The 500 million years ocean history

Brachiopod Paraspirifer bownockeri from the Middle Devonian of Ohio (USA); Width: 5.6 cm. Picture: U. Jansen, Senckenberg Museum, Frankfurt am Main.

GEOMAR coordinates European research and education project BASE-LiNE Earth
02.03.2015 / Kiel. As the history of the oceans can be reconstructed in the past 500 million based on calcareous shells of fossil marine life, busy to date with the research project BASE-LiNE Earth. At the same time it enables talented young scientists and scientists a doctorate in an international research environment. The European Union supports the at GEOMAR Helmholtz Centre for Ocean Research Kiel coordinated project with a total of 3.8 million euros.

Almost all life on earth would be extinct - and that at least five times in the past 500 million years. The environmental changes that have each led to the mass extinction, the oceans play an important role in almost all cases. How did it happen that was phased so hostile to life as a life-giving force sea? And why have some species still survive? These are fundamental questions that will be examined in the next three years as part of the European research project BASE-LiNE Earth with innovative technologies and methods. In addition to answering the research questions BASE LiNE Earth serves as the training of talented young scholars and scientists who are recruited by means of a demanding selection process from all over the world and doctorate within the scope of the project. 

The EU promotes the GEOMAR Helmholtz Centre for Ocean Research Kiel coordinated project under a Marie Skłodowska-Curie Action in Horizon2020-Pogramm with a total of 3.8 million euros. The challenge for the future BASE-LiNE Earth-doctoral students, is to provide information to gain from distant epochs of earth's history. "When historians want to know about events 100 or 200 years ago, they visit libraries or archives where there is written evidence from these times," says project coordinator Prof. Dr. Anton Eisenhauer from GEOMAR. "We also use archives. 
However, they see something different. It is, for example, the calcareous shells of fossil brachiopods in which the relevant data on the chemical history of ocean water are stored reliably, "explains the Kiel geochemist on. 

The information is in the calcite shells of course not writing before, but encrypted in the chemical and mineralogical composition. "If we precise the ratios of elements such as strontium, magnesium, boron, or measure of the isotopic to each other, we can decrypt the information," says Professor Eisenhauer.

This then the age of the shell, as well as the chemical composition of the previous ocean and prevailing environmental conditions such as water temperature and the acidity of the water can be reconstructed. We know, for example, know that during the greatest mass extinction 251 million years ago, the ocean contained no oxygen and was acidified to a large extent. 

"This is similar to some scenarios that we expect for the future of our ocean," explains Professor Eisenhauer. Model calculations are carried out within the framework of the project should show how far the former changes in the environment are transferable to the present day. The challenge is to gain this information and to make it usable. In collaboration with industry partners modern analytical methods for obtaining information in cooperation with business partners in this area in the context of BASE-LiNE Earth therefore be generated and developed. The project involves a total of 21 scientific institutions from eight European countries and partners from Canada, Israel, Palestine and Australia involved. 15 PhD positions will announce the project this spring, two of them for the GEOMAR in Kiel. 

The Integrated School of Ocean Sciences (ISOS) provides at the University of Kiel for a comprehensive training program in which the scholars not only pursue their academic goals, but also learn more professional qualifications, skills and interact with each other.  In the coming years, the parties want to do their topic also by means of exhibitions and school supplies to a wider audience. "Of course we also bind the doctoral students, which thus also learn to communicate their work understandable," says the project coordinator. For more information on the project website www.baseline-earth.eu.

Source: Geomar

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NOAA’s investments in weather models and partnerships paying off

Early improvements effective in forecasting recent Nor’easter; future forecast model upgrades planned
As the Northeast digs out from this week’s blizzard, a new NOAA-led effort to improve the forecasting of such high impact weather events is reaching an important early benchmark. One of the first major improvements - upgrading the resolution of three global forecast models -- has already shown its effectiveness. One of these models, the newly upgraded Global Forecast System (GFS) model, provided one of the most precise forecasts of the track, intensity, precipitation, and distribution of the Nor’easter. The other research models provided important forecast information, as well.

“The Global Forecast System did remarkably well in the recent Nor’easter,” said Louis Uccellini, director of NOAA’s National Weather Service. “This is due to the recent improvements we’ve made to the GFS, including higher resolution, improved physics, and better access to new data. With the help of scientists at NOAA Research, we’re making improvements to all our models, and upgrading supercomputers to improve our ability to translate data into actionable information, and to produce more timely, accurate and reliable forecasts.”

