North Atlantic signalled Ice Age thaw 1,000 years before it happened, reveals new research

The Atlantic Ocean at mid-depths may have given out early warning signals – 1,000 years in advance – that the last Ice Age was going to end, scientists report today in the journal Paleoceanography.

Scientists had previously known that at the end of the last Ice Age, around 14,700 years ago, major changes occurred to the Atlantic Ocean in a period known as the Bolling-Allerod interval. During this period, as glaciers melted and the Earth warmed, the currents of the Atlantic Ocean at its deepest levels changed direction.

The researchers have analysed the chemistry of 24 ancient coral fossils from the North Atlantic Ocean to learn more about the circulation of its waters during the last Ice Age. They found that the corals recorded a high variability in the currents of the Atlantic Ocean at mid-depths, around 2km below the surface, up to 1,000 years prior to the Bolling-Allerod interval. The team suggests that these changes may have been an early warning signal that the world was poised to switch from its glacial state to the warmer world we know today, and that the changes happened first at mid-depths.

The study was carried out by researchers from Imperial College London in conjunction with academics from the Scottish Marine Institute, the University of Bristol and Caltech Division of Geology and Planetary Sciences.

Dr David Wilson, from the Department of Earth Science and Engineering at Imperial College London, said: “The world’s oceans have always been an important barometer when it comes to changes in our planet. Excitingly, the coral fossils we’ve studied are showing us that the North Atlantic Ocean at mid-depths was undergoing changes up to 1,000 years earlier than we had expected. The tantalising prospect is that this high variability may have been a signal that the last Ice Age was about to end.”

The fossil corals analysed by the team come from a species called Desmophyllum dianthus, which are often around 5cm in diameter and look like budding flowers. They typically only live for 100 years, giving the team a rare insight into what was happening to the ocean’s currents during this relatively brief time. Thousands of years ago they grew on the New England Seamounts, which are a chain of undersea mountains approximately 1000km off the east coast of the US, located at mid-depths 2km beneath the surface. This underwater area is important for understanding the North Atlantic’s currents.

While some of the corals analysed by the team come from historical collections, most have been collected by researchers from previous expeditions in 2003 and 2005 to the New England Seamounts. The researchers used deep sea robotic submergence vehicles called Hercules and Alvin to collect the ancient coral fossils.

These ancient coral fossils accumulated rare earth elements from seawater, including neodymium, which leached from rocks on land into the Atlantic Ocean and circulated in its currents, eventually ending up in the coral skeletons. Neodymium isotopes in different regions of the world have specific signatures, created by radioactive decay over billions of years. The scientists studied the chemistry of the coral fossils to determine where the neodymium isotopes had come from, giving them a glimpse into the circulation of the Atlantic Ocean at the end of the Ice Age.

Since the world’s oceans are connected by currents, the next step will see the team integrating the evidence they gathered from the North Atlantic Ocean into a picture of global changes in the mid-depths of oceans around the world. In particular, the team is interested in exploring how the Southern Ocean around Antarctica changed around the same time by analysing neodymium isotopes in a collection of Southern Ocean corals.

Glacier beds can get slipperier at higher sliding speeds

Neal Iverson developed the Iowa State University Sliding Simulator to test how glaciers slide over their beds. -  Bob Elbert/Iowa State University
Neal Iverson developed the Iowa State University Sliding Simulator to test how glaciers slide over their beds. – Bob Elbert/Iowa State University

As a glacier’s sliding speed increases, the bed beneath the glacier can grow slipperier, according to laboratory experiments conducted by Iowa State University glaciologists.

They say including this effect in efforts to calculate future increases in glacier speeds could improve predictions of ice volume lost to the oceans and the rate of sea-level rise.

The glaciologists – Lucas Zoet, a postdoctoral research associate, and Neal Iverson, a professor of geological and atmospheric sciences – describe the results of their experiments in the Journal of Glaciology. The paper uses data collected from a newly constructed laboratory tool, the Iowa State University Sliding Simulator, to investigate glacier sliding. The device was used to explore the relationship between drag and sliding speed for comparison with the predictions of theoretical models.

“We really have a unique opportunity to study the base of glaciers with these experiments,” said Zoet, the lead author of the paper. “The other tactic you might take is studying these relationships with field observations, but with field data so many different processes are mixed together that it becomes hard to untangle the relevant data from the noise.”

Data collected by the researchers show that resistance to glacier sliding – the drag that the bed exerts on the ice – can decrease in response to increasing sliding speed. This decrease in drag with increasing speed, although predicted by some theoreticians a long as 45 years ago, is the opposite of what is usually assumed in mathematical models of the flow of ice sheets.

These are the first empirical results demonstrating that as ice slides at an increasing speed – perhaps in response to changing weather or climate – the bed can become slipperier, which could promote still faster glacier flow.

The response of glaciers to changing climate is one of the largest potential contributors to sea-level rise. Predicting glacier response to climate change depends on properly characterizing the way a glacier slides over its bed. There has been a half-century debate among theoreticians as to how to do that.

