CO2, BIG DINOSAURS AND THE EQUATOR

FROM:  NATIONAL SCIENCE FOUNDATION
Big dinosaurs steered clear of the tropics
Climate swings lasting millions of years too much for dinos

For more than 30 million years after dinosaurs first appeared, they remained inexplicably rare near the equator, where only a few small-bodied meat-eating dinosaurs made a living.

The long absence at low latitudes has been one of the great, unanswered questions about the rise of the dinosaurs.

Now the mystery has a solution, according to scientists who pieced together a detailed picture of the climate and ecology more than 200 million years ago at Ghost Ranch in northern New Mexico, a site rich with fossils.

The findings, reported today in the journal Proceedings of the National Academy of Sciences (PNAS), show that the tropical climate swung wildly with extremes of drought and intense heat.

Wildfires swept the landscape during arid regimes and reshaped the vegetation available for plant-eating animals.

"Our data suggest it was not a fun place," says scientist Randall Irmis of the University of Utah.

"It was a time of climate extremes that went back and forth unpredictably. Large, warm-blooded dinosaurian herbivores weren't able to exist close to the equator--there was not enough dependable plant food."

The study, led by geochemist Jessica Whiteside, now of the University of Southampton, is the first to provide a detailed look at climate and ecology during the emergence of the dinosaurs.

Atmospheric carbon dioxide levels then were four to six times current levels. "If we continue along our present course, similar conditions in a high-CO2 world may develop, and suppress low-latitude ecosystems," Irmis says.

"These scientists have developed a new explanation for the perplexing near-absence of dinosaurs in late Triassic [the Triassic was between 252 million and 201 million years ago] equatorial settings," says Rich Lane, program director in the National Science Foundation's (NSF) Division of Earth Sciences, which funded the research.

"That includes rapid vegetation changes related to climate fluctuations between arid and moist climates and the resulting extensive wildfires of the time."

Reconstructing the deep past

The earliest known dinosaur fossils, found in Argentina, date from around 230 million years ago.

Within 15 million years, species with different diets and body sizes had evolved and were abundant except in tropical latitudes. There the only dinosaurs were small carnivores. The pattern persisted for 30 million years after the first dinosaurs appeared.

The scientists focused on Chinle Formation rocks, which were deposited by rivers and streams between 205 and 215 million years ago at Ghost Ranch (perhaps better known as the place where artist Georgia O'Keeffe lived and painted for much of her career).

The multi-colored rocks of the Chinle Formation are a common sight on the Colorado Plateau at places such as the Painted Desert at Petrified Forest National Park in Arizona.

In ancient times, North America and other land masses were bound together in the supercontinent Pangea. The Ghost Ranch site stood close to the equator, at roughly the same latitude as present-day southern India.

The researchers reconstructed the deep past by analyzing several kinds of data: from fossils, charcoal left by ancient wildfires, stable isotopes from organic matter, and carbonate nodules that formed in ancient soils.

Fossilized bones, pollen grains and fern spores revealed the types of animals and plants living at different times, marked by layers of sediment.

Dinosaurs remained rare among the fossils, accounting for less than 15 percent of vertebrate animal remains.

They were outnumbered in diversity, abundance and body size by reptiles known as pseudosuchian archosaurs, the lineage that gave rise to crocodiles and alligators.

The sparse dinosaurs consisted mostly of small, carnivorous theropods.

Big, long-necked dinosaurs, or sauropodomorphs--already the dominant plant-eaters at higher latitudes--did not exist at the study site nor any other low-latitude site in the Pangaea of that time, as far as the fossil record shows.

Abrupt changes in climate left a record in the abundance of different types of pollen and fern spores between sediment layers.

Fossilized organic matter from decaying plants provided another window on climate shifts. Changes in the ratio of stable isotopes of carbon in the organic matter bookmarked times when plant productivity declined during extended droughts.

Drought and fire

Wildfire temperatures varied drastically, the researchers found, consistent with a fluctuating environment in which the amount of combustible plant matter rose and fell over time.

The researchers estimated the intensity of wildfires using bits of charcoal recovered in sediment layers.

