Scientists return from expedition to drill beneath frozen Russian lake

The project site was near the center of Lake E'gygytgyn; the lake's eastern rim is visible. -  Julie Brigham-Grette, University of Massachusetts
The project site was near the center of Lake E’gygytgyn; the lake’s eastern rim is visible. – Julie Brigham-Grette, University of Massachusetts

A team of scientists from the United States, Germany, Russia and Austria has just returned from a six-month drilling expedition to a frozen lake in Siberia: Lake El’gygytgyn, “Lake E” for short.

Lake E was created 3.6 million years ago when a meteor more than a half-mile wide hit Earth and formed an 11-mile wide crater.

There, the researchers collected the longest sediment core samples retrieved in the Arctic region. Information contained in the cores, say the scientists, is of unprecedented significance for understanding climate change in the Arctic.

Cores collected from three holes drilled under the frozen Lake E are more than 30 times longer than cores from the Greenland Ice Sheet, according to geoscientist Julie Brigham-Grette of the University of Massachusetts at Amherst, the lead U.S. scientist on the project.

The research team will compare this Arctic record with oceanic and land-based records from lower latitudes to better understand global climate change.

Nearly 3.5 tons of temperature-controlled sediment cores are being flown by special cargo plane from Siberia to St. Petersburg in early June, then on to a lab in Germany to begin analysis by paleoclimatologists.

Archived core halves will arrive later at the University of Minnesota’s LacCore facility, where they will be preserved in cold storage.

Brigham-Grette says the team recovered a total of 1,165 feet of sediments; the sediment record collected extends back roughly two million years.

“Studying high-latitude systems is of great importance to an understanding of Earth’s climate at all latitudes,” says Paul Filmer, program director in the National Science Foundation (NSF)’s Division of Earth Sciences, which co-funded the expedition to Lake E with NSF’s Office of Polar Programs. “Of primary interest is determining why and how the Arctic evolved from a warm forested ecosystem to a cold permafrost ecosystem between two and three million years ago.”

The continuous record collected in this unique lake “offers us a way to look at the glacial/interglacial climate change of the past,” Brigham-Grette says.

“Earth’s warm and cold cycles over the past one million years varied every 100,000 years at times. Before that, however, climate change, especially in high latitudes, varied over 41,000- and 23,000-year cycles. The record from Lake E will show the ramp up to that type of change in the Earth’s climate.”

Below the lake’s sediments, cores drilled into bedrock will offer geologists a rare opportunity to study meteor impact melt rocks from one of the best preserved large meteor impact craters on Earth, and the only one formed in silicon-rich volcanic rock.

The team recovered roughly 40 meters (131 feet) of the earliest history of the lake in the warm middle Pliocene. This geologic time interval is fascinating, says Brigham-Grette, as a possible analog for future climate.

Initial results from the drilling are still limited.

The sediment cores could not opened in the field because of the remoteness of the drilling site, and rough transportation overland.

During pilot coring in November, the scientists recovered 141 meters (462 feet) of sediments showing alluvial fan and lake deposits in permafrost at the western edge of the lake outside the talik (unfrozen ground in an area of permafrost).

After drilling, the borehole was permanently instrumented for future ground temperature monitoring as part of the Global Terrestrial Network for Permafrost.

Ancient volcanic eruptions caused global mass extinction

A previously unknown giant volcanic eruption that led to global mass extinction 260 million years ago has been uncovered by scientists at the University of Leeds.

The eruption in the Emeishan province of south-west China unleashed around half a million cubic kilometres of lava, covering an area 5 times the size of Wales, and wiping out marine life around the world.

Unusually, scientists were able to pinpoint the exact timing of the eruption and directly link it to a mass extinction event in the study published today in Science. This is because the eruptions occurred in a shallow sea – meaning that the lava appears today as a distinctive layer of igneous rock sandwiched between layers of sedimentary rock containing easily datable fossilized marine life.

The layer of fossilized rock directly after the eruption shows mass extinction of different life forms, clearly linking the onset of the eruptions with a major environmental catastrophe.

