The extreme wet and dry periods Mongolia has experienced in the late 20th and early 21st centuries are rare but not unprecedented and future droughts may be no worse, according to an international research team that includes a University of Arizona scientist.

Kevin Anchukaitis (plaid shirt) and Oyunsanaa Byambasuren (orange chainsaw chaps) taking pieces of wood from dead trees on Mongolia's Uurgat lava field. The researchers use tree rings to create a record of Mongolia's droughts stretching two centuries into the past [Credit: Neil Pederson © 2013]

The research team developed a climate record stretching 2,060 years into Mongolia's past by using the natural archive of weather conditions stored in the annual rings of Siberian pines. The 10 researchers then combined that information on past climate with computer models that can project future regional climate.

The most recent extended drought in Mongolia lasted from 2000 to 2010 and resulted in major livestock die-offs and a massive migration of nomadic herders to the capital city.

"We were able to quantify how unusual this drought was," said co-author Kevin J. Anchukaitis, a University of Arizona associate professor of geography and development. "The drought was not unprecedented, but it has a 900-year return interval. It's a once-in-a-millennium drought."

Finding that future droughts would likely be no worse than those of the past was a surprise, said Anchukaitis, who led the modeling team. In other semi-arid regions of the world that he has studied such as California and the Mediterranean, global warming has already changed precipitation and temperature patterns and thereby increased the risk of long-term drought.

Mongolia, a landlocked country in central Asia, has long, cold winters and short summers. Much of the country is cold, semi-arid grasslands that resemble eastern Montana.

Lead author Amy Hessl of West Virginia University said, "You would expect, based on everything we've been thinking about and reading as climate scientists, that elevated temperatures are going to lead to more severe droughts in semi-arid regions. But the models did not project increased frequency or severity of droughts."

Researchers Kevin Anchukaitis and Amy Hessl walk across the Khorgo lava field in central Mongolia to collect cross-sections of dead trees. The researchers use tree rings to create a record of Mongolia's droughts stretching two centuries into the past [Credit: Neil Pederson © 2012]

The timing of the rainy season is the likely cause, the researchers said. Mongolia's rainy season is in the summer, the warmer time of the year, whereas California and the Mediterranean have winter rains and dry summers. As global temperatures increase, continental regions with summer rains may get more precipitation, offsetting the effects on plants of higher temperatures.

The team's research paper, "Past and Future Drought in Mongolia," has been published in Science Advances. A complete list of the authors is at the bottom of this release. National Geographic and the National Science Foundation funded the research.

Anchukaitis, who also has appointments in geosciences and in the UA Laboratory of Tree-Ring Research, is interested in how past and current civilizations dealt with drought and climate variability. This new research is an outgrowth of previous research he, Hessl and their colleagues conducted to figure out how past climate influenced the Mongol civilization.

Anchukaitis and his colleagues used their tree-ring record of past climate in Mongolia to reconstruct what the annual Palmer Drought Severity Index, or PDSI, would have been going back in time 2,060 years. The PDSI combines both temperature and precipitation to get a measure of soil moisture, one measure of how water-stressed a plant would be.

He and his colleagues combined the reconstruction of past annual PDSI measures with a set of climate model simulations called the Community Earth System Model to understand what influenced the Mongolian droughts for the period from 850 to 2100.

The Uurgat lava field with the Khangai Mountains in the background and the seasonal homes of nomadic herders in the lower right. An international team of researchers took wood samples of the Siberian pines growing on the lava field to construct a drought chronology reaching two centuries into the past [Credit: Scott Nichols]

The model incorporates information about past solar variability, volcanic eruptions, land use changes and carbon dioxide emissions. For projections to the end of the 21st century, the model uses the future emissions scenario called RCP 8.5, in which the rate of emissions of greenhouse gases continues to increase.

Even with the highest level of greenhouse gas emissions and rising global temperatures, the model simulations indicate that future droughts in Mongolia would be no more severe than those of the past.

"There's a tug of war between trends toward increased rainfall and more evaporative demand because of hotter temperatures. There's uncertainty about which will win this tug of war," Anchukaitis said.

"The simulations say that Mongolia dries between now and about 2050 because of higher temperatures, but then it turns around because of the increase in precipitation," he said.

Many people in Mongolia are nomadic pastoralists. They are particularly affected by the vagaries of weather and climate, because the combination of winter and summer temperatures plus rainfall controls the number of cattle the grassland can support.

"What to me stands out is this deep uncertainty about the future, particularly when you have a society that is so vulnerable to climate variability," he said, adding that uncertainty makes it hard to plan for coping with future climate change.

Anchukaitis said one of his next steps is translating the team's estimates of future soil moisture into estimates of the future productivity of Mongolia's grasslands.

Author: Mari N. Jensen | Source: University of Arizona [March 14, 2018]

It may not rank among the all-time greatest dramas, but the history of ice on Greenland has been a source of scientific controversy for more than a decade.

Iceberg off the coast of Greenland [Credit: Drew Avery/WikiCommons]

A study led by UCLA climate scientist Aradhna Tripati appears to put the debate to rest, with major implications for future research across a range of disciplines, from climate science to geology. The paper, which is published today in the journal Nature Communications, also sheds light on how global climate may change as people continue emitting greenhouse gases, revealing a potential tipping point: atmospheric carbon dioxide concentrations of 500 parts per million or more. Beyond that threshold, major ice sheets at both poles could melt significantly. Current levels are near 400 parts per million.

For years, the prevailing belief was that glaciers first appeared on Greenland between 5 million and 11 million years ago. Then, in 2005, Tripati authored a study suggesting the ice had been present there much earlier: about 35 to 40 million years ago.

Though Tripati's paper was published in Nature—one of the most-respected scientific journals—it was considered controversial. At the heart of the conflict was a simple question: Why weren't similar observations made by other studies? Because the findings were not in line with previous knowledge, the paper was regarded as an outlier.

Tripati, who was then a postdoctoral fellow, admits that her research, which was based on the chemistry of Pacific Ocean samples and what they implied about ancient seawater, was "a pretty indirect indicator." Still, she had confidence in the results. She, her students and other researchers conducted a series of studies using different climate indicators, and they kept reaching the same conclusion.

"Understanding the history of ice at both poles and how they respond to changing carbon dioxide levels is so important that, as we published these papers, controversy built up," said Tripati, who is a member of the UCLA Institute of the Environment and Sustainability. "We dug in and continued to try to understand what the history, in fact, was."

In 2014, Tripati sent Dennis Darby, an Arctic paleoclimate specialist at Old Dominion University who became her co-author on the new paper, promising samples taken from a site in the Greenland Sea where icebergs that broke off—a process known as "calving"—from glaciers on the island would have drifted by.

"As glaciers move across land, they incorporate pieces of sediment," Tripati said. "As glaciers produce icebergs and those icebergs drift through the ocean, those little fragments of rock get released as the ice melts. Each rock fragment has a unique chemistry. That chemistry is a fingerprint—each grain tells you something about where the ice came from."