The simulator features a ring of ice about 8 inches thick and about 3 feet across that is rotated over a model glacier bed. Below the ice is a hydraulic press that can simulate the weight of a glacier several hundred yards thick. Above are motors that can rotate the ice ring over the bed at either a constant speed or a constant stress. A circulating, temperature-regulated fluid keeps the ice at its melting temperature – a necessary condition for significant sliding.

“About six years were required to design, construct, and work the bugs out of the new apparatus,” Iverson said, “but it is performing well now and allowing hypothesis tests that were formerly not possible.”

Hidden movements of Greenland Ice Sheet, runoff revealed

For years NASA has tracked changes in the massive Greenland Ice Sheet. This week scientists using NASA data released the most detailed picture ever of how the ice sheet moves toward the sea and new insights into the hidden plumbing of melt water flowing under the snowy surface.

The results of these studies are expected to improve predictions of the future of the entire Greenland ice sheet and its contribution to sea level rise as researchers revamp their computer models of how the ice sheet reacts to a warming climate.

“With the help of NASA satellite and airborne remote sensing instruments, the Greenland Ice Sheet is finally yielding its secrets,” said Tom Wagner, program scientist for NASA’s cryosphere program in Washington. “These studies represent new leaps in our knowledge of how the ice sheet is losing ice. It turns out the ice sheet is a lot more complex than we ever thought.”

University at Buffalo geophysicist Beata Csatho led an international team that produced the first comprehensive study of how the ice sheet is losing mass based on NASA satellite and airborne data at nearly 100,000 locations across Greenland. The study found that the ice sheet shed about 243 gigatons of ice per year from 2003-09, which agrees with other studies using different techniques. The study was published today in the Proceedings of the National Academy of Sciences.

The study suggests that current ice sheet modeling is too simplistic to accurately predict the future contribution of the Greenland ice sheet to sea level rise, and that current models may underestimate ice loss in the near future.

The project was a massive undertaking, using satellite and aerial data from NASA’s ICESat spacecraft, which measured the elevation of the ice sheet starting in 2003, and the Operation IceBridge field campaign that has flown annually since 2009. Additional airborne data from 1993-2008, collected by NASA’s Program for Arctic Regional Climate Assessment, were also included to extend the timeline of the study.

Current computer simulations of the Greenland Ice Sheet use the activity of four well-studied glaciers — Jakobshavn, Helheim, Kangerlussuaq and Petermann — to forecast how the entire ice sheet will dump ice into the oceans. The new research shows that activity at these four locations may not be representative of what is happening with glaciers across the ice sheet. In fact, glaciers undergo patterns of thinning and thickening that current climate change simulations fail to address, Csatho says.

As a step toward building better models of sea level rise, the research team divided Greenland’s 242 glaciers into 7 major groups based on their behavior from 2003-09.

“Understanding the groupings will help us pick out examples of glaciers that are representative of the whole,” Csatho says. “We can then use data from these representative glaciers in models to provide a more complete picture of what is happening.”

The team also identified areas of rapid shrinkage in southeast Greenland that today’s models don’t acknowledge. This leads Csatho to believe that the ice sheet could lose ice faster in the future than today’s simulations would suggest.

In separate studies presented today at the American Geophysical Union annual meeting in San Francisco, scientists using data from Operation IceBridge found permanent bodies of liquid water in the porous, partially compacted firn layer just below the surface of the ice sheet. Lora Koenig at the National Snow and Ice Data Center in Boulder, Colorado, and Rick Forster at the University of Utah in Salt Lake City, found signatures of near-surface liquid water using ice-penetrating radar.

Across wide areas of Greenland, water can remain liquid, hiding in layers of snow just below the surface, even through cold, harsh winters, researchers are finding. The discoveries by the teams led by Koenig and Forster mean that scientists seeking to understand the future of the Greenland ice sheet need to account for relatively warm liquid water retained in the ice.

Although the total volume of water is small compared to overall melting in Greenland, the presence of liquid water throughout the year could help kick off melt in the spring and summer. “More year-round water means more heat is available to warm the ice,” Koenig said.

Koenig and her colleagues found that sub-surface liquid water are common on the western edges of the Greenland Ice Sheet. At roughly the same time, Forster used similar ground-based radars to find a large aquifer in southeastern Greenland. These studies show that liquid water can persist near the surface around the perimeter of the ice sheet year round.

Another researcher participating in the briefing found that near-surface layers can also contain masses of solid ice that can lead to flooding events. Michael MacFerrin, a scientist at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder, and colleagues studying radar data from IceBridge and surface based instruments found near surface patches of ice known as ice lenses more than 25 miles farther inland than previously recorded.

Ice lenses form when firn collects surface meltwater like a sponge. When this shallow ice melts, as was seen during July 2012, they can release large amounts of water that can lead to flooding. Warm summers and resulting increased surface melt in recent years have likely caused ice lenses to grow thicker and spread farther inland. “This represents a rapid feedback mechanism. If current trends continue, the flooding will get worse,” MacFerrin said.




