Climate capers of the past 600,000 years

The researchers remove samples from a core segment taken from Lake Van at the center for Marine environmental sciences MARUM in Bremen, where all of the cores from the PALEOVAN project are stored. -  Photo: Nadine Pickarski/Uni Bonn
The researchers remove samples from a core segment taken from Lake Van at the center for Marine environmental sciences MARUM in Bremen, where all of the cores from the PALEOVAN project are stored. – Photo: Nadine Pickarski/Uni Bonn

If you want to see into the future, you have to understand the past. An international consortium of researchers under the auspices of the University of Bonn has drilled deposits on the bed of Lake Van (Eastern Turkey) which provide unique insights into the last 600,000 years. The samples reveal that the climate has done its fair share of mischief-making in the past. Furthermore, there have been numerous earthquakes and volcanic eruptions. The results of the drilling project also provide a basis for assessing the risk of how dangerous natural hazards are for today’s population. In a special edition of the highly regarded publication Quaternary Science Reviews, the scientists have now published their findings in a number of journal articles.

In the sediments of Lake Van, the lighter-colored, lime-containing summer layers are clearly distinguishable from the darker, clay-rich winter layers — also called varves. In 2010, from a floating platform an international consortium of researchers drilled a 220 m deep sediment profile from the lake floor at a water depth of 360 m and analyzed the varves. The samples they recovered are a unique scientific treasure because the climate conditions, earthquakes and volcanic eruptions of the past 600,000 years can be read in outstanding quality from the cores.

The team of scientists under the auspices of the University of Bonn has analyzed some 5,000 samples in total. “The results show that the climate over the past hundred thousand years has been a roller coaster. Within just a few decades, the climate could tip from an ice age into a warm period,” says Doctor Thomas Litt of the University of Bonn’s Steinmann Institute and spokesman for the PALEOVAN international consortium of researchers. Unbroken continental climate archives from the ice age which encompass several hundred thousand years are extremely rare on a global scale. “There has never before in all of the Middle East and Central Asia been a continental drilling operation going so far back into the past,” says Doctor Litt. In the northern hemisphere, climate data from ice-cores drilled in Greenland encompass the last 120,000 years. The Lake Van project closes a gap in the scientific climate record.

The sediments reveal six cycles of cold and warm periods


Scientists found evidence for a total of six cycles of warm and cold periods in the sediments of Lake Van. The University of Bonn paleoecologist and his colleagues analyzed the pollen preserved in the sediments. Under a microscope they were able to determine which plants around the eastern Anatolian Lake the pollen came from. “Pollen is amazingly durable and is preserved over very long periods when protected in the sediments,” Doctor Litt explained. Insight into the age of the individual layers was gleaned through radiometric age measurements that use the decay of radioactive elements as a geologic clock. Based on the type of pollen and the age, the scientists were able to determine when oak forests typical of warm periods grew around Lake Van and when ice-age steppe made up of grasses, mugwort and goosefoot surrounded the lake.

Once they determine the composition of the vegetation present and the requirements of the plants, the scientists can reconstruct with a high degree of accuracy the temperature and amount of rainfall during different epochs. These analyses enable the team of researchers to read the varves of Lake Van like thousands of pages of an archive. With these data, the team was able to demonstrate that fluctuations in climate were due in large part to periodic changes in the Earth’s orbit parameters and the commensurate changes in solar insolation levels. However, the influence of North Atlantic currents was also evident. “The analysis of the Lake Van sediments has presented us with an image of how an ecosystem reacts to abrupt changes in climate. This fundamental data will help us to develop potential scenarios of future climate effects,” says Doctor Litt.

Risks of earthquakes and volcanic eruptions in the region of Van

Such risk assessments can also be made for other natural forces. “Deposits of volcanic ash with thicknesses of up to 10 m in the Lake Van sediments show us that approximately 270,000 years ago there was a massive eruption,” the University of Bonn paleoecologist said. The team struck some 300 different volcanic events in its drillings. Statistically, that corresponds to one explosive volcanic eruption in the region every 2000 years. Deformations in the sediment layers show that the area is subject to frequent, strong earthquakes. “The area around Lake Van is very densely populated. The data from the core samples show that volcanic activity and earthquakes present a relatively high risk for the region,” Doctor Litt says. According to media reports, in 2011 a 7.2 magnitude earthquake in the Van province claimed the lives of more than 500 people and injured more than 2,500.