Those samples are dated based on what fossils are present and their magnetic properties, allowing researchers to reconstruct where and when there was ice present on Greenland and other land masses in the Arctic, as well as when there was sea ice in the ocean.

Data visualization showing changes in Greenland’s ice sheet from 2003 to 2012. Rapidly thinning coastal regions are shown in green, blue and purple [Credit: NASA]

Tripati chose to send those new samples to Darby because he had published a study that corroborated her 2005 findings. Using a method he pioneered, Darby analyzed them without knowing what he was looking at, where it came from or how old it was—sort of like a blind taste test.

He found that the samples contained "very high matches" to east Greenland source sites, again confirming Tripati's earlier research. In fact, his analysis showed that large glaciers were present on Greenland even earlier: up to 47.1 million years ago. That was right at the beginning of the middle Eocene epoch, about 20 million years after dinosaurs went extinct.

Darby was also able to match ice from the samples to other locations across the Arctic region.

"That's important," Darby said. "It shows this was not just a local or regional effect in Greenland. It was something climatically induced on a much larger scale, a polar event."

With their new study, Tripati and Darby think the mystery is solved. Darby's technique was rigorously tested in a 2012 study and found to be accurate 98.5 percent of the time. They examined 100 sediment samples and fingerprinted the chemistry of more than 2,000 rock fragments.

Today's paper also contains revelations about how atmospheric conditions relate to the presence or absence of ice. In the years since that first freeze, ice formed and retreated from Greenland several times. The researchers found that ice was usually present when carbon dioxide levels were lower than 500 parts per million.

"What happens if carbon dioxide levels get sustained at 800 parts per million, where some carbon emissions scenarios have us going?" Tripati asked. "Greenland has a lot of ice. If it all melted, it could raise sea level globally by about 20 feet."

Ice comes and goes at both poles under those conditions, the study found. Tripati's research from 2016 that suggested massive ice shelves on Antarctica are also at risk of melting supports this.

Understanding tipping points is important because Earth's climate can change quickly, Darby said. He pointed to 10,000 years ago in Greenland, when temperatures rose 10 degrees Celsius in 10 years.

"Those thresholds need to be researched," Darby said. "They are largely ignored by climate scientists because these things happened way in the past. Many of them are sort of stuck in the past 50 years. And in that time, we don't see any big changes except in the past two decades, when we see very rapid changes that are concerning."

Tripati said that controversies are good for science in general, she said—it shows the scientific process is healthy. She recalled cat-sitting for renowned scientist Sir Nicholas Shackleton around the time she was conducting the early study.

"He said to me 'When you discover something surprising, remember that it's OK to be wrong, but ideally you should be the person to find out. Always try to prove yourself wrong instead of trying to prove yourself right,' " Tripati recalled.

"I think that's excellent advice. With this study, I didn't know what we were going to find. If it didn't work out, fine—we could have written a paper that definitively said 'no evidence for this.' And then we're on the right side of science."

The process also underscored the importance of including diverse perspectives in science, Tripati said. Last summer she launched the UCLA Center for Diverse Leadership in Science—the first initiative of its kind devoted to including people of all backgrounds in environmental science. Dogma that endured for decades can shift dramatically if the scientific community is inclusive and welcomes new perspectives, she said. Inclusion and social belonging will foster diversity, and research shows that leads to more creative approaches and ideas, fueling innovation and scientific breakthroughs.

Tripati and Darby both hope today's findings inspire future research to better understand what will happen to Earth's climate, species and human communities if we continue on our current carbon emissions trajectory.

They also hope it will inform policies aimed at preventing a climate catastrophe—particularly efforts to reduce carbon emissions, Darby said.

"We need to start looking at what we're doing," Darby said. "Some people stick their heads in the sand because they think we'll come up with technology to save us at the last minute. But that's provided we don't hit one of these thresholds first."

Author: David Colgan | Source: University of California, Los Angeles [March 13, 2018]

Researchers from Cardiff University have revealed how sea ice has been contributing to the waxing and waning of ice sheets over the last million years.

Credit: Cardiff University

In a new study published in the journal Nature Communications, the team have shown for the first time that ice ages, occurring every 100,000 years, are accompanied by a rapid build-up of sea ice in the Earth's oceans.

Our planet's ice ages used to occur at intervals of every 40,000 years, which made sense to scientists as the Earth's seasons vary in a predictable way, with colder summers occurring at these intervals. However there was a point, about a million years ago, called the 'Mid-Pleistocene transition', in which the ice age intervals changed from every 40,000 years to every 100,000 years.

The reason why ice ages occur at these timescales has been a mystery to scientists for a long time.

By tracking molecules produced by tiny marine algae preserved in ocean sediments, the team have been able to reconstruct sea-ice conditions during the Mid-Pleistocene transition.

Their results showed that at the same time as the cycles of ice ages changed from 40,000 years to 100,000 years there was a distinct increase in sea ice extent and a change in the rhythm of sea ice build-up across climate cycles.

"Prior to the Mid-Pleistocene transition, sea ice build-up and decay during ice ages was more gradual, whereas in the late Pleistocene, when the cyclicity of ice ages changed, we observed conditions characterised by a prominent short-lived peak in sea ice extent during late ice ages," said Henrieka Detlef, a postgraduate researcher at Cardiff University School of Earth and Ocean Sciences who led the study.

With less water evaporating into the atmosphere, there would be less moisture being transported to continental glaciers which, in turn, would cause them to retreat and help in the transition from an ice age to a warm period.

"It's clear that sea ice plays a fundamental role in the transition from an ice age into a warm stage every 100,000 years," Detlef continued.

"Understanding the interactions of sea ice with the regional ecosystem and oceanography is particularly important with respect to anthropogenic climate change and a rapidly shrinking sea ice cover in the Arctic Ocean. Our study is an important step forward in understanding the role of sea ice for long-term climate change."

Source: Cardiff University [March 09, 2018]

The East Asian summer monsoon and desertification in Eurasia is driven by fluctuating Northern Hemisphere ice volume and global sea level during the Ice Age, as shown in a study published in Nature Communications. Today, two thirds of the world's population is dependent on agriculture sustained by rains of the East Asian summer monsoon, and future climate change in this region can therefore have a major impact on global food production.

The East Asian summer monsoon and desertification in Eurasia is driven by fluctuating Northern Hemisphere ice volume and global sea level during the Ice Age, as shown in a study published in Nature Communications. Today, two thirds of the world's population is dependent on agriculture sustained by rains of the East Asian summer monsoon, and future climate change in this region can therefore have a major impact on global food production [Credit: Thomas Stevens]

Huge areas of central China is covered by a plateau consisting of a fine grained soil type called loess - a sediment deposited here by winds during the Ice Age. The soils formed on loess are very fertile and have been one of the key factors driving cultural development and population growth in China for thousands of years. Additionally, the loess plateau also contains a geological archive that can be used to decipher past climate changes.

