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

Fountain of youth underlies Antarctic Mountains

Images of the ice-covered Gamburtsev Mountains revealed water-filled valleys, as seen by the cluster of vertical lines in this image. -  Tim Creyts
Images of the ice-covered Gamburtsev Mountains revealed water-filled valleys, as seen by the cluster of vertical lines in this image. – Tim Creyts

Time ravages mountains, as it does people. Sharp features soften, and bodies grow shorter and rounder. But under the right conditions, some mountains refuse to age. In a new study, scientists explain why the ice-covered Gamburtsev Mountains in the middle of Antarctica looks as young as they do.

The Gamburtsevs were discovered in the 1950s, but remained unexplored until scientists flew ice-penetrating instruments over the mountains 60 years later. As this ancient hidden landscape came into focus, scientists were stunned to see the saw-toothed and towering crags of much younger mountains. Though the Gamburtsevs are contemporaries of the largely worn-down Appalachians, they looked more like the Rockies, which are nearly 200 million years younger.

More surprising still, the scientists discovered a vast network of lakes and rivers at the mountains’ base. Though water usually speeds erosion, here it seems to have kept erosion at bay. The reason, researchers now say, has to do with the thick ice that has entombed the Gamburtsevs since Antarctica went into a deep freeze 35 million years ago.

“The ice sheet acts like an anti-aging cream,” said the study’s lead author, Timothy Creyts, a geophysicist at Columbia University’s Lamont-Doherty Earth Observatory. “It triggers a series of thermodynamic processes that have almost perfectly preserved the Gamburtsevs since ice began spreading across the continent.”

The study, which appears in the latest issue of the journal Geophysical Research Letters, explains how the blanket of ice covering the Gamburtsevs has preserved its rugged ridgelines.

Snow falling at the surface of the ice sheet draws colder temperatures down, closer to protruding peaks in a process called divergent cooling. At the same time, heat radiating from bedrock beneath the ice sheet melts ice in the deep valleys to form rivers and lakes. As rivers course along the base of the ice sheet, high pressures from the overlying ice sheet push water up valleys in reverse. This uphill flow refreezes as it meets colder temperature from above. Thus, ridgelines are cryogenically preserved.

The oldest rocks in the Gamburtsevs formed more than a billion years ago, in the collision of several continents. Though these prototype mountains eroded away, a lingering crustal root became reactivated when the supercontinent Gondwana ripped apart, starting about 200 million years ago. Tectonic forces pushed the land up again to form the modern Gamburtsevs, which range across an area the size of the Alps. Erosion again chewed away at the mountains until earth entered a cooling phase 35 million years ago. Expanding outward from the Gamburtsevs, a growing layer of ice joined several other nucleation points to cover the entire continent in ice.

The researchers say that the mechanism that stalled aging of the Gamburtsevs at higher elevations may explain why some ridgelines in the Torngat Mountains on Canada’s Labrador Peninsula and the Scandinavian Mountains running through Norway, Sweden and Finland appear strikingly untouched. Massive ice sheets covered both landscapes during the last ice age, which peaked about 20,000 years ago, but many high-altitude features bear little trace of this event.

“The authors identify a mechanism whereby larger parts of mountains ranges in glaciated regions–not just Antarctica–could be spared from erosion,” said Stewart Jamieson, a glaciologist at Durham University who was not involved in the study. “This is important because these uplands are nucleation centers for ice sheets. If they were to gradually erode during glacial cycles, they would become less effective as nucleation points during later ice ages.”

Ice sheet behavior, then, may influence climate change in ways that scientists and computer models have yet to appreciate. As study coauthor Fausto Ferraccioli, head of the British Antarctic Survey’s airborne geophysics group, put it: “If these mountains in interior East Antarctica had been more significantly eroded then the ice sheet itself
may have had a different history.”

Other Authors

Hugh Carr and Tom Jordan of the British Antarctic Survey; Robin Bell, Michael Wolovick and Nicholas Frearson of Lamont-Doherty; Kathryn Rose of University of Bristol; Detlef Damaske of Germany’s Federal Institute for Geosciences and Natural Resources; David Braaten of Kansas University; and Carol Finn of the U.S. Geological Survey.

Copies of the paper, “Freezing of ridges and water networks preserves the Gamburtsev Subglacial Mountains for millions of years,” are available from the authors.

Scientist Contact

Tim Creyts



Sediment supply drives floodplain evolution in Amazon Basin

A new study of the Amazon River basin shows lowland rivers that carry large volumes of sediment meander more across floodplains and create more oxbow lakes than rivers that carry less sediment.

The findings have implication for the Amazonian river system, which may be significantly altered by proposed mega-dams that would disrupt sediment supplies.

Researchers from Cardiff University’s School of Earth and Ocean Sciences examined 20 reaches within the Amazon Basin from Landsat imagery spanning nearly 20 years (1985 to 2013).

They found rivers transporting larger amounts of sediment migrated more, and noted that channel movement did not depend on either the slope of the channel or the river discharge.

The research gives scientists insight into the contrasting behavioural properties of rivers where sediment is an imposed variable – e.g. resulting from glacial, volcanic, or human activity – and rivers were the main sediment supply is from local bank erosion.