Video
Click on this image to view the .mp4 video
This animation (from March 2014) portrays the changes occurring in the surface elevation of the Greenland Ice Sheet since 2003 in three drainage areas: the southeast, the northeast and the Jakobshavn regions. In each region, the time advances to show the accumulated change in elevation, 2003-2012.

Downloadable video: http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4022 – NASA SVS NASA’s Goddard Space Flight Center

Massive study provides first detailed look at how Greenland’s ice is vanishing

The surface of the Greenland Ice Sheet. A new study uses NASA data to provide the first detailed reconstruction of how the ice sheet and its many glaciers are changing. The research was led by University at Buffalo geologist Beata Csatho. -  Beata Csatho
The surface of the Greenland Ice Sheet. A new study uses NASA data to provide the first detailed reconstruction of how the ice sheet and its many glaciers are changing. The research was led by University at Buffalo geologist Beata Csatho. – Beata Csatho

The Greenland Ice Sheet is the second-largest body of ice on Earth. It covers an area about five times the size of New York State and Kansas combined, and if it melts completely, oceans could rise by 20 feet. Coastal communities from Florida to Bangladesh would suffer extensive damage.

Now, a new study is revealing just how little we understand this northern behemoth.

Led by geophysicist Beata Csatho, PhD, an associate professor of geology at the University at Buffalo, the research provides what the authors think is the first comprehensive picture of how Greenland’s ice is vanishing. It suggests that current ice sheet modeling studies are too simplistic to accurately predict the future contributions of the entire Greenland Ice Sheet to sea level rise, and that Greenland may lose ice more rapidly in the near future than previously thought.

“The great importance of our data is that for the first time, we have a comprehensive picture of how all of Greenland’s glaciers have changed over the past decade,” Csatho says.

“This information is crucial for developing and validating numerical models that predict how the ice sheet may change and contribute to global sea level over the next few hundred years,” says Cornelis J. van der Veen, PhD, professor in the Department of Geography at the University of Kansas, who played a key role in interpreting glaciological changes.

The project was a massive undertaking, using satellite and aerial data from NASA’s ICESat spacecraft and Operation IceBridge field campaign to reconstruct how the height of the Greenland Ice Sheet changed at nearly 100,000 locations from 1993 to 2012.

Ice loss takes place in a complex manner, with the ice sheet both melting and calving ice into the ocean.
The study had two major findings:

  • First, the scientists were able to provide new estimates of annual ice loss at high spatial resolution (see below).

  • Second, the research revealed that current models fail to accurately capture how the entire Greenland Ice Sheet is changing and contributing to rising oceans.

The second point is crucial to climate change modelers.

Today’s simulations use the activity of four well-studied glaciers — Jakobshavn, Helheim, Kangerlussuaq and Petermann — to forecast how the entire ice sheet will dump ice into the oceans.

But the new research shows that activity at these four locations may not be representative of what is happening with glaciers across the ice sheet. In fact, glaciers undergo patterns of thinning and thickening that current climate change simulations fail to address, Csatho says.

“There are 242 outlet glaciers wider than 1.5 km on the Greenland Ice Sheet, and what we see is that their behavior is complex in space and time,” Csatho says. “The local climate and geological conditions, the local hydrology — all of these factors have an effect. The current models do not address this complexity.”

The team identified areas of rapid shrinkage in southeast Greenland that today’s models don’t acknowledge. This leads Csatho to believe that the ice sheet could lose ice faster in the future than today’s simulations would suggest.

The results will be published on Dec. 15 in the Proceedings of the National Academy of Sciences, and the study and all information in this press release are embargoed until 3 p.m. Eastern Time that day.

Photos, data visualizations and video are available by contacting Charlotte Hsu at the University at Buffalo at chsu22@buffalo.edu.

How much ice is the Greenland Ice Sheet losing?

To analyze how the height of the ice sheet was changing, Csatho and UB research professor and photogrammetrist Anton Schenk, PhD, developed a computational technique called Surface Elevation Reconstruction And Change detection to fuse together data from NASA satellite and aerial missions.

The analysis found that the Greenland Ice Sheet lost about 243 metric gigatons of ice annually — equivalent to about 277 cubic kilometers of ice per year — from 2003-09, the period for which the team had the most comprehensive data. This loss is estimated to have added about 0.68 millimeters of water to the oceans annually.

The figures are averages, and ice loss varied from year to year, and from region to region.

Why are today’s projections of sea level rise flawed, and how can we fix them?

Glaciers don’t just gradually lose mass when the temperature rises. That’s one reason it’s difficult to predict their response to global warming.

In the study, scientists found that some of Greenland’s glaciers thickened even when the temperature rose. Others exhibited accelerated thinning. Some displayed both thinning and thickening, with sudden reversals.

As a step toward building better models of sea level rise, the research team divided Greenland’s 242 glaciers into 7 major groups based on their behavior from 2003-09.

