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The Anthropocene: Hard evidence for a human-driven Earth

The evidence for a new geological epoch which marks the impact of human activity on Earth is now overwhelming according to a recent paper by an international group of geoscientists. The Anthropocene, which is argued to start in the mid-20th Century, is marked by the spread of materials such as aluminium, concrete, plastic, fly ash and fallout from nuclear testing across the planet, coincident with elevated greenhouse gas emissions and unprecedented trans-global species invasions.

An international group of scientists is studying whether human activity has driven Earth into a new geological epoch — the Anthropocene. They ask: to what extent are human actions recorded as measurable signals in geological strata, and is the Anthropocene world markedly different from the stable Holocene Epoch of the last 11,700 years that allowed human civilization to develop?

The Holocene Epoch has been a time during which human societies advanced by gradually domesticating the land to increase food production, built urban settlements and became proficient at developing the water, mineral and energy resources of the planet. The proposed Anthropocene Epoch, however, is marked as a time of rapid environmental change brought on by the impact of a surge in human population and increased consumption during the ‘Great Acceleration’ of the mid-20th century.

Dr Colin Waters of the British Geological Survey said: “Humans have long affected the environment, but recently there has been a rapid global spread of novel materials including aluminium, concrete and plastics, which are leaving their mark in sediments. Fossil-fuel combustion has dispersed fly ash particles worldwide, pretty well coincident with the peak distribution of the ‘bomb spike’ of radionuclides generated by atmospheric testing of nuclear weapons.” “All of this shows that there is an underlying reality to the Anthropocene concept,” commented Jan Zalasiewicz of the University of Leicester, a co-author and working group Chair.

The study, co-authored by 24 members of the Anthropocene Working Group, shows that humans have changed the Earth system sufficiently to produce a range of signals in sediments and ice, and these are sufficiently distinctive to justify recognition of an Anthropocene Epoch in the Geological Time Scale. In 2016 the Anthropocene Working Group will gather more evidence on the Anthropocene, which will help inform recommendations on whether this new time unit should be formalized and, if so, how it might be defined and characterized.

A number of UK members of the group have contributed to this study, Colin Waters (lead author and Secretary of the group) and Michael Ellis, both from the British Geological Survey, Jan Zalasiewicz, Mark Williams and Matt Edgeworth from Leicester University and Colin Summerhayes from Cambridge University have provided significant input to this study and maintain the UK’s strong involvement in research into the Anthropocene concept.

Reference:
Colin N. Waters, Jan Zalasiewicz, Colin Summerhayes, Anthony D. Barnosky, Clément Poirier, Agnieszka Gałuszka, Alejandro Cearreta, Matt Edgeworth, Erle C. Ellis, Michael Ellis, Catherine Jeandel, Reinhold Leinfelder, J. R. McNeill, Daniel deB. Richter, Will Steffen, James Syvitski, Davor Vidas, Michael Wagreich, Mark Williams, An Zhisheng, Jacques Grinevald, Eric Odada, Naomi Oreskes, and Alexander P. Wolfe. The Anthropocene is functionally and stratigraphically distinct from the Holocene. Science, 2016: 351 (6269) DOI: 10.1126/science.aad2622

Note: The above post is reprinted from materials provided by University of Leicester.

Deep-water ocean circulation, marine biodiversity and climate change

Fossil collecting in Putilovo Quarry, Russia. Credit: David Harper

A direct link has been shown between the greatest increase in Phanerozoic marine biodiversity and the onset of a sudden icehouse. The onset of sudden icehouse conditions during the Mid Ordovician was an abrupt change in climate. Prior to this, Earth was exposed to a prolonged super-greenhouse with sea surface temperatures estimated above 40 degree Celsius, thus, seriously affecting the ability of life to evolve and diversify. The researchers now speculate that the sudden emergence of icehouse conditions brought about fundamental changes in ocean circulation, instigating thermohaline circulation in the oceans.

The great increase in biodiversity took place during the geological period known as the Ordovician.

“This was a time in Earth history previously believed to be characterized by extreme CO2 levels. Due to the occurrence of a short-lived ice age towards the end of the Ordovician, this has been viewed by some climate skeptics as proof that fluctuating CO2 levels does not affect climate. Thus, human-made emissions due to the burning of fossil fuels therefore could not facilitate global warming,” lead author Christian M. Ø. Rasmussen explains.

“With this new study, that assumption can no longer be supported as we demonstrate clear-cut evidence for glaciations some 30 million years prior to the end Ordovician ice age,” he continues.

A culmination of a long-term international co-operative effort

Throughout the last 15 years the research team has analyzed a massive palaeontological dataset sampled in the field in western Russia and Estonia. More than 45,000 fossil trilobites and brachiopods were collected in the field and, thus, form the basis for the study.

They are applied to resolve palaeoecological details that reveal fluctuations in past climate. Based on the occurrences and ranges in time of key species within these two animal groups, a statistically supported relative sea level curve is constructed. With this sea level curve the research team demonstrate that sea level fell some 150 meters up though the 11 million years long investigated interval.

Two independent proxies both demonstrate a sudden cooling event

This sea level fall is supported by geochemical evidence based on stable isotope studies on Oxygen and Carbon. By extracting the mineral calcite from the shells of brachiopods collected bed-by-bed and analyzing the relationship between different naturally occurring oxygen isotopes the researchers show that sea bottom temperatures fell at least 5 degree Celsius in the same interval as the sea fall is registered.

Despite being a considerable temperature drop in itself, it is only a minimum estimate. This is because of the fact that the palaeocontinent of Baltica — on which the study area is located — drifted from about 40 degree S to 30 degree S in the interval covered by the study. Thus, Baltica moved at least 1,000 kilometers closer to the equator and thus one would expect ocean water temperatures to increase. However, the opposite is the case.

An Ice Age of great importance to biodiversity

The onset of sudden icehouse conditions during the Mid Ordovician was an abrupt change in climate. Prior to this, Earth was exposed to a prolonged super-greenhouse with sea surface temperatures estimated above 40 degree Celsius, thus, seriously affecting the ability of life to evolve and diversify. The researchers therefore speculate that the sudden emergence of icehouse conditions brought about fundamental changes in ocean circulation, instigating thermohaline circulation in the oceans.

Today this thermohaline ‘pump’ has a fundamental importance with respect to bioproductivity in the oceans. Thus, back in the Ordovician, an initiation of this pump which circulates warm surface waters with cold bottom waters could have sparked a massive increase in bioproductivity thereby facilitating the Great Ordovician Biodiversification Event.