The global effect of the eruption is also due to the proximity of the volcano to a shallow sea. The collision of fast flowing lava with shallow sea water caused a violent explosion at the start of the eruptions – throwing huge quantities of sulphur dioxide into the stratosphere.

“When fast flowing, low viscosity magma meets shallow sea it’s like throwing water into a chip pan – there’s spectacular explosion producing gigantic clouds of steam,” explains Professor Paul Wignall, a palaeontologist at the University of Leeds, and the lead author of the paper.

The injection of sulphur dioxide into the atmosphere would have lead to massive cloud formation spreading around the world – cooling the planet and ultimately resulting in a torrent of acid rain. Scientists estimate from the fossil record that the environmental disaster happened at the start of the eruption.

“The abrupt extinction of marine life we can clearly see in the fossil record firmly links giant volcanic eruptions with global environmental catastrophe, a correlation that has often been controversial,” adds Professor Wignall.

Previous studies have linked increased carbon dioxide produced by volcanic eruptions with mass extinctions. However, because of the very long term warming effect that occurs with increased atmospheric carbon dioxide (as we see with current climate change) the causal link between global environmental changes and volcanic eruptions has been hard to confirm.

A research work will be the reference to characterize the climatic impact of desert dust

In the context of the climatic change of the planet, those research works that throw light on global warming are of great interest. That is the case of the studies on atmospheric aerosol, a suspension of solid or liquid particles on a gaseous environment that can contribute to the warming or cooling of the atmosphere.

Juan Luis Guerrero Rascado developed his doctoral thesis “Lidar Technique for atmospheric characterization by elastic and Raman dispersion” precisely in this research line, supervised by the Professor of the University of Granada, Lucas Alados Arboledas, director of the Group of Atmospheric Physics of the Andalusian Centre for Environmental Studies, CEAMA.

“The interest of studying the atmospheric aerosol resides in the fact that these particles influence enormously the radioactive balance of Earth, so that they can modify it and, according to the effects, there can be an atmospheric warming or cooling”, says Guerrero Rascado.

Use and fine tuning of the LIDAR technique


According to Professor Alados, “the implementation of the Lidar technique is much more useful than the traditional techniques used in similar studies, as it permits us to get to know the vertical distribution of atmospheric aerosol, in which levels, in which quantity and the characteristics of such aerosol in every moment”.

This technique is very similar to a radar, says the researcher, “as it consists in emitting an electromagnetic radiation, in this case laser light, which propagates in the atmosphere, interacts with the particles in suspension and afterwards, collects the radiation returned to the instrument to study from that received sign the features and the position of particles”.

The research work, which has required a four-year effort, was organized in three main lines: the fine tuning of the equipment; the development of algorithms for profile inversion of aerosol optical properties by active tele-detection, using the Lidar technique; an the taking of measures (from the CEAMA, in Granada) both routine and intensive campaigns of phenomenon as mineral dust intrusions from the desert of Sahara, and in the framework of programmes of validation of satellites of the NASA.

The Lidar technique has been used in different countries all over the world. The station of the Andalusian Centre for Environmental Studies, in Granada, belongs to the European network EARLINET, which also interacts with a global network of solar photometry, Aeronet, coordinated by the Nasa. At present, the EARLINET network is centred on the validation of the data of the satellite Calipso, so that a monitoring of the atmospheric aerosol with vertical resolution at a global scale global can be carried out, for a better understanding of the climatic system of Earth.

Microfossils challenge prevailing views of the effects of ‘Snowball Earth’ glaciations on life

This is Robin Nagy on a UCSB geology field trip to Death Valley. -  Susie Leska-Anderson
This is Robin Nagy on a UCSB geology field trip to Death Valley. – Susie Leska-Anderson

New fossil findings discovered by scientists at UC Santa Barbara challenge prevailing views about the effects of “Snowball Earth” glaciations on life, according to an article in the June issue of the journal Nature Geoscience.

By analyzing microfossils in rocks from the bottom of the Grand Canyon, the authors have challenged the view that has been generally assumed to be correct for the widespread die-off of early life on Earth.

