First Exploration of a Sub-Glacial Antarctic Lake

Subglacial Lakes, Antarctica. (Credit: NASA map by Robert Simmon, based on data from the Radarsat Antarctic Mapping Project, Ted Scambos, Chris Shuman, and Martin J. Siegert / Courtesy of NASA's Earth Observatory -- http://earthobservatory.nasa.gov)

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Drilling Into the Unknown: First Exploration of a Sub-Glacial Antarctic Lake Is a Major Step Closer

Scientists have located the ideal drill site for the first ever exploration of an Antarctic sub-glacial lake, a development that is likely to facilitate a revolution in climate-change research and which may lead to the discovery of life-forms cut off from the main line of evolution for millions of years.

In a paper published in Geophysical Research Letters this week, scientists from Northumbria University, the University of Edinburgh and the British Antarctic Survey have revealed the optimal drill site for exploring Lake Ellsworth -- a sub-glacial lake, comparable in size to England's Lake Windermere, that is covered by three kilometers of ice.

No one has yet drilled into an Antarctic sub-glacial lake. But microbiologists believe that such lakes could harbor uniquely adapted life-forms cut off from other lines of evolution. Paleoclimatologists also suggest that sediments on the lake floors could contain records of ice sheets and climate history that would revolutionize research into global warming.

In order to access the lake water and the undisturbed sediment containing the climate record, it is essential to drill in the right place.

The optimal drilling site has to avoid possible areas of in-coming water that would disturb the sediment, as well as areas of so-called basal freezing -- where lake water freezes to the underside of the ice. It also has to avoid any concentrations of trapped gases which could rush up the bore hole to cause a potentially dangerous blowout at the surface.

The Scientific Committee on Arctic Research identified Lake Ellsworth as an excellent candidate for the first drill site.

Dr John Woodward, from Northumbria University's School of Applied Sciences, commented: "The location provides a deep water column for sampling and reduces the risk from possible basal-freezing mechanisms. It optimizes the chances of recovering an undisturbed, continuous sedimentary sequence from the lake floor, and minimizes the potential for trapped gases to gain entry to the borehole."

Dr Andy Smith of the British Antarctic Survey added: "This is an eagerly anticipated result -- the final piece of the jigsaw that we need to plan the exploration of Lake Ellsworth. That exploration can now go ahead at full speed."

To locate the optimal drill site, the team had to conduct the first detailed characterization of the physiography of a sub-glacial lake. Between 2007-2009, the lake was subject to a ground-based geophysics campaign involving an ice-penetrating radar to investigate ice thickness, seismic surveys to calculate lake water depths and flow measurements to calculate how the ice sheet flows over the underlying lake.

The climactic stage in the project will take place in the 2012-13 Antarctic summer when the Lake Ellsworth Consortium will use the data in this paper to access a sub-glacial lake for the first time.

Professor Martin Siegert, of the University of Edinburgh's School of GeoSciences, said: "Pinpointing the perfect spot from which to access the sub-glacial lake helps us to find out all we can about this interesting and pristine environment, without the risk of contaminating it."

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Journal Reference:

1. J. Woodward, A. M. Smith, N. Ross, M. Thoma, H. F. J. Corr, E. C. King, M. A. King, K. Grosfeld, M. Tranter, M. J. Siegert. Location for direct access to subglacial Lake Ellsworth: An assessment of geophysical data and modeling. Geophysical Research Letters, 2010; 37 (11): L11501 DOI: 10.1029/2010GL042884

Mass Loss from Alaskan Glaciers Overestimated?

Mass Loss from Alaskan Glaciers Overestimated? Previous Melt Contributed a Third Less to Sea-Level Rise Than Estimated

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 NAU geographer Erik Schiefer surveys a debris-covered glacier margin.

(Credit: Photo by Amanda Stan)

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The melting of glaciers is well documented, but when looking at the rate at which they have been retreating, a team of international researchers steps back and says not so fast.

Previous studies have largely overestimated mass loss from Alaskan glaciers over the past 40-plus years, according to Erik Schiefer, a Northern Arizona University geographer who coauthored a paper in the February issue of Nature Geoscience that recalculates glacier melt in Alaska.

The research team, led by Étienne Berthier of the Laboratory for Space Studies in Geophysics and Oceanography at the Université de Toulouse in France, says that glacier melt in Alaska between 1962 and 2006 contributed about one-third less to sea-level rise than previously estimated.

Schiefer said melting glaciers in Alaska originally were thought to contribute about .0067 inches to sea-level rise per year. The team's new calculations put that number closer to .0047 inches per year. The numbers sound small, but as Schiefer said, "It adds up over the decades."

While the team looked at three-fourths of all the ice in Alaska, Schiefer noted, "We're also talking about a small proportion of ice on the planet. When massive ice sheets (such as in the Antarctic and Greenland) are added in, you're looking at significantly greater rates of sea-level rise."