The super-greenhouse that turned out to be an icehouse

“Our findings demonstrates the onset of icehouse conditions to occur some 30 million years prior to what was previously believed. The Late Ordovician Ice Age is thus no longer an enigmatic paradox in an otherwise prolonged super-greenhouse interval. Rather it was the climax in a prolonged icehouse interval spanning some 30-40 million years — thus representing very similar conditions to what Earth has witnessed since Oligocene-Miocene times (~30 million years),” says Rasmussen and elaborates

“Raging high CO2 levels during the Ordovician can thus no longer be supported. Therefore, the greatest increase in marine biodiversity in Earth history is now associated with icehouse conditions, not as previously believed, extreme greenhouse conditions.”

Video

Reference:
Christian M. Ø. Rasmussen, Clemens V. Ullmann, Kristian G. Jakobsen, Anders Lindskog, Jesper Hansen, Thomas Hansen, Mats E. Eriksson, Andrei Dronov, Robert Frei, Christoph Korte, Arne T. Nielsen, David A.T. Harper. Onset of main Phanerozoic marine radiation sparked by emerging Mid Ordovician icehouse. Scientific Reports, 2016; 6: 18884 DOI: 10.1038/srep18884

Note: The above post is reprinted from materials provided by Faculty of Science – University of Copenhagen.

First ever digital geologic map of Alaska

The Alaska Geologic Map shows the generalized geology of the state, each color representing a different type or age of rock. Credit: Frederic Wilson, USGS

A new digital geologic map of Alaska is being released today providing land users, managers and scientists geologic information for the evaluation of land use in relation to recreation, resource extraction, conservation, and natural hazards.

For the first time, this new geologic map of Alaska incorporates one of geology’s most significant paradigm shifts, the theory of plate tectonics, into this fully digital product. The map gives visual context to the abundant mineral and energy resources found throughout the state in a beautifully detailed and accessible format.

“I am pleased that Alaska will now have a state-wide digital map detailing both surface and subsurface geologic resources and conditions,” said USGS newly confirmed director Suzette Kimball. “This geologic map provides important information for the mineral and energy industries for exploration and remediation strategies. It will enable resource managers and land management agencies to evaluate resources and land use, and to prepare for natural hazards, such as earthquakes.”

“The data contained in this digital map will be invaluable,” said National Park Service Director Jonathan B. Jarvis. “It is a great resource and especially enhances the capacity for science-informed decision making for natural and cultural resources, interpretive programs, and visitor safety.”

“A better understanding of Alaska’s geology is vital to our state’s future. This new map makes a real contribution to our state, from the scientific work it embodies to the responsible resource production it may facilitate. Projects like this one underscore the important mission of the U.S. Geological Survey, and I’m thankful to them for completing it,” said Sen. Lisa Murkowski, R-Alaska.

This map is a completely new compilation, with this version carrying the distinction of being the first 100 percent digital statewide map. Alaska’s new map reflects the changes in our modern understanding of geology as it builds on the past. More than 750 references were used in creating the map, some as old as 1908 and as new as 2015. It shows an uncommon level of detail for state geologic maps. Being 100 percent digital this map has multiple associated databases that allow the creation of a variety of derivative maps and other products.

“This work is an important synthesis that will both increase public access to critical information and enhance the fundamental understanding of Alaska’s history, natural resources and environment,” said Mark Myers, Commissioner of Alaska’s Department of Natural Resources. “I applaud the collaborative nature of this effort, including the input provided by the Alaska Division of Geological and Geophysical Surveys, which will be useful for natural disaster preparation, resource development, land use planning and management, infrastructure and urban planning and management, education, and scientific research.”

Geologists and resource managers alike can utilize this latest geologic map of Alaska, but even the lay person will enjoy the visual feast of attractive color patterns on the map which shed light on the state’s geologic past and present. Nearly 20 years in the making, this release marks the 200th anniversary of the release of the world’s first geologic map by William Smith of England in 1815.

More than any other area of the United States, Alaska reflects a wide range of past and current geologic environments and processes. The map sheds light on the geologic past and present; today, geologic processes are still very important in Alaska; with many active volcanoes, frequent earthquakes, receding and advancing glaciers and visible climate impacts.

“This map is the continuation of a long line of USGS maps of Alaska, reflecting ever increasing knowledge of the geology of the state,” said Frederic Wilson, research geologist with the USGS and lead author of the new map. “In the past, starting in 1904, the maps came out about every 20 years; the 35-year gap between this edition and the last has been a time of major new mapping efforts by the USGS, as well as a revolution in the science of geology through the paradigm shift to plate tectonics, and the development of digital methods.”

Reference:
Frederic H. Wilson, Chad P. Hults, Charles G. Mull, and Susan M. Karl. Geologic Map of Alaska. Scientific Investigations Map 3340, 2016 DOI: 10.3133/sim3340

Note: The above post is reprinted from materials provided by United States Geological Survey.

Last meal reflects spiral-shaped intestine

Extinct predatory fish Saurichthys. Credit: UZH

A last meal provides new insights: The fossilized food remains of the extinct predatory fish Saurichthys reflect its spiral-shaped intestine. The spiral valve in fossils from Southern Switzerland is similar to that of sharks and rays. Paleontologists from the University of Zurich have thus closed a gap in the knowledge concerning the evolution of the gastrointestinal tract in vertebrates.

A last supper has provided some interesting findings. The digested and undigested remains of the last meal eaten by a Saurichthys, a Triassic bony fish, were discovered in a extraordinary case of preservation that paleontologists at the University of Zurich were quick to take advantage of. They used the fossilized gut contents to prepare the first complete documentation on the gastrointestinal anatomy of this primitive vertebrate.

The UZH researchers prepared the fossil, which came from the repository in Monte San Giorgio in Ticino. The preserved gut contents reflect the shape of the gut – as the team under Prof. Marcelo Sánchez was able to see and describe in detail using UV light. To investigate the evolutionary and functional implications of their observations, the researchers assembled a large dataset containing information on extinct and extant fishes. “We also performed statistical analyses that revealed unknown patterns of distribution of the intestinal structure”, explains Marcelo Sánchez. All of this led to the finding that Saurichthys had a straight stomach and a spiral valve.

Energetic lifestyle

The findings by the Zurich-based paleontologists unveil previously unexpected convergences with the gastrointestinal anatomy of present-day sharks and rays. “The anatomy of the gastrointestinal tract of Saurichthys, in particular the many windings in the spiral valve, show the most original digestion organs of earlier fishes”, says Thodoris Argyriou, a PhD student at the Paleontological Institute and Museum of the University of Zurich. The spiral valve of Saurichthys indicates an energy-laden lifestyle that was adjusted to the predatory and reproductive behavior of the genus. “The large number of windings increased the surface area for digestion, which is sure to have provided the fish with more energy”, says Thodoris Argyriou.