“Understanding the groupings will help us pick out examples of glaciers that are representative of the whole,” Csatho says. “We can then use data from these representative glaciers in models to provide a more complete picture of what is happening.”

In a new project, she and colleagues are investigating why different glaciers respond differently to warming. Factors could include the temperature of the surrounding ocean; the level of friction between a glacier and the bedrock below; the amount of water under a glacier; and the geometry of the fjord.

“The physics of these processes are not well understood,” Csatho says.

The NASA missions: A colossal undertaking

The study combined data from various NASA missions, including:

  • NASA’s Ice, Cloud and Land Elevation Satellite (ICESat), which measured the ice sheet’s elevation multiple times a year at each of the nearly 100,000 locations from 2003-09.

  • NASA’s, massive aerial survey that employs highly specialized research aircrafts to collect data at less frequent intervals than ICESat. These missions began measuring the Greenland Ice Sheet’s elevation in 1993. Operation IceBridge was started in 2009 to bridge the time between ICESat-1 and ICESat-2, and will continue until at least 2017, when NASA’s next generation ICESat-2 satellite is expected to come online.

Csatho says the new study shows why careful monitoring is critical: Given the complex nature of glacier behavior, good data is crucial to building better models.

Collaborators

Besides Csatho, Schenk and van der Veen, the project included additional researchers from the University at Buffalo, Utrecht University in The Netherlands, the Technical University of Denmark and Florida Atlantic University.

Research links soil mineral surfaces to key atmospheric processes

Pictured are, from left, are David Bish, Melissa Donaldson and Jonathan Raff. -  Indiana University
Pictured are, from left, are David Bish, Melissa Donaldson and Jonathan Raff. – Indiana University

Research by Indiana University scientists finds that soil may be a significant and underappreciated source of nitrous acid, a chemical that plays a pivotal role in atmospheric processes such as the formation of smog and determining the lifetime of greenhouse gases.

The study shows for the first time that the surface acidity of common minerals found in soil determines whether the gas nitrous acid will be released into the atmosphere. The finding could contribute to improved models for understanding and controlling air pollution, a significant public health concern.

“We find that the surfaces of minerals in the soil can be much more acidic than the overall pH of the soil would suggest,” said Jonathan Raff, assistant professor in the School of Public and Environmental Affairs and Department of Chemistry. “It’s the acidity of the soil minerals that acts as a knob or a control lever, and that determines whether nitrous acid outgasses from soil or remains as nitrite.”

The article, “Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid,” will be published this week in the journal Proceedings of the National Academy of Sciences. Melissa A. Donaldson, a Ph.D. student in the School of Public and Environmental Affairs, is the lead author. Co-authors are Raff and David L. Bish, the Haydn Murray Chair of Applied Clay Mineralogy in the Department of Geological Sciences.

Nitrous acid, or HONO, plays a key role in regulating atmospheric processes. Sunlight causes it to break down into nitric oxide and the hydroxyl radical, OH. The latter controls the atmospheric lifetime of gases important to air quality and climate change and initiates the chemistry leading to the formation of ground-level ozone, a primary component of smog.

Scientists have known about the nitrous acid’s role in air pollution for 40 years, but they haven’t fully understood how it is produced and destroyed or how it interacts with other substances, because HONO is unstable and difficult to measure.

“Only in the last 10 years have we had the technology to study nitrous acid under environmentally relevant conditions,” Raff said.

Recent studies have shown nitrous acid to be emitted from soil in many locations. But this was unexpected because, according to basic chemistry, the reactions that release nitrous acid should take place only in extremely acidic soils, typically found in rain forests or the taiga of North America and Eurasia.

The standard method to determine the acidity of soil is to mix bulk soil with water and measure the overall pH. But the IU researchers show that the crucial factor is not overall pH but the acidity at the surface of soil minerals, especially iron oxides and aluminum oxides. At the molecular level, the water adsorbed directly to these minerals is unusually acidic and facilitates the conversion of nitrite in the soil to nitrous acid, which then volatilizes.

“With the traditional approach of calculating soil pH, we were severely underestimating nitrous acid emissions from soil,” Raff said. “I think the source is going to turn out to be more important than was previously imagined.”

The research was carried out using soil from a farm field near Columbus, Ind. But aluminum and iron oxides are ubiquitous in soil, and the researchers say the results suggest that about 70 percent of Earth’s soils could be sources of nitrous acid.

Ultimately, the research will contribute to a better understanding of how nitrous acid is produced and how it affects atmospheric processes. That in turn will improve the computer models used by the U.S. Environmental Protection Agency and other regulatory agencies to control air pollution, which the World Health Organization estimates contributes to 7 million premature deaths annually.

“With improved models, policymakers can make better judgments about the costs and benefits of regulations,” Raff said. “If we don’t get the chemistry right, we’re not going to get the right answers to our policy questions regarding air pollution.”