Publication: “Results from the PALEOVAN drilling project: A 600,000 year long continental archive in the Near East”, Quaternary Science Reviews, Volume 104, online publication: (http://dx.doi.org/10.1016/j.quascirev.2014.09.026)

Comprehensive analysis of impact spherules supports theory of cosmic impact 12,800 years ago

This is UCSB Earth Sciences professor emeritus James Kennett. -  Courtesy photo
This is UCSB Earth Sciences professor emeritus James Kennett. – Courtesy photo

About 12,800 years ago when the Earth was warming and emerging from the last ice age, a dramatic and anomalous event occurred that abruptly reversed climatic conditions back to near-glacial state. According to James Kennett, UC Santa Barbara emeritus professor in earth sciences, this climate switch fundamentally — and remarkably — occurred in only one year, heralding the onset of the Younger Dryas cool episode.

The cause of this cooling has been much debated, especially because it closely coincided with the abrupt extinction of the majority of the large animals then inhabiting the Americas, as well as the disappearance of the prehistoric Clovis culture, known for its big game hunting.

“What then did cause the extinction of most of these big animals, including mammoths, mastodons, giant ground sloths, American camel and horse, and saber- toothed cats?” asked Kennett, pointing to Charles Darwin’s 1845 assessment of the significance of climate change. “Did these extinctions result from human overkill, climatic change or some catastrophic event?” The long debate that has followed, Kennett noted, has recently been stimulated by a growing body of evidence in support of a theory that a major cosmic impact event was involved, a theory proposed by the scientific team that includes Kennett himself.

Now, in one of the most comprehensive related investigations ever, the group has documented a wide distribution of microspherules widely distributed in a layer over 50 million square kilometers on four continents, including North America, including Arlington Canyon on Santa Rosa Island in the Channel Islands. This layer — the Younger Dryas Boundary (YDB) layer — also contains peak abundances of other exotic materials, including nanodiamonds and other unusual forms of carbon such as fullerenes, as well as melt-glass and iridium. This new evidence in support of the cosmic impact theory appeared recently in a paper in the Proceedings of the National Academy of the Sciences.

This cosmic impact, said Kennett, caused major environmental degradation over wide areas through numerous processes that include continent-wide wildfires and a major increase in atmospheric dust load that blocked the sun long enough to cause starvation of larger animals.

Investigating 18 sites across North America, Europe and the Middle East, Kennett and 28 colleagues from 24 institutions analyzed the spherules, tiny spheres formed by the high temperature melting of rocks and soils that then cooled or quenched rapidly in the atmosphere. The process results from enormous heat and pressures in blasts generated by the cosmic impact, somewhat similar to those produced during atomic explosions, Kennett explained.

But spherules do not form from cosmic collisions alone. Volcanic activity, lightning strikes, and coal seam fires all can create the tiny spheres. So to differentiate between impact spherules and those formed by other processes, the research team utilized scanning electron microscopy and energy dispersive spectrometry on nearly 700 spherule samples collected from the YDB layer. The YDB layer also corresponds with the end of the Clovis age, and is commonly associated with other features such as an overlying “black mat” — a thin, dark carbon-rich sedimentary layer — as well as the youngest known Clovis archeological material and megafaunal remains, and abundant charcoal that indicates massive biomass burning resulting from impact.

The results, according to Kennett, are compelling. Examinations of the YDB spherules revealed that while they are consistent with the type of sediment found on the surface of the earth in their areas at the time of impact, they are geochemically dissimilar from volcanic materials. Tests on their remanent magnetism — the remaining magnetism after the removal of an electric or magnetic influence — also demonstrated that the spherules could not have formed naturally during lightning strikes.

“Because requisite formation temperatures for the impact spherules are greater than 2,200 degrees Celsius, this finding precludes all but a high temperature cosmic impact event as a natural formation mechanism for melted silica and other minerals,” Kennett explained. Experiments by the group have for the first time demonstrated that silica-rich spherules can also form through high temperature incineration of plants, such as oaks, pines, and reeds, because these are known to contain biologically formed silica.

Additionally, according to the study, the surface textures of these spherules are consistent with high temperatures and high-velocity impacts, and they are often fused to other spherules. An estimated 10 million metric tons of impact spherules were deposited across nine countries in the four continents studied. However, the true breadth of the YDB strewnfield is unknown, indicating an impact of major proportions.

“Based on geochemical measurements and morphological observations, this paper offers compelling evidence to reject alternate hypotheses that YDB spherules formed by volcanic or human activity; from the ongoing natural accumulation of space dust; lightning strikes; or by slow geochemical accumulation in sediments,” said Kennett.