Reference:
Thodoris Argyriou et al. Exceptional preservation reveals gastrointestinal anatomy and evolution in early actinopterygian fishes, Scientific Reports (2016). DOI: 10.1038/srep18758

Note: The above post is reprinted from materials provided by University of Zurich.

An apatite for progress

Apatite crystals. Credit: Bruand et al.

Apatite has recently gained considerable attention as a mineral with many uses within the Earth and planetary sciences. Apatite chemistry has recently given new insight into a wide range of geological processes and tools, such as magmatism, metasomatism, planetary geochemistry, and geochronology. In their open-access Geology article, Emilie Bruand and colleagues expand the utility of apatite by presenting a novel way to fingerprint magma chemistry and petrogenesis using apatite inclusions within robust titanite and zircon.

Bruand and colleagues present trace element data from apatite mineral inclusions shielded within magmatic zircon and titanite. Importantly, apatite inclusion and host titanite chemistries detailed in this study allow estimation of the whole-rock Sr and SiO2. They show how these data can be used to assess the degree of fractionation of the host magma and to calculate key trace element abundances and ratios. They also demonstrate that the inclusions can be linked to discrete periods in the crystallization history of the host phases, thus providing insight into petrogenesis.

These results highlight the fact that apatite compositions might discriminate modern granitoids (younger than 2.5 Ga) from Archean-Proterozoic transitional granitoid compositions (sanukitoid signatures). Development of such a petrological tool has important potential for interpretation of provenance and a better understanding of the secular evolution of the continental crust, including that of early Earth.

Reference:
An apatite for progress: Inclusions in zircon and titanite constrain petrogenesis and provenance
Emilie Bruand et al., School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth PO1 3QL, UK. This paper is OPEN ACCESS online at DOI: 10.1130/G37301.1

Note: The above post is reprinted from materials provided by Geological Society of America.

Current pace of environmental change is unprecedented in Earth’s history

University of Bristol Cabot Institute researchers and their colleagues today published research that further documents the unprecedented rate of environmental change occurring today, compared to that which occurred during natural events in Earth’s history.

The research, published online on 4 January in Nature Geosciences reconstructs the changes in atmospheric carbon dioxide (pCO2) during a global environmental change event that occurred about 120 Million years ago. New geochemical data provide evidence that pCO2 increased in response to volcanic outgassing and remained high for around 1.5-2 million years, until enhanced organic matter burial in an oxygen-poor ocean caused areturn to original levels.

Lead author Dr David Naafs explained: ‘Past records of climate change must be well characterised if we want to understand how it affected or will affect ecosystems. It has been suggested that the event we studied is a suitable analogue to what is happening today due to human activity and that a rapid increase in pCO2 caused ocean acidification and a biological crisis amongst a group of calcifying marine algae. Our work confirms that there was a large increase in pCO2. The change, however, appears to have been far slower than that of today, taking place over hundreds of thousands of years, rather than the centuries over which human activity is increasing atmospheric carbon dioxide levels. So despite earlier claims, our research indicates that it is extremely unlikely that widespread surface ocean acidification occurred during this event.’

The observation that yet another putative ‘rapid’ geological event is occurring perhaps a thousand times slower than today and not associated with widespread surface ocean acidification has been the focus of much recent research at the University of Bristol. Co-author Professor Daniela Schmidt, who was also a Lead Author on the IPCC WGII report on Ocean systems, emphasised that today’s finding builds on one of the IPCC’s key conclusions: that the rate of environmental change occurring today is largely unprecedented in Earth history. She said, ‘This is another example that the current rate of environmental change has few if any precedents in Earth history, and this has big implications for thinking about both past and future change.’

The research was possible due to the exceptional Spanish section that the team analysed. Co-author Professor José Manuel Castro of the University of Jaen adds, ‘The sediments at Cau accumulated very rapidly resulting in an expanded section. This allowed the high resolution multidisciplinary analysis that are the basis for this important study.’

Senior Author and Director of the University’s Cabot Institute, Professor Rich Pancost, added, ‘We often use the geological record to help us test or expand our understanding of climate change, for example, determining the sensitivity of Earth’s temperature to higher CO2 levels. But testing the risks associated with the pace of modern environmental change is proving problematic, due to a lack of similar rapid changes in the geological past. Consequently, these risks, in this case to the marine ecosystems on which so many of us depend, remain associated with profound uncertainty. Decreasing CO2 emissions, as recently agreed in Paris, will be necessary to avoid these risks.’

Reference:
B. D. A. Naafs et al. Gradual and sustained carbon dioxide release during Aptian Oceanic Anoxic Event 1a, Nature Geoscience (2016). DOI: 10.1038/ngeo2627

Note: The above post is reprinted from materials provided by University of Bristol.

Enough oxygen on Earth long before animals rose

Oxygen is crucial for the existence of animals on Earth. But, an increase in oxygen did not apparently lead to the rise of the first animals. New research shows that 1.4 billion years ago there was enough oxygen for animals — and yet over 800 million years went by before the first animals appeared on Earth.

Animals evolved by about 600 million years ago, which was late in Earth’s history. The late evolution of animals, and the fact that oxygen is central for animal respiration, has led to the widely promoted idea that animal evolution corresponded with a late a rise in atmospheric oxygen concentrations.

“But sufficient oxygen in itself does not seem to be enough for animals to rise. This is indicated by our studies,” say postdoc Emma Hammarlund and Professor Don Canfield, Nordic Center for Earth Evolution, University of Southern Denmark.

Together with colleagues from the China National Petroleum Corporation and the University of Copenhagen, Hammarlund and Canfield have analyzed sediment samples from the Xiamaling Formation in China. Their analyses reveal that a deep ocean 1.4 billion years ago contained at least 4% of modern oxygen concentrations.

The new study is published in the journal Proceedings of National Academy of Sciences.

Usually it is very difficult to precisely determine past oxygen concentrations. The new study, however, combines several approaches to break new ground in understanding oxygen concentrations 1.4 billion years ago.

The study uses trace metal distributions to show that the bottom waters where the Xiamaling Formation sediments deposited contain oxygen. The distribution of biomarkers, molecules derived from ancient organisms, demonstrate that waters of intermediate depth contain no oxygen. Therefore, the Xiamaling Formation deposited in an ancient oxygen-minimum zone, similar to (but also different) from those found off the present coasts of Chile and Peru.

With this backdrop, the researchers used a simple ocean model to estimate the minimum concentrations to atmospheric oxygen required to reproduce the distribution of water-column oxygen in the Xiamaling Formation.

“The water column had an oxygen concentration at least 4 % of present atmospheric levels (PAL). That should be sufficient for animals to exist and evolve,” says Canfield.