Through detailed examination of the loess sediments, a group led by researchers at Uppsala Univirsity together with colleagues from Denmark has identified how changes in climatological phenomena such as ice volume and sea level also affected the extent of deserts in China, as well as the behavior of the East Asian summer monsoon.

"We have conducted the most detailed dating of the loess to date, which has enabled us to identify changes in the monsoon and desertification processes in more detail and with much greater accuracy than previously possible. We can now compare these changes to other known climate changes such as variation in ice volume, sea level and even the Earth's orbit during the Ice Age", says Dr. Thomas Stevens, first author and researcher at Uppsala University.

"We can now show that when ice volume decreased and sea level rose, the summer monsoon rainfalls in East Asia intensified and spread further inland, while sandy deserts in China retreated", says Dr. Stevens.

With today's shrinking ice caps and rising sea levels, this has implications for how the Eurasian continent will once again experience changes in the summer monsoon rainfall and desertification.

Source: Uppsala University [March 07, 2018]

A new NASA study has, for the first time, cut a clear path through a nettlesome problem: accurately measuring a powerful effect on global sea level that lingers from the last ice age.

Glacial isostatic adjustment is the ongoing movement of land once burdened by ice-age glaciers [Credit: NASA/John Sonntag]

Just how quickly Earth's deep, rocky mantle is rebounding from the heavy burden of ancient ice sheets and oceans remains somewhat uncertain. But this rebound effect, known as glacial isostatic adjustment (GIA), is critical to properly understanding the causes of sea level change.

Even getting a solid handle on the level of uncertainty associated with estimates of GIA has proven elusive. The new study offers a more rigorous way out of this thicket – establishing a formal system for assessing this uncertainty. That should lead to more realistic estimates of sea level change, and greater precision in projections of future sea level rise, according to the study's authors.

"Knowing how much we don't know is the first step," said Lambert Caron, a post-doctoral researcher at NASA's Jet Propulsion Laboratory in Pasadena, California and lead author of the new study published today in Geophysical Research Letters, a journal of the American Geophysical Union,

Try out a NASA simulation of GIA from JPL’s Virtual Earth Systems Laboratory here.

While new findings based on strong data get most of the headlines, gauging levels of uncertainty also is important to scientific investigations. It's an especially thorny problem in the study of sea level change.

Interpreting data from NASA's twin GRACE (Gravity Recovery and Climate Experiment) satellites offers one example. By measuring subtle shifts in gravity across Earth's surface, the GRACE satellites gathered an important 15-year-long data set, now being used to help determine how much sea level rise is caused by additional water mass. GRACE also can be used to track varying quantities of ocean water, changes in polar ice and the movement of water between oceans and land.

GIA looms in the background of such measurements. Pinning down the uncertainty connected with it more precisely helps scientists separate ice age and present-day processes, including how much of sea-level rise is driven by expansion of ocean water as it warms. Knowledge of GIA also helps clarify trends in water storage on land, measured by satellite as well as ground-based instruments. Another question it can help clear up: how alterations in the shape of ocean basins caused by GIA contributes to apparent sea level changes.

Measurement and uncertainty

Previous studies attempted to put a fence around uncertainty using various methods, Caron said. These included running repeated computer models and culling out all but a handful that seemed to provide the best match, or "fit," to what the data gathered by GRACE and other observation platforms show.

Differences among the "best fit" models then can be used to reveal likely levels of uncertainty in interpreting the data.

"People started comparing a handful of models, some of them relying on similar assumptions and setups, and concluding that the differences between them were essentially how much uncertainty we had over GIA," Caron said. "That's fine, but it doesn't allow us to explore the entire range of possible scenarios. We need a more formal approach."

The new study relies on technological improvements, which have only become possible within the past decade, to carry out a high number of computer simulations – in this case, more than 100,000. By more systematically exploring the range of GIA scenarios, Caron's team seeks to turn discrepancies among different models into a virtue. They framed the question in a new way: How different can models be while still matching the data? From this spread of models and a method called the Bayesian approach, better statistics on uncertainty can be retrieved.

The new assessment also is based on GPS time series measurements from 459 sites in Europe, North America and Antarctica, and more than 11,000 records of relative sea level – that is, sea level in relation to coastal elevation. This allows the parameters controlling the GIA rebound to be more thoroughly scrutinized.

The new framework translates into what Caron calls the first formal uncertainties for GIA on a global scale.

The study reveals an underestimate of uncertainty levels for GIA estimates, he said – from a typical 20 percent uncertainty in previous studies to a median value of 44 percent. In polar regions, GIA has a large impact on the interpretation of gravity data.

That leads to refinements in uncertainty levels for sea level rise in specific locations around the world. In the New Orleans region, for example, applying the new method yields a prediction of a 1 millimeter rise in relative sea level per year, with an uncertainty of 0.4 millimeters per year.

Caron said he hopes the new formal uncertainties will be a useful tool not only for researchers, but for city planners as well.

"We want to give them a measure of confidence for the average scenario, and what is the worst-case scenario they would have to plan for – how much the country has to invest in modernizing infrastructure, reconstructing piers, or to mitigate flooding," he said.

Author: Pat Brennan | Source: American Geophysical Union [March 07, 2018]

This story is republished courtesy of AGU Blogs, hosted by the American Geophysical Union. Read the original story here.

The simple story says that during the last ice age, temperatures were colder and ice sheets expanded around the planet. That may hold true for most of Europe and North America, but new research from the University of Washington tells a different story in the high-altitude, desert climates of Mongolia.

The Gobi-Altai mountain range in western Mongolia is in a very dry region but ice can accumulate on mountaintops, such  as Sutai Mountain, the tallest peak in the range. In the picture, friends of Jigjidsurengiin Batbaatar descend this mountain after helping to install a weather station [Credit: Jigjidsurengiin Batbaatar/University of Washington]

The recent paper in Quaternary Science Reviews is the first to date ancient glaciers in the high mountains of Mongolia's Gobi Desert. It compares them with glacial records from nearby mountains to reveal how glaciers behave in extreme climates.

On some of the Gobi mountain ranges included in the study, glaciers started growing thousands of years after the last ice age ended. In contrast, in slightly wetter parts of Mongolia the largest glaciers did date from the ice age but reached their maximum lengths tens of thousands of years earlier in the glacial period rather than at its culmination, around 20,000 years ago, when glaciers around most of the planet peaked.

Both trends differ from the typical chronology of glacier growth during an ice age.

"In some of the Gobi mountains, the largest glaciers didn't happen during the last ice age," said first author Jigjidsurengiin Batbaatar, a UW doctoral student in Earth and Space Sciences. "Some of these glaciers were starving for precipitation then. Our measurements show that they actually shrank as cold, dry conditions of the ice age became more intense. Then they grew when the warming climate of the Holocene brought more moist air, feeding the glaciers with more snow."

Batbaatar and co-author Alan Gillespie, a UW research professor emeritus in Earth and Space Sciences, collected samples from moraines, which are long ridges of rocky debris dropped at a glacier's edge. They used a dating technique perfected in the last 20 years that measures elemental changes in the rock that occur when the rock gets bombarded by cosmic rays after the glacier's retreat.

