Slice of ice core from Berkner Island, depth 120m. Trapped air bubbles (an archive of the past atmosphere) are visible in the ice.

Previous analysis of ice cores has shown that the climate consists of ice ages and warmer interglacial periods roughly every 100,000 years. This new investigation shows temperature ‘spikes’ within some of the interglacial periods over the last 340,000 years. This suggests Antarctic temperature shows a high level of sensitivity to greenhouse gases at levels similar to those found today.

Lead author Louise Sime of British Antarctic Survey said, “We didn’t expect to see such warm temperatures, and we don’t yet know in detail what caused them. But they indicate that Antarctica’s climate may have undergone rapid shifts during past periods of high CO₂.”

During the last warm period, about 125,000 years ago, sea level was around 5 metres higher than today. Ice core scientist Eric Wolff of British Antarctic Survey is a world-leading expert on past climate. He said, “If we can pin down how much warmer temperatures were in Antarctica and Greenland at this time, then we can test predictions of how melting of the large ice sheets may contribute to sea level rise.”

The Paper: Evidence for warmer interglacials in East Antarctic ice cores by Louise C. Sime, Eric W. Wolff, Kevin I. C. Oliver and Julia C. Tindall is published online this week in the journal Nature.

By the British Antarctic Survey (BAS) Press Office

Atlanta —Tropical Cyclone Nargis made landfall in the Asian nation of Myanmar on May 2, 2008, causing the worst natural disaster in the country’s recorded history—with a death toll that may have exceeded 138,000. In the July 2009 issue of the journal Nature Geoscience, researchers report on a field survey done three months after the disaster to document the extent of the flooding and resulting damage.

Cyclone Nargis caused significant coastal erosion and land loss, shown here at Aya near the Ayeyarwady estuary in Myanmar. At top left is the golden Buddhist stupa, which was originally built on dry land. (Photo: Hermann Fritz)

The information—which may be the first reliable measurements of cyclone damage in the area—could lead to development of computer models for predicting how future storms may impact the geologically complex Ayeyarwady River delta. Those models could be the basis for planning, construction and education that would dramatically reduce future loss of life.

Among the findings of the study: the cyclone created a storm surge as much as five meters high—topped by two-meter storm waves—that together inundated areas as much as 50 kilometers inland. Fatality rates reached 80 percent in the hardest-hit villages, and an estimated 2.5 million people in the area lived in flood-prone homes less than 10 feet above sea level.

“The recorded high water marks serve as benchmarking for numerical models for the complex hydraulic response of the giant Ayeyarwady delta,” noted Hermann M. Fritz, an associate professor in the School of Civil and Environmental Engineering at the Georgia Institute of Technology. “Ongoing numerical simulations will allow us to determine flood zones and vulnerabilities for future cyclone scenarios. Based on those, evacuation scenarios and evaluation plans will be derived in collaboration with international partners and the Myanmar government.”

Already, a local non-governmental organization in the nation has developed a cyclone education program to raise awareness among residents, said Fritz, who was the only international scientist leading a team that surveyed 150 kilometers of the country’s coastline during a two-week period August 9-23, 2008.

“The aim of our project was to document the extent of the flooding and associated damage in the delta,” Fritz explained. “Field surveys in the immediate aftermath of major disasters focus on perishable data, which would otherwise be lost forever—such as infrastructure damage prior to repair and reconstruction.”

In the flood zone, for instance, the researchers searched for evidence of water marks on buildings, scars on trees and rafted debris as indicators of the maximum water height.

“Nargis washed away entire settlements, often without leaving a single structure standing, which forced us to focus on evidence left on large trees,” added Fritz, who has studied other natural disasters in Asia, Africa and the United States. “High water marks were photographed and located using global positioning system instruments. Transects from the nearest beach or waterway to the high water marks were recorded with a laser range finder.”

The survey team documented soil erosion of as much as one meter vertically and more than 100 meters horizontally. Highlighting the loss of land was a golden Buddhist stupa—originally constructed on dry land—that was left 150 meters offshore following the storm. Cyclone Nargis also scoured several drinking water wells, leaving them in the beach surf zone—and depriving survivors of safe water supplies.

While the storm surge and waves weren’t unusually high, the impact may have been worsened by the lack of nearby high ground for evacuation and loss of coastal mangrove forests that could have slowed the storm waves, Fritz said. Structures in the area were not built to survive cyclones, and there was no evacuation plan for the area—where people had no previous experience with such storms.