“Having determined the lowest concentration of oxygen in the air almost one and a half billion years ago is unique,” says Hammarlund, adding:

“Researchers know of simple animals, such as sponges and worms, that today are capable of managing with less than 4% PAL, even much less.”

“Sponges probably resemble some of the first animals on Earth. If they manage with less than 4 % today’s oxygen levels, it is likely that the first animals could do with these concentrations or less,” says Canfield.

The results differ from other studies and raise several questions, such as: Why then did animals rise so late in Earth’s history?

“The sudden diversification of animals probably was a result of many factors. Maybe the oxygen rise had less to do with the animal revolution than we previously assumed,” says Hammarlund.

Reference:
Shuichang Zhang, Xiaomei Wang, Huajian Wang, Christian J. Bjerrum, Emma U. Hammarlund, M. Mafalda Costa, James N. Connelly, Baomin Zhang, Jin Su, Donald E. Canfield. Sufficient oxygen for animal respiration 1,400 million years ago. Proceedings of the National Academy of Sciences, 2016; 201523449 DOI: 10.1073/pnas.1523449113

Note: The above post is reprinted from materials provided by University of Southern Denmark.

Study finds ‘frictional heat’ as a new trigger for explosive volcanic eruptions

A new study into magma ascent by geoscientists at the University of Liverpool has found that temperature may be more important than pressure in generating gas bubbles which trigger explosive volcanic eruptions.

In a paper published in Nature, researchers at the University’s School of Environmental Sciences showed that as magma ascends in volcanic conduits, it heats up which can melt its crystal cargo and forces the formation of bubbles. Importantly, they also showed that more bubbles are formed by heating than through decompression, which had been previously thought.

Astonishing finding

The study, which combined field observation, interpretation of monitored data and controlled laboratory experimentations, provides a strong argument for the integration of temperature as a key control in volcanic eruption models.

Yan Lavallée, Liverpool Professor of Volcanology who led the research, said: “A good analogy to this is peanut butter: when it is too cold and viscous, we plunge a knife into it and stir to warm it up and make it more runny. With volcanoes, magma ascending in volcanic conduit also heats up and this helps them foam and erupt explosively.”

He added: “The fact that temperature may be more important than pressure in the generation of gas bubbles in ascending magmas is astonishing and requires immediate consideration from the scientific community. The fundamental nature of this thermal process will very likely find other important applications in earth sciences as well as in engineering in the years to come.”

Forecasting disaster

Understanding magma ascent is central to forecasting volcanic disasters. It is not possible to always successfully predict volcanic events due to the lack of complete knowledge of the signals leading to catastrophes.

To reproduce the volcanic process, the researchers designed laboratory experiments to study friction in volcanic rocks. They found that friction causes a substantial amount of heat between two rocks which melts the rock and makes it foam.

In the study, they were also able to show how the action of ascending magma can be understood using seismometers to monitor earthquakes and tiltmeters to measure ground deformation.

Champagne analogy

Volcanic eruptions are often compared to uncorking a bottle of champagne. Pop the cork out slowly and the wine bubbles up (foams), gas comes out and the wine settles. When it is uncorked rapidly, the cork shoots up in the air, followed by a messy splash of wine across the kitchen.

These two opposite scenarios also occur with volcanoes which can erupt lava flows or explosively erupt fragmented bits of lava, including volcanic ash. It had been thought that the decrease in pressure experienced by magma as it ascends through the crust and erupts at the Earth’s surface, causes it to foam. This new work suggests that heating may be more important than this decompression in controlling eruptions.

Reference:
Yan Lavallée, Donald B. Dingwell, Jeffrey B. Johnson, Corrado Cimarelli, Adrian J. Hornby, Jackie E. Kendrick, Felix W. von Aulock, Ben M. Kennedy, Benjamin J. Andrews, Fabian B. Wadsworth, Emma Rhodes, Gustavo Chigna. Thermal vesiculation during volcanic eruptions. Nature, 2015; 528 (7583): 544 DOI: 10.1038/nature16153

Note: The above post is reprinted from materials provided by University of Liverpool.

Guatemala warily monitors erupting volcano

The Fuego volcano, seen from San Juan Alotenango municipality, Sacatepequez departament, about 50 km southwest of Guatemala City, erupts on November 10, 2015

Guatemalan authorities Monday warily monitored the eruption of a volcano near its capital that spewed columns of ash up to seven kilometers (four miles) high.

Fuego Volcano, located just 50 kilometers (30 miles) from Guatemala City, rumbled back into higher intensity explosive activity on Sunday after months of fitfulness.

Guatemala’s Volcanological Institute has advised aviation authorities to ensure flights do not come into contact with the ash cloud.

A spokesman for the country’s disaster response agency, David de Leon, said the ash billowing from the 3,763-meter (12,346-foot) high volcano was fanning dozens of kilometers (miles) to the south and west. Light tremors were also being felt in nearby villages.

He said no evacuation order had yet been given, but that civil protection officials were closely watching the eruption.

In February 2015, Fuego Volcano had a powerful eruption that prompted an alert and the closure of the capital’s airport.

Note: The above post is reprinted from materials provided by AFP.

Melting of massive ice ‘lid’ resulted in huge release of CO2 at the end of the ice age

Foraminifera Credit: Jenny Roberts

A new study reconstructing conditions at the end of the last ice age suggests that as the Antarctic sea ice melted, massive amounts of carbon dioxide that had been trapped in the ocean were released into the atmosphere.

The study includes the first detailed reconstruction of the Southern Ocean density of the period and identified how it changed as the Earth warmed. It suggests a massive reorganisation of ocean temperature and salinity, but finds that this was not the driver of increased concentration of carbon dioxide in the atmosphere. The study, led by researchers from the University of Cambridge, is published in the journal Proceedings of the National Academy of Sciences.

The ocean is made up of different layers of varying densities and chemical compositions. During the last ice age, it was thought that the deepest part of the ocean was made up of very salty, dense water, which was capable of trapping a lot of CO2. Scientists believed that a decrease in the density of this deep water resulted in the release of CO2 from the deep ocean to the atmosphere.

However, the new findings suggest that although a decrease in the density of the deep ocean did occur, it happened much later than the rise in atmospheric CO2, suggesting that other mechanisms must be responsible for the release of CO2 from the oceans at the end of the last ice age.

“We set out to test the idea that a decrease in ocean density resulted in a rise in CO2 by reconstructing how it changed across time periods when the Earth was warming,” said the paper’s lead author Jenny Roberts, a PhD student in Cambridge’s Department of Earth Sciences who is also a member of the British Antarctic Survey. “However what we found was not what we were expecting to see.”