Schiefer said the team plans to use the same methodologies from the Alaskan study in other glacial regions to determine if further recalibrations of ice melt are in order. These techniques use satellite imagery that spans vast areas of ice cover.

Previous methods estimated melt for a smaller subset of individual glaciers. The most comprehensive technique previously available used planes that flew along the centerlines of selected glaciers to measure ice surface elevations. These elevations were then compared to those mapped in the 1950s and 1960s. From this, researchers inferred elevation changes and then extrapolated this to other glaciers.

Two factors led to the original overestimation of ice loss with this method, Schiefer said. One is the impact of thick deposits of rock debris that offer protection from solar radiation and, thus, melting. The other was not accounting for the thinner ice along the edges of glaciers that also resulted in less ice melt.

Schiefer and his colleagues used data from the SPOT 5 French satellite and the NASA/Japanese ASTER satellite and converted the optical imagery to elevation information. They then compared this information to the topographical series maps of glacial elevations dating back to the 1950s.

While the team determined a lower rate of glacial melt during a greater than 40-year span, Schiefer said other studies have demonstrated the rate of ice loss has more than doubled in just the last two decades.

"With current projections of climate change, we expect that acceleration to continue," Schiefer said. This substantial increase in ice loss since the 1990s is now pushing up the rise in sea level to between .0098 inches and .0118 inches per year -- more than double the average rate for the last 40 years.

Working on the Alaskan glacial melt revision with Schiefer and Berthier were Garry Clarke of the University of British Columbia, Brian Menounos of the University of Northern British Columbia and Frédérique Rémy of the Université de Toulouse.
Adapted from materials provided by Northern Arizona University.

Journal Reference:
E. Berthier, E. Schiefer, G. K. C. Clarke, B. Menounos & F. Rémy. Contribution of Alaskan glaciers to sea-level rise derived from satellite imagery. Nature Geoscience, 2010; 3 (2): 92 DOI: 10.1038/ngeo737

Fast Pace of Glacier Melt in the 1940s: Lower Aerosol Pollution

Gorner glacier. In the 1940s, the glaciers were melting at a faster pace than today.

(Credit: Matthias Huss / ETH Zurich)

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The most recent studies by researchers at ETH Zurich show that in the 1940s Swiss glaciers were melting at an even-faster pace than at present. This is despite the fact that the temperatures in the 20th century were lower than in this century. Researchers see the main reason for this as the lower level of aerosol pollution in the atmosphere.

In Switzerland, the increase in snow in wintertime and the glacier melt in summertime have been measured at measurement points at around 3,000 metres above sea level -- on the Clariden Firn, the Great Aletsch glacier and the Silvretta glacier -- without interruption for almost 100 years. As part of his doctoral work, Matthias Huss used this unique range of measurements to examine how climate change in the last century affected the glaciers. The work was carried out under the supervision of Martin Funk, professor and head of the Department for Glaciology at the Laboratory for Hydraulics, Hydrology and Glaciology ('VAW') at ETH Zurich, who is also co-author of the study.

Solar radiation as the decisive factor

In its work, the research team took into account the solar radiation measured on the Earth's surface in Davos since 1934. Studies over the past two decades have shown that solar radiation varies substantially due to aerosols and clouds, and this is assumed to influence climate fluctuations. Recent years have seen the emergence of the terms 'global dimming' and 'global brightening' to describe these phenomena of reduced and increased solar radiation respectively. These two effects are currently the subject of more and more scientific research, in particular by ETH Zurich, as experts feel that they should be taken into account in the climate models.

The new study, published in the journal 'Geophysical Research Letters', confirms this requirement. This is because, taking into account the data recorded for the level of solar radiation, the scientists made a surprising discovery: in the 1940s and in the summer of 1947 especially, the glaciers lost the most ice since measurements commenced in 1914. This is in spite of the fact that temperatures were lower than in the past two decades. "The surprising thing is that this paradox can be explained relatively easily with radiation," says Huss, who was recently appointed to the post of senior lecturer at the Department of Geosciences at the University of Fribourg in Switzerland.

On the basis of their calculations, the researchers have concluded that the high level of short-wave radiation in the summer months is responsible for the fast pace of glacier melt. In the 1940s, the level was 8% higher than the long-term average and 18 Watts per square metres above the levels of the past ten years. Calculated over the entire decade of the 1940s, this resulted in 4% more snow and ice melt compared with the past ten years.

Furthermore, the below-average melt rates at the measurement points during periods in which the glacier snouts were even advancing correlate with a phase of global dimming, between the 1950s and the 1980s.

Less snow fall and longer melt periods

The researchers arrived at their findings by calculating the daily melt rates with the aid of climate data and a temperature index model, based on the half-yearly measurements on the glaciers since 1914. These results were then compared with the long-term measurements of solar radiation in Davos.

Huss points out that the strong glacier melt in the 1940s puts into question the assumption that the rate of glacier decline in recent years "has never been seen before." "Nevertheless," says the glaciologist, "this should not lead people to conclude that the current period of global warming is not really as big of a problem for the glaciers as previously assumed." This is because it is not only the pace at which the Alpine glaciers are currently melting that is unusual, but the fact that this sharp decline has been unabated for 25 years now.