"We were expecting to find rocks exposed for 20,000 years, the date of the peak of the last ice age, but these moraines were much younger. That means that these glaciers were smaller when the climate was the coldest," Batbaatar said. "The results were so surprising that we went back to double check."

At a moraine, a band of boulders left by a retreating glacier, co-author Ari Matmon collects rock samples with his son. This site is in the Khangai Mountains in Mongolia [Credit: Jigjidsurengiin Batbaatar/University of Washington]

The study was possible both because of advances in the cosmic-ray dating method, and political changes that allow more access to Central Asia.

"After the fall of the Soviet Union, Russia opened up, China opened up, and Mongolia opened up to Western researchers with these novel dating techniques. And we see a very different pattern of glacial advances compared to North America and Europe," Batbaatar said.

The data collected in 2007 and 2010 confirm a theoretical study by Summer Rupper, a former UW doctoral student now at the University of Utah, and UW faculty member Gerard Roe. In very cold and dry environments, where rain and snow are scarce, it predicted that temperature would not always be the main factor driving a glacier's growth.

"Because the melting is so dominant a process, and the melting is mostly controlled by temperature, people think of glaciers as thermometers. But we all know that precipitation plays a role," Batbaatar said.

The new study confirms that so-called "starving glaciers" in dry, high-altitude environments are indeed controlled by precipitation. They grow so slowly that they seldom reach the lower altitudes where melting is possible. Instead, they shrink when sunlight hits the surface and transforms ice into water vapor, a process called sublimation. These glaciers are thus less sensitive to temperature shifts, but very sensitive to precipitation amounts.

"Generally, people have assumed from well-documented North American and European records that the largest glaciers should have come in the peak of the last ice age," Batbaatar said. "But in Mongolia, our results show that this was not the case. Glacier behavior there was different from the better-studied areas of the Alps or the Sierra Nevada in the U.S. Even within Mongolia we observe very different behavior from range to range."

Jigjidsurengiin Batbaatar chisels rock from the surface of a boulder dropped by a glacier in the Gobi-Altai range in  Mongolia. The elemental traces of exposure to cosmic rays show that this glacier reached its maximum size 7,500 years ago, much later than the last ice age [Credit: Alan Gillespie/University of Washington]

The conditions at the Gobi-Altai mountain range are extreme, with precipitation at the five research sites Batbaatar established there ranging from roughly 50 to 300 millimeters (2 inches to 1 foot) per year. Nearby mountains in Mongolia with more precipitation have more typically behaving glaciers. But other extreme climates, for example the driest parts of Tibet or the Andes, can produce glaciers with similar paradoxical trends.

"Even in this current warming climate, some mountains are so high that the temperatures are still below freezing, and the warming ocean may provide more precipitation to drive some of the glaciers to advance," Batbaatar said.

He is now working to interpret more measurements collected from a wider geographic area in Central Asia.

"Batbaatar has shown that glaciers growing in cold, arid, desert mountains may be out of sync with those in wetter, warmer environments such as the Alps," Gillespie said. "His findings move us toward a more complete understanding of how glaciers advance and retreat in response to climatic fluctuations."

Source: University of Washington [March 06, 2018]

New research, published in Scientific Reports, has outlined a new methodology for estimating ancient atmospheric water content based on fossil plant leaf waxes.

This is the Calatayud-Daroca Basin in Central Spain [Credit: Michael Hren]

As the Earth's surface and atmosphere warm, the amount of moisture - water vapour - in the atmosphere will increase. Understanding the size of this increase is important for predicting future climates as water vapour is a significant greenhouse gas. Atmospheric moisture content also influences the patterns and intensity of rainfall events.

The relationship between temperature and moisture content can be explored by the study of intervals in Earth's history when climates where significantly warmer than those seen in modern times, which necessitates a method for estimating ancient atmospheric moisture content.

Dr Yvette Eley, from the University of Birmingham, explained, "If we want to understand how the Earth would work with a climate substantially warmer than today, we have to study intervals millions of years in the past - made difficult because these warm climates are much older than our oldest climate records from Antarctic ice cores (less than one million years old)."

To try and understand climate properties related to the atmosphere - like rainfall and atmospheric moisture content - in such ancient times is very challenging. Existing methods, using calcium carbonate concretions that form in soils, or the chemistry of fossilised mammal teeth, are both hampered by their relative rarity in ancient sediments.

Dr Eley added, "Our new approach to quantifying ancient atmospheric moisture content relies on the fundamental properties of plant leaves, and how they alter their protective waxy coverings in response to water stress. These leaf waxes are tough and resistant, and are regularly found as what we call biomarker compounds in ancient river, lake and even marine sediments."

A method of estimating ancient moisture content based on these plant wax compounds overcomes the limitations of other methods because plant waxes are commonly found in soils and sediments stretching back tens or even hundreds of millions of years and across many environments.

The validity of this new tool was proven in studies of modern soils across the US and Central America, carried out by the research team of Associate Professor Michael Hren in the Center for Integrative Geosciences at the University of Connecticut. These studies showed a clear relationship between the chemistry of these waxy compounds and the amount of moisture in the atmosphere.

"What we see is that the distribution of organic compounds preserved in soils seems to be strongly related to the difference between how much water is in an air mass, and how much the air mass can hold, or what is known as the vapour pressure deficit," says Dr Hren.

Eley and Hren then applied their new proxy to reconstruct atmospheric moisture content in Central Spain during an interval 15 to 17 million years ago.

Although consistently much warmer than pre-industrial conditions, this interval marks one of the cooling steps that led to the development of the modern world. The new data confirms the expectations of climate models, that atmospheric cooling is coupled to less atmospheric moisture. The reconstructed changes in atmospheric moisture also align with results from other independent proxies used to investigate changes in temperature and rainfall in the region.

Dr Eley said, "This gives us the confidence that our proxy works, and we have every reason to believe that it will do so for future exploration into the even deeper past. We hope the results of this exploration will provide direct data to test our understanding of the relationship between global warming, atmospheric moisture content and rainfall systems."

Source: University of Birmingham [March 01, 2018]

Fields, streets and cities, but also forests planted in rank and file, and dead straight rivers: humans shape nature to better suit their purposes, and not only since the onset of industrialization. Such influences are well documented in the Amazonian rainforest. On the other hand, the influence of humans was debated in Central Africa where major interventions seem to have occurred there 2,600 years ago: Potsdam geoscientist Yannick Garcin and his team have published a report on their findings in the Proceedings of the National Academy of Sciences. The research team examined lake sediments in southern Cameroon to solve the riddle of the "rainforest crisis." They found that the drastic transformation of the rainforest ecosystem at this time wasn't a result of climatic change, it was humankind.