In order to determine how the oceans have changed over time and to identify what might have caused the massive release of CO2, the researchers studied the chemical composition of microscopic shelled animals that have been buried deep in ocean sediment since the end of the ice age. Like layers of snow, the shells of these tiny animals, known as foraminifera, contain clues about what the ocean was like while they were alive, allowing the researchers to reconstruct how the ocean changed as the ice age was ending.

They found that during the cold glacial periods, the deepest water was significantly denser than it is today. However, what was unexpected was the timing of the reduction in the deep ocean density, which happened some 5,000 years after the initial increase in CO2, meaning that the density decrease couldn’t be responsible for releasing CO2 to the atmosphere.

“Before this study there were these two observations, the first was that glacial deep water was really salty and dense, and the second that it also contained a lot of CO2, and the community put two and two together and said these two observations must be linked,” said Roberts. “But it was only through doing our study, and looking at the change in both density and CO2 across the deglaciation, that we found they actually weren’t linked. This surprised us all.”

Through examination of the shells, the researchers found that changes in CO2 and density are not nearly as tightly linked as previously thought, suggesting something else must be causing CO2 to be released from the ocean.

Like a bottle of wine with a cork, sea ice can prevent CO2-rich water from releasing its CO2 to the atmosphere. The Southern Ocean is a key area of exchange of CO2 between the ocean and atmosphere. The expansion of sea ice during the last ice age acted as a ‘lid’ on the Southern Ocean, preventing CO2 from escaping. The researchers suggest that the retreat of this sea ice lid at the end of the last ice age uncorked this vintage CO2, resulting in an increase in carbon dioxide in the atmosphere.

“Although conditions at the end of the last ice age were very different to today, this study highlights the importance that dynamic features such as sea ice have on regulating the climate system, and emphasises the need for improved understanding and prediction as we head into our ever warming world,” said Roberts.

Reference:
Evolution of South Atlantic density and chemical stratification across the last deglaciation, PNAS, DOI: 10.1073/pnas.1511252113

Note: The above post is reprinted from materials provided by University of Cambridge.

New enantiornithine bird with an aerodynamic tail found in China

Fig.1 Reconstruction and specimen of Chiappeavis magnapremaxillo. Credit: Jingmai O’Connor

A new species of Mesozoic bird was published on December 31 in Current Biology by a collaboration of scientists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences and the Shandong Tianyu Museum of Nature, providing strong evidence that enantiornithines possessed aerodynamic rectricial fans.

The specimen is part of the collections of the Tianyu Museum and comes from the Jehol deposits in Liaoning Province. The new species is a member of the family Pengornithidae, the most basal recognized lineage of enantiornithines. The shape of the beak of the new species differs from that of other pengornithids suggesting that its diet differed from other known species.

The new species, Chiappeavis magnapremaxillo, is named after Dr. Luis Chiappe, Ph D advisor of the lead author, Professor Jingmai O’Connor of the IVPP. Dr. Chiappe is an Argentine paleontologist most famous for discovering the Auca Mahuevo sauropod nesting ground in Patagonia. He is also a major contributor to the study of Mesozoic birds; notably, he was the first to provide cladistic support for the validity of the Enantiornithes making it fitting to name this species of enantiornithine in his honor. Dr. Chiappe is the head of the Dinosaur Institute and Vice President of Research and Collections at the Natural History Museum of Los Angeles County, where Dr. O’Connor was a ‘Graduate Student in Residence’ from 2004 to 2009.

The most interesting aspect of the new specimen is the preserved plumage. Only the flight feathers of the wings and tail are preserved. The tail is formed by approximately ten feathers overlapping to form a cohesive surface capable of generating lift (tail fan). This is the first unequivocal evidence of an aerodynamic tail morphology in the Enantiornithes. All other known specimens, including other closely related pengornithid species, preserve ornamental tail feathers or none at all. A previous study, lead by Dr. Xiaoli Wang of Lingyi University – also an author of the current study, hypothesized that a tail fan represents the primitive condition within Enantiornithes. The discovery of Chiappeavis fulfills this prediction.

The discovery of this new specimen has also led O’Connor and colleagues to suggest for the first time that rectricial bulbs may have been present in enantiornithines, if not a larger group of birds that includes the primitive Sapeornis. The rectricial bulbs are a paired soft tissue structure associated with the pygostyle in living birds that, together with the bulbi rectricium muscle, allows birds to manipulate the shape of their tail in order to maximize aerodynamic function. This structure was previously thought to only exist in the advanced avian lineage, the Ornithuromorpha, which includes all living birds. However, similarities between the pygostyle in pengornithid enantiornithines, ornithuromorphs, and Sapeornis – which also has an aerodynamic tail fan, lead the authors to suggest that all three groups possessed rectricial bulbs or their structural equivalents.

“It is unclear if this feature evolved once or if it had multiple origins,” says Dr. O’Connor, “But if we imagine a single origination, clearly the bulbs would have been very rudimentary in the common ancestor of these groups.” The authors suggest that the bulbs were so poorly developed in basal enantiornithines that this feature was abandoned in most more advanced taxa, thus explaining the dominance of ornamental tail morphologies in this clade.

Reference:
Jingmai K. O’Connor et al. An Enantiornithine with a Fan-Shaped Tail, and the Evolution of the Rectricial Complex in Early Birds, Current Biology (2015). DOI: 10.1016/j.cub.2015.11.036

Note: The above post is reprinted from materials provided by Chinese Academy of Sciences.

Virgin births may be common among snakes

This undated photo provided by the University of Sao Paulo in Brazil shows the newly discovered fossil. Credit: Hussam Zaher/University of Sao Paulo via AP

A new review provides intriguing insights on parthenogenesis, or virgin birth, in snakes.

Interestingly, facultative parthenogenesis, or asexual reproduction in an otherwise sexually reproducing species, appears to be quite common among snakes and may represent a potentially important feature of vertebrate evolution. On the other hand, obligate parthogenesis — when organisms exclusively reproduce through asexual means — is extremely rare in snakes.

While researchers’ understanding of these reproductive phenomena is in its infancy, the review provides the necessary first steps for investigating the origin and evolution of parthenogenesis in snakes.

“Once considered a evolutionary novelty, facultative parthenogenesis has now been documented in an increasing number of vertebrate species, ranging from the hammerhead shark to domestic turkeys, komodo dragons to snakes; however it is this last group that offers us the greatest insight into this unusual reproductive trait,” said Dr. Warren Booth, co-author of the Biological Journal of the Linnean Society article. “Having recently been documented in natural populations and across a variety of lineages within the snake phylogeny, ranging from the boas and pythons through to the water snakes and pitvipers, we revisit previous studies identifying commonalities and variations that offer new insight into this remarkable trait within snakes. Based on our findings we propose splitting facultative parthenogenesis within snakes into two forms, and thus identify snakes as ideal model species to study the evolution of vertebrate parthenogenesis.”