Rafted debris in trees showed how high the flood waters reached during Cyclone Nargis in Myanmar. (Photo: Hermann Fritz)

Those finding point to recommendations, including implementation of a cyclone education program, development of flood and vulnerability maps, construction of cyclone-safe buildings to serve as shelters, implementation of an improved warning system, and planning for evacuation, Fritz said. Partial reconstruction of the mangroves that had been removed for agriculture and fuel could also help protect the coastline.

The expedition’s itinerary was planned based on unofficial damage reports, physical storm and cyclone track data, satellite imagery, numerical model benchmark requirements and experience gained in surveying other disasters. The group traveled to the country by cargo boat and did most surveying from the vessel.

The research was in part supported by the Pyoe Pin Programme of the Department for International Development in the United Kingdom. The program is also sponsoring detailed modeling and a follow up study being done at Georgia Tech by Fritz and Christopher Blount, one of his doctoral students.

A Category 4 storm, Nargis was the eighth deadliest cyclone recorded worldwide. It is one of seven tropical cyclones generated in the Bay of Bengal that had death tolls in excess of 100,000. With damage estimated at more than $10 billion, the storm is the most destructive ever recorded in the Indian Ocean.

Fritz hopes the work done by the survey team—which also included Swe Thwin of the Myanmar Coastal Conservation Society and Moe Kyaw and Nyein Chan of the Mingalar Myanmar NGO—will ultimately help reduce the human cost of major cyclones.

“In the 21st century with modern communication and all that has been learned about cyclones in the Bay of Bengal, there is no need for 138,000 people to be killed by a storm like this,” Fritz said. “With adequate planning, education and shelters, it should be possible to reduce fatality rates from future cyclones by at least one order of magnitude.”

Related Links

• School of Civil and Environmental Engineering
• Hermann Fritz

By John Toon- Georgia Institute of Technology – Georgia Tech

Noctilucent clouds observed from Donnelley Dome near Fairbanks, Alaska, resulting from a post-space shuttle plume in August 2007. M.J. Taylor and C.D. Burton / Utah State University

The research, accepted for publication (June 24) by the journal Geophysical Research Letters, published by the American Geophysical Union, connects the two events by what followed each about a day later: brilliant, night-visible clouds, or noctilucent clouds, that are made up of ice particles and only form at very high altitudes and in extremely cold temperatures.

“It’s almost like putting together a 100-year-old murder mystery,” said Michael Kelley, the James A. Friend Family Distinguished Professor of Engineering at Cornell, who led the research team. “The evidence is pretty strong that the Earth was hit by a comet in 1908.” Previous speculation had ranged from comets to meteors to black holes.

The researchers contend that the massive amount of water vapor spewed into the atmosphere by the comet’s icy nucleus was caught up in swirling eddies with tremendous energy by a process called two-dimensional turbulence, which explains why the noctilucent clouds formed a day later many thousands of miles away.

Noctilucent clouds are the Earth’s highest clouds, forming naturally in the mesosphere at about 55 miles over the polar regions during the summer months when the mesosphere is around minus 180 degrees Fahrenheit (minus 117 degrees Celsius).

The space shuttle exhaust plume, the researchers say, resembled the water vapor from the comet. A single space shuttle flight injects 300 metric tons of water vapor into the Earth’s thermosphere, and the water particles have been found to travel to the Arctic and Antarctic regions, where they form the clouds after settling into the mesosphere. The thermosphere is the layer of the atmosphere above the mesosphere.

Kelley and collaborators saw the noctilucent cloud phenomenon days after the space shuttle Endeavour (STS-118) launched on Aug. 8, 2007. Similar cloud formations had been observed following launches in 1997 and 2003.

Following the 1908 explosion, known as the Tunguska Event, the night skies shone brightly for several days across Europe, particularly Great Britain — more than 3,000 miles away. Kelley said he became intrigued by the historical eyewitness accounts of the aftermath, and concluded that the bright skies must have been the result of noctilucent clouds. The comet would have started to break up at about the same altitude as the release of the exhaust plume from the space shuttle following launch. In both cases, water vapor was injected into the atmosphere.

The scientists have attempted to answer how this water vapor traveled so far without scattering and diffusing, as conventional physics would predict.

“There is a mean transport of this material for tens of thousands of kilometers in a very short time, and there is no model that predicts that,” Kelley said. “It’s totally new and unexpected physics.”

This “new” physics, the researchers contend, is tied up in counter-rotating eddies with extreme energy. Once the water vapor got caught up in these eddies, the water traveled very quickly — close to 300 feet per second.

Scientists have long tried to study the wind structure in these upper regions of the atmosphere, which is difficult to do by such traditional means as sounding rockets, balloon launches and satellites, explained Charles Seyler, Cornell professor of electrical engineering and paper co-author.