Farming activities in North-West Region of Cameroon [Credit: Better World Cameroon]

More than 20 years ago, the analysis of lake sediments from Lake Barombi in southern Cameroon showed that older sediment layers mainly contained tree pollen reflecting a dense forested environment. In contrast, the newer sediments contained a significant proportion of savannah pollen: the dense primitive forest quickly transformed into savannahs around 2,600 years ago, followed by an equally abrupt recovery of the forest approximately 600 years later. For a long time, the most probable cause of this sudden change, dubbed the "rainforest crisis," was thought to be climate change brought about by a decrease in precipitation amount and increase in precipitation seasonality. Despite some controversy, the origin of the rainforest crisis was thought to be settled.

High volumes of precipitation in the region (over 3,000 mm annually) have ensured that the lake has not dried out over the millenia. This heavy rainfall has created large volumes of sediment, which are then washed into the lake. These circumstances make it possible to perform sediment analyses with the utmost precision [Credit: B. Brademann/GFZ]

Yet Garcin, a postdoctoral researcher at the University of Potsdam, and his international team of scientists from UP, CEREGE, IRD, ENS Lyon, GFZ, MARUM, AMU, AWI, and from Cameroon suspected that other causes could have led to the ecosystem's transformation. By reconstructing both vegetation and climate change independently -- through stable isotope analysis of plant waxes, molecular fossils preserved in the sediment -- the team confirmed that there was a large change in vegetation during the rainforest crisis, but indicated that this was not accompanied by a change in precipitation.

"The rainforest crisis is proven, but it cannot be explained by a climate change," says Garcin. "In fact, in over 460 archaeological finds in the region, we have found indications that humans triggered these changes in the ecosystem." Archaeological remains older than 3,000 years are rare in Central Africa. Around 2,600 years ago, coincident with the rainforest crisis, the number of sites increased significantly, suggesting a rapid human population growth -- probably related to the expansion of the Bantu-speaking peoples in Central Africa. This period also saw the emergence of pearl millet cultivation, oil palm use, and iron metallurgy in the region.

This floating platform can be completely taken apart and transported overseas. The platform enabled the collection of sediment samples in the approximately 100-meter-deep Lake Barombi, which were then analyzed in the laboratory [Credit: Y. Garcin/University of Potsdam]

"The combination of regional archaeological data and our results from the sediments of Lake Barombi shows convincingly that humans strongly impacted the tropical forests of Central Africa thousands of years ago, and left detectable anthropogenic footprints in geological archives," says Dirk Sachse at the Helmholtz Center Potsdam -- Research Center for Geosciences (GFZ). Sachse was one of the major contributors to the development of the method for analyzing plant wax molecular fossils (termed biomarkers).

"We are therefore convinced that it was not climate change that caused the rainforest crisis 2,600 years ago, but it was the growing populations that settled in the region and needed to clear the forest for exploiting arable land," says Garcin. "We are currently observing a similar process underway in many parts of Africa, South America, and Asia." But the work of Garcin and his team also shows that nature has powerful regenerative abilities. When anthropogenic pressure decreased 2,000 years ago forest ecosystems reconstituted, but not necessarily as before: as in the Amazonian rainforest, field studies show that the presence of certain species is very often related to past human activity.

Source: GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre [February 26, 2018]

A team led by geochemist Dr. Katharina Pahnke from Oldenburg has discovered important evidence that the rise in atmospheric carbon dioxide levels at the end of the last ice age was triggered by changes in the Antarctic Ocean. The researchers from the University of Oldenburg's Institute for Chemistry and Biology of the Marine Environment (ICBM), the Max Planck Institute for Marine Microbiology in Bremen and the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) were able to demonstrate that the deep South Pacific was strongly stratified during the last ice age, and could thus have facilitated long-term, deep-sea storage of the greenhouse gas carbon dioxide (CO2). The study, which has now been published in the academic journal Science, also indicates that in the course of the warming following the end of the last ice age the mixing of the deep water masses increased, releasing stored CO2 and enhancing global warming.

Snapshot from aboard RV Polarstern [Credit: Mario Hoppmann]

The Southern Ocean plays an important role in climate events because CO2 can be absorbed from the atmosphere into the ocean. When increased amounts of dust are deposited in the seawater, microscopic algae multiply because the iron contained in the dust acts as a fertilizer. When these single celled algae die, they sink to the ocean floor, taking the sequestered carbon dioxide with them. To ensure long-term removal of the CO2 from the atmosphere, however, it must be stored in stable conditions in deep water over long periods of time.

In order to find out how water masses in the deep South Pacific have developed over the last 30,000 years, the team recovered sediment cores from water depths of between 3,000 and more than 4,000 metres during an expedition of the research vessel "Polarstern" to the South Pacific. The geochemists Dr. Chandranath Basak and Dr. Henning Fröllje of the ICBM - the two main authors of the study - extracted tiny teeth and other skeletal debris of fossil fish from the sediment to analyse their content of isotopes of the rare earth metal neodymium.

"Neodymium is particularly useful for identifying water masses of different origin," said Pahnke, the head of the Max Planck Research Group for Marine Isotope Geochemistry based at the ICBM and the Max Planck Institute for Marine Microbiology in Bremen, explaining that each layer of water has its own characteristic neodymium signature. The isotope ratios of this element vary depending on which ocean basin the water comes from. For instance, the coldest and therefore deepest water mass in the Southern Pacific forms on the continental shelf of Antarctica and carries a distinct neodymium signature. Overlying this mass is a layer that combines water from the North Atlantic, the South Pacific and the North Pacific and hence is marked by a different signature.

View from RV Polarstern while collecting sediment samples used in the study by Basak et al. [Credit: Dr. Katharina Pahnke]

Using fish debris in deep-sea sediments, the researchers were able to trace the variations in neodymium concentrations at different depths over the course of time. The result: at the peak of the last ice age approximately 20,000 years ago, the neodymium signature of samples taken from depths below 4,000 metres was significantly lower than at lower depths. "The only explanation for such a pronounced difference is that there was no mixing of the water masses at that time," said Fröllje, who currently works at the University of Bremen. He and his colleagues concluded from this that the deep waters were strongly stratified during the glacial period.

As the climate in the southern hemisphere grew warmer towards the end of the last ice age around 18,000 years ago, the stratification of the water masses was broken up and neodymium values at different depths converged. "There was probably more mixing because the density of the water decreased as a result of the warming," Pahnke explained. This then led to the release of the carbon dioxide stored in deep waters.

For some time now climate researchers have been speculating on why fluctuations in atmospheric CO2 levels followed the same pattern as temperature in the southern hemisphere whereas the temperature in the north at times ran counter to these fluctuations. One theory is that certain processes in the Southern Ocean played an important role.

"With our analyses we have for the first time provided concrete evidence supporting the theory that there is a connection between the CO2 fluctuations and stratification in the Southern Ocean," said co-author of the study Dr. Frank Lamy of the AWI in Bremerhaven. The current study supports the hypothesis that the warming of the southern hemisphere broke up stable stratification in the Antarctic Ocean, resulting in the release of the carbon dioxide that was stored in these waters.