By the end of January, the $13 million project called the High Impact Weather Prediction Project (HIWPP), funded by Congress in the wake of Hurricane Sandy, will have improved the resolution on the global forecast model operated by NOAA Research Earth System Research Laboratory and the model operated by the U.S. Navy.

Improving global models
Scientists at NOAA’s Earth System Research Laboratory are running a high resolution global forecast model called the FIM, or Flow following finite volume Icoschedral Model. As depicted here, the FIM uses a unique grid that allows for a more uniform representation of the Earth. Higher resolution models are helping improve severe weather prediction. (NOAA)

In addition, NOAA researchers have written and installed programs to enable these three global models to work together effectively, which provides greater accuracy and confidence in forecasts. The third improvement is a plan to actively involve the broader weather forecasting community, including other public, academic and private sector scientists, in the evaluation of how these models work together to refine and improve forecasts.

“We are always looking for ways to improve the reliability and accuracy of our forecasts and models,” said John Cortinas, director of NOAA’s Office of Weather and Air Quality, who is overseeing HIWPP, which involves researchers from NOAA’s Oceanic and Atmospheric Research, NOAA’s National Weather Service, cooperative institutes, other government and academic partners.

“The goal of the project is to develop the next generation of weather forecast models that will eventually extend our ability to skillfully forecast high-impact weather out to several weeks and beyond,” Cortinas said. “By extending lead time for forecasts on storms like the one we’ve just experienced, cities and towns can better plan for these events, potentially saving lives and helping protect valuable land, homes and businesses. Businesses and industry can better plan everything from shipping to safe routing of air traffic to energy consumption. For ordinary citizens, it will be easier to plan an event or a trip.”

Over the last decades, weather forecasts have improved steadily so that we now have accurate forecasts out to five days, with reasonable accuracy to seven days. “We’ve gained about a day a decade in accuracy,” said Timothy Schneider, a research meteorologist at NOAA’s Earth System Research Laboratory, who is working to improve global forecast models. “Gaining a day of accuracy involves a combination of improving the science, adding computer power and increasing the necessary observations. With this project, we’re trying to accelerate this progress to make quicker gains.”

Global weather data key to improved local forecasts

“We know we can get better weather forecasts by improving the resolution of global forecast models so they depict weather in finer and finer detail,” explained Schneider. The resolution of NOAA’s two global forecast models has improved from grids that are 24 kilometers, to ones that are about 13 kilometers.  “The finer you chop up the picture, the more you can see of what is happening inside a particular storm. This helps us make better forecasts.”

 “If we’re going to predict weather out beyond seven and 10 days, we need even better global weather forecast models that show us what’s occurring on the other side of the Earth,” added Schneider. “Weather patterns on one side of the globe travel around the Earth and evolve. Storms born in the western Pacific follow air patterns that can create major winter storms on the West Coast, and weather patterns off the coast of Africa can spawn hurricanes in the U.S.”

Source: NOAA

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Antarctic ozone hole similar to last year

The Antarctic ozone hole, which forms annually in the August to October period, reached its peak size on September 11, stretching to 9.3 million square miles (24.1 million square kilometers), roughly the same size as last year’s peak of 9.3 million square miles (24 million square kilometers) on September 16, 2013. This is an area similar in size to North America.

Ozone hole
This image, using NOAA satellite data, shows the ozone hole (areas below 220 Dobson units) in shades of red. (Credit: NOAA Visualization Lab; http://www.nnvl.noaa.gov/MediaDetail2.php?MediaID=1636&MediaTypeID=1)

In comparison, the largest ozone hole area recorded to date on a single day was on September 9, 2000, at 11.5 million square miles (29.9 million square kilometers). The ozone layer helps shield life on Earth from potentially harmful ultraviolet (UV) radiation that can cause skin cancer, damage plants and phytoplankton—the top of the oceanic food chain.

“The good news is that our measurements show less thinning of the ozone over the South Pole during the past three years,” said Bryan Johnson, a researcher with NOAA’s Earth System Research Laboratory in Boulder, Colorado. “However, the rate at which ozone thins during the month of September has remained about the same for the past two decades. A decrease in this rate will be an important sign of recovery.”

South Pole balloon-borne ozonesonde observations measured a minimum amount of 120 Dobson Units of ozone this year on September 29. Ozonesonde measurements of 250 Dobson Units in August are common just before the rapid destruction of ozone in September.  NOAA releases about 50-60 ozonesonde balloons per year since 1986 to measure the ozone layer at the South Pole.  Over the last 50 years satellite and ground-based records over Antarctica show ozone column amounts ranging from 100 to 400 Dobson units, which translates to about 1 millimeter (1/25 inch) to 4 millimeters (1/6 inch) of ozone in a layer if all of the ozone were brought down to the surface.