Dr José Constantine, Lecturer in Earth Sciences at Cardiff University’s School of Earth & Ocean Sciences and lead author of the paper said: “We found that the speed at which the meanders migrated for each of the rivers studied depended on the river’s supply of sand and silt. The meanders of rivers carrying more sediment migrated faster than those carrying less sediment, and were also more frequently cut off and abandoned to form U-shaped lakes. If sediment loads are reduced — by a dam, for example — meander migration is expected to slow, and thus the reshaping of the floodplain environment is affected.

Life in Earth’s primordial sea was starved for sulfate

This is a research vessel on Lake Matano, Indonesia -- a modern lake with chemistry similar to Earth's early oceans. -  Sean Crowe, University of British Columbia.
This is a research vessel on Lake Matano, Indonesia — a modern lake with chemistry similar to Earth’s early oceans. – Sean Crowe, University of British Columbia.

The Earth’s ancient oceans held much lower concentrations of sulfate–a key biological nutrient–than previously recognized, according to research published this week in Science.

The findings paint a new portrait of our planet’s early biosphere and primitive marine life. Organisms require sulfur as a nutrient, and it plays a central role in regulating atmospheric chemistry and global climate.

“Our findings are a fraction of previous estimates, and thousands of time lower than current seawater levels,” says Sean Crowe, a lead author of the study and an assistant professor in the Departments of Microbiology and Immunology, and Earth, Ocean and Atmospheric Sciences at the University of British Columbia.

“At these trace amounts, sulfate would have been poorly mixed and short-lived in the oceans–and this sulfate scarcity would have shaped the nature, activity and evolution of early life on Earth.”

UBC, University of Southern Denmark, CalTech, University of Minnesota Duluth, and University of Maryland researchers used new techniques and models to calibrate fingerprints of bacterial sulfur metabolisms in Lake Matano, Indonesia — a modern lake with chemistry similar to Earth’s early oceans.

Measuring these fingerprints in rocks older than 2.5 billion years, they discovered sulfate 80 times lower than previously thought.

The more sensitive fingerprinting provides a powerful tool to search for sulfur metabolisms deep in Earth’s history or on other planets like Mars.


Previous research has suggested that Archean sulfate levels were as low as 200 micromolar– concentrations at which sulfur would still have been abundantly available to early marine life.

The new results indicate levels were likely less than 2.5 micromolar, thousands of times lower than today.

What the researchers did

Researchers used state-of-the-art mass spectrometric approaches developed at California Institute of Technology to demonstrate that microorganisms fractionate sulfur isotopes at concentrations orders of magnitude lower than previously recognized.

They found that microbial sulfur metabolisms impart large fingerprints even when sulfate is scarce.

The team used the techniques on samples from Lake Matano, Indonesia–a sulfate-poor modern analogue for the Earth’s Archean oceans.

“New measurements in these unique modern environments allow us to use numerical models to reconstruct ancient ocean chemistry with unprecedented resolution” says Sergei Katsev an Associate Professor at the Large Lakes Observatory, University of Minnesota Duluth.

Using models informed by sulfate isotope fractionation in Lake Matano, they established a new calibration for sulfate isotope fractionation that is extensible to the Earth’s oceans throughout history. The researchers then reconstructed Archean seawater sulfate concentrations using these models and an exhaustive compilation of sulfur isotope data from Archean sedimentary rocks.


Crowe initiated the research while a post-doctoral fellow with Donald Canfield at the University of Southern Denmark.

2015 DOE JGI’s science portfolio delves deeper into the Earth’s data mine

The U.S. Department of Energy Joint Genome Institute (DOE JGI), a DOE Office of Science user facility, has announced that 32 new projects have been selected for the 2015 Community Science Program (CSP). From sampling Antarctic lakes to Caribbean waters, and from plant root micro-ecosystems, to the subsurface underneath the water table in forested watersheds, the CSP 2015 projects portfolio highlights diverse environments where DOE mission-relevant science can be extracted.

“These projects catalyze JGI’s strategic shift in emphasis from solving an organism’s genome sequence to enabling an understanding of what this information enables organisms to do,” said Jim Bristow, DOE JGI Science Deputy who oversees the CSP. “To accomplish this, the projects selected combine DNA sequencing with large-scale experimental and computational capabilities, and in some cases include JGI’s new capability to write DNA in addition to reading it. These projects will expand research communities, and help to meet the DOE JGI imperative to translate sequence to function and ultimately into solutions for major energy and environmental problems.”

The CSP 2015 projects were selected by an external review panel from 76 full proposals received that resulted from 85 letters of intent submitted. The total allocation for the CSP 2015 portfolio is expected to exceed 60 trillion bases (terabases or Tb)-or the equivalent of 20,000 human genomes of plant, fungal and microbial genome sequences. The full list of projects may be found at http://jgi.doe.gov/our-projects/csp-plans/fy-2015-csp-plans/. The DOE JGI Community Science Program also accepts proposals for smaller-scale microbial, resequencing and DNA synthesis projects and reviews them twice a year. The CSP advances projects that harness DOE JGI’s capability in massive-scale DNA sequencing, analysis and synthesis in support of the DOE missions in alternative energy, global carbon cycling, and biogeochemistry.