“Snowball Earth” is the popular term for glaciations that occurred between approximately 726 and 635 million years ago and are hypothesized to have entombed the planet in ice, explained co-author Susannah Porter, assistant professor of earth science at UCSB. It has long been noted that these glaciations are associated with a big drop in the fossil diversity, suggesting a mass die-off at this time, perhaps due to the severity of the glaciations. However, the authors of the study found evidence suggesting that this drop in diversity occurred some 16 million or more years before the glaciations. And, they offer an alternative reason for the drop.

A location called the Chuar Group in the Grand Canyon serves as “one of the premier archives of mid-Neoproterozoic time,” according to the article. This time period, before Snowball Earth, is preserved as a sort of “snapshot” in the canyon walls.

The scientists found that diverse assemblages of microscopic organic-walled fossils called acritarchs, which dominate the fossil record of this time, are present in lower rocks of the Chuar Group, but are absent from higher strata. In their place, there is evidence for the bacterial blooms that, the authors hypothesize, most likely appeared because of an increase in nutrients in the surface waters. This process is known as eutrophication, and occurs today in coastal areas and lakes that receive abundant runoff from fertilizers used in farming.

“One or a few species of phytoplankton monopolizes nutrients at the expense of others,” said Porter, explaining the die-off of diverse acritarchs. “In addition, the algal blooms result in high levels of organic matter production, which we see evidence of in the high organic carbon content in upper Chuar Group rocks. In fact, the organic carbon content is so high in the upper Chuar Group, oil companies were interested in the Chuar Group as a possible source of oil and natural gas.” As a result of high levels of organic matter, oxygen levels in the water can become depleted, resulting in widespread “dead zones.” Porter and colleagues also found evidence for extreme anoxia in association with the bacterial blooms.

In an accompanying article describing the process of discovering the microfossils, Porter described a highlight of the trip, “?when we rode through the rapids and descended into ‘Powell’s bowels’ — where the oldest rocks in the Grand Canyon frame the river passage. These rocks formed deep in the Earth approximately 1.8 billion years ago, and are very different in appearance from the overlying rocks.”

The scientists braved extreme sun, rattlesnakes, scorpions, and dehydration to gather their data. They traveled by foot, helicopter, and river rafts, the last of which capsized on one occasion — although the samples remained intact.

A hidden drip, drip, drip beneath Earth’s surface

There are very few places in the world where dynamic activity taking place beneath Earth’s surface goes undetected.

Volcanoes, earthquakes, and even the sudden uplifting or sinking of the ground are all visible results of restlessness far below, but according to research by Arizona State University (ASU) seismologists, dynamic activity deep beneath us isn’t always expressed on the surface.

The Great Basin in the western United States is a desert region largely devoid of major surface changes. The area consists of small mountain ranges separated by valleys and includes most of Nevada, the western half of Utah and portions of other nearby states.

For tens of millions of years, the Great Basin has been undergoing extension–the stretching of Earth’s crust.

While studying the extension of the region, geologist John West of ASU was surprised to find that something unusual existed beneath this area’s surface.

West and colleagues found that portions of the lithosphere–the crust and uppermost mantle of the Earth–had sunk into the more fluid upper mantle beneath the Great Basin and formed a large cylindrical blob of cold material far below the surface of central Nevada.

It was an extremely unexpected finding in a location that showed no corresponding changes in surface topography or volcanic activity, West says.

West compared his unusual results of the area with tomography models–CAT scans of the inside of Earth–done by geologist Jeff Roth, also of ASU. West and Roth are graduate students; working with their advisor, Matthew Fouch, the team concluded that they had found a lithospheric drip.

Results of their research, funded by the National Science Foundation (NSF), were published in the May 24 issue of the journal Nature Geoscience.

“The results provide important insights into fine-scale mantle convection processes, and their possible connections with volcanism and mountain-building on Earth’s surface,” said Greg Anderson, program director in NSF’s Division of Earth Sciences.

A lithospheric drip can be envisioned as honey dripping off a spoon, where an initial lithospheric blob is followed by a long tail of material.

When a small, high-density mass is embedded near the base of the crust and the area is warmed up, the high-density piece will be heavier than the area around it and it will start sinking. As it drops, material in the lithosphere starts flowing into the newly created conduit.