“Our observations show that current understanding of the mesosphere-lower thermosphere region is quite poor,” Seyler said.

The paper is also co-authored by Clemson University physicist Miguel Larsen, Ph.D. ‘79, a former student of Kelley. The work performed at Cornell was funded by the Atmospheric Science Section of the National Science Foundation.

On July 1, Kelley will give a lecture, “Two-dimensional Turbulence, Space Shuttle Plume Transport in the Thermosphere, and a Possible Relation to the Great Siberian Impact Event,” at a plenary session of the annual meeting of Coupling, Energetics and Dynamics of Atmospheric Regions in Santa Fe, N.M.

The paper is available at: http://www.agu.org/journals/gl/papersinpress.shtml.

By Anne Ju – Cornell University - Cornell Chronicle Online

Oxygen gas in ice cores has shown evidence for abrupt climate change.Credit: Zina Deretsky, National Science Foundation

When the climate warmed relatively quickly about 14,700 years ago, seasonal monsoons moved southward, dropping more rain on the Earth’s oceans at the expense of tropical areas, according to climate researchers. If the same pattern occurs in the coming decades as the Earth’s temperatures rises due to climate change, the highly-populated regions of the world that depend on monsoons could face more wildfires, water shortages and lower agricultural production.

In an article to be published in the June 12 issue of the journal Science, researchers from the Desert Research Institute in Nevada, the Scripps Institution of Oceanography and Oregon State University present their findings after comparing oxygen isotopes in air that was captured in ice cores and previously published data from ancient stalagmites found in caves. The research was supported by the National Science Foundation.

The ice cores, gathered from different locations in Antarctica and Greenland, contain air bubbles that were trapped as the ice formed over tens of thousands of years. By measuring the amount of certain oxygen isotopes in those air bubbles, the researchers were able to determine patterns in vegetation growth worldwide over that same span of time.

The researchers found that beginning about 14,700 years ago, the mixture of oxygen isotopes began to change in a way that suggests less vegetation growth, and this process continued for at least 200 years. The researchers then compared these findings with data from an earlier study that determined the amount of rainfall that fell in China over many millennia by examining stalagmites in caves. They discovered that this period of low vegetation growth corresponded with a time of reduced monsoon rainfall.

By climate standards, the researchers say, this shift happened abruptly over a few decades. They also caution that observations of past climate events may not be able predict future conditions. Given the vital roll that monsoons play in sustaining billions of people, however, this connection between climate change and monsoon patterns may be an ominous sign of what climate change in the 21^st century may bring.

The National Science Foundation

Steelhead trout return to spawn. The photographer is John McMillan.

The poor reproductive fitness – the ability to survive and reproduce – of the wild-born offspring of hatchery fish means that adding hatchery fish to wild populations may ultimately be hurting efforts to sustain those wild runs, scientists said.

The study found that a fish born in the wild as the offspring of two hatchery-reared steelhead averaged only 37 percent the reproductive fitness of a fish with two wild parents, and 87 percent the fitness if one parent was wild and one was from a hatchery. Most importantly, these differences were still detectable after a full generation of natural selection in the wild.

The effect of hatcheries on reproductive fitness in succeeding generations had been predicted in theory, experts say, but until now had never been demonstrated in actual field experiments.

“If anyone ever had any doubts about the genetic differences between hatchery and wild fish, the data are now pretty clear,” said Michael Blouin, an OSU professor of zoology. “The effect is so strong that it carries over into the first wild-born generation. Even if fish are born in the wild and survive to reproduce, those adults that had hatchery parents still produce substantially fewer surviving offspring than those with wild parents. That’s pretty remarkable.”

An earlier report, published in 2007 in the journal Science, had already shown that hatchery fish that migrate to the ocean and return to spawn leave far fewer offspring than their wild relatives. The newest findings suggest the problem does not end there, but carries over into their wild-born descendants.

The implication, Blouin said, is that hatchery salmonids – many of which do survive to reproduce in the wild– could be gradually reducing the fitness of the wild populations with which they interbreed. Those hatchery fish provide one more hurdle to overcome in the goal of sustaining wild runs, along with problems caused by dams, loss or degradation of habitat, pollution, overfishing and other causes.

Aside from weakening the wild gene pool, the release of captive-bred fish also raises the risk of introducing diseases and increasing competition for limited resources, the report noted.