The Antarctic ozone hole began making a yearly appearance in the early 1980s, grew in size through the 1980s and has been consistently large since 1990, with annual variability attributed to stratospheric meteorological conditions over Antarctica. The hole is caused by chlorine released by manmade chemicals called chlorofluorocarbons or CFCs that were extensively used as aerosol sprays and in refrigerators.

Ozonesonde release
NOAA Corps LTJG Joseph Phillips releases an ozonesonde that's attached to a helium balloon. The instrument will rise 18 miles into the atmosphere to measure the thickness of ozone. (Credit: Chet Waggoner, NOAA)

These chlorine compounds lead to ozone depletion in certain upper atmospheric conditions. These conditions are at their peak over Antarctica as the dark cold winter gives way to the Antarctic spring in September. Just before the sun rises over Antarctica, extremely cold temperatures in the stratosphere allow for polar stratospheric clouds to form, a rare event in the earth’s atmosphere, but a regular occurrence in the winter over Antarctica. Chemical reactions on the cloud particles convert stable chlorine compounds into unstable or reactive forms. The sun light triggers reactive chlorine and ozone chemistry that depletes ozone in a large volume over Antarctica.

Scientists first made the connection that CFCs were depleting the earth’s protective layer in 1974. In 1987, 46 nations, including the U.S., signed the Montreal Protocol, a landmark agreement to phase out production of ozone-depleting chemicals. The slow recovery of this ozone layer is one of the great international efforts to restore the planet from manmade damage.

The 2014 level of ozone depleting substances over Antarctica has declined about 9 percent below the 2000 recorded maximum. But CFCs can remain in the atmosphere for more than 50 years. The ozone layer above Antarctica likely will not return to its 1980 state until about 2070, said Paul Newman, chief scientist for atmospheres at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Climate change may also affect the rate of ozone recovery by cooling the stratosphere, which can slow Antarctic ozone recovery.

“Year-to-year weather variability significantly impacts Antarctica ozone because warmer stratospheric temperatures can reduce ozone depletion,” said Paul A. Newman, chief scientist for atmospheres at NASA's Goddard Space Flight Center in Greenbelt, Maryland. “The ozone hole area is smaller than what we saw in the late-1990s and early 2000s, and we know that chorine levels are decreasing. However, we are still uncertain about whether a long-term Antarctic stratospheric temperature warming might be reducing this ozone depletion.”

Under the mandate of the Clean Air Act, NOAA and NASA scientists keep a close eye on the ozone layer’s health with satellite data, ground-based measurements and instruments sent up through the ozone layer via balloons. Together, these instruments provide a big picture of the thickness and area extent of the ozone hole. NOAA measures the thickness of the ozone using ground-based instruments and by sending balloons with measurement devices up 18 miles into the atmosphere from NOAA’s Antarctic station.

NOAA and NASA also use data taken by the Ozone Mapping Profiler Suite (OMPS) instrument on board the Suomi-National Polar-Orbiting Partnership satellite to monitor the earth’s ozone layer. This instrument replaced the NOAA Solar Backscatter UltraViolet/2 ozone profiler and NASA Total Ozone Mapping Spectrometer.  NOAA’s Climate Prediction Center has been monitoring the Earth’s ozone layer for over 30 years, analyzing ozone concentration at various altitudes in the ozone layer as well as the total column amount of ozone. These measurements provide a three dimensional perspective of the ozone layer. This provides the means to monitor the ozone layer’s health and to make sure it is on the road to recovery.

Source: NOAA

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Putting the Blizzard of 2015 into Historical Context

                    January-25-28-2015-Snowfall-Totals-Map Credit: NOAA

The recent “Blizzard of 2015” shutdown several major metropolitan areas in the Northeast and left several locations across Connecticut, Maine, Massachusetts, New Hampshire, and New York covered in over two feet of snow. But, how did this snowstorm compare to the region’s most historic storms? To place this storm and its societal impacts into historical context, NCDC used the Regional Snowfall Index or RSI to rank it on a scale from 1 to 5—similar to the Fujita scale for tornadoes or the Saffir-Simpson scale for hurricanes. These ranks are based on the snowfall amount within the region’s borders, the spatial extent of the storm, and the relationship of these elements to the area’s population.