The overall picture is that of a climate punctuated by extreme shifts in precipitation and in which plant die-offs fueled hotter fires. That in turn killed more plants, damaged soils and increased erosion.

Atmospheric carbon dioxide levels, calculated from stable isotope analyses of soil carbonate and preserved organic matter, rose from about 1,200 parts per million (ppm) at the base of the section, to about 2,400 ppm near the top.

At these high CO2 concentrations, climate models predict more frequent and more extreme weather fluctuations consistent with the fossil and charcoal evidence.

Continuing shifts between extremes of dry and wet likely prevented the establishment of the dinosaur-dominated communities found in the fossil record at higher latitudes across South America, Europe, and southern Africa, where aridity and temperatures were less extreme and humidity was consistently higher.

Resource-limited conditions could not support a diverse community of fast-growing, warm-blooded, large dinosaurs, which require a productive and stable environment to thrive.

"The conditions would have been something similar to the arid western United States today, although there would have been trees and smaller plants near streams and rivers, and forests during humid times," says Whiteside.

"The fluctuating and harsh climate with widespread wildfires meant that only small two-legged carnivorous dinosaurs could survive."

-NSF-
Media Contacts
Cheryl Dybas, NSF

SECRETARY KERRY'S STATEMENT ON 'CLIMATE CHANGE ADAPTATION AND RESILIENCE'

FROM:  U.S. STATE DEPARTMENT
Climate Change Adaptation and Resilience
Press Statement
John Kerry
Secretary of State
Washington, DC
June 9, 2015

Climate change poses a threat to every country on Earth, and we all need to do what we can to take advantage of the small window of opportunity we still have to stave off its worst, most disastrous impacts. But even as we take unprecedented steps to mitigate the climate threat, we also have to ensure our communities are prepared for the impacts we know are headed our way – and the impacts we are already seeing all over the world in the form of heat waves, floods, historic droughts, ocean acidification and more.

Thanks to President Obama’s Climate Action Plan, we’ve taken a number of important steps to increase the resilience of American communities. But as the President has always said, this is a global challenge, and we’re not going to get very far if we keep our efforts contained within our borders. That’s why the United States is deeply committed to helping the rest of the world – especially the poorest and most vulnerable nations – adapt to the changing climate as well.

As part of that commitment, last fall, President Obama announced his intention to create a private-public partnership to provide climate data and information to help promote resilient development worldwide. Today we formally launched the Climate Services for Resilient Development partnership, along with the government of the United Kingdom and our partners at the American Red Cross, the Asian Development Bank, Esri, Google, the Inter-American Development and the Skoll Global Threats Fund. In addition to the $34 million we and our partners are putting toward that new partnership, we also announced a series of individual steps we’re taking to make adapting to climate change easier around the globe – including, for example, the volunteer “climate resilience corps” that the Peace Corps and AmeriCorps will be launching in developing countries, and NASA’s release of the first-ever climate modeling system that breaks data down to the country level, which will enable countries to better target their individual adaptation planning efforts.

In the United States, we’ve developed some of the most advanced technologies and scientific expertise on climate change, and we want to make sure these tools are reaching those who need it the most. Each of the commitments announced today will make it easier for people to take control of their own futures and play an active role in helping to prepare their communities, their countries, and ultimately their planet for the changes ahead.

When it comes to confronting climate change, no country should be forced to go it alone – because no country can possibly address this threat alone. It will require all of us – every country, around the world, doing what it can to contribute to the solution. That understanding is at the core of the initiatives we are unveiling today, it’s what is driving our work toward an ambitious global agreement in Paris later this year, and it’s what will continue to guide our leadership in the fight against climate change in the months and years to come.

RESEARCH SHOWS FLOODS IN MIDWEST HAVE BEEN INCREASING IN FREQUENCY

FROM:  NATIONAL SCIENCE FOUNDATION
Scientists confirm that Midwest floods are more frequent
Floods happening more often over past half-century
February 9, 2015

The U.S. Midwest region and surrounding states have endured increasingly more frequent floods during the last half-century, according to results of a new study.