Among the CSP 2015 projects selected is one from Regina Lamendella of Juniata College, who will investigate how microbial communities in Marcellus shale, the country’s largest shale gas field, respond to hydraulic fracturing and natural gas extraction. For example, as fracking uses chemicals, researchers are interested in how the microbial communities can break down environmental contaminants, and how they respond to the release of methane during oil extraction operations.

Some 1,500 miles south from those gas extraction sites, Monica Medina-Munoz of Penn State University will study the effect of thermal stress on the Caribbean coral Orbicella faveolata and the metabolic contribution of its coral host Symbiodinium. The calcium carbonate in coral reefs acts as carbon sinks, but reef health depends on microbial communities. If the photosynthetic symbionts are removed from the coral host, for example, the corals can die and calcification rates decrease. Understanding how to maintain stability in the coral-microbiome community can provide information on the coral’s contribution to the global ocean carbon cycle.

Longtime DOE JGI collaborator Jill Banfield of the University of California (UC), Berkeley is profiling the diversity of microbial communities found in the subsurface from the Rifle aquifer adjacent to the Colorado River. The subsurface is a massive, yet poorly understood, repository of organic carbon as well as greenhouse gases. Another research question, based on having the microbial populations close to both the water table and the river, is how they impact carbon, nitrogen and sulfur cycles. Her project is part of the first coordinated attempt to quantify the metabolic potential of an entire subsurface ecosystem under the aegis of the Lawrence Berkeley National Laboratory’s Subsurface Biogeochemistry Scientific Focus Area.

Banfield also successfully competed for a second CSP project to characterize the tree-root microbial interactions that occur below the soil mantle in the unsaturated zone or vadose zone, which extends into unweathered bedrock. The project’s goal is to understand how microbial communities this deep underground influence tree-based carbon fixation in forested watersheds by the Eel River in northwestern California.

Several fungal projects were selected for the 2015 CSP portfolio, including one led by Kabir Peay of Stanford University. He and his colleagues will study how fungal communities in animal feces decompose organic matter. His project has a stated end goal of developing a model system that emulates the ecosystem at Point Reyes National Seashore, where Tule elk are the largest native herbivores.

Another selected fungal project comes from Timothy James of University of Michigan, who will explore the so-called “dark matter fungi” – those not represented in culture collections. By sequencing several dozen species of unculturable zoosporic fungi from freshwater, soils and animal feces, he and his colleagues hope to develop a kingdom-wide fungal phylogenetic framework.

Christian Wurzbacher of Germany’s the Leibniz Institute of Freshwater Ecology and Inland Fisheries, IGB, will characterize fungi from the deep sea to peatlands to freshwater streams to understand the potentially novel adaptations that are necessary to thrive in their aquatic environments. The genomic information would provide information on their metabolic capabilities for breaking down cellulose, lignin and other plant cell wall components, and animal polymers such as keratin and chitin.

Many of the selected projects focus on DOE JGI Flagship Plant Genomes, with most centered on the poplar (Populus trichocarpa.) For example, longtime DOE JGI collaborator Steve DiFazio of West Virginia University is interested in poplar but will study its reproductive development with the help of a close relative, the willow (Salix purpurea). With its shorter generation time, the plant is a good model system and comparator for understanding sex determination, which can help bioenergy crop breeders by, for example, either accelerating or preventing flowering.

Another project comes from Posy Busby of the University of Washington, who will study the interactions between the poplar tree and its fungal, non-pathogenic symbionts or endophytes. As disease-causing pathogens interact with endophytes in leaves, he noted in his proposal, understanding the roles and functions of endophytes could prove useful to meeting future fuel and food requirements.

Along the lines of poplar endophytes, Carolin Frank at UC Merced will investigate the nitrogen-fixing endophytes in poplar, willow, and pine, with the aim of improving growth in grasses and agricultural crops under nutrient-poor conditions.

Rotem Sorek from the Weizmann Institute of Science in Israel takes a different approach starting from the hypothesis that poplar trees have an adaptive immunity system rooted in genome-encoded immune memory. Through deep sequencing of tissues from single poplar trees (some over a century old, others younger) his team hopes to gain insights into the tree genome’s short-term evolution and how its gene expression profiles change over time, as well as to predict how trees might respond under various climate change scenarios.

Tackling a different DOE JGI Flagship Plant Genome, Debbie Laudencia-Chingcuangco of the USDA-ARS will develop a genome-wide collection of several thousand mutants of the model grass Brachypodium distachyon to help domesticate the grasses that are being considered as candidate bioenergy feedstocks. This work is being done in collaboration with researchers at the Great Lakes Bioenergy Research Center, as the team there considers Brachypodium “critical to achieving its mission of developing productive energy crops that can be easily processed into fuels.”

Continuing the theme of candidate bioenergy grasses, Kankshita Swaminathan from the University of Illinois will study gene expression in polyploidy grasses Miscanthus and sugarcane, comparing them against the closely related diploid grass sorghum to understand how these plants recycle nutrients.

Baohong Zhang of East Carolina University also focused on a bioenergy grass, and his project will look at the microRNAs in switchgrass. These regulatory molecules are each just a couple dozen nucleotides in length and can downregulate (decrease the quantity of) a cellular component. With a library of these small transcripts, he and his team hope to identify the gene expression variation associated with desirable biofuel traits in switchgrass such as increased biomass and responses to drought and salinity stressors.