Reference:
Warren Booth, Gordon W. Schuett. The emerging phylogenetic pattern of parthenogenesis in snakes. Biological Journal of the Linnean Society, 2015; DOI: 10.1111/bij.12744

Note: The above post is reprinted from materials provided by Wiley.

Volcano in Nicaragua spews gas and lava

A volcano in Nicaragua that has been dormant for 110 years spewed gas and lava Sunday for the second time in a month.

The volcano known as Momotombo in the west of the Central American country rumbled into activity before dawn, but then calmed down again, the Nicaraguan Institute for Territorial Studies said.

No one living near the mountain was hurt, it said.

Momotombo stands 1,297 meters (4,255 feet) high, some 40 kilometers (25 miles) from the capital Managua, separated by a large lake called Lago Xolotlan.

On December 1 the volcano belched gas and ash and then lava that poured onto uninhabited areas on the slopes of the mountain.

Then on Christmas Day the volcano was rattled by some 20 small earthquakes of up to 3.0 on the Richter scale, at a depth of 10 kilometers (6 miles).

Its last big eruption dates back to 1905.

In 1980, the volcano emitted lava, but there was no eruptive explosion. In 2006 it emitted gases only.

Note: The above post is reprinted from materials provided by AFP.

Traces of icelandic volcanoes in a northeastern German lake

Microscope fotos of volcanic glass particles from two islandic eruptions of the Dyngjufjöll volcanic centre in North-eastern Iceland found in lakes Tiefer See (North-eastern Germany) and Czechowskie (Poland): Askja-S eruption from ca 11000 years ago and the Askja AD1875 eruption Credit: Sabine Wulf, GFZ

Traces of volcanic ash originating from islandic volcanoes have been found in the sediments of Laker Tiefer See in the Nossentiner-Schwinzer Heide natural park in Mecklenburg-Vorpommern. This allows to more precisely date climate changes of the last 11500 years. An international team of geoscientists lead by the GFZ German Research Centre for Geosciences detected traces of in total eight volcanic eruptions on Island of which six could be precisely identified. The oldest eruption occurred 11400 years ago and the youngest from AD 1875 has been also described in historical documents.

Seasonally laminated lake sediments represent ideal geoarchives for reconstructing natural climate variability in the past. Achim Brauer from the Research Centre for Geosciences explained the particular importance of the identified volcanic ash deposits: “Particles of three of the volcanic ashes detected in Lake Tiefer See have been also found 500 km further East in a lake in Poland. For the first time, this allows to synchronize both sediment archives to the year precise, which enables us to decipher even subtle regional differences of climate changes in the past. This information, in turn, provides the chance to better anticipate regional aspects of future climate change.”

The particular challenge of this approach was the fact that volcanic ash was not deposited as visible layers, but only as a few tiny volcanic glass particles scattered in the lake sediments. “These small glass particles commonly are smaller than 50 micrometer”, explained GFZ-scientist Sabine Wulf. “We applied a novel combination of chemical and microscopic methods to detect these fine traces in the lake sediments and to separate them for further analyses.” Geochemical analyses of individual glass shards and their comparison with volcanic ash from the source region on Island ideally allows to precisely tracing back the corresponding volcanic eruption. Moreover, this approach allows reconstructing the distribution of volcanic ash clouds from eruptions in the past over large areas and thus provides new insights into past wind conditions.

Reference:
Sabine Wulf et al. Holocene tephrostratigraphy of varved sediment records from Lakes Tiefer See (NE Germany) and Czechowskie (N Poland), Quaternary Science Reviews (2016). DOI: 10.1016/j.quascirev.2015.11.007

Note: The above post is reprinted from materials provided by Helmholtz Association of German Research Centres.

The giant ape went extinct 100000 years ago, due to its inability to adapt

Estimated size of Giganthopithecus in comparison with a human. Credit: H. Bocherens

Scientists from the Senckenberg Center for Human Evolution and Palaeoenvironment in Tübingen and from the Senckenberg Research Institute in Frankfurt examined the demise of the giant ape Gigantopithecus. In their study, published recently in the scientific journal Quaternary International, they reach the conclusion that the presumably largest apes in geological history died due to their insufficient adaptability. Analyses of fossil tooth enamel show that the primates were restricted to forested habitats.

It is well documented that the giant ape Gigantopithecus was huge – but beyond this fact, there are many uncertainties regarding the extinct ancestor of the orangutan. Size indications vary from 1.8 to 3 meters, and weight estimates between 200 and 500 kilograms. And there are various theories regarding its diet as well: Some scientists assume a strictly vegetarian lifestyle, while others consider the ape a meat eater, and a few believe that its diet was exclusively limited to bamboo. “Unfortunately, there are very few fossil finds of Gigantopithecus – only a few large teeth and bones from the lower mandible are known,” explains Prof. Dr. Hervé Bocherens of the Senckenberg Center for Human Evolution and Palaeoenvironment (HEP) at the University of Tübingen, and he continues, “But now, we were able to shed a little light on the obscure history of this primate.”

Together with his colleagues from the Senckenberg Research Institute, Prof. Dr. Friedmann Schrenk and PD Dr. Ottmar Kullmer, as well as other international scientists, the biogeologist from Tübingen examined the fossil giant ape’s tooth enamel in order to make inferences on its diet and to define potential factors for its extinction. “Our results indicate that the large primates only lived in the forest and obtained their food from this habitat,” explains Bocherens, and he adds, “Gigantopithecus was an exclusive vegetarian, but it did not specialize on bamboo.”

The team of researchers studied stable carbon isotopes in the tooth enamel of the large primates – which are able to reveal information about the animals’ dietary habits even after several million years. The examined teeth came from China and Thailand – among them the first record of Gigantopithecus, which was discovered by paleoanthropologist Gustav Heinrich Ralph von Koenigswald in 1935 among a collection of fossils from a Chinese pharmacy. The results show that the giant ape’s habitat was restricted to forested areas – even though the ape was presumably too heavy to climb trees. This was the case both in China and Thailand, where open savannas would have been available in addition to the wooded landscapes.

“In order to be able to comprehend the evolutionary history of primates, it is important to take a look at their diet,” explains Bocherens, and he adds, “Our results also contribute to a better understanding of the reasons that led to the giant ape’s extinction.”

Bocherens and his colleagues work on the assumption that Gigantopithecus’s size, in connection with its restriction to one habitat type, doomed the giant apes. “Relatives of the giant ape, such as the recent orangutan, have been able to survive despite their specialization on a certain habitat. However, orangutans have a slow metabolism and are able to survive on limited food. Due to its size, Gigantopithecus presumably depended on a large amount of food. When during the Pleistocene era more and more forested areas turned into savanna landscapes, there was simply an insufficient food supply for the giant ape,” concludes the scientist from Tübingen.