Source: Alfred Wegener Institute [February 22, 2018]

Moth scales, preserved in the mud of a coniferous forest lake, have been used to identify outbreaks of these insects over the past 10,000 years. This groundbreaking new technique, reported in the open-access journal Frontiers in Ecology and Evolution, can tell us more about the frequency and intensity of past and future insect epidemics, their impact on the forest environment and how they are linked to climate change.

Dead Spruce Budworm moths (Choristoneura fumiferana) floating on the surface of a boreal lake during an insect outbreak period in 2017. The lake is north of Lake Saint-Jean in Quebec, Canada [Credit: Emy Tremblay, Karoline Pitre, Miguel Montoro Girona, Lionel Navarro, Guillaume Grosbois]

"This is an exciting discovery, which will greatly increase our knowledge of prehistoric forest ecosystems," says Dr. Miguel Montoro Girona, joint-lead author of this paper, based at the Swedish University of Agricultural Sciences, Umeå, Sweden. "It is comparable to the fossil pollen and charcoal markers in sediments, which revolutionized prehistoric research to provide information on plants, climate and forest fires going back thousands of years. Our new method can be applied to many ecosystems where moths and butterflies have a marked influence on the landscape."

Moths are one of the most widespread and recognizable insects in the world. In the boreal forests of North America, which are mainly comprised of coniferous, evergreen trees, the larva of one moth species -- the Spruce Budworm -- can periodically cause severe and widespread damage. This leads to millions of dollars of lost revenue to the forest-based economy.

It was during a routine observation of one of these outbreaks that the researchers had a 'eureka' moment.

Thousands of scales cover the moth body and wings like shingles on a roof, arranged in rows and anchored in a socket. Image taken using a x100 optical microscope from the Université de Québec à Chicoutimi. Scale size = 50 μ; original colour has been modified [Credit: Emy Tremblay, Hubert Morin, Miguel Montoro Girona]

"Together with an insect specialist, we recently identified a 'strange' structure in a colleague's lake-water sample, which turned out to be a scale from a moth wing," says Dr. Hubert Morin, co-author, based at the Québec University, Canada. "Afterwards, during a Spruce Budworm outbreak, I noticed the lakes were covered in dead moths. Knowing they are made from a material that is likely to be well-preserved in the sediments of lakes, I realized they had the potential to provide information about these swarms going back thousands of years."

This hunch turned out to be true. Taking a 5-meter-long core of sediment from a forest lake near Québec, which represented 10,000 years' worth of sediment deposit, the researchers at the Québec University spent five years perfecting their method of extracting, examining and counting moth scales under the microscope from each sediment layer.

"Our analysis revealed peaks of moth scales that corresponded to known periods of insect outbreak. This means we can work out when these epidemics occurred before records began," says Dr. Lionel Navarro joint-lead author, based at the Québec University, who spent a lot of time in the laboratory processing these samples. "This new method will be of enormous help to future research in areas as wide as ecology and evolution, biodiversity conservation, climate change and forestry."

The diversity in shapes and colors makes moth scales a potential proxy to identify Lepidoptera species. Image taken using an optical microscope from the Université de Québec à Chicoutimi. Scale size = 50 μ [Credit: Emy Tremblay, Miguel Montoro Girona]

The authors explain, "Using the Spruce Budworm as an example, moths and butterflies can be one of the most important natural disturbances, changing the forest structure and species composition, with strong economic implications to forestry and agriculture. They are an 'umbrella species' -- the second most diverse animal group in the world -- so improving our understanding of these creatures will in turn provide a lot of information about other species and the state of the ecosystem they are in."

They continue, "Currently, climate change is one of the biggest challenges of our planet. Understanding our past ecosystems is essential to predicting the future. Based on climate-change predictions, insect outbreaks will be more frequent, with higher severity. Our new technique can help us understand how moths and butterflies react to different climatic scenarios and environmental changes, so we can predict their response to climate change, as well as their vulnerability and extinction risk."

Source: Frontiers [February 22, 2018]

The vestiges of lakes long extinct dot the landscape of the American desert west. These fossilized landforms provide clues of how dynamic climate has been over the past few million years.

Erosional Pleistocene shorelines in Surprise Valley, California, USA [Credit: Anne Egger]

Identification of ancient lake shoreline features began with early explorers of the continent. The first detailed studies were conducted by pioneering American geologists such as G.K. Gilbert and I.C. Russell in the late 1800s, who studied Lake Bonneville, now the remnant Great Salt Lake in Utah, and Lake Lahonton, located in northwestern Nevada.

Through this long history of studying fossil shorelines and lake sediments, we know that these lakes existed during two periods with distinct environmental conditions during the geologically recent past. The first was during ice age maxima, such as the last ice age, 14 to 30 thousand years ago, when global temperatures were 4 to 6 degrees colder and continental ice sheets expanded into the continental United States.

The second time period was about three million years ago during the middle of the Pliocene epoch--a global climate characterized by warmer temperatures and atmospheric CO2 levels roughly equivalent to today's values, which has led many scientists to view the Pliocene as a potential analogue for future climate change.

These observations lead to an important question, says the study's lead author, Daniel Ibarra, "Why are there lake systems under both colder and warmer climates, but not today?" Of particular interest, he says, is the presence of lakes under warmer conditions, which, under a "wet gets wetter, dry gets drier" paradigm, goes against projections of future warming.

Shorelines of Lake Bonneville along the Oquirrh Mountains, Utah, USA. (H.H. Nichols [artist] and G.K. Gilbert, in Gilbert, 1884) [Credit: H.H. Nichols [artist] and G.K. Gilbert, in Gilbert, 1884. Public domain]

To answer this question, Ibarra and colleagues looked at the competing influences of temperature and precipitation, and how they combine to allow for the existence of lakes under these dual climate states.

The authors compiled evidence for, and created models of, lakes during both colder and warmer than modern periods of the Pliocene-Pleistocene (the last 5 million years). During colder glacial periods, they found that increased precipitation and decreased evaporation combined to form large lakes that occupied the inward draining basins in the western United States, particularly in northern Nevada and Utah.

Increased precipitation also drove the formation of lakes, particularly in southern Nevada and southern California during the warmer middle Pliocene, outpacing higher temperatures and evaporation rates during that time. This increase in precipitation during the middle Pliocene and dominantly southwestern distribution of lake deposits is similar to the pattern of precipitation during modern El Niño years, corroborating previous hypotheses for mean "El Niño-like" conditions during the mid-Pliocene.

The team's interdisciplinary approach explains the conditions driving lake systems in mid-latitude regions today and over the geologic past. Further, notes Ibarra, "This work illustrates the importance of understanding how the El Niño Southern Oscillation drives precipitation patterns in arid regions, which is important for future water resources planning for the western United States."

The study appears in the Geological Society of America Bulletin.

Source: Geological Society of America [February 22, 2018]

Pine trees become temporarily sterile when exposed to ultraviolet radiation as intense as some scientists believe Earth experienced 252 million years ago during the planet's largest mass extinction, lending support to the theory that ozone depletion contributed to the crisis.