Another aspect to consider -- and this is evidenced by the researchers' findings -- is that temperature-based opposing mechanisms came into play around 30 years ago. These have led to a 12% decrease in the amount of precipitation that falls as snow as a percentage of total precipitation, accompanied by an increase of around one month in the length of the melt period ever since this time. Scientists warn that these effects could soon be matched by the lower level of solar radiation we have today compared with the 1940s.
Story Source:
Adapted from materials provided by ETH Zurich.

Journal Reference:
Huss et al. Strong Alpine glacier melt in the 1940s due to enhanced solar radiation. Geophysical Research Letters, 2009; 36 (23): L23501 DOI: 10.1029/2009GL040789

Black Carbon Deposits on Himalayan Ice Threaten Earth's 'Third Pole'

To better understand the role that black soot has on glaciers, researchers trekked high into the Himalayas to collect ice cores that contain a record of soot deposition that spans back to the 1950s.

(Credit: Institute of Tibetan Plateau Research, Chinese Academy of Sciences)

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Black soot deposited on Tibetan glaciers has contributed significantly to the retreat of the world's largest non-polar ice masses, according to new research by scientists from NASA and the Chinese Academy of Sciences. Soot absorbs incoming solar radiation and can speed glacial melting when deposited on snow in sufficient quantities.

Temperatures on the Tibetan Plateau -- sometimes called Earth's "third pole" -- have warmed by 0.3°C (0.5°F) per decade over the past 30 years, about twice the rate of observed global temperature increases. New field research and ongoing quantitative modeling suggests that soot's warming influence on Tibetan glaciers could rival that of greenhouse gases.

"Tibet's glaciers are retreating at an alarming rate," said James Hansen, coauthor of the study and director of NASA's Goddard Institute for Space Studies (GISS) in New York City. "Black soot is probably responsible for as much as half of the glacial melt, and greenhouse gases are responsible for the rest."

"During the last 20 years, the black soot concentration has increased two- to three-fold relative to its concentration in 1975," said Junji Cao, a researcher from the Chinese Academy of Sciences in Beijing and a coauthor of the paper.

The study was published December 7th in the Proceedings of the National Academy of Sciences.

"Fifty percent of the glaciers were retreating from 1950 to 1980 in the Tibetan region; that rose to 95 percent in the early 21st century," said Tandong Yao, director of the Chinese Academy's Institute of Tibetan Plateau Research. Some glaciers are retreating so quickly that they could disappear by mid-century if current trends continue, the researchers suggest.

Since melt water from Tibetan glaciers replenishes many of Asia's major rivers -- including the Indus, Ganges, Yellow, and Brahmaputra -- such losses could have a profound impact on the billion people who rely on the rivers for fresh water. While rain and snow would still help replenish Asian rivers in the absence of glaciers, the change could hamper efforts to manage seasonal water resources by altering when fresh water supplies are available in areas already prone to water shortages.

Researchers led by Baiqing Xu of the Chinese Academy drilled and analyzed five ice cores from various locations across the Tibetan Plateau, looking for black carbon (a key component of soot) as well as organic carbon. The cores support the hypothesis that black soot amounts in the Himalayan glaciers correlate with black carbon emissions in Europe and South Asia.

At Zuoqiupu glacier -- a bellwether site on the southern edge of the plateau and downwind from the Indian subcontinent -- black soot deposition increased by 30 percent between 1990 and 2003. The rise in soot levels at Zuoqiupu follows a dip that followed the enacting of clean air regulations in Europe in the 1970s.

Most soot in the region comes from diesel engines, coal-fired power plants, and outdoor cooking stoves. Many industrial processes produce both black carbon and organic carbon, but often in different proportions. Burning diesel fuel produces mainly black carbon, for example, while burning wood produces mainly organic carbon. Since black carbon is darker and absorbs more radiation, it's thought to have a stronger warming effect than organic carbon.

To refine this emerging understanding of soot's impact on glaciers, scientists are striving to gather even more robust measurements. "We can't expect this study to clarify the effect of black soot on the melting of Tibetan snow and glaciers entirely," said Cao. "Additional work that looks at albedo measurements, melting rate, and other types of reconnaissance is also needed."

For example, scientists are using satellite instruments such as the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the NASA satellites Terra and Aqua to enhance understanding of the region's albedo. And a new NASA climate satellite called Glory, which will launch late in 2010, will carry a new type of aerosol sensor that should be able to distinguish between aerosol types more accurately than previous instruments.

"Reduced black soot emissions, in addition to reduced greenhouse gases, may be required to avoid demise of Himalayan glaciers and retain the benefits of glaciers for seasonal fresh water supplies," Hansen said.

Adapted from materials provided by NASA/Goddard Space Flight Center, via EurekAlert!, a service of AAAS.