Reference:
Hervé Bocherens et al. Flexibility of diet and habitat in Pleistocene South Asian mammals: Implications for the fate of the giant fossil ape Gigantopithecus, Quaternary International (2015). DOI: 10.1016/j.quaint.2015.11.059

Note: The above post is reprinted from materials provided by Senckenberg Research Institute and Natural History Museum.

Reptile fossils offer clues about elevation history of Andes Mountains and climate change

The fossil shell from an extinct tortoise of the genus Chelonoidis, found near Quebrada Honda, Bolivia, is among the fossils suggesting the Altiplano was less than a kilometer in altitude 13 million years ago. Credit: Darin Crof

On an arid plateau in the Andes Mountains of southern Bolivia, a Case Western Reserve University researcher flagged what turned out to be the fossil remains of a tortoise nearly five feet long—a find indicating this highland was likely less than a kilometer above sea level 13 million years ago.

Fossilized shell pieces of a much smaller, aquatic turtle found nearby support the altitude estimate and also indicate the climate was much wetter than today.

The remains are the first records of fossil turtles from the Miocene epoch in Bolivia, and their presence challenges a recent isotope-based study that estimated the massive plateau, called the Altiplano, near what is now the town of Quebrada Honda, was 2 to 3.2 kilometers high at that time.

In addition, the fossils provide a glimpse into climate change caused by rising mountains, which may help scientists understand climate change underway now.

The research is published in the Journal of South American Earth Sciences.

“We’re trying to understand how tectonic plate activity and changing climate affected species diversity in the past,” said Darin Croft, an anatomy professor at Case Western Reserve University School of Medicine and a paleomammalogist. “One way all this diversity we see in the South American tropics today was generated was through elevation. Mountains create many different climates and ecosystems in a small area, which promotes speciation.”

Croft found the tortoise remains in an embankment after he missed a turn on a path near Quebrada Honda and was working his way back toward his regular research site. Croft and Federico Anaya, a member of the geological engineering faculty at Universidad Autónoma Tomás Friás in Posotí, later identified other, more fragmentary tortoise remains from other sites in the area.

After returning to the United States, Croft sent photographs and three-dimensional computer-generated images of the remains to Edwin Cadena, a turtle expert now at Yachay Tech University in Ecuador.

Cadena identified the tortoise as a member of the same genus as the Galápagos tortoise, Chelonoidis. He identified the extinct freshwater turtle as belonging to the genus Acanthochelys, whose surviving members occur throughout much of tropical South America.

The animals are ectotherms, commonly called cold-blooded. Their reliance on the outside air to control their body temperature can be used as a proxy for the temperature where they lived and, therefore, elevation.

The ancient tortoise and aquatic turtle most likely would have had physiological requirements much like their modern relatives, which generally live at altitudes of up to about 500 meters and can’t thrive or reproduce at much higher elevations because of the cooler temperatures, Croft said.

Miocene fossilized leaf remains are scant in Bolivia, but those that have been found tend to support the findings of warmer temperatures, lower altitude, and greater precipitation than today.

The Andes were formed by subduction—a process in which one tectonic plate is shoved under another. How quickly the mountains rose to their current elevation is not fully answered.

As the highest geological feature in South America, the mountain chain affects global air circulation patterns and plays a major role in global climate.

“With current global climate change, we’d like to have a better idea of what to expect under different scenarios—how 1-degree warming or 2-degree warming will affect sea levels and animals,” Croft continued. “If we want to model the future, we need to understand and model the past.”

Looking back, if the Andes Mountains were less than 1 kilometer high during the late Miocene, they would have had a much smaller effect on global circulation than if they were two or three times as high, close to their modern elevation near Quebrada Honda.

The researchers believe they have more evidence from extinct animals that this part of the Altiplano was less than a kilometer above sea level 13 million years ago. They found fossil remains of a large snake in the same rock layer as the turtles. Those bones are currently under study by Croft and colleagues.

Note: The above post is reprinted from materials provided by Case Western Reserve University.

Geomorphic impact of the flooding caused by tropical storm Lee in September 2011

Examples of erosion and deposition in north-central Pennsylvania from Tropical Storm Lee. (A) Extensive gravel bars formed in a disequilibrium zone on lower Fishing Creek. (B) Washed out bridge in upper Muncy Creek. (C) Eroded road along Big Bear Creek, upper Loyalsock Creek watershed. (D) House eroded on a Pleistocene terrace, Loyalsock Creek. Credit: R. Craig Kochel et al. and Geosphere.

In their article for Geosphere, R. Craig Kochel and colleagues discuss the geomorphic impact of the flooding caused Tropical Storm Lee in September 2011 on several large watersheds of the Susquehanna River in the Appalachian Plateau region of north-central Pennsylvania. Unlike many Appalachian floods, the physical impacts to channels and floodplains were extensive.

Channel widening (in places >100%) and bank erosion were common, and huge volumes of gravel were transported during the flood. Flood flows resulted in a significant threshold, crossing where channel patterns shifted from single-channel to multi-thread along many reaches.

Kochel and colleagues suggest that part of the reason for such extensive changes from the flood were related to the land-use history of these watersheds. Watershed-scale deforestation occurred in these streams between 1850 and 1920, resulting in hillslope erosion and downstream floodplain sedimentation. In addition, the former multi-thread gravel-bed channel system was altered by the construction of berms, narrowing the active part of the streams to a single channel.

After the logging era, infrastructure (including homes, highways, and farms) was established on the floodplain that was protected by the berms. The 2011 flood breached these berms, aggraded channels with gravel bars to floodplain elevations, and resulted in numerous avulsions and chutes eroded through the insides of meander bends. These changes reconnected the modified single-channel system with its preexisting multi-thread channel system and resulted in extensive damage to highways, bridges, farms, homes, and other infrastructure in the region.

The increased coarse gravel load available to channels is causing rivers to adjust their morphology and return to multi-thread systems where flood flows occupy numerous channels across valley-wide floodplains. Understanding the trajectory of the geomorphic adjustment of streams in this region is critical to making wise management and land-use policy decisions. Watershed managers would find prudence in evaluating fluvial systems on a watershed scale that addresses adjustments in sediment load and discharge produced by natural changes as well as historical land-use practices.

Reference:
R. Craig Kochel et al. Geomorphic response to catastrophic flooding in north-central Pennsylvania from Tropical Storm Lee (September 2011): Intersection of fluvial disequilibrium and the legacy of logging, Geosphere (2015). DOI: 10.1130/GES01180.1

Note: The above post is reprinted from materials provided by Geological Society of America.