The researchers, affiliated with the University of Iowa (UI) and funded by the National Science Foundation (NSF), based their findings on daily records collected by the U.S. Geological Survey at 774 stream gauges in 14 states from 1962-2011, a data collection period in common for all the stations.

They found that 264, or 34 percent, of the stations had an increase in frequency in the number of flood events, while only 66 stations, 9 percent, showed a decrease.

"We have been experiencing a larger number of big floods," says Gabriele Villarini, UI civil and environmental engineer and corresponding author of a paper reporting the results published today in the journal Nature Climate Change.

The findings likely come as no surprise to millions of people in the Midwest and bordering states.

During the past several decades, large floods have plagued the region in 1993, 2008, 2011, 2013 and again in 2014.

"Floods have the potential to take an immense toll on society in economic damages and other long-term effects," says Anjuli Bamzai, program director in NSF's Division of Atmospheric and Geospace Sciences, which funded the research.

"This study looks at how such events may have changed over recent decades across the central U.S."

The floods caused agricultural and other economic losses in the billions of dollars, displaced people and led to loss of life.

"There is a pattern with increasing frequency of flood events from North Dakota south to Iowa and Missouri and east into Illinois, Indiana and Ohio," says Iman Mallakpour, UI civil and environmental engineer and lead author of the paper.

"We related this increasing number of big floods to changes in rainfall and temperature," adds Villarini.

"There was an overall good match between the areas with increasing frequency of floods and areas experiencing increasing frequency of heavy rainfall."

Seasonal analysis revealed that most of the flood peaks in the upper Midwest occur in the spring and stem primarily from snowmelt, rain falling on frozen ground, and rain-on-snow events.

Spring--a season with heavy rains--also has the strongest increase in temperature over most of the northern part of the region studied.

The findings fit well with current thinking among scientists about how the hydrologic cycle is being affected by climate change.

In general, as the atmosphere becomes warmer, it can hold more moisture. One consequence of higher water vapor concentrations is more frequent, intense precipitation.

Villarini says the current study did not attempt to link the increase in the number of episodes with climate change.

"What causes the observed changes in precipitation and temperature is not something we have addressed because of the difficulties in doing so based on observational records," he says.

The study region included Iowa, Illinois, Indiana, Wisconsin, Ohio, Michigan, Minnesota, Kansas, Nebraska, Missouri, West Virginia, Kentucky, North Dakota and South Dakota.

The method used involved establishing a threshold level of two flood events per year, on average, for each of the 774 stream gauges in the study.

To avoid counting the same event twice, the researchers allowed for the recording of only one event within a 15-day period.

The research was also funded by the U.S. Army Corps of Engineers Institute for Water Resources, the Iowa Flood Center and IIHR-Hydroscience & Engineering.

-NSF-
Media Contacts
Cheryl Dybas, NSF

NEW LOOK AT EARTH'S CLIMATE RHYTHMS

FROM:  NATIONAL SCIENCE FOUNDATION 

Ancient ocean currents may have changed pace and intensity of ice ages
Slowing of currents may have flipped switch.

Climate scientists have long tried to explain why ice-age cycles became longer and more intense some 900,000 years ago, switching from 41,000-year cycles to 100,000-year cycles.

In a paper published this week in the journal Science, researchers report that the deep ocean currents that move heat around the globe stalled or may have stopped at that time, possibly due to expanding ice cover in the Northern Hemisphere.

"The research is a breakthrough in understanding a major change in the rhythm of Earth's climate, and shows that the ocean played a central role," says Candace Major, program director in the National Science Foundation (NSF)'s Division of Ocean Sciences, which funded the research.

The slowing currents increased carbon dioxide (CO2) storage in the oceans, leaving less CO2 in the atmosphere. That kept temperatures cold and kicked the climate system into a new phase of colder, but less frequent, ice ages, the scientists believe.

"The oceans started storing more carbon dioxide for a longer period of time," says Leopoldo Pena, the paper's lead author and a paleoceanographer at Columbia University's Lamont-Doherty Earth Observatory (LDEO). "Our evidence shows that the oceans played a major role in slowing the pace of the ice ages and making them more severe."