At the end of the Permian 252 million years ago, the continents were part of one supercontinent called Gondwana. Fossils from many areas of Gondwana contain malformed pollen and evidence of forest decline at the same time as most animals on land and in the oceans died out [Credit: UC Berkeley]

The effect of high UV on conifers and potentially other trees also suggests caution today in introducing chemicals that deplete Earth's ozone layer, which has yet to recover after a global ban on chlorofluorocarbon refrigerants in the 1980s instituted after ozone holes developed over the poles. Some industrial chemicals also destroy atmospheric ozone, which is the planet's sunscreen, protecting all life from excessive UV rays, in particular UV-B wavelengths, which causes mutations in DNA.

Results of the experiment, which was conducted by University of California, Berkeley graduate student Jeffrey Benca, will be published in the online journal Science Advances.

Benca irradiated 18-inch-tall, bonsai-like pines with UV-B dosages up to 13 times stronger than on Earth today, simulating the effects of ozone depletion caused by immense volcanic eruptions that occurred at the end of the Permian Period. During the two-month experiment, none of the trees died but all seed cones, or pine cones, shriveled up only days after emerging, leaving the trees sterile.

When placed outside, the trees regained the ability to produce healthy seed cones in later years.

Normal and abnormal fossilized pollen from the Permian (top) and similar pollen from Pinus mugo in normal trees (bottom left) and those exposed to high levels of UV-B [Credit: UC Berkeley]

Scientists have proposed that ozone depletion caused by periodic volcanic eruptions over nearly a million years was one cause of the end-Permian extinction, but how has been unclear. Acid rain would have been a local effect, but the extinction of nearly 70 percent of known land animals, 95 percent of marine life and many plant lineages was global.

Previous paleoclimate modeling studies suggest the volcanic spurts could have wiped out the ozone layer worldwide, though temporarily. Nevertheless, even if ancient trees regained their fertility, repeated bouts of sterility could have hampered population growth over time, leading to collapse of the biosphere planet-wide, according to Benca.

Long-term biosphere collapse

"During the end-Permian crisis, the forests may have disappeared in part or fully because of increased UV exposure," Benca said. "With pulses of volcanic eruptions happening, we would expect pulsed ozone shield weakening, which may have led to forest declines previously observed in the fossil record."

Dwarf pines in a growth chamber under simulated sunlight plus extra UV-B from two high-intensity lamps. The UV light is invisible to the naked eye [Credit: Jeffrey Benca]

"If you disrupt some of the dominant plant lineages globally repeatedly, you could trigger trophic cascades by destabilizing the food web base, which doesn't work out very well for land animals," he added.

The surprise findings tell scientists something about past extinctions and Earth's future prospects as climate change, habitat destruction and pollution set us up for Earth's sixth mass extinction.

"Paleontologists have come up with various kill scenarios for mass extinctions, but plant life may not be affected by dying suddenly as much as through interrupting one part of the life cycle, such as reproduction, over a long period of time, causing the population to dwindle and potentially disappear," said co-author Cindy Looy, a UC Berkeley associate professor of integrative biology.

"Global biodiversity catastrophes are not about death but about the pruning of evolutionary branches on the tree of life at a rate much higher than the sprouting of new shoots," added co-author Ivo Duijnstee, an adjunct assistant professor of integrative biology. "Jeff, who used his plant growth chambers as a time machine to test the potential of a hypothesis about what may have happened 252 million years ago, provides an excellent example illustrating how the slowly unfolding extinction on land over maybe tens or hundreds of thousands of years may have been caused by reproductive troubles at the base of the food chain."

Siberian volcanoes

The extinction at the end of the Permian is thought to have been caused by volcanic eruptions in Siberia over hundreds of thousands if not a million years that produced what are known today as the Siberian Traps: lava fields covering much of northern Russia and originally encompassing nearly 3 million square miles with an average thickness of about 1,000 feet.

Normal seed cones of the pine tree (left) compared to shriveled cones produced when the pines were irradiated with UV-B light [Credit: Jeffrey Benca]

In 2004, Looy and her former Ph.D. advisor Henk Visscher proposed one way this might have played out, bases on fossilized abnormal plant spores found worldwide: volcanic gases -- halocarbons like methyl chloride and methyl bromide -- destroyed much or all of Earth's ozone layer, boosting UV-B exposure that would have affected life and potentially increased the genetic mutation rates in pollen and spores of plants worldwide.

Evidence for this hypothesis grew in 2005 when an independent research team led by Clinton Foster of Geoscience Australia discovered malformed pollen grains from end-Permian seed plants. The rise in the percentage of malformed pollen, which is seen in both the Northern and Southern Hemispheres, coincided with the decline of forests globally.

Finding evidence of malformation mechanisms in 252 million year old pollen fossils is impossible, so Looy and others have looked for other ways to determine whether increased UV-B disrupted the end-Permian ecosystem. Benca came up with a series of experiments using living plants to test the hypothesis.

The first experiment, using pines, was designed to find out whether high levels of UV-B could cause malformed pollen grains in today's seed plants similar to those described by Foster, and whether these malformations could affect reproduction. Squeezing a mature pine tree into a laboratory was a sticking point until Benca hit upon a novel solution: using a dwarf cultivar selected for bonsai that readily produces pollen and seed cones.


In 2013, he trucked 60 dwarf clonal pines to Berkeley from a conifer nursery in Boring, Oregon. After acclimating them for a year outdoors in full sun with sparse water and nutrient-poor soil -- typical conditions for this alpine species, Pinus mugo -- ran a 56-day indoor experiment using high-intensity UV-B-emitting lamps.

In three separate indoor UV chambers, Benca exposed the dwarf pines to 7.5, 10 and 13 times Berkeley's normal UV-B intensity, in line with estimates of the impact Siberian Trap eruptions would have had on the ozone layer if their emissions occurred over various lengths of time, ranging from 400,000 years to less than 200,000 years.

Indeed, the pines did produce malformed pollen. At the medium and extreme exposures, 12 to 15 percent of pollen grains were misshapen, versus 3 percent in normal and low-exposure trees. Foster's previous study suggested that pollen yields having more than 3 percent malformed grains are associated with environmental stress in modern conifers, Benca said. In total, he spent three years conducting the experiments and comparing more than 57,000 pollen grains produced by trees in the chambers.

To the researchers' amazement, however, all trees subjected to increased UV levels became sterile. Their seed cones shriveled up before they had a chance to be fertilized. This seemed to be a systemic reaction to the UV-B stress, since even seed cones hidden among foliage died.

"The system we used was really quite conservative," Benca said. "Unlike the relatively unprotected seed-bearing structures of affected end-Permian seed plants, today's pines have elaborate and very heavily reinforced, interlocking cone scales that shield their seeds from predators and the external environment. Even so, these trees just ditched all their seed cones. Pinus mugo is an alpine species that should be quite resilient to increased UV levels."