Returning chinook salmon on the Umatilla River. Photo by Lynn Ketchum

This research, which was just published in Biology Letters, was supported by grants from the Bonneville Power Administration and the Oregon Department of Fish and Wildlife. It was based on years of genetic analysis of thousands of steelhead trout in Oregon’s Hood River, in field work dating back to 1991. Scientists have been able to genetically “fingerprint” three generations of returning fish to determine who their parents were, and whether or not they were wild or hatchery fish.

The underlying problem, experts say, is Darwinian natural selection.

Fish that do well in the safe, quiet world of the hatcheries are selected to be different than those that do well in a much more hostile and predatory real-world environment. Using wild fish as brood stock each year should lessen the problem, but it was just that type of hatchery fish that were used in the Hood River study. This demonstrates that even a single generation of hatchery culture can still have strong effects.

Although this study was done with steelhead trout, it would be reasonable to extrapolate its results to other salmonids, researchers said. It’s less clear what the findings mean to the many other species that are now being bred in captivity in efforts to help wild populations recover, Blouin said, but it’s possible that similar effects could be found.

Captive breeding is now a cornerstone of recovery efforts by conservation programs for many threatened or endangered species, the researchers noted in their report. Thousands of species may require captive breeding to prevent their extinction in the next 200 years – which makes it particularly important to find out if such programs will ultimately work. This study raises doubts.

“The message should be clear,” the researchers wrote in their report’s conclusion. “Captive breeding for reintroduction or supplementation can have a serious, long-term downside in some taxa, and so should not be considered as a panacea for the recovery of all endangered populations.”

Oregon State University

David Hu, an assistant professor in mechanical engineering at Georgia Tech, is able to visualize snakes slithering by watching them undulate on a mirrored surface, lifting the curves of their bodies. (Photo: David Hu and Grace Pryor)

“We found that snakes’ belly scales are oriented so that snakes resist sliding toward their tails and flanks,” said the paper’s lead author, David Hu, a former postdoctoral researcher at NYU’s Courant Institute of Mathematical Sciences and now an assistant professor in Georgia Tech’s George W. Woodruff School of Mechanical Engineering. “These scales give the snakes a preferred direction of motion, which makes snake movement a lot like that of wheels, cross-country skis, or ice skates. In all these examples, sliding forwards takes less work than does sliding sideways.”

The study’s other co-authors were Jasmine Nirody and Terri Scott, both undergraduate researchers at NYU, and Michael Shelley, a professor of mathematics and neural science and the Lilian and George Lyttle Professor of Applied Mathematics at Courant.

The study centered on the frictional anisotropy—or resistance to sliding in certain directions—of a snake’s belly scales. While previous investigators had suggested that the frictional anisotropy of these scales might play a role in locomotion over flat surfaces, the details of this process had not been understood.

By shining light through a gelatin, David Hu observes the forces applied by a snake as it slithers. White regions show high force, indicating that the snake lifts the peaks and troughs of its body when slithering. (Photo: David Hu and Grace Pryor)

To explore this matter, the researchers first developed a theoretical model of a snake’s movement. The model determined the speed of a snake’s center of mass as a function of the speed and size of its body waves, taking into account the laws of friction and the scales’ frictional anisotropy. The model suggested that a snake’s motion arises by the interaction of surface friction and its internal body forces.

To confirm movement as predicted by the model, the researchers then measured the sliding resistance of snake scales and monitored the movement of snakes through a series of experiments on flat and inclined surfaces. They employed video and time-lapse photography to gauge their movements.

The results showed a close relationship between what the model predicted and the snakes’ actual movements. The theoretical predictions of the model were generally consistent with the snakes’ actual body speeds on both flat and inclined surfaces.

By James Devitt – The Georgia Institute of Technology

The research team analyzed three classes of antibiotics (macrolides, quinolones and sulfonamides) and the compound trimethoprim present in the urban waste waters of East Asia, Europe and North America. The scientists found higher concentrations of these pharmaceuticals in raw wastewater compared to treated wastewater. “Rivers, creeks, lakes, estuar­ies, basins, sea waters and wells have been reported to be contaminated by several of these compounds,” says Dr. Sauvé.

The review warns the increased concentration of farms may augment the levels of anti-infectives in agricultural wastewater in the future. The investigations also predicts that vital urban water conservation strategies produce a side effect – specifically less wastewater that causes lower dilution and more anti-infectives in water. “Anti-infectives might have a greater impact in developing countries, where sewage infrastructure can be lacking, self-prescription rates higher and industrial emissions less strictly regulated,” adds first author Pedro A. Segura, a Université de Montréal PhD student.

Source: Université de Montréal

On the Web:
About the cited article in Environmental Health Perspectives
About the Université de Montréal
About the Department of Chemistry
About Sébastien Sauvé