Migrating ‘supraglacial’ lakes could trigger future Greenland ice loss

Supraglacial lakes on the Greenland ice sheet can be seen as dark blue specks in the center and to the right of this satellite image. -  USGS/NASA Landsat
Supraglacial lakes on the Greenland ice sheet can be seen as dark blue specks in the center and to the right of this satellite image. – USGS/NASA Landsat

Predictions of Greenland ice loss and its impact on rising sea levels may have been greatly underestimated, according to scientists at the University of Leeds.

The finding follows a new study, which is published today in Nature Climate Change, in which the future distribution of lakes that form on the ice sheet surface from melted snow and ice – called supraglacial lakes – have been simulated for the first time.

Previously, the impact of supraglacial lakes on Greenland ice loss had been assumed to be small, but the new research has shown that they will migrate farther inland over the next half century, potentially altering the ice sheet flow in dramatic ways.

Dr Amber Leeson from the School of Earth and Environment and a member of the Centre for Polar Observation and Modelling (CPOM) team, who led the study, said: “Supraglacial lakes can increase the speed at which the ice sheet melts and flows, and our research shows that by 2060 the area of Greenland covered by them will double.”

Supraglacial lakes are darker than ice, so they absorb more of the Sun’s heat, which leads to increased melting. When the lakes reach a critical size, they drain through ice fractures, allowing water to reach the ice sheet base which causes it to slide more quickly into the oceans. These changes can also trigger further melting.

Dr Leeson explained: “When you pour pancake batter into a pan, if it rushes quickly to the edges of the pan, you end up with a thin pancake. It’s similar to what happens with ice sheets: the faster it flows, the thinner it will be.

“When the ice sheet is thinner, it is at a slightly lower elevation and at the mercy of warmer air temperatures than it would have been if it were thicker, increasing the size of the melt zone around the edge of the ice sheet.”

Until now, supraglacial lakes have formed at low elevations around the coastline of Greenland, in a band that is roughly 100 km wide. At higher elevations, today’s climate is just too cold for lakes to form.

In the study, the scientists used observations of the ice sheet from the Environmental Remote Sensing satellites operated by the European Space Agency and estimates of future ice melting drawn from a climate model to drive simulations of how meltwater will flow and pool on the ice surface to form supraglacial lakes.

Since the 1970s, the band in which supraglacial lakes can form on Greenland has crept 56km further inland. From the results of the new study, the researchers predict that, as Arctic temperatures rise, supraglacial lakes will spread much farther inland – up to 110 km by 2060 – doubling the area of Greenland that they cover today.

Dr Leeson said: “The location of these new lakes is important; they will be far enough inland so that water leaking from them will not drain into the oceans as effectively as it does from today’s lakes that are near to the coastline and connected to a network of drainage channels.”

“In contrast, water draining from lakes farther inland could lubricate the ice more effectively, causing it to speed up.”

Ice losses from Greenland had been expected to contribute 22cm to global sea-level rise by 2100. However, the models used to make this projection did not account for changes in the distribution of supraglacial lakes, which Dr Leeson’s study reveals will be considerable.

If new lakes trigger further increases in ice melting and flow, then Greenland’s future ice losses and its contribution to global sea-level rise have been underestimated.

The Director of CPOM, Professor Andrew Shepherd, who is also from the School of Earth and Environment at the University of Leeds and is a co-author of the study, said: “Because ice losses from Greenland are a key signal of global climate change, it’s important that we consider all factors that could affect the rate at which it will lose ice as climate warms.

“Our findings will help to improve the next generation of ice sheet models, so that we can have greater confidence in projections of future sea-level rise. In the meantime, we will continue to monitor changes in the ice sheet losses using satellite measurements.”

Further information:


The study was funded by the Natural Environment Research Council (NERC) through their support of the Centre for Polar Observation and Modelling and the National Centre for Earth Observation.

The research paper, Supraglacial lakes on the Greenland ice sheet advance inland under warming climate, is published in Nature Climate Change on 15 December 2014.

Dr Amber Leeson and Professor Andrew Shepherd are available for interview. Please contact the University of Leeds Press Office on 0113 343 4031 or email pressoffice@leeds.ac.uk

No laughing matter: Nitrous oxide rose at end of last ice age

Researchers measured increases in atmospheric nitrous oxide concentrations about 16,000 to 10,000 years ago using ice from Taylor Glacier in Antarctica. -  Adrian Schilt
Researchers measured increases in atmospheric nitrous oxide concentrations about 16,000 to 10,000 years ago using ice from Taylor Glacier in Antarctica. – Adrian Schilt

Nitrous oxide (N2O) is an important greenhouse gas that doesn’t receive as much notoriety as carbon dioxide or methane, but a new study confirms that atmospheric levels of N2O rose significantly as the Earth came out of the last ice age and addresses the cause.

An international team of scientists analyzed air extracted from bubbles enclosed in ancient polar ice from Taylor Glacier in Antarctica, allowing for the reconstruction of the past atmospheric composition. The analysis documented a 30 percent increase in atmospheric nitrous oxide concentrations from 16,000 years ago to 10,000 years ago. This rise in N2O was caused by changes in environmental conditions in the ocean and on land, scientists say, and contributed to the warming at the end of the ice age and the melting of large ice sheets that then existed.