Nitin Baliga of the Institute of Systems Biology will use DOE JGI genome sequences to build a working model of the networks that regulate lipid accumulation in Chlamydomonas reinhardtii, still another DOE JGI Plant Flagship Genome and a model for characterizing biofuel production by algae.

Other accepted projects include:

The study of the genomes of 32 fungi of the Agaricales order, including 16 fungi to be sequenced for the first time, will be carried out by Jose Maria Barrasa of Spain’s University of Alcala. While many of the basidiomycete fungi involved in wood degradation that have been sequenced are from the Polyporales, he noted in his proposal, many of the fungi involved in breaking down leaf litter and buried wood are from the order Agaricales.

Now at the University of Connecticut, Jonathan Klassen conducted postdoctoral studies at GLBRC researcher Cameron Currie’s lab at University of Wisconsin-Madison. His project will study interactions in ant-microbial community fungus gardens in three states to learn more about how the associated bacterial metagenomes contribute to carbon and nitrogen cycling.

Hinsby Cadillo-Quiroz, at Arizona State University, will conduct a study of the microbial communities in the Amazon peatlands to understand their roles in both emitting greenhouse gases and in storing and cycling carbon. The peatlands are hotspots of soil organic carbon accumulation, and in the tropical regions, they are estimated to hold between 11 percent and 14 percent, or nearly 90 gigatons, of the global carbon stored in soils.

Barbara Campbell, Clemson University will study carbon cycling mechanisms of active bacteria and associated viruses in the freshwater to marine transition zone of the Delaware Bay. Understanding the microbes’ metabolism would help researchers understand they capabilities with regard to dealing with contaminants, and their roles in the nitrogen, sulfur and carbon cycles.

Jim Fredrickson of Pacific Northwest National Laboratory will characterize functional profiles of microbial mats in California, Washington and Yellowstone National Park to understand various functions such as how they produce hydrogen and methane, and break down cellulose.

Joyce Loper of USDA-ARS will carry out a comparative analysis of all Pseudomonas bacteria getting from DOE JGI the sequences of just over 100 type strains to infer a evolutionary history of the this genus — a phylogeny — to characterize the genomic diversity, and determine the distribution of genes linked to key observable traits in this non-uniform group of bacteria.

Holly Simon of Oregon Health & Science University is studying microbial populations in the Columbia River estuary, in part to learn how they enhance greenhouse gas CO2 methane and nitrous oxide production.

Michael Thon from Spain’s University of Salamanca will explore sequences of strains of the Colletotrichum species complex, which include fungal pathogens that infect many crops. One of the questions he and his team will ask is how these fungal strains have adapted to break down the range of plant cell wall compositions.

Kathleen Treseder of UC Irvine will study genes involved in sensitivity to higher temperatures in fungi from a warming experiment in an Alaskan boreal forest. The team’s plan is to fold the genomic information gained into a trait-based ecosystem model called DEMENT to predict carbon dioxide emissions under global warming.

Mary Wildermuth of UC Berkeley will study nearly a dozen genomes of powdery mildew fungi, including three that infect designated bioenergy crops. The project will identify the mechanisms by which the fungi successfully infect plants, information that could lead to the development of crops with improved resistance to fungal infection and limiting fungicide use to allow more sustainable agricultural practices.

Several researchers who have previously collaborated with the DOE JGI have new projects:

Ludmila Chistoserdova from the University of Washington had a pioneering collaboration with the DOE JGI to study microbial communities in Lake Washington. In her new project, she and her team will look at the microbes in the Lake Washington sediment to understand their role in metabolizing the potent greenhouse gas methane.

Rick Cavicchioli of Australia’s University of New South Wales will track how microbial communities change throughout a complete annual cycle in three millennia-old Antarctic lakes and a near-shore marine site. By establishing what the microbes do in different seasons, he noted in his proposal, he and his colleagues hope to learn which microbial processes change and about the factors that control the evolution and speciation of marine-derived communities in cold environments.

With samples collected from surface waters down to the deep ocean, Steve Hallam from Canada’s University of British Columbia will explore metabolic pathways and compounds involved in marine carbon cycling processes to understand how carbon is regulated in the oceans.

The project of Hans-Peter Klenk, of DSMZ in Germany, will generate sequences of 1,000 strains of Actinobacteria, which represent the third most populated bacterial phylum and look for genes that encode cellulose-degrading enzymes or enzymes involved in synthesizing novel, natural products.

Han Wosten of the Netherlands’ Utrecht University will carry out a functional genomics approach to wood degradation by looking at Agaricomycetes, in particular the model white rot fungus Schizophyllum commune and the more potent wood-degrading white rots Phanaerochaete chrysosporium and Pleurotus ostreatus that the DOE JGI has previously sequenced.

Wen-Tso Liu of the University of Illinois and his colleagues want to understand the microbial ecology in anaerobic digesters, key components of the wastewater treatment process. They will study microbial communities in anaerobic digesters from the United States, East Asia and Europe to understand the composition and function of the microbes as they are harnessed for this low-cost municipal wastewater strategy efficiently removes waster and produces methane as a sustainable energy source.

Another project that involves wastewater, albeit indirectly, comes from Erica Young of the University of Wisconsin. She has been studying algae grown in wastewater to track how they use nitrogen and phosphorus, and how cellulose and lipids are produced. Her CSP project will characterize the relationship between the algae and the bacteria that help stabilize these algal communities, particularly the diversity of the bacterial community and the pathways and interactions involved in nutrient uptake and carbon sequestration.