Seismic images of mantle structure beneath the region provided additional evidence, showing a large cylindrical mass 100 km wide and at least 500 km tall (about 60 by 300 miles).

“As a general rule, I have been anti-drip since my early days as a scientist,” admits Fouch. “The idea of a lithospheric drip has been used many times over the years to explain things like volcanism, surface uplift, surface subsidence, but you could never really confirm it–and until now no one has caught a drip in the act, so to speak.”

Originally, the team didn’t think any visible signs appeared on the surface.

“We wondered how you could have something like a drip that is drawing material into its center when the surface of the whole area is stretching apart,” says Fouch.

“But it turns out that there is an area right above the drip, in fact the only area in the Great Basin, that is currently undergoing contraction. John’s finding of a drip is therefore informing geologists to develop a new paradigm of Great Basin evolution.”

Scientists have known about the contraction for some time, but have been arguing about its cause.

As a drip forms, surrounding material is drawn in behind it; this means that the surface should be contracting toward the center of the basin. Since contraction is an expected consequence of a drip, a lithospheric drip could well be the answer to what is being observed in the Great Basin.

“Many in the scientific community thought it couldn’t be a drip because there wasn’t any elevation change or surface manifestation, and a drip has historically always been connected with major surface changes,” says West.

“But those features aren’t required to have the drip. Under certain conditions, like in the Great Basin, drips can form with little or no corresponding changes in surface topography or volcanic activity.”

All the numerical models computed by the team suggest that the drip isn’t going to cause things to sink down or pop up quickly, or cause lots of earthquakes.

There would likely be little or no impact on the people living above the drip. The team believes that the drip is a transient process that started some 15-20 million years ago, and probably recently detached from the overlying plate.

“This finding would not have been possible without the incredible wealth of seismic data captured by EarthScope’s Transportable Array (TA) as it moved across the western United States,” says West.

“We had access to data from a few long-term stations in the region, but the excellent data and 75-km grid spacing of the TA is what made these results possible.”

This is a great example “of science in action,” says Fouch.

“We went in not expecting to find this. Instead, we came up with a hypothesis that was not what anyone had proposed previously for the area, and then we tested the hypothesis with as many different types of data as we could find.

“In all cases so far it has held up. We’re excited to see how this discovery plays a role in the development of new ideas about the geologic history of the western U.S.”

Threat from West Antarctica less than previously believed

The potential contribution to sea level rise from a collapse of the West Antarctic Ice Sheet (WAIS) have been greatly overestimated, according to a new study published in the journal Science. Scientists estimate global sea level would rise 3.3 metres, not five or six, as previously thought. The Atlantic and Pacific seaboards of the US, even in the case of a partial collapse, would experience the largest increases, threatening cities such as New York, Washington DC and San Francisco.

Long thought of as the sleeping giant with respect to sea level rise, Antarctica holds about nine times the volume of ice of Greenland. Its western ice sheet is of particular interest to scientists due to its unusual below-sea level topography, which is believed to make it inherently unstable. But the area’s potential contribution to sea level has been greatly overestimated, according to new calculations.

Professor Jonathan Bamber at Bristol University, lead author of the study, said: “There’s a vast body of research that’s looked at the likelihood of a WAIS collapse and what implications such a catastrophic event would have for the globe. Yet all of these studies have assumed a five- to-six-metre contribution to sea level rise. Our calculation shows those estimates are much too large, even on a thousand year timescale.”

Jonathan Bamber, Professor in Physical Geography, at the University’s School of Geographical Sciences is currently a Visiting Fellow at the University of Colorado at Boulder’s Cooperative Institute for Research in Environmental Sciences, or CIRES.

Instead of assuming a complete disintegration of the whole WAIS, Bamber and colleagues used models, based on glaciological theory, to simulate how the massive ice sheet would respond if the floating ice shelves fringing the continent broke free. Vast ice shelves currently block the WAIS from spilling into the Weddell and Ross Seas, limiting total ice loss to the ocean.

