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May 20, 2013
Last July, something unprecedented in the 34-year satellite record happened: 98 percent of the Greenland Ice Sheet’s surface melted, compared to roughly 50 percent during an average summer. Snow that usually stays frozen and dry turned wet with melt water. Research led by the Cooperative Institute for Research in Environmental Sciences now shows last summer’s extreme melt could soon be the new normal.
“Greenland is warming rapidly, and such ice-sheet-wide, surface-melt events will occur more frequently over the next couple of decades,” said Dan McGrath, a University of Colorado Boulder doctoral student who works at CIRES. McGrath is lead author of a paper published online May 20 in Geophysical Research Letters and which reports a significant warming trend on the Greenland Ice Sheet.
A new study shows summer melt events on the Greenland Ice Sheet are increasing in frequency due to rising temperatures. Photo courtesy CIRES.
McGrath and his coauthors calculate that by 2025 ice-sheet-wide melt events will have a 50 percent chance of occurring each year. That would signal the loss of the last major dry-snow zone -- regions where the snow stays almost perpetually frozen -- in the Northern Hemisphere, McGrath said.
In the study, the researchers used air and snow temperature data from meteorological stations and boreholes to generate a 60-year record of air temperatures at the Summit research station, the highest and coldest station on the ice sheet.
From 1982 to 2011, near-surface temperatures increased by an average of 0.16 degrees Fahrenheit every year. “This is six times faster than the global average,” McGrath said.
The warming at Summit is also accelerating. From 1950 to 2011, the average rate of warming was 0.04 degrees F per year. But from 1992 to 2011, that number jumped to 0.22 degrees F per year.
The warming has had a dramatic effect on the ice sheet’s structure, the scientists report. The ice sheet’s ablation zone -- the lower parts that lose more snow and ice each year than they accumulate -- is expanding up the ice sheet by about 145 feet per year.
“This increases the area over which the ice sheet sheds mass while shrinking the zone that gains mass,” McGrath said. “That will have an obvious impact on the ice sheet’s mass balance.”
Additionally, the dry-snow line -- above which the snow doesn’t melt -- is migrating up the ice sheet by about 115 feet per year. “These zones are indicators of the health of the ice sheet,” McGrath said. “And the changes we are observing are an early but important sign that the ice sheet is in transition.”
The changes could increase the amount of solar radiation the ice sheet absorbs -- since wet snow reflects less sunlight than dry snow -- increasing the melt rate as well. It also could potentially speed up the ice sheet’s flow, though more work needs to be done to untangle these impacts.
These findings are supported by results from other researchers who have found that the ice sheet is losing more than 275 billion tons of ice per year -- equivalent to the weight of 750,000 Empire State Buildings. “This imbalance is making a significant contribution to sea-level rise,” McGrath said.
The summit of the Greenland Ice Sheet has experienced surface melt in the past, McGrath says. But the melt events in the past were rare, happening once every century or two -- in fact, only eight times in the last 1,500 years -- the exception rather than the norm. Now the norm is shifting toward a new, slushy set point.
“Progressive increases in surface melt have occurred throughout the satellite record, but the last decade has been exceptional,” McGrath said. “If each of these events keeps being so far above the average, the average will change to reflect that.”
The scientists’ findings come at a time when Arctic sea ice extent is also at record lows. “Ice-sheet-wide melting coupled with the loss of Arctic sea ice points to profound changes occurring to the Arctic climate system,” McGrath said. “These are not small, insignificant events we’re witnessing.”
NASA Cryospheric Sciences funded the research, with additional field logistical support provided by the National Science Foundation’s Office of Polar Programs. Co-authors include former CIRES Director Konrad Steffen, CIRES adjunct research associate William Colgan, former CIRES doctoral student Atsuhiro Muto, and current CIRES doctoral student Nicolas Bayou.
May 16, 2013
While 99 percent of Earth's land ice is locked up in the Greenland and Antarctic ice sheets, the remaining ice in the world's glaciers contributed just as much to sea rise as the two ice sheets combined from 2003 to 2009, says a new study led by Clark University and involving the University Colorado Boulder.
The new research found that all glacial regions lost mass from 2003 to 2009, with the biggest ice losses occurring in Arctic Canada, Alaska, coastal Greenland, the southern Andes and the Himalayas. The glaciers outside of the Greenland and Antarctic sheets lost an average of roughly 260 billion metric tons of ice annually during the study period, causing the oceans to rise 0.03 inches, or about 0.7 millimeters per year.