Previous CSP projects and other DOE JGI collaborations are highlighted in some of the DOE JGI Annual User Meeting talks that can be seen here: http://usermeeting.jgi.doe.gov/past-speakers/. The 10th Annual Genomics of Energy and Environment Meeting will be held March 24-26, 2015 in Walnut Creek, Calif. A preliminary speakers list is posted here (http://usermeeting.jgi.doe.gov/) and registration will be opened in the first week of November.

Snail shells show high-rise plateau is much lower than it used to be

This is the Zhada Basin on the southwest Tibetan Plateau, with the Himalayas to the south. -  Joel Saylor
This is the Zhada Basin on the southwest Tibetan Plateau, with the Himalayas to the south. – Joel Saylor

The Tibetan Plateau in south-central Asia, because of its size, elevation and impact on climate, is one of the world’s greatest geological oddities.

At about 960,000 square miles it covers slightly more land area than Alaska, Texas and California combined, and its elevation is on the same scale as Mount Rainier in the Cascade Range of Washington state. Because it rises so high into the atmosphere, it helps bring monsoons over India and other nations to the south while the plateau itself remains generally arid.

For decades, geologists have debated when and how the plateau reached such lofty heights, some 14,000 feet above sea level, about half the elevation of the highest Himalayan peaks just south of the plateau.

But new research led by a University of Washington scientist appears to confirm an earlier improbable finding – at least one large area in southwest Tibet, the plateau’s Zhada Basin, actually lost 3,000 to 5,000 feet of elevation sometime in the Pliocene epoch.

“This basin is really high right now but we think it was a kilometer or more higher just 3 million to 4 million years ago,” said Katharine Huntington, a UW associate professor of Earth and space sciences and the lead author of a paper describing the research.

Co-authors are Joel Saylor of the University of Houston and Jay Quade and Adam Hudson, both of the University of Arizona. The paper was published online in August and will appear in a future print edition of the Geological Society of America Bulletin.

The Zhada Basin has rugged terrain, with exposed deposits of ancient lake and river sediments that make fossil shells of gastropods such as snails easily accessible, and determining their age is relatively straightforward. The researchers studied shells dating from millions of years ago and from a variety of aquatic environments. They also collected modern shell and water samples from a variety of environments for comparison.

The work confirms results of a previous study involving Saylor and Quade that examined the ratio of heavy isotope oxygen-18 to light isotope oxygen-16 in ancient snail shells from the Zhada Basin. They found the ratios were very low, which suggested the basin had a higher elevation in the past.

Oxygen-18 levels decrease in precipitation at higher elevations in comparison with oxygen-16, so shells formed in lakes and rivers that collect precipitation at higher elevations should have a lower heavy-to-light oxygen ratio. However, those lower ratios depend on a number of other factors, including temperature, evaporation and precipitation source, which made it difficult to say with certainty whether the low ratios found in the ancient snail shells meant a loss of elevation in the Zhada Basin.

So the scientists also employed a technique called clumped isotope thermometry, which Huntington has used and worked to refine for several years, to determine the temperature of shell growth and get an independent estimate of elevation change in the basin.

Bonding, or “clumping” together, of heavy carbon-13 and oxygen-18 isotopes in the carbonate of snail shells happens more readily at colder temperatures, and is measured using a tool called a mass spectrometer that provides data on the temperature of the lake or river water in which the snails lived.

The scientists found markedly greater “clumping,” as well as lower ratios of oxygen-18 to oxygen-16 in the ancient shells, indicating the shells formed at temperatures as much as 11 degrees Celsius (20 F) colder than average temperatures today, the equivalent of as much as 5,000 feet of elevation loss.

Just why the elevation decline happened is open to speculation. One possibility is that as faults in the region spread, the Zhada Basin lowered, Huntington said. It is unknown yet whether other parts of the southern plateau also lowered at the same time, but if elevation loss was widespread it could be because of broader fault spreading. It also is possible the crust thickened and forced large rock formations even deeper into the Earth, where they heated until they reached a consistency at which they could ooze out from beneath the crust, like toothpaste squeezed from the tube.

She noted that climate records from deep-sea fossils indicate Earth was significantly warmer when the cold Zhada Basin snail shells were formed.

“Our findings are a conservative estimate,” Huntington said. “No one can say this result is due to a colder climate, because if anything it should have been warmer.”

Scientists obtain new data on the weather 10,000 years ago from sediments of a lake in Sierra Nevada

University of Granada researchers are collecting samples in an Alpine lake in Sierra Nevada (Granada). -  UGRdivulga
University of Granada researchers are collecting samples in an Alpine lake in Sierra Nevada (Granada). – UGRdivulga

A research project which counts with the participation of the University of Granada has revealed new data on the climate change that took place in the Iberian Peninsula around the mid Holocene (around 6.000 years ago), when the amount of atmospheric dust coming from the Sahara increased. The data came from a study of the sediments found in an Alpine lake in Sierra Nevada (Granada)

This study, published in the journal Chemical Geology, is based on the sedimentation of atmospheric dust from the Sahara, a very frequent phenomenon in the South of the Iberian Peninsula. This phenomenon is easily identified currently, for instance, when a thin layer of red dust can be occasionally found on vehicles.