According to theory, if these floating ice shelves were removed, sizeable areas of the WAIS would become, in effect, undammed, triggering an acceleration of the ice sheet towards the ocean and a “rapid” inland migration of the grounding line, the point where the ice sheet’s margins meets the ocean and begins to float.

The most unstable areas of the WAIS are those grounded below sea level on bedrock with negative bedslope, where the bedrock slopes downwards inland. Once undammed, these areas would quickly become buoyant, forming new floating ice shelves further inland and, in time, precipitating further break up and collapse.

For their calculations, the researchers assumed that only these areas would collapse and contribute to sea level rise. In contrast, they assumed areas grounded above sea level, or on bedrock that slopes upwards inland, would likely retain substantial ice masses.

Professor Bamber said: “Unlike the world’s other major ice sheets – the East Antarctic Ice Sheet and Greenland – WAIS is the only one with such an unstable configuration.”

Just how “rapid” a collapse of the WAIS would be is largely unknown. Though if such a large mass of ice steadily melted over 500 years, as suggested in an early study, it would add about 6.5 millimetres per year to sea level rise: twice the current rate due to all sources.

Professor Bamber added: “Interestingly, the pattern of sea level rise is independent of how fast or how much of the WAIS collapses. Even if the WAIS contributed only a metre of sea level rise over many years, sea levels along North America’s shorelines would still increase 25 per cent more than the global average.”

Regional variations in sea level would be largely driven by the redistribution of ice mass from the Antarctic continent to the oceans, according to the study. With less mass at the South Pole, Earth’s gravity field would weaken in the Southern Hemisphere and strengthen in the North, causing water to pile up in the northern oceans.

This redistribution of mass would also affect Earth’s rotation, which in turn would cause water to build up along the North American continent and in the Indian Ocean.

Asteroid attack 3.9 billion years ago may have enhanced early life on Earth

The bombardment of Earth by asteroids 3.9 billion years ago may have enhanced early life, according to a new University of Colorado study. -  NASA/JPL
The bombardment of Earth by asteroids 3.9 billion years ago may have enhanced early life, according to a new University of Colorado study. – NASA/JPL

The bombardment of Earth nearly 4 billion years ago by asteroids as large as Kansas would not have had the firepower to extinguish potential early life on the planet and may even have given it a boost, says a new University of Colorado at Boulder study.

Impact evidence from lunar samples, meteorites and the pockmarked surfaces of the inner planets paints a picture of a violent environment in the solar system during the Hadean Eon 4.5 to 3.8 billion years ago, particularly through a cataclysmic event known as the Late Heavy Bombardment about 3.9 million years ago. Although many believe the bombardment would have sterilized Earth, the new study shows it would have melted only a fraction of Earth’s crust, and that microbes could well have survived in subsurface habitats, insulated from the destruction.

“These new results push back the possible beginnings of life on Earth to well before the bombardment period 3.9 billion years ago,” said CU-Boulder Research Associate Oleg Abramov. “It opens up the possibility that life emerged as far back as 4.4 billion years ago, about the time the first oceans are thought to have formed.”

A paper on the subject by Abramov and CU-Boulder geological sciences Professor Stephen Mojzsis appears in the May 21 issue of Nature.

Because physical evidence of Earth’s early bombardment has been erased by weathering and plate tectonics over the eons, the researchers used data from Apollo moon rocks, impact records from the moon, Mars and Mercury, and previous theoretical studies to build three-dimensional computer models that replicate the bombardment. Abramov and Mojzsis plugged in asteroid size, frequency and distribution estimates into their simulations to chart the damage to the Earth during the Late Heavy Bombardment, which is thought to have lasted for 20 million to 200 million years.

The 3-D models allowed Abramov and Mojzsis to monitor temperatures beneath individual craters to assess heating and cooling of the crust following large impacts in order to evaluate habitability, said Abramov. The study indicated that less than 25 percent of Earth’s crust would have melted during such a bombardment.

The CU-Boulder researchers even cranked up the intensity of the asteroid barrage in their simulations by 10-fold — an event that could have vaporized Earth’s oceans. “Even under the most extreme conditions we imposed, Earth would not have been completely sterilized by the bombardment,” said Abramov.