The researchers reconstructed the past strength of Earth's system of ocean currents by sampling deep-sea sediments off the coast of South Africa, where powerful currents originating in the North Atlantic Ocean pass on their way to Antarctica.

How vigorously those currents moved can be inferred by how much North Atlantic water made it that far, as measured by isotope ratios of the element neodymium bearing the signature of North Atlantic seawater.

Like tape recorders, the shells of ancient plankton incorporate these seawater signals through time, allowing scientists to approximate when currents grew stronger and when weaker.

Over the last 1.2 million years, the conveyor-like currents strengthened during warm periods and lessened during ice ages, as previously thought.

But at about 950,000 years ago, ocean circulation slowed significantly and stayed weak for 100,000 years.

During that period the planet skipped an interglacial--the warm interval between ice ages. When the system recovered, it entered a new phase of longer, 100,000-year ice age cycles.

After this turning point, deep ocean currents remained weak during ice ages, and ice ages themselves became colder.

"Our discovery of such a major breakdown in the ocean circulation system was a big surprise," said paper co-author Steven Goldstein, a geochemist at LDEO. "It allowed the ice sheets to grow when they should have melted, triggering the first 100,000-year cycle."

Ice ages come and go at predictable intervals based on the changing amount of sunlight that falls on the planet, due to variations in Earth's orbit around the sun.

Orbital changes alone, however, are not enough to explain the sudden switch to longer ice age intervals.

According to one earlier hypothesis for the transition, advancing glaciers in North America stripped away soils in Canada, causing thicker, longer-lasting ice to build up on the remaining bedrock.

Building on that idea, the researchers believe that the advancing ice might have triggered the slowdown in deep ocean currents, leading the oceans to vent less carbon dioxide, which suppressed the interglacial that should have followed.

"The ice sheets must have reached a critical state that switched the ocean circulation system into a weaker mode," said Goldstein.

Neodymium, a key component of cellphones, headphones, computers and wind turbines, also offers a good way of measuring the vigor of ancient ocean currents.

Goldstein and colleagues had used neodymium ratios in deep-sea sediment samples to show that ocean circulation slowed during past ice ages.

They used the same method to show that changes in climate preceded changes in ocean circulation.

A trace element in Earth's crust, neodymium washes into the oceans through erosion from the continents, where natural radioactive decay leaves a signature unique to the land mass from which it originated.

When Goldstein and Lamont colleague Sidney Hemming pioneered this method in the late 1990s, they rarely worried about surrounding neodymium contaminating their samples.

The rise of consumer electronics has changed that.

"I used to say you could do sample processing for neodymium analysis in a parking lot," said Goldstein. "Not anymore."

-NSF-


Media Contacts
Cheryl Dybas, NSF

THE FOX WHO GOT READY FOR AN ICE AGE

FROM:  NATIONAL SCIENCE FOUNDATION 

"Out of Tibet" hypothesis: Cradle of evolution for cold-adapted mammals is in Tibet

Extinct Tibetan fox, ancestor of today's arctic fox, used Tibet as training ground for Ice Age climate

June 11, 2014

For the last 2.5 million years, Earth has experienced millennial-long cold and warm cycles. During cold periods, continental-scale ice sheets have blanketed large tracts of the Northern Hemisphere.

As climate warmed, glaciers receded, leaving Yosemite-like valleys and similar geologic features behind.

The advance and retreat of the ice sheets also had a profound influence on the evolution and geographic distribution of many animals, including those that live in far northern regions.

New results from research conducted in the Himalayan Mountains and published this week in the journal Proceedings of the Royal Society B: Biological Sciences identify a recently discovered three to five million-year-old Tibetan fox, Vulpes qiuzhudingi, as the likely ancestor of the living arctic fox, Vulpes lagopus.

The finding lends support to the idea that the evolution of present-day animals in the Arctic traces back to ancestors that adapted to life in cold regions in the high-altitude Tibetan Plateau.