Scientists have studied an Alpine lake in Sierra Nevada, 3020 metres above sea level, called Rio Seco lake. They collected samples from sediments 1,5 metres deep, which represent approximately the last 11.000 years (a period known as Holocene), and they found, among other paleoclimate indicators, evidence of atmospheric dust coming from the Sahara. According to one of the researchers in this study, Antonio García-Alix Daroca, from the University of Granada, “the sedimentation of this atmospheric dust over the course of the Holocene has affected the vital cycles of the lakes in Sierra Nevada, since such dust contains a variety of nutrients and / or minerals which do not abound at such heights and which are required by certain organisms which dwell there.”

More atmospheric dust from the Sahara

This study has also revealed the existence of a relatively humid period during the early phase of the Holocene (10.000 – 6.000 years approximately). This period witnessed the onset of an aridification tendency which has lasted until our days, and it has coincided with an increase in the fall of atmospheric dust in the South of the Ibeian Peninsula, as a result of African dust storms.

“We have also detected certain climate cycles ultimately related to solar causes or the North Atlantic Oscillacion (NAO)”, according to García-Alix. “Since we do not have direct indicators of these climate and environmental changes, such as humidity and temperature data, in order to conduct this research we have resorted to indirect indicators, such as fossil polen, carbons and organic and inorganic geochemistry within the sediments”.

Ancient shellfish remains rewrite 10,000-year history of El Nino cycles

The middens are ancient dumping sites that typically contain a mix of mollusk shells, fish and bird bones, ceramics, cloth, charcoal, maize and other plants. -  M. Carré / Univ. of Montpellier
The middens are ancient dumping sites that typically contain a mix of mollusk shells, fish and bird bones, ceramics, cloth, charcoal, maize and other plants. – M. Carré / Univ. of Montpellier

The planet’s largest and most powerful driver of climate changes from one year to the next, the El Niño Southern Oscillation in the tropical Pacific Ocean, was widely thought to have been weaker in ancient times because of a different configuration of the Earth’s orbit. But scientists analyzing 25-foot piles of ancient shells have found that the El Niños 10,000 years ago were as strong and frequent as the ones we experience today.

The results, from the University of Washington and University of Montpellier, question how well computer models can reproduce historical El Niño cycles, or predict how they could change under future climates. The paper is now online and will appear in an upcoming issue of Science.

“We thought we understood what influences the El Niño mode of climate variation, and we’ve been able to show that we actually don’t understand it very well,” said Julian Sachs, a UW professor of oceanography.

The ancient shellfish feasts also upend a widely held interpretation of past climate.

“Our data contradicts the hypothesis that El Niño activity was very reduced 10,000 years ago, and then slowly increased since then,” said first author Matthieu Carré, who did the research as a UW postdoctoral researcher and now holds a faculty position at the University of Montpellier in France.

In 2007, while at the UW-based Joint Institute for the Study of the Atmosphere and Ocean, Carré accompanied archaeologists to seven sites in coastal Peru. Together they sampled 25-foot-tall piles of shells from Mesodesma donacium clams eaten and then discarded over centuries into piles that archaeologists call middens.

While in graduate school, Carré had developed a technique to analyze shell layers to get ocean temperatures, using carbon dating of charcoal from fires to get the year, and the ratio of oxygen isotopes in the growth layers to get the water temperatures as the shell was forming.

The shells provide 1- to 3-year-long records of monthly temperature of the Pacific Ocean along the coast of Peru. Combining layers of shells from each site gives water temperatures for intervals spanning 100 to 1,000 years during the past 10,000 years.

The new record shows that 10,000 years ago the El Niño cycles were strong, contradicting the current leading interpretations. Roughly 7,000 years ago the shells show a shift to the central Pacific of the most severe El Niño impacts, followed by a lull in the strength and occurrence of El Niño from about 6,000 to 4,000 years ago.

One possible explanation for the surprising finding of a strong El Niño 10,000 years ago was that some other factor was compensating for the dampening effect expected from cyclical changes in Earth’s orbit around the sun during that period.

“The best candidate is the polar ice sheet, which was melting very fast in this period and may have increased El Niño activity by changing ocean currents,” Carré said.

Around 6,000 years ago most of the ice age floes would have finished melting, so the effect of Earth’s orbital geometry might have taken over then to cause the period of weak El Niños.

In previous studies, warm-water shells and evidence of flooding in Andean lakes had been interpreted as signs of a much weaker El Niño around 10,000 years ago.

The new data is more reliable, Carré said, for three reasons: the Peruvian coast is strongly affected by El Niño; the shells record ocean temperature, which is the most important parameter for the El Niño cycles; and the ability to record seasonal changes, the timescale at which El Niño can be observed.

“Climate models and a variety of datasets had concluded that El Niños were essentially nonexistent, did not occur, before 6,000 to 8,000 years ago,” Sachs said. “Our results very clearly show that this is not the case, and suggest that current understanding of the El Niño system is incomplete.