Instead, hydrothermal vents may have provided sanctuaries for extreme, heat-loving microbes known as “hyperthermophilic bacteria” following bombardments, said Mojzsis. Even if life had not emerged by 3.9 billion years ago, such underground havens could still have provided a “crucible” for life’s origin on Earth, Mojzsis said.

The researchers concluded subterranean microbes living at temperatures ranging from 175 degrees to 230 degrees Fahrenheit would have flourished during the Late Heavy Bombardment. The models indicate that underground habitats for such microbes increased in volume and duration as a result of the massive impacts. Some extreme microbial species on Earth today — including so-called “unboilable bugs” discovered in hydrothermal vents in Yellowstone National Park — thrive at 250 F.

Geologic evidence suggests that life on Earth was present at least 3.83 billion years ago, said Mojzsis. “So it is not unreasonable to suggest there was life on Earth before 3.9 billion years ago. We know from the geochemical record that our planet was eminently habitable by that time, and this new study sews up a major problem in origins of life studies by sweeping away the necessity for multiple origins of life on Earth.”

Most planetary scientists believe a rogue planet as large as Mars smacked Earth with a glancing blow 4.5 billion years ago, vaporizing itself and part of Earth. The collision would have created an immense vapor cloud from which moonlets, and later our moon, coalesced, Mojzsis said. “That event, which preceded the Late Heavy Bombardment by at least 500 million years, would have effectively hit Earth’s re-set button,” he said.

“But our results strongly suggest that no events since the moon formation were capable of destroying Earth’s crust and wiping out any biosphere that was present,” Mojzsis said. “Instead of chopping down the tree of life, our view is that the bombardment pruned it.”

The results also support the potential for microbial life on other planets like Mars and perhaps even rocky, Earth-like planets in other solar systems that may have been resurfaced by impacts, said Abramov.

“Exactly when life originated on Earth is a hotly debated topic,” says
NASA’s Astrobiology Discipline Scientist Michael H. New, manager of the
Exobiology and Evolutionary Biology program. “These findings are significant
because they indicate life could have begun well before the LHB, during the
so-called Hadean Eon of Earth’s history 3.8 billion to 4.5 billion years
ago.”

Researchers make first direct observations of biological particles in high-altitude ice clouds

<IMG SRC="/Images/786419093.jpg" WIDTH="350" HEIGHT="133" BORDER="0" ALT="Scripps researcher Kerri Pratt with aerosol time-of-flight mass spectrometer (ATOFMS) aboard a specially outfitted C-130 aircraft operated by the National Center for Atmospheric Research in the skies over Wyoming. Scripps-led researchers made the first direct detections of airborne bacteria in clouds aboard the aircraft, and reported the results in the May 17 online edition of the journal Nature Geoscience. – Andrew J. Heymsfield, NCAR”>
Scripps researcher Kerri Pratt with aerosol time-of-flight mass spectrometer (ATOFMS) aboard a specially outfitted C-130 aircraft operated by the National Center for Atmospheric Research in the skies over Wyoming. Scripps-led researchers made the first direct detections of airborne bacteria in clouds aboard the aircraft, and reported the results in the May 17 online edition of the journal Nature Geoscience. – Andrew J. Heymsfield, NCAR

A team of UC San Diego-led atmospheric chemistry researchers moved closer to what is considered the “holy grail” of climate change science when it made the first-ever direct detection of biological particles within ice clouds.

The team, led by Kerri Pratt, a Ph.D. student of atmospheric chemistry Professor Kim Prather, who also holds appointments at Scripps Institution of Oceanography as well as the Department of Chemistry and Biochemistry at UCSD, sampled water droplet and ice crystal residues at high speeds from an aircraft flying through clouds in the skies over Wyoming in fall 2007. Analysis of the ice crystals revealed that they were made up almost entirely of either dust or biological particles such as bacteria, fungal spores and plant material. While it has long been known that microorganisms or parts of them get airborne and travel great distances, this study is the first to yield in-situ data on their participation in cloud ice processes.

Results of the Ice in Clouds Experiment – Layer Clouds (ICE-L), funded by the National Science Foundation (NSF) and the National Center for Atmospheric Research (NCAR), appear May 17 in the advance online edition of the journal Nature Geoscience.