The findings add an important new element to studies of how Earth may respond to a warming climate in the future. Results of the study, which was funded by the U.S. National Science Foundation and the Swiss National Science Foundation, are being published this week in the journal Nature.

“We found that marine and terrestrial sources contributed about equally to the overall increase of nitrous oxide concentrations and generally evolved in parallel at the end of the last ice age,” said lead author Adrian Schilt, who did much of the work as a post-doctoral researcher at Oregon State University. Schilt then continued to work on the study at the Oeschger Centre for Climate Change Research at the University of Bern in Switzerland.

“The end of the last ice age represents a partial analog to modern warming and allows us to study the response of natural nitrous oxide emissions to changing environmental conditions,” Schilt added. “This will allow us to better understand what might happen in the future.”

Nitrous oxide is perhaps best known as laughing gas, but it is also produced by microbes on land and in the ocean in processes that occur naturally, but can be enhanced by human activity. Marine nitrous oxide production is linked closely to low oxygen conditions in the upper ocean and global warming is predicted to intensify the low-oxygen zones in many of the world’s ocean basins. N2O also destroys ozone in the stratosphere.

“Warming makes terrestrial microbes produce more nitrous oxide,” noted co-author Edward Brook, an Oregon State paleoclimatologist whose research team included Schilt. “Greenhouse gases go up and down over time, and we’d like to know more about why that happens and how it affects climate.”

Nitrous oxide is among the most difficult greenhouse gases to study in attempting to reconstruct the Earth’s climate history through ice core analysis. The specific technique that the Oregon State research team used requires large samples of pristine ice that date back to the desired time of study – in this case, between about 16,000 and 10,000 years ago.

The unusual way in which Taylor Glacier is configured allowed the scientists to extract ice samples from the surface of the glacier instead of drilling deep in the polar ice cap because older ice is transported upward near the glacier margins, said Brook, a professor in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences.

The scientists were able to discern the contributions of marine and terrestrial nitrous oxide through analysis of isotopic ratios, which fingerprint the different sources of N2O in the atmosphere.

“The scientific community knew roughly what the N2O concentration trends were prior to this study,” Brook said, “but these findings confirm that and provide more exact details about changes in sources. As nitrous oxide in the atmosphere continues to increase – along with carbon dioxide and methane – we now will be able to more accurately assess where those contributions are coming from and the rate of the increase.”

Atmospheric N2O was roughly 200 parts per billion at the peak of the ice age about 20,000 years ago then rose to 260 ppb by 10,000 years ago. As of 2014, atmospheric N2Owas measured at about 327 ppb, an increase attributed primarily to agricultural influences.

Although the N2O increase at the end of the last ice age was almost equally attributable to marine and terrestrial sources, the scientists say, there were some differences.

“Our data showed that terrestrial emissions changed faster than marine emissions, which was highlighted by a fast increase of emissions on land that preceded the increase in marine emissions,” Schilt pointed out. “It appears to be a direct response to a rapid temperature change between 15,000 and 14,000 years ago.”

That finding underscores the complexity of analyzing how Earth responds to changing conditions that have to account for marine and terrestrial influences; natural variability; the influence of different greenhouse gases; and a host of other factors, Brook said.

“Natural sources of N2O are predicted to increase in the future and this study will help up test predictions on how the Earth will respond,” Brook said.

Technology-dependent emissions of gas extraction in the US

The KIT measurement instrument on board of a minivan directly measures atmospheric emissions on site with a high temporal resolution. -  Photo: F. Geiger/KIT
The KIT measurement instrument on board of a minivan directly measures atmospheric emissions on site with a high temporal resolution. – Photo: F. Geiger/KIT

Not all boreholes are the same. Scientists of the Karlsruhe Institute of Technology (KIT) used mobile measurement equipment to analyze gaseous compounds emitted by the extraction of oil and natural gas in the USA. For the first time, organic pollutants emitted during a fracking process were measured at a high temporal resolution. The highest values measured exceeded typical mean values in urban air by a factor of one thousand, as was reported in ACP journal. (DOI 10.5194/acp-14-10977-2014)

Emission of trace gases by oil and gas fields was studied by the KIT researchers in the USA (Utah and Colorado) together with US institutes. Background concentrations and the waste gas plumes of single extraction plants and fracking facilities were analyzed. The air quality measurements of several weeks duration took place under the “Uintah Basin Winter Ozone Study” coordinated by the National Oceanic and Atmospheric Administration (NOAA).