Volcano discovered smoldering under a kilometer of ice in West Antarctica

Mount Sidley, at the leading edge of the Executive Committee Range in Marie Byrd Land is the last volcano in the chain that rises above the surface of the ice. But a group of seismologists has detected new volcanic activity under the ice about 30 miles ahead of Mount Sidley in the direction of the range's migration. The new finding suggests that the source of magma is moving beyond the chain beneath the crust and the Antarctic Ice Sheet. -  Doug Wiens
Mount Sidley, at the leading edge of the Executive Committee Range in Marie Byrd Land is the last volcano in the chain that rises above the surface of the ice. But a group of seismologists has detected new volcanic activity under the ice about 30 miles ahead of Mount Sidley in the direction of the range’s migration. The new finding suggests that the source of magma is moving beyond the chain beneath the crust and the Antarctic Ice Sheet. – Doug Wiens

It wasn’t what they were looking for but that only made the discovery all the more exciting.

In January 2010 a team of scientists had set up two crossing lines of seismographs across Marie Byrd Land in West Antarctica. It was the first time the scientists had deployed many instruments in the interior of the continent that could operate year-round even in the coldest parts of Antarctica.

Like a giant CT machine, the seismograph array used disturbances created by distant earthquakes to make images of the ice and rock deep within West Antarctica.

There were big questions to be asked and answered. The goal, says Doug Wiens, professor of earth and planetary science at Washington University in St. Louis and one of the project’s principle investigators, was essentially to weigh the ice sheet to help reconstruct Antarctica’s climate history. But to do this accurately the scientists had to know how the earth’s mantle would respond to an ice burden, and that depended on whether it was hot and fluid or cool and viscous. The seismic data would allow them to map the mantle’s properties.

In the meantime, automated-event-detection software was put to work to comb the data for anything unusual.

When it found two bursts of seismic events between January 2010 and March 2011, Wiens’ PhD student Amanda Lough looked more closely to see what was rattling the continent’s bones.

Was it rock grinding on rock, ice groaning over ice, or, perhaps, hot gases and liquid rock forcing their way through cracks in a volcanic complex?

Uncertain at first, the more Lough and her colleagues looked, the more convinced they became that a new volcano was forming a kilometer beneath the ice.

The discovery of the new as yet unnamed volcano is announced in the Nov. 17 advanced online issue of Nature Geoscience.

Following the trail of clues

The teams that install seismographs in Antarctica are given first crack at the data. Lough had done her bit as part of the WUSTL team, traveling to East Antarctica three times to install or remove stations in East Antarctica.

In 2010 many of the instruments were moved to West Antarctica and Wiens asked Lough to look at the seismic data coming in, the first large-scale dataset from this part of the continent.

“I started seeing events that kept occurring at the same location, which was odd, “Lough said. “Then I realized they were close to some mountains-but not right on top of them.”

“My first thought was, ‘Okay, maybe its just coincidence.’ But then I looked more closely and realized that the mountains were actually volcanoes and there was an age progression to the range. The volcanoes closest to the seismic events were the youngest ones.”

The events were weak and very low frequency, which strongly suggested they weren’t tectonic in origin. While low-magnitude seismic events of tectonic origin typically have frequencies of 10 to 20 cycles per second, this shaking was dominated by frequencies of 2 to 4 cycles per second.

Ruling out ice

But glacial processes can generate low-frequency events. If the events weren’t tectonic could they be glacial?

To probe farther, Lough used a global computer model of seismic velocities to “relocate” the hypocenters of the events to account for the known seismic velocities along different paths through the Earth. This procedure collapsed the swarm clusters to a third their original size.

It also showed that almost all of the events had occurred at depths of 25 to 40 kilometers (15 to 25 miles below the surface). This is extraordinarily deep-deep enough to be near the boundary between the earth’s crust and mantle, called the Moho, and more or less rules out a glacial origin.

It also casts doubt on a tectonic one. “A tectonic event might have a hypocenter 10 to 15 kilometers (6 to 9 miles) deep, but at 25 to 40 kilometers, these were way too deep,” Lough says.

A colleague suggested that the event waveforms looked like Deep Long Period earthquakes, or DPLs, which occur in volcanic areas, have the same frequency characteristics and are as deep. “Everything matches up,” Lough says.

An ash layer encased in ice

The seismologists also talked to Duncan Young and Don Blankenship of the University of Texas who fly airborne radar over Antarctica to produce topographic maps of the bedrock. “In these maps, you can see that there’s elevation in the bed topography at the same location as the seismic events,” Lough says.

The radar images also showed a layer of ash buried under the ice. “They see this layer all around our group of earthquakes and only in this area,” Lough says.

“Their best guess is that it came from Mount Waesche, an existing volcano near Mt Sidley. But that is also interesting because scientists had no idea when Mount Waesche was last active, and the ash layer is sets the age of the eruption at 8,000 years ago. “

What’s up down there?

The case for volcanic origin has been made. But what exactly is causing the seismic activity?

“Most mountains in Antarctica are not volcanic,” Wiens says, “but most in this area are. Is it because East and West Antarctica are slowly rifting apart? We don’t know exactly. But we think there is probably a hot spot in the mantle here producing magma far beneath the surface.”

“People aren’t really sure what causes DPLs,” Lough says. “It seems to vary by volcanic complex, but most people think it’s the movement of magma and other fluids that leads to pressure-induced vibrations in cracks within volcanic and hydrothermal systems.”

Will the new volcano erupt?

“Definitely,” Lough says. “In fact because of the radar shows a mountain beneath the ice I think it has erupted in the past, before the rumblings we recorded.