“If we understand the sources of particles that nucleate clouds and their relative abundance, then we can determine the impact of these different sources on climate,” said Pratt.

The effects of tiny airborne particles called aerosols on cloud formation have been some of the most difficult aspects of weather and climate for scientists to understand. In the climate change science field, which derives many of its projections from computer simulations of climate phenomena, the actions of aerosols on clouds represent what scientists consider the greatest uncertainty in modeling predictions for the future.

“By sampling clouds in real time from an aircraft, these investigators were able to get information about ice particles in clouds at an unprecedented level of detail,” said Anne-Marine Schmoltner of the NSF’s Division of Atmospheric Sciences. “By determining the chemical composition of the very cores of individual ice particles, they discovered that both mineral dust, and, surprisingly, biological particles play a major role in the formation of clouds.”

Aerosols, ranging from dust, soot, sea salt to organic materials, some of which travel thousands of miles, form the skeletons of clouds. Around these nuclei, water and ice in the atmosphere condense and grow leading to precipitation. Scientists are trying to understand how they form as clouds play a critical role by both cooling the atmosphere and affect regional precipitation processes.


ICE-L was the first aircraft-based deployment of the aircraft aerosol time-of-flight mass spectrometer (A-ATOFMS) nicknamed “Shirley,” which was recently developed at UCSD with funding from NSF. The ICE-L team mounted the mass spectrometer and an ice chamber run by Colorado State University researcher Paul DeMott onto a C-130 aircraft operated by NCAR and made a series of flights through a type of cloud known as a wave cloud. The researchers performed in-situ measurements of cloud ice crystal residues and found that half were mineral dust and about a third contained nitrogen, phosphorus and carbon – the signature elements of biological matter.

The second-by-second analysis speed allowed the researchers to make distinctions between residues of water droplets and ice nuclei in real-time. Ice nuclei are rarer than droplet nuclei and are more likely to create precipitation.

The A-ATOFMS also allowed the unambiguous measurement of biological particles in the cloud ice, which scientists previously concluded serve as ice nuclei based on simulations in laboratory experiments and precipitation measurements. Based on modeling and the chemical composition of measured dust, the ICE-L team was able to identify the source of the dust as Asia or Africa. “This has really been kind of a holy grail measurement for us,” said Prather. “Understanding which particles form ice nuclei, which occur at extremely low concentrations and are inherently difficult to measure, means you can further understand processes that result in precipitation. Any new piece of information you can get is critical.”

The findings suggest that the biological particles that get swept up in dust storms help to induce the formation of cloud ice and that their region of origin makes a difference. Prather said initial evidence is increasingly suggesting that dust transported from Asia could be influencing precipitation in North America, for example.

Researchers hope to use the ICE-L data to design future studies timed to events when such particles may be playing a bigger role in triggering rain- or snowfall.

Arctic river deltas may hold clues to future global climate

Scientists struggling to understand how Earth’s climate will change in the next few decades have neglected a potential treasure trove of information-sediments deposited in the ocean by major Arctic rivers such as the Colville and Mackenzie rivers-according to geoscientists at The University of Texas at Austin and Texas A&M University.

The researchers’ study was published in the May 19 edition of Proceedings of the National Academy of Sciences.

Sediments deposited in large river deltas around the world record information about past sea level, productivity and storminess on the ocean margin, climate on the adjacent continents (including temperatures and precipitation) and human factors that affect sediment delivery to the margin (such as dams and levees), among other things. In addition to these climate factors, Arctic sediments, in particular, could contain records of changes on land due to warming, including permafrost temperature and melting of upland glaciers.

Mead Allison, senior research scientist at The University of Texas at Austin’s Jackson School of Geosciences and co-author of the study, said Arctic river deltas have been neglected as records of past climate because the far north is a challenging and expensive environment to work in and it only came to be seen as a bellwether for climate change in the last decade or so.