The study compared traditional ground measurements to satellite data from NASA's Ice, Cloud and Land Elevation Satellite, or ICESat, and the Gravity Recovery and Climate Experiment, or GRACE, missions to estimate ice loss for glaciers in all regions of the planet.
"For the first time, we've been able to very precisely constrain how much these glaciers as a whole are contributing to sea rise," said geography Assistant Professor Alex Gardner of Clark University in Worcester, Mass., lead study author. "These smaller ice bodies are currently losing about as much mass as the ice sheets."
A paper on the subject is being published in the May 17 issue of the journal Science.
"Because the global glacier ice mass is relatively small in comparison with the huge ice sheets covering Greenland and Antarctica, people tend to not worry about it," said CU-Boulder Professor Tad Pfeffer, a study co-author. "But it's like a little bucket with a huge hole in the bottom: it may not last for very long, just a century or two, but while there's ice in those glaciers, it's a major contributor to sea level rise," said Pfeffer, a glaciologist at CU-Boulder's Institute of Arctic and Alpine Research.
ICESat, which ceased operations in 2009, measured glacier changes using laser altimetry, which bounces laser pulses off the ice surface to determine changes in the height of ice cover. The GRACE satellite system, still operational, detects variations in Earth's gravity field resulting from changes in the planet's mass distribution, including ice displacements.
GRACE does not have a fine enough resolution and ICESat does not have sufficient sampling density to study small glaciers, but mass change estimates by the two satellite systems for large glaciated regions agree well, the scientists concluded.
"Because the two satellite techniques, ICESat and GRACE, are subject to completely different types of errors, the fact that their results are in such good agreement gives us increased confidence in those results," said CU-Boulder physics Professor John Wahr, a study co-author and fellow at the university's Cooperative Institute for Research in Environmental Sciences.
Ground-based estimates of glacier mass changes include measurements along a line from a glacier's summit to its edge, which are extrapolated over a glacier's entire area. Such measurements, while fairly accurate for individual glaciers, tend to cause scientists to overestimate ice loss when extrapolated over larger regions, including individual mountain ranges, according to the team.
Current estimates predict if all the glaciers in the world were to melt, they would raise sea level by about two feet. In contrast, an entire Greenland ice sheet melt would raise sea levels by about 20 feet, while if Antarctica lost its ice cover, sea levels would rise nearly 200 feet.
The study involved 16 researchers from 10 countries. In addition to Clark University and CU-Boulder, major research contributions came from the University of Michigan, the Scripps Institution of Oceanography in San Diego, Trent University in Ontario, Canada, and the University of Alaska Fairbanks.
Built by Ball Aerospace & Technologies in Boulder, NASA's ICESat satellite was successfully operated from the CU-Boulder campus by a team made up primarily of undergraduates from its launch in 2003 to its demise in 2009 when the science payload failed. The students participated in the unusual decommissioning of a functioning satellite in 2010, bringing the craft into Earth re-entry to burn up. ICESat's successor, ICESat-2, is slated for launch in 2016 by NASA.
May 13, 2013
For all the energy prospects bandied about concerning the Arctic – including a new White House strategy paper for the region – oil drilling in US Arctic waters has come to a temporary pause.
Three major oil companies with operations in the region have pulled out for the year, citing harsh weather and regulatory difficulties.
Home to an estimated 13 percent of the world's undiscovered oil resources and 30 percent of undiscovered natural gas, the Arctic is sure to lure them back. How they return is crucial. If energy companies can show it's possible to recover those resources responsibly, it will have enormous consequences – for those companies' balance sheets, for the diplomatic relations of the eight nations whose borders fall within the Arctic circle, and for the health of the planet.
"Interest in the Arctic is not waning," Kara Moriarty, executive director of the Alaska Oil and Gas Association, wrote in an e-mail. "In fact, the interest is as strong as ever. Companies are already planning for the 2014 season and are working diligently to have the right equipment and plans in place to be successful." The group represents companies responsible for the majority of oil and gas activities in Alaska.
May 9, 2013
AMHERST, Mass. – Analyses of the longest sediment core ever collected on land in the Arctic, recently completed by an international team led by Julie Brigham-Grette of the University of Massachusetts Amherst, provide “absolutely new knowledge” of Arctic climate from 2.2 to 3.6 million years ago and show that with estimated atmospheric carbon dioxide (CO2) similar to today’s levels, the Arctic was very warm, with no ice sheets.
“While existing geologic records from the Arctic contain important hints about this time period, what we are presenting is the most continuous archive of information about past climate change from the entire Arctic borderlands. As if reading a detective novel, we can go back in time and reconstruct how the Arctic evolved with only a few pages missing here and there,” says Brigham-Grette.