Will the eruptions punch through a kilometer or more of ice above it?

The scientists calculated that an enormous eruption, one that released a thousand times more energy than the typical eruption, would be necessary to breach the ice above the volcano.

On the other hand a subglacial eruption and the accompanying heat flow will melt a lot of ice. “The volcano will create millions of gallons of water beneath the ice-many lakes full,” says Wiens. This water will rush beneath the ice towards the sea and feed into the hydrological catchment of the MacAyeal Ice Stream, one of several major ice streams draining ice from Marie Byrd Land into the Ross Ice Shelf.

By lubricating the bedrock, it will speed the flow of the overlying ice, perhaps increasing the rate of ice-mass loss in West Antarctica.

“We weren’t expecting to find anything like this,” Wiens says

Study finds earlier peak for Spain’s glaciers

Jane Willenbring (upper right) takes samples to date a boulder in Spain's Bejar mountain range. Her findings helped show that ancient glaciers in the region reached their maximum size several thousands of years earlier than once believed. -  University of Pennsylvania
Jane Willenbring (upper right) takes samples to date a boulder in Spain’s Bejar mountain range. Her findings helped show that ancient glaciers in the region reached their maximum size several thousands of years earlier than once believed. – University of Pennsylvania

The last glacial maximum was a time when Earth’s far northern and far southern latitudes were largely covered in ice sheets and sea levels were low. Over much of the planet, glaciers were at their greatest extent roughly 20,000 years ago. But according to a study headed by University of Pennsylvania geologist Jane Willenbring, that wasn’t true in at least one part of southern Europe. Due to local effects of temperature and precipitation, the local glacial maximum occurred considerably earlier, around 26,000 years ago.

The finding sheds new light on how regional climate has varied over time, providing information that could lead to more-accurate global climate models, which predict what changes Earth will experience in the future.

Willenbring, an assistant professor in Penn’s Department of Earth and Environmental Science in the School of Arts and Sciences, teamed with researchers from Spain, the United Kingdom, China and the United States to pursue this study of the ancient glaciers of southern Europe.

“We wanted to unravel why and when glaciers grow and shrink,” Willenbring said.

In the study site in central Spain, it is relatively straightforward to discern the size of ancient glaciers, because the ice carried and dropped boulders at the margin. Thus a ring of boulders marks the edge of the old glacier.

It is not as easy to determine what caused the glacier to grow, however. Glaciers need both moisture and cold temperatures to expand. Studying the boulders that rim the ancient glaciers alone cannot distinguish these contributions. Caves, however, provide a way to differentiate the two factors. Stalagmites and stalactites – the stony projections that grow from the cave floor and ceiling, respectively – carry a record of precipitation because they grow as a result of dripping water.

“If you add the cave data to the data from the glaciers, it gives you a neat way of figuring out whether it was cold temperatures or higher precipitation that drove the glacier growth at the time,” Willenbring said.

The researchers conducted the study in three of Spain’s mountain ranges: the Bejár, Gredos and Guadarrama. The nearby Eagle Cave allowed them to obtain indirect precipitation data.

To ascertain the age of the boulders strewn by the glaciers and thus come up with a date when glaciers were at their greatest extent, Willenbring and colleagues used a technique known as cosmogenic nuclide exposure dating, which measures the chemical residue of supernova explosions. They also used standard radiometric techniques to date stalagmites from Eagle Cave, which gave them information about fluxes in precipitation during the time the glaciers covered the land.

“Previously, people believe the last glacial maximum was somewhere in the range of 19-23,000 years ago,” Willenbring said. “Our chronology indicates that’s more in the range of 25-29,000 years ago in Spain.”

The geologists found that, although temperatures were cool in the range of 19,000-23,000 years ago, conditions were also relatively dry, so the glaciers did not regain the size they had obtained several thousand years earlier, when rain and snowfall totals were higher. They reported their findings in the journal Scientific Reports.

Given the revised timeline in this region, Willenbring and colleagues determined that the increased precipitation resulted from changes in the intensity of the sun’s radiation on the Earth, which is based on the planet’s tilt in orbit. Such changes can impact patterns of wind, temperature and storms.

“That probably means there was a southward shift of the North Atlantic Polar Front, which caused storm tracks to move south, too,” Willenbring said. “Also, at this time there was a nice warm source of precipitation, unlike before and after when the ocean was colder.”

Willenbring noted that the new date for the glacier maximum in the Mediterranean region, which is several thousands of years earlier than the date the maximum was reached in central Europe, will help provide more context for creating accurate global climate models.

“It’s important for global climate models to be able to test under what conditions precipitation changes and when sources for that precipitation change,” she said. “That’s particularly true in some of these arid regions, like the American Southwest and the Mediterranean.”

When glaciers were peaking in the Mediterranean around 26,000 years ago, the American Southwest was experiencing similar conditions. Areas that are now desert were moist. Large lakes abounded, including Lake Bonneville, which covered much of modern-day Utah. The state’s Great Salt Lake is what remains.

“Lakes in this area were really high for 5,000-10,000 years, and the cause for that has always been a mystery,” Willenbring said. “By looking at what was happening in the Mediterranean, we might eventually be able to say something about the conditions that led to these lakes in the Southwest, too.”