenland Ice Loss
Sea Levels To Rise More Than Expected Due To Warming-Driven Surge In Greenland Ice Loss
JOE ROMM AND JEFF SPROSS MARCH 17, 2014
JOE ROMM AND JEFF SPROSS MARCH 17, 2014
Greenland’s contribution to global sea level has soared in the past two decades. An important new study finds that the massive northeastern part of the ice sheet, previously thought to be stable, has begun shedding ice. If this trend continues — and researchers say “a self-perpetuating feedback process may have been triggered” — actual sea level rise this century will likely be higher than many current models had projected.
Covering 660,000 square miles — roughly 80 percent of the country — Greenland’s ice sheet is second only in size to Antarctica’s. Scientists estimate that melting from the ice sheet as a whole has accounted for about 16 percent of sea level rise every year for the last two decades.
Research had also long suggested the northeastern portion of the ice sheet was stable. As a result, it was largely left out of the models used to anticipate future sea level rise.
But the new study, “Sustained mass loss of the northeast Greenland ice sheet triggered by regional warming,” published in Nature Climate Change (subs. req’d), suggests the northeastern portion began melting rapidly around 2003. And after first jumping from an ice loss rate of zero to about 10 billion metric tons per year, it’s now approaching 15 or 20 billion metric tons per year and may well keep accelerating.
“Most projections of the future behaviour of the ice sheet have no, or little, contribution from this part of Greenland,” said Professor Jeremy Bamber of Bristol University, a co-author of the study. “But these new results suggest that this region is sensitive to changes in climate and has the potential to contribute significantly now and in the future.”
The team arrived at their conclusion using a combination of surface elevation data from airplanes and four different satellites, along with a GPS-linked network of 50 stations located along the coast of Greenland’s ice sheet. The overall collection of data spanned 1978 to 2012 and was used to essentially weigh the ice sheet’s mass.
Specifically, the study suggests a series of particularly warm summers leading up to 2003 — bringing higher temperatures in both the atmosphere and the surrounding ocean — triggered the speed up in melting.
Much of the ice melt was also historically held in check by an ice barrier at the coast, which itself is now melting as well, allowing the entire system to speed up. Coauthor Prof. Kurt Kjær explains that there was “a clear acceleration in loss of mass after 2006.” He warns:
Another cause for concern is Greenland’s ice streams. These are essentially “rivers” of ice that drain ice sheets in much the same way networks of streams and rivers drain water from huge areas on land. And the drainage basin for Greenland’s northeast portion is enormous — covering 16 percent of the ice sheet and reaching 373 miles inland, all the way to the center of the country.
Covering 660,000 square miles — roughly 80 percent of the country — Greenland’s ice sheet is second only in size to Antarctica’s. Scientists estimate that melting from the ice sheet as a whole has accounted for about 16 percent of sea level rise every year for the last two decades.
Research had also long suggested the northeastern portion of the ice sheet was stable. As a result, it was largely left out of the models used to anticipate future sea level rise.
But the new study, “Sustained mass loss of the northeast Greenland ice sheet triggered by regional warming,” published in Nature Climate Change (subs. req’d), suggests the northeastern portion began melting rapidly around 2003. And after first jumping from an ice loss rate of zero to about 10 billion metric tons per year, it’s now approaching 15 or 20 billion metric tons per year and may well keep accelerating.
“Most projections of the future behaviour of the ice sheet have no, or little, contribution from this part of Greenland,” said Professor Jeremy Bamber of Bristol University, a co-author of the study. “But these new results suggest that this region is sensitive to changes in climate and has the potential to contribute significantly now and in the future.”
The team arrived at their conclusion using a combination of surface elevation data from airplanes and four different satellites, along with a GPS-linked network of 50 stations located along the coast of Greenland’s ice sheet. The overall collection of data spanned 1978 to 2012 and was used to essentially weigh the ice sheet’s mass.
Specifically, the study suggests a series of particularly warm summers leading up to 2003 — bringing higher temperatures in both the atmosphere and the surrounding ocean — triggered the speed up in melting.