“This evidence continues to point to a major cosmic impact as the primary cause for the tragic loss of nearly all of the remarkable American large animals that had survived the stresses of many ice age periods only to be knocked out quite recently by this catastrophic event.”

Middle East river basin has lost Dead Sea-sized quantity of water

Already strained by water scarcity and political tensions, the arid Middle East along the Tigris and Euphrates rivers is losing critical water reserves at a rapid pace, from Turkey upstream to Syria, Iran and Iraq below.

Unable to conduct measurements on the ground in the politically unstable region, UC Irvine scientists and colleagues used data from space to uncover the extent of the problem. They took measurements from NASA’s Gravity Recovery and Climate Experiment satellites, and found that between 2003 and 2010, the four nations lost 144 cubic kilometers (117 million acre feet) of water – nearly equivalent to all the water in the Dead Sea. The depletion was especially striking after a drought struck the area in 2007. Researchers attribute the bulk of it – about 60 percent – to pumping of water from underground reservoirs.

They concluded that the Tigris-Euphrates watershed is drying up at a pace second only to that in India. “This rate is among the largest liquid freshwater losses on the continents,” the scientists report in a paper to be published online Feb. 15 in Water Resources Research, a journal of the American Geophysical Union.

Water management is a complex issue in the Middle East, “a region that is dealing with limited water resources and competing stakeholders,” said Katalyn Voss, lead author and a water policy fellow with the University of California’s Center for Hydrologic Modeling in Irvine.

Turkey has jurisdiction over the Tigris and Euphrates headwaters, as well as the reservoirs and infrastructure of its Southeastern Anatolia Project, which dictates how much water flows downstream into Syria, Iran and Iraq. And due to varied interpretations of international laws, the basin does not have coordinated water management. Turkey’s control of water distribution to adjacent countries has caused tension, such as during the 2007 drought, when it continued to divert water to irrigate its own agricultural land.

“That decline in stream flow put a lot of pressure on downstream neighbors,” Voss said. “Both the United Nations and anecdotal reports from area residents note that once stream flow declined, the northern part of Iraq had to switch to groundwater. In a fragile social, economic and political environment, this did not help.”

The Gravity Recovery and Climate Experiment, which NASA launched in 2002 to measure the Earth’s local gravitation pull from space, is providing a vital picture of global trends in water storage, said hydrologist Jay Famiglietti, the study’s principal investigator and a UC Irvine professor of Earth system science.

GRACE is “like having a giant scale in the sky,” he said. “Whenever you do international work, it’s exceedingly difficult to obtain data from different countries. For political, economic or security reasons, neighbors don’t want each other to know how much water they’re using. In regions like the Middle East, where data are relatively inaccessible, satellite observations are among the few options.”

Rising or falling water reserves alter the Earth’s mass in particular areas, influencing the strength of the local gravitational attraction. By periodically quantifying that gravity, the satellites provide information about how much each region’s water storage changes over time.

The 754,000-square-kilometer (291,000-square-mile) Tigris-Euphrates River Basin jumped out as a hot spot when researchers from UC Irvine, NASA’s Goddard Space Flight Center and the National Center for Atmospheric Research looked at global water trends. Over the seven-year period, they calculated that available water there shrank by an average of 20 cubic kilometers (16 million acre feet) annually.

Meanwhile, the area’s demand for freshwater is rising at the worst possible time. “They just do not have that much water to begin with, and they’re in a part of the world that will be experiencing less rainfall with climate change. Those dry areas are getting drier,” Famiglietti said. “Everyone in the world’s arid regions needs to manage their available water resources as best they can.”

Drilling in the holy land

About 50 miles from Bethlehem, a drilling project is determining the climate and earthquake activity of the Holy Land. Scientists from eight nations are examining the ground below the Dead Sea, by placing a borehole in this deepest basin in the world. The International Continental Scientific Drilling Program ICDP brings together research teams from Israel, Japan, Norway, Switzerland, the USA and Germany. Particularly noteworthy: Researchers from Jordan and Palestine are also involved.

Scientists and technicians of the GFZ German Research Centre for Geosciences have now completed a geophysical measurement procedure in the hole and helped with the initial examination of the cores in a field laboratory. “We have drilled through about half a million years of sedimentary deposits,” estimates Dr. Ulrich Harms from the ICDP’s operational support group at the GFZ. “From this, we can deduce not only the climate history, but also the earthquake activity in this seismically very active region.” The direction and inclination of the well were determined with high precision below this lake which is around 300 meters deep here, and the physical properties of the rocks were measured down to the bottom of the 460 meters deep borehole.