The KIT measurements focused on health-damaging aromatic hydrocarbons in air, such as carcinogenic benzene. Maximum concentrations were determined in the waste gas plumes of boreholes. Some extraction plants emitted up to about a hundred times more benzene than others. The highest values of some milligrams of benzene per cubic meter air were measured downstream of an open fracking facility, where returning drilling fluid is stored in open tanks and basins. Much better results were reached by oil and gas extraction plants and plants with closed production processes. In Germany, benzene concentration at the workplace is subject to strict limits: The Federal Emission Control Ordinance gives an annual benzene limit of five micrograms per cubic meter for the protection of human health, which is smaller than the values now measured at the open fracking facility in the US by a factor of about one thousand. The researchers published the results measured in the journal Atmospheric Chemistry and Physics ACP.

“Characteristic emissions of trace gases are encountered everywhere. These are symptomatic of gas and gas extraction. But the values measured for different technologies differ considerably,” Felix Geiger of the Institute of Meteorology and Climate Research (IMK) of KIT explains. He is one of the first authors of the study. By means of closed collection tanks and so-called vapor capture systems, for instance, the gases released during operation can be collected and reduced significantly.

“The gas fields in the sparsely populated areas of North America are a good showcase for estimating the range of impacts of different extraction and fracking technologies,” explains Professor Johannes Orphal, Head of IMK. “In the densely populated Germany, framework conditions are much stricter and much more attention is paid to reducing and monitoring emissions.”

Fracking is increasingly discussed as a technology to extract fossil resources from unconventional deposits. Hydraulic breaking of suitable shale stone layers opens up the fossil fuels stored there and makes them accessible for economically efficient use. For this purpose, boreholes are drilled into these rock formations. Then, they are subjected to high pressure using large amounts of water and auxiliary materials, such as sand, cement, and chemicals. The oil or gas can flow to the surface through the opened microstructures in the rock. Typically, the return flow of the aqueous fracking liquid with the dissolved oil and gas constituents to the surface lasts several days until the production phase proper of purer oil or natural gas. This return flow is collected and then reused until it finally has to be disposed of. Air pollution mainly depends on the treatment of this return flow at the extraction plant. In this respect, currently practiced fracking technologies differ considerably. For the first time now, the resulting local atmospheric emissions were studied at a high temporary resolution. Based on the results, emissions can be assigned directly to the different plant sections of an extraction plant. For measurement, the newly developed, compact, and highly sensitive instrument, a so-called proton transfer reaction mass spectrometer (PTR-MS), of KIT was installed on board of a minivan and driven closer to the different extraction points, the distances being a few tens of meters. In this way, the waste gas plumes of individual extraction sources and fracking processes were studied in detail.

Warneke, C., Geiger, F., Edwards, P. M., Dube, W., Pétron, G., Kofler, J., Zahn, A., Brown, S. S., Graus, M., Gilman, J. B., Lerner, B. M., Peischl, J., Ryerson, T. B., de Gouw, J. A., and Roberts, J. M.: Volatile organic compound emissions from the oil and natural gas industry in the Uintah Basin, Utah: oil and gas well pad emissions compared to ambient air composition, Atmos. Chem. Phys., 14, 10977-10988, doi:10.5194/acp-14-10977-2014, 2014.

West Antarctic melt rate has tripled: UC Irvine-NASA

A comprehensive, 21-year analysis of the fastest-melting region of Antarctica has found that the melt rate of glaciers there has tripled during the last decade.

The glaciers in the Amundsen Sea Embayment in West Antarctica are hemorrhaging ice faster than any other part of Antarctica and are the most significant Antarctic contributors to sea level rise. This study is the first to evaluate and reconcile observations from four different measurement techniques to produce an authoritative estimate of the amount and the rate of loss over the last two decades.

“The mass loss of these glaciers is increasing at an amazing rate,” said scientist Isabella Velicogna, jointly of the UC Irvine and NASA’s Jet Propulsion Laboratory. Velicogna is a coauthor of a paper on the results, which has been accepted for Dec. 5 publication in the journal Geophysical Research Letters.

Lead author Tyler Sutterley, a UCI doctoral candidate, and his team did the analysis to verify that the melting in this part of Antarctica is shifting into high gear. “Previous studies had suggested that this region is starting to change very dramatically since the 1990s, and we wanted to see how all the different techniques compared,” Sutterley said. “The remarkable agreement among the techniques gave us confidence that we are getting this right.”

The researchers reconciled measurements of the mass balance of glaciers flowing into the Amundsen Sea Embayment. Mass balance is a measure of how much ice the glaciers gain and lose over time from accumulating or melting snow, discharges of ice as icebergs, and other causes. Measurements from all four techniques were available from 2003 to 2009. Combined, the four data sets span the years 1992 to 2013.

The glaciers in the embayment lost mass throughout the entire period. The researchers calculated two separate quantities: the total amount of loss, and the changes in the rate of loss.

The total amount of loss averaged 83 gigatons per year (91.5 billion U.S. tons). By comparison, Mt. Everest weighs about 161 gigatons, meaning the Antarctic glaciers lost a Mt.-Everest’s-worth amount of water weight every two years over the last 21 years.

The rate of loss accelerated an average of 6.1 gigatons (6.7 billion U.S. tons) per year since 1992.