The paper's lead author is Xiaoming Wang of the Natural History Museum of Los Angeles County. Co-authors are Zhijie Jack Tseng from the University of Southern California, Qiang Li from the Chinese Academy of Sciences, Gary Takeuchi from the Page Museum at the La Brea Tar Pits and Guangpu Xie from the Gansu Provincial Museum.

The scientists, part of a team of geologists and paleontologists led by Wang, uncovered fossil specimens of the Tibetan fox in the Zanda Basin in southern Tibet.

In addition to the fox, the team also discovered extinct species of a wooly rhino (Coelodonta thibetana), three-toed horse (Hipparion), Tibetan bharal (Pseudois, known as blue sheep), chiru (Pantholops, known as Tibetan antelope), snow leopard (Uncia), badger (Meles), and 23 other mammals.

The new fossil assemblage lends credence to a scenario the scientists call the "Out of Tibet" hypothesis.

It argues that some Ice Age megafauna--which in North America include the woolly mammoth, saber-toothed cat and giant sloth--used ancient Tibet as a training ground for developing adaptations that allowed them to cope with a harsh climate.

"The concept 'Out of Tibet' is an exciting insight for the origin of cold-adapted mammals of the Pleistocene," says Rich Lane, program director in the National Science Foundation's (NSF) Division of Earth Sciences, which funded the research.

"It parallels the 'Out of Africa' theory for the evolution of hominids. Together they may be a model for wider application in biological history and geography."

Tibet, Wang says, is a rich but grueling location for paleontological fieldwork.

Fifteen summer field seasons and a great deal of luck have led to his and his colleagues' successes.

Their expeditions involve a one-week journey to Lhasa, then a four-day drive into the remote "layer cake" sediments of the Zanda Basin--a drive made in old-model Land Cruisers known for becoming mired in streambeds.

At the more than 14,000-foot elevation, it's difficult to breathe, water freezes overnight in camps, and the scientists often must walk alone in search of fossils.

They've trained their eyes to search for ancient lake margins, where megafauna are reliably found.

Despite the challenges, Wang says that it's his favorite place to look for fossils.

"It's a pristine environment, the Tibetan people are kind, and in paleontological terms," he says, "it's relatively unexplored."

-- Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov
-- Kristin Friedrich, L.A. County Museum of Natural History (213) 763-3532 kfriedri@nhm.org
Investigators
Xiaoming Wang

NSF INVESTIGATES PRECURSORS OF AN EL NINO

FROM:  NATIONAL SCIENCE FOUNDATION 

World Oceans Day: 12 things to know about El Niño: Is it coming, and when?

How will it affect coastal species--and the fish on our dinner tables?

June 5, 2014

Just in time for World Oceans Day on June 8, cometh El Niño. But is El Niño really on the horizon? How certain are we of its arrival? And how will we know it's here? What effect will it have on the weather, on coastal species and on what's on our dinner tables?

To find out, the National Science Foundation (NSF) talked with biological oceanographer Mark Ohman and physical oceanographer Dan Rudnick of California's Scripps Institution of Oceanography. Their work is funded by NSF's Division of Ocean Sciences.

1) What is El Niño?

(Ohman) El Niño is the formation of warmer-than-usual ocean waters in the equatorial Pacific, with extensive temperature changes along the coast of South America during the month of December--hence the Spanish name "El Niño," the Christmas child. Scientists refer to the phenomenon as the El Niño-Southern Oscillation (ENSO). Its warm ocean phase is termed El Niño, and cool ocean phase La Niña.

2) Is El Niño predictable?

(Rudnick) Yes, to some extent. Scientists have identified the precursors of an El Niño; observations to monitor them are taking place near the equator. These observations are used in sophisticated models to predict the timing and magnitude of a developing El Niño. Right now, the models show anything from a weak to a strong El Niño ahead.

3) How do we know that changes in the ocean are the result of El Niño?

(Ohman) El Niño is the strongest year-to-year "signal" on Earth, with distinct temperature and precipitation changes over land and in the sea. Because the ocean is variable on many time scales (tidal, seasonal, year-to-year and decade-to-decade), it's essential to have a baseline of ocean measurements against which to measure departures from normal conditions.