These unique measurements are used to record a continuous survey of the deposits in the Dead Sea and to compare it with the recovered cores. Although scientific drilling attempts to recover cores over the entire length of a hole, it is not always possible. These special borehole measurements are conducted to cover the gaps. In addition, a second series of cores is obtained from a second well in order to verify and secure the data.

“If everything goes perfectly, we may soon be able to provide information about past climate and environmental changes in the Bethlehem area,” says Ulrich Harms. His colleague Professor Achim Brauer, a paleo-climatologist at the GFZ, is one of the initiators of the ICDP project. He and his team will analyze the drill cores. They are not just interested in the climate at the time of Jesus’ birth but in the climate of the whole history of mankind. The region of the Holy Land is considered a land bridge across which early man migrated in several waves from Africa to the north. The climate history of the land of the Bible is therefore closely connected with the history of mankind.

Research Team Finds Evidence of Ancient Subtropical Environment in the Arid Emirate





Today The Arabian Peninsula is a vast desert, but 8 million years ago it was covered with forests and grasslands.
Today The Arabian Peninsula is a vast desert, but 8 million years ago it was covered with forests and grasslands.

Six to eight million years ago, the Western Region of the Abu Dhabi Emirate was a lush landscape teeming with subtropical wildlife, according to Andrew Hill, the Clayton Stephenson Class of 1954 Professor of Anthropology at Yale.



Before a meeting on January 8 in Abu Dhabi organized by the Abu Dhabi Authority on Culture and Heritage (ADACH) and the Emirates Natural History Group, Hill described the joint ADACH-Yale project leading to the startling discovery that the arid desert of the Emirate’s Western Region was once the river-fed habitat of crocodiles, hippos, turtles and elephants.



Working with geological investigators, the paleontologists based their conclusion on fossils they recovered from the geological deposits of the Emirate’s Baynunah Formation.



In the late Miocene Epoch, 6 to 8 million years ago, the researchers say, a vast system of shallow rivers ran through Abu Dhabi providing forests and grasslands that supported such fauna as ostriches, antelopes, catfish and horses.



Not only do the fossils offer a record of Abu Dhabi’s particular environmental heritage, Hill said, but, situated at the intersection of Asia, Africa and Europe, Abu Dhabi, with its rich repository of fossils, provides a key to understanding the three great bio-geographic zones of the world at a period of significant biological development.



The ADACH-Yale project, directed by Hill, who also heads the Division of Anthropology and is a curator at the Yale Peabody Museum of Natural History, and Ph.D. student Faysal Bibi (Yale Department of Geology & Geophysics), began its work in Abu Dhabi December 8, 2007.


Additional Yale team members included Marilyn Fox (Chief Preparator), and Walter Joyce (Collections Manager), both in the Division of Vertebrate Paleontology of the Peabody Museum, and Professor David Evans and Ph.D. student Daniel Peppe, of the Yale Department of Geology and Geophysics.



The field team also included Professor Ali Haidar, a geologist from the American University of Beirut, Lebanon, as well as members of ADACH’s Historic Environment Department. These included Dr. Walid Yasin (Head of Division: Archaeology), Dr. Mark Beech (Head of Division: Cultural Landscapes), Ali El-Meqbali and Hamdan Al-Rashidi (Field archaeologists).



In his talk, Hill described the current work of the ADACH-Yale team involving surveys of about a dozen sites, most located along the coastline. Among several important new fossil specimens recovered recently are the pelvic bones of a now extinct ancestor of the ostrich, jawbones of elephants and a hippopotamus and the partial skeleton of a small crocodile.



The team has also been studying track marks of elephants and other animals preserved at inland sites.



Most of the late-Miocene fossils are found in a region that is rapidly being developed, and the Yale team is providing ADACH with recommendations for site protection.



Hill stressed in his talk that the Peabody Museum with more than 12 million specimens, very active research programs and a large number of public and educational programs is well placed to provide advice and training to colleagues in Abu Dhabi and to assist in displays of the invaluable fossil records they find.



It is expected that this visit will be just the first in an annual series of ADACH-Yale projects in the Western Region over the next four or five years, during which more deeply buried clues to Abu Dhabi’s remote past will come to light.



The ADACH-Yale research project is principally supported by ADACH, as well as by other grants from the Revealing Hominid Origins Initiative (U.S. National Science Foundation), the Division of Vertebrate Paleontology of the Yale Peabody Museum, and the Office of the Provost, Yale University.