Remote Sensing Downloader

RS Downloader offers access to satellite image data pools. Via web interface the user is able to search and download specified satellite images.

This version is an alpha and while running stable, currently only retrieves products from NASAs LP DAAC data pool. Further versions will include updated parsers and spatial selection UIs to access other available sources.

NASAs LP DAAC data pool: Click Here

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Frictional heat dehydrates magma

The volcano Santiaguito in Guatemala. Credit: Lavallée et. al./Nature

In contrast to the conventional view, new findings demonstrate that frictional heat in rising magma can drive outgassing of water vapor, which contributes to the dehydration of molten magma – and reduces the pressure in the system.

The lava dome of the volcano Santiaguito in Guatemala simmers away all day and all night: Clouds of ash belch from ring-shaped fissures around the mountain several times a day. The overlying crust of cool lava is torn apart at various points by mounting pressure from below, and the ash that is released can form overlapping rings. This unceasing activity is driven by frictional heat, as has now been demonstrated by an international team, which included a group of Munich volcanologists led by Donald Dingwell, Director of the Department of Earth and Environmental Sciences at LMU. The work is reported in the leading journal Nature.

The vent atop Santiaguito’s magma chamber is plugged by a flat crust of solidified lava, which forms localized bulges prior to an eruption and then subsides again. Ash issues from the vent only if this cycle of build-up and collapse is completed very rapidly, i.e., when the surface of the dome locally rises and falls by a meter – within a single second. Electron microscopic studies have revealed that the particles of ash that are expelled under these conditions are unusually inhomogeneous in structure and look as if they are shot through with vesicles. “We have observed similar inhomogeneities in laboratory experiments in which magma was rapidly heated by means of friction,” says Dingwell.

Through cracks in the lava dome

On the basis of these studies, the researchers concluded that a significant amount of frictional heat is generated as magma is forced through cracks in the lava dome, and that this heat suffices to melt the rock very rapidly. “As the magma rises, friction develops between the viscous material and its solid surroundings, and this interaction can raise the local temperatures by several hundred degrees Celsius,” Dingwell explains. This finding provides a new perspective on the play of forces which drives the outgassing of molten magma and, in particular, the expulsion of water vapor: Until now, it was assumed that the solubility of the gases in the magma, and hence the onset of foaming, is essentially determined by the local pressure – the higher the magma rises in the vent, the lower the pressure, and the lower the solubility of the dissolved gases. So bubbles begin to form, rise to the surface and the magma starts to foam.

“But the solubility of water vapor also depends on the local temperature – the hotter things get, the less water can be kept in solution,” says Dingwell. The volcanologists therefore experimentally measured the interrelationships between temperature, pressure and the solubility of water vapor in magma. The results reveal that the level of frictional heat generated as magma rises in the conduit – and not so much the fall in pressure – is often the factor that determines the point at which outgassing of water vapor, and thus foaming of the magma, takes place. “Foaming increases the buoyancy of the magma, but foaming magma is also less stable and more readily fragments – and this helps to relieve the stresses in the system,” says Dingwell. “This is presumably the reason why eruptions at Santiaguito have not produced any large-scale explosions recently. The magma rises very rapidly through the network of fissures, producing so much frictional heat that it foams. Foaming in turn relieves the tensions and stresses within the system so effectively that the volcano remains in an active but stable state overall,” Dingwell concludes.

Reference:
Yan Lavallée et al. Thermal vesiculation during volcanic eruptions, Nature (2015). DOI: 10.1038/nature16153

Note: The above post is reprinted from materials provided by Ludwig Maximilian University of Munich.

Insights into the origins of sodium and other metallic layers in the Earth’s upper atmosphere

An all-sky image above Tromsø at 21:00 UT on 15 December 2012, captured by a color digital camera with 15 s exposure. The five laser beams in the lidar observation can be seen as orange lines, which were directed to vertical, south, north, west, and east directions. The zenith angle in the oblique beams was 30°.

Takuo Tsuda, assistant professor, Graduate School of Informatics and Engineering, discusses recent work. The Earth’s atmosphere is critical for the existence of mankind. A close inspection of reveals that the atmosphere consists of several regions: troposphere is where humans live (ca. 0-15 km); stratosphere and thin layer of ozone (ca. 15-50 km) that absorbs ultra-violet radiation; and the mesosphere/ionosphere (ca. 50-100 km) and thermosphere (where aurora occur) (ca. 100-600 km). For reference, the International Space Station orbits at approximately 400 km above the Earth.

Intriguingly, in the late 1920s scientists first reported that the glow of light in the Earth’s atmosphere contained light from sodium at a wavelength of 589 nm. In the 1960s a layer of sodium at approximately 90 km above the Earth was discovered. Later, layers of potassium, iron and calcium were reported to exist near the sodium layer.

These observations raise many questions such as the origins of these well-defined narrow regions of metal layers, and could they be useful for monitoring climate change.

At UEC, Takuo Tsuda, is literally shed light on the sodium layer surrounding the Earth. “My interest in the sodium layer is inspired by the desire to expand our knowledge of the outer atmosphere for future space utility and for insights into climate change,” says Tsuda. “So far I have used facilities in northern Europe, Japan’s Showa Base in Antarctica, and monitoring stations in Japan to measure levels of sodium and other metals at 80-100 km.”

Tsuda uses the so-called resonance fluorescence lidar technique where a pulsed laser beam is pointed at the upper atmosphere and scattered light from sodium and other metals is detected by a telescope on the ground for determining the concentration and location of the metals in the upper atmosphere.

Recent research findings include the first ever observation of ‘thermospheric Na layers’ above 110 km. “These experiments were conducted at the Syowa Station in Antarctica,” explains Tsuda. “Other metal layers have been observed above 110 km but our report was the first such observation of a sodium layer at this high altitude.

In research on the stability of metal layers in the upper atmosphere, Tsuda and co-workers reported on the observation of a so-called ‘sporadic sodium layer event’ from a site in Norway. This event was proposed to be “advected by the background wind”.

These metals layers are most likely due to dust left by comets orbiting the Sun and from asteroids from other parts of the Solar System. “In addition to enhancing our knowledge of the Earth and near space, this research is expected to yield insights into the atmospheres of other planets in our galaxy,” says Tsuda.

Reference:

  1. A thermospheric Na layer event observed up to 140 km over Syowa Station (69.0ºS, 39.6ºE) in Antarctica, Geophys. Res. Lett., 42, 3647-3653, (2015).
  2. A sporadic sodium layer event detected with five-directional lidar and simultaneous wind, electron density, and electric field observation at Tromsø, Norway, Geophys. Res. Lett., 42, 9190-9196, (2015).

Note: The above post is reprinted from materials provided by University of Electro Communications.

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