Results of analyses that provide “an exceptional window into environmental dynamics” never before possible were published this week in Science and have “major implications for understanding the pacing and context of how the Arctic transitioned from a forested landscape without ice sheets to the ice- and snow-covered land we know today,” she adds.
Their data come from analyzing sediment cores collected in the winter of 2009 from under ice-covered Lake El’gygytgyn, the oldest deep lake in the northeast Russian Arctic. “Lake E” was formed 3.6 million years ago when a huge meteorite hit the Earth and blasted out an 11-mile (18 km) wide crater. It has been collecting sediment layers ever since. Luckily for geoscientists, it lies in one of the few Arctic areas not eroded by continental glaciers, so a thick, continuous sediment record was left remarkably undisturbed. Cores from Lake E reach back in geologic time nearly 30 times farther than Greenland ice cores that cover the past 140,000 years.
May 7, 2013
U.S. Agriculture Secretary Tom Vilsack announced a grant for researching agriculture and the climate, during a visit to Wisconsin today.
Few industries depend on the climate as much as farming. Bad weather can spell disaster for crops and animals. So the U.S. Department of Agriculture is funding a $10-million climate research project that includes the University of Wisconsin (UW)-Madison. During a visit to the campus, Vilsack says a department study indicates that weather patterns are becoming more intense and more variable: “Two years ago there was too much water last year there wasn't enough water and now, it depends on where you are — you may have too much or too little.”
Other universities involved in the national project will examine how to make plants and animals more resilient. At UW-Madison, soil scientist Matt Ruark will research ways to make farm systems better manage carbon and nitrogen, by using alternative farming practices that reduce erosion.
Reduction in tillage; use of cover crops; timing and application of manure; the source of manure. Has it been processed? Has it been separated? Has it been digested? All of those things will be evaluated after they're applied to soil.”
Some farmers in the United States are trying to reduce how much energy they use and convert waste to energy with manure digestors. Vilsack recently extended a memorandum of understanding with the Innovation Center for U.S. Dairy. The long term goal of that agreement is to reduce greenhouse gas emissions 25 percent by 2020.
May 2, 2013
When we think of the companies and organizations concerned with climate change, we don't often think of major automakers. But maybe we should think again.
Yesterday, General Motors became the first automaker to sign onto the Climate Declaration, a statement drafted by Ceres and its Business for Innovative Climate & Energy Policy project.
Ceres is a nonprofit launched in the wake of the 1989 Exxon Valdez oil spill, and it boasts a fairly unique vision. Ceres believes that green, sustainable practices are consistent with good business practices -- in fact, the two are inseparable. Ceres builds coalitions among corporations, investors, and individuals to share that vision with the world.
One of Ceres' biggest projects to date is its Business for Innovative Climate & Energy Policy group, or BICEP, "an advocacy coalition of businesses committed to working with policy makers to pass meaningful energy and climate legislation enabling a rapid transition to a low-carbon, 21st century economy – an economy that will create new jobs and stimulate economic growth while stabilizing our planet’s fragile climate."
Waleed Abdalati, CU Professor of Geography featured in PBS News Hour article, “Antarctica’s Ice Paradox
May 1, 2013
It's no secret that the ice sheet is melting in Greenland. Last year, the Arctic ice cap shrunk to a record low, with only 24 percent of the Arctic Ocean covered by ice, a 50 percent drop from its 1979-2000 summer average. At the height of the 2012 summer, Greenland had experienced melting across 90 percent of its surface. For a journalist, it's an easy story to tell: temperatures climb, the ice shrinks.
But at the opposite end of the world, in Antarctica, the picture isn't quite as clear. Satellite images from 2012 showed that Antarctic sea ice reached its highest levels extent on record, evidence skeptics often point to as proof that climate change isn't happening. And for years, the East Antarctic ice sheet, which covers the majority of the continent, appeared to be stable or perhaps even gaining mass.
There are several reasons why changes in Antarctica are simply harder to explain than those in the Arctic, says Waleed Abdalati, professor of geography at the University of Colorado. The geography is different and data collection is challenging, he said. Plus, the climate and a large hole in the ozone layer have buffered large parts of the continent from warmer air.
"The fact that you have a large, tall, thick ice sheet situated at the South Pole creates a climate down there that tends to isolate it from the rest of the world," Abdalati said. "And it does that in large part by setting up a circulation pattern where winds blow around the perimeter of the continent and block warmer air from lower latitudes."