"That Jeff's UV-B-blast experiment -- somewhat of a calculated long shot -- produced pollen abnormalities in a modern conifer similar to abnormalities observed in 252-million-year old microfossils was one of the most exciting things I've seen this decade," Duijnstee said.

Author: Robert Sanders | Source: University of California - Berkeley [February 07, 2018]

Hundreds of methane flares observed offshore Western Svalbard in the Arctic are caused by a process that started at the end of the last ice age, according to the study. The methane release happens because the gas is freed from melting hydrates - an icy substance found below the ocean floor, containing methane in a cage of frozen water.

Gas hydrates are formed under cold temperature and high pressure conditions beneath the ocean floor. They contain large amounts of greenhouse gas methane [Credit: CAGE]

Ocean water warming was previously thought to be the cause of the hydrate melt in this particular area. But the study in Nature Communications suggests otherwise.

"Our investigations show that uplift of the sea floor in this region, caused by the melting of the ice masses since the end of the last ice age, is probably the reason for the dissolution of methane hydrate." says first author of the study Professor Klaus Wallmann at GEOMAR.

Leaking methane for 8000 years

Methane hydrate forms in cold temperatures and under high pressure - conditions that can be found at the bottom of the ocean.

When the Earth's crust naturally rebounds as ice sheets begin to shrink, the seafloor changes position. That and a subsequent shallowing of the water column above can cause he hydrates to destabilise and dissolve. Through a combination of sediment cores analyses and ice-sheet modelling, the study shows that this area has probably been steadily leaking methane from hydrates for 8000 years.

Ice sheet reconstruction

An important part of the study is the reconstruction of the Eurasian ice sheet that once covered the area. It was developed by scientists at CAGE - Centre for Arctic Gas Hydrate Environment and Climate, and shows that seafloor off Western Svalbard was covered by a large ice sheet during the last glaciation.

The load of ice in the area during the last glacial maximum would have added significant pressure to the crust below. Depression of the crust in the area off Western Svalbard was caused by the heavy load of the ice [Credit: Henry Patton/CAGE]

As that ice sheet retreated, some 20,000 years ago, the sea floor started bouncing back. The process is called isostatic rebound: the rise of land masses that were depressed by the huge weight of ice sheets.

The uplift of the crust is a very slow process that is still happening and affecting the environment. Instead of abrupt release of methane which is evident in other parts of the Arctic, the hydrate melt in ocean floor off Western Svalbard caused slow and steady seeps that are ongoing.

"This study illustrates the colossal influence that the ice sheets that once covered Eurasia had on their surrounding environment" says co-author Henry Patton, researcher at CAGE. Another example according to Patton is the uplift in the Baltic, which is still observable today, though the pace of rebound has now slowed significantly to less than a centimetre per year.

Anthropogenic influence open for discussion

The scientists behind the study suggest that warming of the oceans due to recent anthropogenic climate change is not to blame for the methane seeps off Western Svalbard.

"But gas hydrates are still widespread elsewhere beneath the Barents Sea and across the Arctic. How these reservoirs respond to any future changes in ocean bottom-water temperatures, natural or anthropogenic, is still a topic very much open for discussion." says Patton.

One of the other conclusions from the study is that the impact of future seabed methane fluxes may be underestimated. Hydrates should be seen as a seal blocking the flux of methane from underlying reservoirs, and not the total source of gas in themselves.

Source: CAGE - Center for Arctic Gas Hydrate, Climate and Environment [February 07, 2018]

The oldest studied rodent fauna in this work, which inhabited the Iberian Peninsula from twelve million years ago, progressively shifted north looking for humid environments to survive climate change that caused prominent dry and cold environments in central Iberia. According to an investigation leading by Universidad Complutense de Madrid (UCM).

Life restoration of a flying squirrel (at the forefront) in the forest environments from the northern region (Catalonia and south of France) around 10 million years ago [Credit: Oscar Sanisidro (Vertebrate Paleontology. Biodiversitiy Institute, University of Kansas)]

The results of this study, published this week in the Nature Publishing Group Scientific Reports, allow us to know the effects of climate change on past biodiversity. Based on the analysis of changes in faunas with different ecological features (dietary habits, habitat preferences, etc).

The study focuses on the rodent faunas that inhabited the Iberian Peninsula between 12 and 5 million years ago. This timeframe is particularly relevant for the evolution of past climate as it is a period of intense cooling coupled with increased aridity at a global scale. This global trend radically transformed landscapes in Southwestern Europe, which became increasingly more arid.

'We compiled information from all the rodent species present at more than hundred fossil sites of Iberian Peninsula and the South of France, which allow us to statistically evaluate how this rodent communities were grouped based on their ecological affinities. Then, we tested how these associations were affected by the critical environmental changes happening in the region between 12 and 5 million years ago' explains Fernando Blanco researcher at the Department of Geodynamics, Stratigraphy and Palaeontology (UCM).

This work has confirmed the strong influence two important environmental events had in mammal communities: the Vallesian crisis, ten million years ago and, more remarkably the Messinian crisis, six million years ago, where nearly the whole Mediterraean basin was completely drained.

A group with valuable information

During the studied time interval the climatic changes provoked diversity and distribution changes on rodent communities. 'One of the main outcomes of this study is that older faunas, linked to environments that were disappearing due to increased aridity at the time, were displaced to the north surviving temporally in local refugia with more humid conditions, particularly in the region of Catalonia and the South of France' adds Manuel Hernández Fernández, professor at Universidad Complutense de Madrid and senior author of the study.

Rodents are an ideal group to conduct palaeoecological research: 1) they are among the most diverse groups of mammals, 2) they are widely distributed geographically across a huge range of ecosystems and 3) they are particularly sensitive to environmental changes. Furthermore, their fossil record is extraordinarily rich.

'Only in the Iberian Peninsula, the number of fossil localities with rich assemblages of rodents are counted by the hundreds' explains Fernando Blanco. 'This study sets a primer to move the field toward more comprehensive studies spanning larger geographical regions and longer timeframes to ultimately understand in higher detail the effects of past climate change in extinct faunas' adds Ana Rosa Gómez Cano from Institut Català de Paleontologia and coauthor of the article.

In addition to UCM, there are several institutions collaborating, including Consejo Superior de Investigaciones Científicas, Institut Català de Paleontologia, Museum für Naturkunde of Berlin and Harvard University, under the coordination of Universidad Complutense de Madrid. This study, are the result of more than 50 years of digging and research experience in Iberian Peninsula and southern France fossil sites.

As a final remark, it is important to underline that this kind of studies are essential to create explanatory, or even predictive, models to anticipate the effects that the climate change that we are experiencing might have upon current biodiversity. 'By understanding in depth the effects of past climatic conditions on extinct biodiversity we might be able to anticipate these trends in the future. In this sense, I believe Palaeontology has a crucial role in the study of modern global change" explains Fernando Blanco.

Source: Universidad Complutense de Madrid [February 06, 2018]