The RSI value for January 25­–28, 2015, snowstorm is 6.16, which makes it a Category 3 or major event for the Northeast. With that RSI value, the snowstorm ranks 26th out of the 423 northeastern snowstorms NCDC has analyzed since 1900. The area of snowfall and population affected by 20 inches of snow or more were the primary drivers for this storm’s raw RSI score. Almost 5 million people experienced over 20 inches of snow and 15 million experienced over 10 inches of new snow. While these are significant impacts, the footprint of the heavy snow was relatively small compared to RSI Category 5 storms. These rare events typically have over 45 million people experiencing over 10 inches of snow. Nonetheless, this storm is well within the top 10% of storms analyzed for the Northeast.

The late February snowstorm of 1969 remains the strongest storm to hit the Northeast, with an RSI value of 34.03 making it a Category 5 or extreme event. The March 1993 “Storm of the Century” remains the second strongest snowstorm to hit the Northeast, with an RSI value of 22.12 also making it a Category 5 event.

Learn more about the Regional Snowfall Index and use our interactive mapping tool to see RSI rankings for almost 600 snowstorms since 1900.

Source: NOAA

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New research shows ocean warming poses "immediate threat" to keystone reef-building coral in the Caribbean

New research published in The Proceeding of the Royal Society - Biological Sciences provides new insights on the threat  ocean warming poses on coral growth in Mesoamerican barrier reefs.  The research, partially funded by CPO's Climate Monitoring program, used laboratory experiments to examine the adverse effects of ocean warming and acidification, and showed that the warming predicted by the IPCC for the end of the 21st century produced a five-fold decrease in coral calcification - the process by which corals produce calcium carbonate (CaCO3) and build reefs.

“The reef-building coral Siderastrea siderea exhibits parabolic responses to ocean acidification and warming,” is part of on-going work of NOAA-funded researcher Dr. Justin Ries that is looking at various aspects of climate variability, change, and ocean acidification on coral growth.  Dr. Ries and colleagues have been examining long term coral reef growth patterns at one of the largest barrier reefs in the world, off the coast of southern Belize. The research aims to create100 year records of coral growth at this reef by examining growth rates and environmental factors. As part of this work, Dr. Ries and his team found substantially decreasing growth rates over the last several years, at the same time that ocean acidification and temperature have been increasing.

Massive Starlet Coral (Siderastrea siderea) Image courtesy: D. Gordon E. Robertson via Creative Commons

This new research, led by post-doctoral researcher Dr. Karl Castillo, was designed to isolate the effects increasing ocean acidification and temperature had on Siderastrea sidereal, an important keystone and reef building coral species at the reef. By extracting coral colonies and returning them to the lab, researchers were able to design separate experiments around increasing temperature and decreasing ocean pH, and measure the coral response. While the most adverse effects on corals may arise from both acidification and temperature warming, researchers wanted to better understand the specific responses to these individually, which could aid efforts to predict and potentially mitigate the impacts of changing ocean conditions on coral.

They found that both ocean acidification and ocean warming had a “parabolic effect” on this important coral species. This means that while moderate decreases in the pH of seawater and moderate rises in temperature led to increases in coral building, in both cases researchers found a “tipping point” at which the coral calcification rates started decreasing. For ocean acidification, researchers recreated seawater conditions that would occur from the atmospheric carbon dioxide concentration from pre-industrial up through the present, the predicted end-of-century value, and up to six times the present condition. They found the “tipping point” at which calcification started leveling off and finally decreasing was actually well past the acidifications that would be expected by the end of century. For this particular species, they concluded, ocean acidification expected over the next century alone may not have a significant adverse effect.

Figure 1: Rates of reef-building calcification observed during the experiment for (left panel) increasing levels of ocean acidification and (right panel) temperatures ranging from 25C to 32C.

For warming ocean temperatures, however, the results were very different.  For the temperature experiments, researchers grew the coral colonies in temperatures from 25C to 32C, which covers the range of annual minimum and maximum temperatures of ocean temperatures recorded near the reef over 2002-2014, as well as annual average seawater temperatures expected over the next century. Thus the researchers were hoping to capture how the coral responds to the year to year variability seen now as well as what general conditions are predicted to by like by the end of the century. They found that while reef-building calcification rates increased for corals at 28C relative to 32C, skeletal building dropped off dramatically – nearly 80% - in corals growing at 32C. This parabolic response indicates that for this important reef building species, ocean warming over the next few decades could be an immediate serious threat, as conditions pass what the research found to be a species tipping point. Researchers note that the actual reef will experience changes in both stressors – ocean acidification and ocean warming – together over the next century, and will continue to work to understand how this and other reefs may respond.