Unlike the Arctic, it has been almost impossible at times to collect data in Antarctica. Satellite data only dates back to 1979; research station data to the mid-1950s, in some areas. The ice sheet east of the Transantarctic mountains was less explored and less understood until recently; parts are still inaccessible. And throughout the continent, which is larger than the United States, the ice sheet varies dramatically, making the ice losses and gains more difficult to tease out, Abdalati said. Greenland, on the other hand is smaller, easier to access and has been therefore studied in greater detail.
April 29, 2013
Scientists monitoring global atmospheric carbon dioxide concentrations report that, for the first time in human history, CO2 levels could soon rise above 400 parts per million for a sustained period of time in much of the Northern Hemisphere.
Hourly readings have surpassed 400 ppm in the past week, but daily averages remain just below 400, reported The Guardian. Daily readings are expected to surpass 400 ppm in early May. They will reach their annual peak by mid-month.
The measurements come from the NOAA-operated Mauna Loa Observatory in Hawaii, which has maintained a continuous record of atmospheric CO2 concentrations since 1958. Records of earlier levels come from air bubbles inside Antarctic ice core samples.
"I wish it weren't true, but it looks like the world is going to blow through the 400-ppm level without losing a beat," said Scripps Institution geochemist Ralph Keeling in a press statement. Keeling's late father began taking the measurements which have come to form the "Keeling Curve."
"At this pace we'll hit 450 ppm within a few decades," he added.
The symbolic CO2 milestone comes amid an apparent slowdown from Obama on the climate and energy front, despite bold words at the outset of the president's second term.
Yet the Senate Finance Committee may soon take up discussion of a carbon tax, while Obama's former Climate Czar, Carol Browner, has suggested the White House will act on power plant emissions.
April 29, 2013
(Reuters) - Plants help to slow climate change by emitting gases as temperatures rise that lead to the formation of a sunshade of clouds over the planet, scientists said on Sunday.
The tiny sun-dimming effect could offset about one percent of warming worldwide and up to 30 percent locally such as over vast northern forests in Siberia, Canada or the Nordic nations, they wrote in the journal Nature Geoscience.
While proportionally small, some scientists said the study provided further evidence of the importance of protecting forests, which help to slow climate change by absorbing greenhouse gases as they grow and to preserve wildlife.
Observations of forests from 11 sites around the world showed that plants emitted tiny particles that float on the wind as temperatures warm and act as seeds for water droplets that create clouds, they wrote.
Clouds' white tops in turn reflect sunlight back into space and offset warming, they wrote.
The study focused on forests in Europe, North America, Russia and southern Africa. The effect is believed to be smaller over far hotter tropical forests such as in the Amazon or the Congo basin.
"It's a small effect - one percent is not much," said lead author Pauli Paasonen of the University of Helsinki and the International Institute for Applied Systems Analysis in Austria.
"If temperatures were to increase by 1 degree without this effect, they'd rise 0.99 degrees with it," he told Reuters of a study that included researchers in the United States, Canada, Germany, the Netherlands, South Africa, Hungary and Sweden.
April 22, 2013
Nearly 34 million years ago, the Earth underwent a transformation from a warm, high-carbon dioxide “greenhouse” state to a lower-CO2, variable climate similar to the modern “icehouse” world. Massive ice sheets grew across the Antarctic continent, major animal groups shifted, and ocean temperatures decreased by as much as 5 degrees.
But studies of how this drastic change affected temperatures on land have had mixed results. Some show no appreciable terrestrial climate change; others find cooling of up to 8 degrees and large changes in seasonality.
Now a group of American and British scientists have used a new chemical technique to measure the change in terrestrial temperature associated with this shift in global atmospheric CO2 concentrations.
Their results suggest a drop of as much as 10 degrees for fresh water during the warm season and 6 degrees for the atmosphere in the North Atlantic, giving further evidence that the concentration of atmospheric carbon dioxide and Earth’s surface temperature are inextricably linked.
“One of the key principles of geology is that the past is the key to the present: records of past climate inform us of how the Earth system functions,” says Michael Hren, assistant professor of chemistry and geosciences at the University of Connecticut and the study’s lead author. “By understanding past climate transitions, we can better understand the present, and predict impacts for the future.”
The transition between the Late Eocene and the Oligocene epochs (between 34 million and 33.5 million years ago) was triggered in part, the authors write in their April 22 paper in Proceedings of the National Academy of Sciences, by changes in the concentration of atmospheric CO2 that enabled ice to build up on the Antarctic continent.