From 2003 to 2009, when all four observational techniques overlapped, the melt rate increased an average of 16.3 gigatons per year — almost three times the rate of increase for the full 21-year period. The total amount of loss was close to the average at 84 gigatons.

The four sets of observations include NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites, laser altimetry from NASA’s Operation IceBridge airborne campaign and earlier ICESat satellite, radar altimetry from the European Space Agency’s Envisat satellite, and mass budget analyses using radars and the University of Utrecht’s Regional Atmospheric Climate Model.

The scientists noted that glacier and ice sheet behavior worldwide is by far the greatest uncertainty in predicting future sea level. “We have an excellent observing network now. It’s critical that we maintain this network to continue monitoring the changes,” Velicogna said, “because the changes are proceeding very fast.”

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About the University of California, Irvine:

Founded in 1965, UCI is the youngest member of the prestigious Association of American Universities. The campus has produced three Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UCI has more than 30,000 students and offers 192 degree programs. Located in one of the world’s safest and most economically vibrant communities, it’s Orange County’s second-largest employer, contributing $4.8 billion annually to the local economy.

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New research highlights the key role of ozone in climate change

Many of the complex computer models which are used to predict climate change could be missing an important ozone ‘feedback’ factor in their calculations of future global warming, according to new research led by the University of Cambridge and published today (1 December) in the journal Nature Climate Change.

Computer models play a crucial role in informing climate policy. They are used to assess the effect that carbon emissions have had on the Earth’s climate to date, and to predict possible pathways for the future of our climate.

Increasing computing power combined with increasing scientific knowledge has led to major advances in our understanding of the climate system during the past decades. However, the Earth’s inherent complexity, and the still limited computational power available, means that not every variable can be included in current models. Consequently, scientists have to make informed choices in order to build models which are fit for purpose.

“These models are the only tools we have in terms of predicting the future impacts of climate change, so it’s crucial that they are as accurate and as thorough as we can make them,” said the paper’s lead author Peer Nowack, a PhD student in the Centre for Atmospheric Science, part of Cambridge’s Department of Chemistry.

The new research has highlighted a key role that ozone, a major component of the stratosphere, plays in how climate change occurs, and the possible implications for predictions of global warming. Changes in ozone are often either not included, or are included a very simplified manner, in current climate models. This is due to the complexity and the sheer computational power it takes to calculate these changes, an important deficiency in some studies.

In addition to its role in protecting the Earth from the Sun’s harmful ultraviolet rays, ozone is also a greenhouse gas. The ozone layer is part of a vast chemical network, and changes in environmental conditions, such as changes in temperature or the atmospheric circulation, result in changes in ozone abundance. This process is known as an atmospheric chemical feedback.

Using a comprehensive atmosphere-ocean chemistry-climate model, the Cambridge team, working with researchers from the University of East Anglia, the National Centre for Atmospheric Science, the Met Office and the University of Reading, compared ozone at pre-industrial levels with how it evolves in response to a quadrupling of CO2 in the atmosphere, which is a standard climate change experiment.

What they discovered is a reduction in global surface warming of approximately 20% – equating to 1° Celsius – when compared with most models after 75 years. This difference is due to ozone changes in the lower stratosphere in the tropics, which are mainly caused by changes in the atmospheric circulation under climate change.

“This research has shown that ozone feedback can play a major role in global warming and that it should be included consistently in climate models,” said Nowack. “These models are incredibly complex, just as the Earth is, and there are an almost infinite number of different processes which we could include. Many different processes have to be simplified in order to make them run effectively within the model, but what this research shows is that ozone feedback plays a major role in climate change, and therefore should be included in models in order to make them as accurate as we can make them. However, this particular feedback is especially complex since it depends on many other climate processes that models still simulate differently. Therefore, the best option to represent this feedback consistently might be to calculate ozone changes in every model, in spite of the high computational costs of such a procedure.

“Climate change research is all about having the best data possible. Every climate model currently in use shows that warming is occurring and will continue to occur, but the difference is in how and when they predict warming will happen. Having the best models possible will help make the best climate policy.”

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For more information, or to speak with the researchers, contact:

Sarah Collins, Office of Communications University of Cambridge Tel: +44 (0)1223 765542, Mob: +44 (0)7525 337458 Email: sarah.collins@admin.cam.ac.uk

Notes for editors:

1.The paper, “A large ozone-circulation feedback and its implications for global warming assessments” is published in the journal Nature Climate Change. DOI: 10.1038/nclimate2451

2.The mission of the University of Cambridge is to contribute to society through the pursuit of education, learning and research at the highest international levels of excellence. To date, 90 affiliates of the University have won the Nobel Prize. http://www.cam.ac.uk

3.UEA’s school of Environmental Sciences is one of the longest established, largest and most fully developed of its kind in Europe. It was ranked 5th in the Guardian League Table 2015.In the last Research Assessment Exercise, 95 per cent of the school’s activity was classified as internationally excellent or world leading. http://www.uea.ac.uk/env

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