You can watch a YouTube video on this and other aspects of Dr. Ries coral reef research here:  



Source: CRO

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Scientists find 240-million-year-old parasite that infected mammals' ancestor

Scott Gardner. Credit: Craig Chandler, University Communications.

An egg much smaller than a common grain of sand and found in a tiny piece of fossilized dung has helped scientists identify a pinworm that lived 240 million years ago.

It is believed to be the most ancient pinworm yet found in the fossil record.

The discovery confirms that herbivorous cynodonts -- the ancestors of mammals -- were infected with the parasitic nematodes. It also makes it even more likely that herbivorous dinosaurs carried pinworms.

Scott Gardner, a parasitologist and director of the Harold W. Manter Laboratory of Parasitology at the University of Nebraska-Lincoln, was among an international group of scientists who published the study in the journal Parasites & Vectors.

"This discovery represents a first for our team and I think it opens the door to finding additional parasites in other species of fossil organisms," he said.

The team found the pinworm egg in a coprolite -- fossilized feces -- collected in 2007 at an excavation site in Rio Grande do Sul state in southern Brazil.

The coprolite was collected at a site with abundant fossilized remains of cynodonts. Previously, an Ascarid-like egg -- resembling a species of nematode commonly found in modern-day mammals -- was found in the coprolite.

The pinworm egg, representing an undescribed or "new species," was named Paleoxyuriscockburni, in honor of Aidan Cockburn, founder of the Paleopathology Association.

The structure of the pinworm egg placed it in a biological group of parasites that occur in animals that ingest large amounts of plant material. Its presence helped scientists deduce which cynodont species, of several found at the collection site, most likely deposited the coprolite.

Since the field of paleoparasitology, or the study of ancient parasites, emerged in the early 20th century, scientists have identified parasites of both plants and animals that date back as far as 500 million years ago.

The study of parasites in ancient animals can help determine the age of fossilized organisms and help establish dates of origin and diversification for association between host species and parasites. Coprolites are a key part of the study, enabling a better understanding of the ecological relationships between hosts and parasites.

Other members of the team were Jean-Pierre Hugot of the National Museum of Natural History in Paris; Victor Borba, Juliana Dutra, Luiz Fernando Ferreira and Adauto Araujo of Oswaldo Cruz Foundation in Rio de Janeiro; Prisiclla Araujo and Daniela Leles of Fluminense Federal University in Rio de Janeiro; and Atila August Stock Da-Rosa of the Federal University of Santa Maria in Rio Grande do Sul.

Source: University of Nebraska-Lincoln

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The tsunami-early warning system for the indian ocean: Ten years after

Technical concept of GITEWS.

The day after Christmas this year will mark the 10 anniversary of the tsunami disaster in the Indian Ocean. On 26 December 2004, a quarter of a million people lost their lives, five million required immediate aid and 1.8 million citizens were rendered homeless. The natural disaster, which caused extreme devastation over huge areas and the accompanying grief and anxiety, especially in Indonesia, Thailand and Sri Lanka exceeded the imaginable and reached such drastic dimensions, mainly due to the lack of a warning facility and a disaster management plan for the entire Indian Ocean region at this time.

Germany and the international community of states reacted with immediate support. Within the framework of the German Flood Victim Aid the Federal Government commissioned the Helmholtz Association of German Research Centres under the direction of the GFZ German Research Centre for Geosciences with the development of an Early Warning System for the Indian Ocean. From 2005 to 2011, with the large-scale project GITEWS (German-Indonesian Tsunami Early Warning System), the core of an integrated, modern, and effective Tsunami Early Warning System in Indonesia was established. With the follow-up project PROTECTS (Project for Training, Education and Consulting for Tsunami Early Warning Systems, 2011-2014) the personnel of the participating Indonesian institutions were trained to proceed independently and to take over responsibility for the operation of the Early Warning System as well as for the diverse technical and organizational components. In this ways PROTECTS which started in June 2011 and comprised a total of 192 training courses, internships, and hands-on-practice courses, covering all aspects of operation and maintenance of the Tsunami-Early Warning System contributed significantly to the sustainability of InaTEWS.

Under the auspices of the IntergovernmentalOceanographicCommission of UNESCO and with the collaboration of international partner institutes from Germany, the USA, China and Japan, GITEWS was integrated into a Tsunami Early Warning System for Indonesia. GITEWS was positively reviewed by a commission of international experts in 2010 and handed over to Indonesia in March 2011. Since then it has been providing its services under the name InaTEWS -- Indonesian Tsunami Early Warning System and is operated by the Indonesian Service for Meteorology, Climatology and Geophysics BMKG.