Scientists at the NSF California Current Ecosystem Long-Term Ecological Research site, located in Southern California waters, have access to records of ocean conditions as far back as 1916.

4) Are all El Niños alike?

(Ohman) Not at all. Not only do El Niños vary in intensity, there are at least two major types. In one El Niño, termed Eastern Pacific, the most extreme temperature changes happen off the South American coast. In Central Pacific (CP) El Niños, the center of ocean temperature changes is much farther to the west. Some evidence suggests that the frequency of CP El Niños may be increasing.

(Rudnick) Ultimately every El Niño is different, and only some will strongly affect the coasts of the Americas.

5) When are the effects of El Niño the strongest?

(Ohman) The development of an El Niño is seasonal. The first ocean temperature changes usually begin during the Northern summer (June through September) then continue to grow, reaching their maximum during winter, from November to the following January. But precursors can sometimes be detected as early as February or March of the year of an El Niño's onset.

6) How often do El Niños occur, and how long do they last?

(Ohman) El Niños happen about every two to seven years. The last one was in 2009-10. Their duration is variable, but is usually six to eight months along the equator, with shorter time periods in higher latitudes. There have been exceptional cases of very long El Niños that lasted for two or more years, such as in 1957-59.

7) Are there new ways of observing developing El Niños?

(Rudnick) Yes, we're doing transects--criss-crossings of the ocean--using bullet-shaped, winged robotic gliders that collect underwater data. They're part of a project called Repeat Observations by Gliders in the Equatorial Region (ROGER).

These futuristic-looking gliders, called Spray gliders, traverse the oceans under their own power and are taking measurements in the Pacific Ocean near the Galapagos Islands. The information that returns with a glider tells us how the ocean is changing, and whether those changes indicate the coming of an El Niño.

8) How do the Spray gliders work?

(Rudnick) Spray gliders dive from the surface down to 1,000 meters (3,281 feet) and back, completing a cycle in six hours and covering six kilometers (3.7 miles) during that time.

The gliders carry sensors to measure temperature, salinity, current velocity, chlorophyll fluorescence (a measure of the abundance of phytoplankton), and acoustic backscatter (a measure of zooplankton). Spray gliders are launched for missions lasting about 100 days.

9) How do you know when to send out the gliders?

(Rudnick) The ROGER project wasn't originally designed to observe an El Niño, but the gliders were always capable of doing so. With a scientific project funded by NSF for two years, we couldn't realistically expect to catch an El Niño.

But science does involve serendipity, and we're fortunate to have the gliders in position just as an El Niño is appearing. We expect our data to include the most high-resolution repeated ocean transects ever done across the equator during an El Niño. Results from the gliders are showing the classic signs of an El Niño, including a strengthening equatorial undercurrent.

10) What effects will El Niño have on marine ecosystems along the U.S. West Coast?

(Ohman) During El Niño, the spawning grounds of coastal fish like sardines and anchovies often move closer to the coast. As warming waters from the open ocean come ever nearer to the California coast, cool upwelled water is found mostly along the edge of the land.

Warm-water plankton and fish may be transported far to the north of their normal ranges. In some El Niños, species that live along the coast of Baja California, Mexico, may be found as far north as off British Columbia.

11) Do seabirds and marine mammals respond to El Niño?

(Ohman) It all comes down to where the fish are. Some seabirds, especially those with limited foraging ranges or narrow food preferences, may have reduced reproductive success during an El Niño. California sea lions may have less fish prey available and therefore depressed birth weights of pups. Some whales, dolphins and porpoises may move to different foraging grounds where the fishing is better.

12) Will fisheries off California be affected?

(Ohman) El Niño may have a substantial effect on the catch of, for example, market squid, one of the most commercially important species off California. The spawning of this cool-water species may be severely curtailed, or take place in deeper waters than usual.

During an El Niño, U.S. West Coast sportfishers often catch more warm-water fish such as yellowfin tuna, dolphinfish (dorado), and yellowtail, and fewer cool-water fish like rockfish and lingcod. What's on your dinner table may, for a time, look just a bit different.

-- Cheryl Dybas, NSF