Arctic river deltas are critical to explore, the researchers reason, because the largest changes in climate are projected for the Arctic. Large amounts of carbon are stored in Arctic permafrost. As those soils thaw, rivers will transport much of their organic carbon to the oceans. As global warming speeds up the melting of shorefast ice (ice attached to the shore), it will likely accelerate coastal erosion from storms, providing a further supply of organic carbon to the coastal zone.

Allison described several ways these sediments could advance scientists’ understanding of the global climate system.

They could help answer a hotly debated question about the role of river deltas in the global carbon cycle. Scientists don’t know whether large river deltas are a net source or a net sink of carbon. Do they store more carbon than they produce? That’s a critical question because carbon dioxide is a major greenhouse gas. Large river deltas are the interface between the land and the oceans and they deliver large amounts of carbon carried along in sediments. As humans alter river systems by adding nutrients from fertilizers, damming water for power and diverting water for drinking and farming, they may be shifting the ability of those systems to fix, burn and store carbon.

“It’s a glaring gap in our understanding of the global carbon cycle,” Allison said. “It’s a potential gotcha in the global climate models. Each river system is different, but we have to get a handle on the net effects.”

Arctic river deposits could also confirm the existence of natural climate cycles that climate models need to take into account. For example, there is evidence supporting the existence of a climate cycle called the Arctic Oscillation that affects temperatures, precipitation and storminess at high latitudes. This cycle oscillates over several decades. But because there are only about 50 years of high quality climate data from the Arctic, it’s hard to determine to what extent changes now being observed are natural or due to human influence. River delta sediments might allow scientists to reconstruct Arctic climate for thousands of years into the past, and possibly confirm this natural baseline.

Finally, these sediments would establish past climate proxies for specific locations that could be monitored in the future to track the changing climate of the Arctic. If it is a region that will experience the biggest climate changes in this century, it will be important to establish how climate is recorded in sediments.

One advantage of studying margin sediments adjacent to large rivers in the Arctic and elsewhere is that they are deposited at a very high rate. This makes it possible to extract information on a year-to-year basis with high resolution.

Andes Mountains are older than previously believed

Sediments that gather at the base of mountains provide important clues about how and when the mountains were formed. -  Carlos Jaramillo, STRI
Sediments that gather at the base of mountains provide important clues about how and when the mountains were formed. – Carlos Jaramillo, STRI

The geologic faults responsible for the rise of the eastern Andes mountains in Colombia became active 25 million years ago-18 million years before the previously accepted start date for the Andes’ rise, according to researchers at the Smithsonian Tropical Research Institute in Panama, the University of Potsdam in Germany and Ecopetrol in Colombia.

“No one had ever dated mountain-building events in the eastern range of the Colombian Andes,” said Mauricio Parra, a former doctoral candidate at the University of Potsdam (now a postdoctoral fellow with the University of Texas) and lead author. “This eastern sector of America’s backbone turned out to be far more ancient here than in the central Andes, where the eastern ranges probably began to form only about 10 million years ago.”

The team integrated new geologic maps that illustrate tectonic thrusting and faulting, information about the origins and movements of sediments and the location and age of plant pollen in the sediments, as well as zircon-fission track analysis to provide an unusually thorough description of basin and range formation.

As mountain ranges rise, rainfall and erosion wash minerals like zircon from rocks of volcanic origin into adjacent basins, where they accumulate to form sedimentary rocks. Zircon contains traces of uranium. As the uranium decays, trails of radiation damage accumulate in the zircon crystals. At high temperatures, fission tracks disappear like the mark of a knife disappears from a soft block of butter. By counting the microscopic fission tracks in zircon minerals, researchers can tell how long ago sediments formed and how deeply they were buried.

Classification of nearly 17,000 pollen grains made it possible to clearly delimit the age of sedimentary layers.

The use of these complementary techniques led the team to postulate that the rapid advance of a sinking wedge of material as part of tectonic events 31 million years ago may have set the stage for the subsequent rise of the range.

“The date that mountain building began is critical to those of us who want to understand the movement of ancient animals and plants across the landscape and to engineers looking for oil and gas,” said Carlos Jaramillo, staff scientist from STRI. “We are still trying to put together a big tectonic jigsaw puzzle to figure out how this part of the world formed.”