On 12 October 2011 the exercise drill "IOWAVE11" was carried out in the Indian Ocean. With this drill, InaTEWS successfully demonstrated that it could, furthermore, take over the role of a Regional Tsunami Service Provider (RTSP). Since then Indonesia, in addition to Australia und India, performs the double function as a National Tsunami Warning Center (NTWC) and also as a RTSP and takes over the responsibility for the timely warning of 28 states around the Indian Ocean in the event of a threatening Tsunami. With the on-going step-by-step development, a comprehensive all-encompassing InaTEWS could be successfully realized.

Indonesia now avails of one of the most modern Tsunami Early Warning Systems. On the basis of data from approx. 300 measuring stations a warning can be issued at a maximum of five minutes after an earthquake. These measuring stations include e.g. seismometers, GPS stations und coastal tide gauges. With the data gained from the sensors and using the most modern evaluation systems such as SeisComP3 which was developed by GFZ scientists for the analyses of earthquake data and a Tsunami simulation system in the Warning Centre it is possible to compile a comprehensive picture of the situation. With the aid of a decision support system respectively classified warnings for the affected coastal areas can then be issued. A total of 70 people are involved the operation of the Warning Centre in Jakarta, with 30 employees working solely in a full shift system. According to information provided by the BMKG a total of 1700 earthquakes with a magnitude of more than M= 5 and 11 quakes with a magnitude of 7 and higher have been evaluated and six Tsunami Warnings have been issued to the public by the Earthquake Monitoring and Tsunami Early Warning Centre since the hand over in March 2011.

Schooling, training and disaster precautions (capacity development) for the local community and Town and District councils have received special emphasis. This Capacity Development has been carried out since 2006 in three "typical" regions: Padang (Sumatra), Chilacap (South-Java) and Denpassar (Bali, tourist stronghold). Here particular emphasis was placed on understanding both the warnings issued and the planned evacuation measures.

Local disaster management structures are established with local decision-makers and Disaster Risk Reduction Strategies are developed. Specifically, the education of trainers who are, in turn, responsible for the further spreading of the developed concepts plays a significant role.

Another key element is the determination of hazard and risk maps as a basis for the local evacuation planning as well as for future town and land-use planning. In Bali communication with the hotel industry was an additional factor.

No Early Warning System will ever be able to prevent a strong earthquake and a resulting tsunami and also, in the future, there will be loss of life and material damage. However, through the existence of an Early Warning System and the integration of organizational measures together with comprehensive capacity building the adverse effects of such a natural disaster can certainly be reduced.

Source: Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

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Is Sahara Desert several million years older than previously thought?

Sahara desert. Credit: © mrks_v / Fotolia

A team of scientists from Norway, France and China have revised the view that the Sahara desert has existed for only the last 2 to 3 million years.

The Sahara is the world's largest subtropical desert. During the last decades, numerous scientific studies have probed its geological and archeological archives seeking to reveal its history. Despite some important breakthroughs, there are still basic questions that lack satisfactory answers.

For example, how old is the Sahara desert? It is widely believed that Sahara desert first appeared during the last 2 to 3 million years, but recent discoveries such as ancient sand dunes and dust records in marine cores push the possible onset of Saharan aridity back in time by several million years. Until now, however, there have been no good explanations for such an early Sahara onset.

This study pinpoints the Tortonian stage (~7-11 million years ago) as a pivotal period for triggering North African aridity and creating the Sahara desert. Using snapshot simulations with the Norwegian Earth System Model (NorESM) model suite, the international team explored the climate evolution of North Africa through major tectonic shifts over the last 30 million years. They found that the region undergoes aridification with the shrinkage of the Tethys -- a giant ocean that was the origin of the modern Mediterranean, Black and Caspian Seas -- during the Tortonian.

The simulations are the first to show that the Tethys shrinkage has two main consequences for North African climate. First, it weakens the African summer monsoon circulations and dries out North Africa. Second, it enhances the sensitivity of the African summer monsoon and its associated rainfall to orbital forcing. The Tortonian stage thus marks the time when North Africa shifted from a permanently lush, vegetated landscape to a landscape experiencing arid/humid cycles on orbital time scales.

Interestingly, these major changes in North African climate and environment are coincident with an important time period for the emergence of early hominids.

Source: Uni Research

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