Much of the ice melt was also historically held in check by an ice barrier at the coast, which itself is now melting as well, allowing the entire system to speed up. Coauthor Prof. Kurt Kjær explains that there was “a clear acceleration in loss of mass after 2006.” He warns:
“This acceleration has since continued and even increased. The increased loss of mass can be explained by a combination of warmer air in the summer and a rise in sea temperatures. This has reduced the extent of sea ice, which otherwise helps to stabilize the glaciers. Our results also demonstrate that after 2009 both air and, in particular, sea temperatures have returned to the level from before 2006. At the same time, the sea ice has maintained its previous extent, although the loss in mass has increased even further. This indicates that a self-perpetuating feedback process may have been triggered….”The loss of Arctic sea ice creates a well-known amplifying feedback whereby white ice is replaced by the dark blue sea, which absorbs far more sunlight and hence far more solar energy. Back in 2011, scientists warned that the Greenland ice sheet “could undergo a self-amplifying cycle of melting and warming“ that is “difficult to halt.” A 2012 study found we may be close to a “tipping point” in which “the summer melt area covers the entire land mass.”
Another cause for concern is Greenland’s ice streams. These are essentially “rivers” of ice that drain ice sheets in much the same way networks of streams and rivers drain water from huge areas on land. And the drainage basin for Greenland’s northeast portion is enormous — covering 16 percent of the ice sheet and reaching 373 miles inland, all the way to the center of the country.
Regional warming has triggered rapid ice loss in a vast portion of the northeastern Greenland Ice Sheet (NEGIS). Red indicates the fastest melting. (Via Ohio State)
“This implies that changes at the margin can affect the mass balance deep in the center of the ice sheet,” said Shfaqat Abbas Khan, a senior researcher at the National Space Institute at the Technical University of Denmark, and the leader of the research team. “Furthermore, due to the huge size of the northeast Greenland ice stream, it has the potential of significantly changing the total mass balance of the ice sheet in the near future.”
In short, the research adds to the case that actual sea level rise in the future will be on the high end of the projections from the Intergovernmental Panel on Climate Change — which ranged from one to three feet by the end of the century. Other climate scientists have projected even higher numbers.
Most climate scientists and glaciologists that Climate Progress has spoken to in recent years have said humanity should plan for at least three feet of sea level rise this century — and considerably more than that if we stay on our current high-end emissions path.
Sunday, March 16, 2014
Study Says Climate Change Accelerating Greenland’s Ice Loss
Part of the glacial ice sheet that covers about 80 percent of the country is seen on July 17, 2013 on the Glacial Ice Sheet, Greenland.Joe Raedle—Getty ImagesNew research is upending scientists' long-held belief that Greenland's ice sheets are stable, showing instead that global climate change is melting the country's ice at a much faster rate than once believed, leading to an increase in the world's sea levels
Greenland’s ice sheet is rapidly melting in areas previously believed to be stable, leading to accelerated rises in global sea levels, according to a study published Sunday.
While scientists have been aware that climate change has caused Greenland’s ice sheet to thin for decades, melting in the sheet’s northeast region has been discovered for the first time, USA Todayreports. Ice loss in the northeast region of Greenland has nearly tripled since 2003, with the ice sheet retreating 12.4 miles over the past decade and losing 10 billion tons of ice per year from April 2003 to April 2012, according to the new study
The rapid change in the northeast region “surprised everyone,” said study co-author Michael Bevis, a professor of earth sciences at Ohio State University.
The loss of Greenland’s ice sheet has been a major contributor to global sea level rise over the past 20 years, accounting for one-sixth of the annual rise. As humans emit increasing quantities of carbon into the atmosphere, the atmosphere more readily absorbs sunlight, warming the planet and causing sea levels to rise. Ice deflects most sunlight from the earth’s surface, but water absorbs heat from the sun. This causes a positive feedback loop: as temperatures rise, more ice becomes water, causing the temperature to rise further and ice sheets like the one in Greenland to melt at an increasing pace.
Saturday, February 22, 2014
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