Geoengineering plan is criticized

BOULDER, Colo., Aug. 23 (UPI) -- U.S. scientists criticized a geoengineering proposal that would emulate volcanic eruptions as a means of combating global warming.

Global warning occurs when greenhouse gases, such as carbon dioxide, build up in the atmosphere and alter outgoing longwave radiation. Some scientists have proposed mitigating global warming by emulating a volcanic eruption, since volcanic aerosols scatter incoming sunlight, reducing outgoing radiation.

But Kevin Trenberth and Aiguo Dai of the U.S. National Center for Atmospheric Research cautioned against the mitigation proposal.

The scientists examined precipitation and streamflow records from 1950 to 2004 to document the effects of volcanic eruptions from Mexico's El Chichon in 1982 and the Philippines' Mount Pinatubo in 1991.

They found that following the Pinatubo eruption there was a substantial global decrease in precipitation over land, a record decrease in runoff and river discharge into the oceans and widespread drying over land during the following year.

Thus, the authors conclude, major adverse effects, including drought, could arise from geoengineering solutions to global warming.

Their study is reported in the journal Geophysical Research Letters.

This is an article from ScienceDaily

Permafrost – the perpetually frozen foundation of North America – isn’t so permanent anymore, and scientists are scrambling to understand the pros and cons when terra firma goes soft.

Permafrost serves like a platform underneath vast expanses of northern forests and wetlands that are rooted, literally, in melting permafrost in many northern ecosystems. But rising atmospheric temperatures are accelerating rates of permafrost thaw in northern regions, says MSU researcher Merritt Turetsky.

In the report, “The Disappearance of Relict Permafrost in Boreal North America: Effects on Peatland Carbon Storage and Fluxes,” in a recent online edition of Global Change Biology, Turetsky and others explore whether melting permafrost can lead to a viscous feedback of carbon exchange that actually fuels future climate change.

“The loss of permafrost usually means the loss of terra firma in an otherwise often boggy landscape,” Turetsky said. “Roads, buildings and whole communities will have to cope with this aspect of climate change. What this means for ecosystems and humans residing in the North remains of the most pressing issues in the climate change arena.”

Working closely with researchers from Southern Illinois University, Villanova University and the National Renewable Energy Laboratory, Turetsky, assistant professor of crop and soil sciences and fisheries and wildlife, found that permafrost degradation has complex impacts on greenhouse gas fluxes from northern wetlands.

Their study focused on peatlands, a common type of wetland in boreal regions that slowly accumulates peat, which is an accumulation of partially decayed vegetation. Today, peatlands represent a massive reservoir of stockpiled carbon that accumulated from the atmosphere over many thousands of years. Peat blankets the permafrost and protects it like a thick layer of insulation.

“We find permafrost in peatlands further south than in other boreal ecosystems due to the insulating qualities of peat.So we have argued that these ecosystems serve as a very sensitive indicator of climate change,” Turetsky said. “What will happen to peatlands when climate change disrupts these frozen layers, or perhaps more importantly what will happen to all of that stored carbon in peat, have remained big questions for us.”

Their results were surprising.Turetsky and her colleagues studied areas affected by permafrost degradation across a large region of Canada. They initially expected to find that the melting ice would trigger a release of greenhouse gases to the atmosphere, as previously frozen plant and animal remains became susceptible to decay.

“This could serve as a positive feedback to climate change, where typically warming causes changes that release more greenhouse gases, which in turn causes more warming, and more emissions, and so on,” she said.

But what the researchers actually found is not such a clear-cut climate story.

Permafrost collapse in peatlands tends to result in the slumping of the soil surface and flooding, followed by a complete change in vegetation, soil structure, and many other important aspects of these ecosystems, Turetsky said.The study showed that vegetation responds to the flooding with a boost in productivity. More vegetation sequesters more carbon away from the atmosphere in plant biomass.

“This is actually good news from a greenhouse gas perspective,” Turetsky said.

However, the report also cautions that this flooding associated with collapsing permafrost also increases methane emissions.Methane is an important greenhouse gas, which is more powerful than carbon dioxide in its ability to trap heat in the earth’s atmosphere.

Turetsky said it seems the permafrost degradation initially causes increased soil carbon sequestration, rather than the large releases of carbon to the atmosphere originally predicted.But over time high methane emissions will balance – or outweigh – the reduction of carbon in the atmosphere.

“Not all ecosystems underlain by permafrost will respond the same way,” Turetsky cautioned. “It will depend on the history of the permafrost and the nature of both vegetation and soils.”

What is clear, she said, is that not even northern ecosystems can escape the wide reach of climate change.

The research was funded by the National Science Foundation, the Canadian NSERC, and the Society of Wetland Scientists. Turetsky’s work also is supported by the MSU Michigan Agricultural Experiment Station.

This is an article from ScienceDaily

Synchronized Chaos: Mechanisms For Major Climate Shifts

In the mid-1970s, a climate shift cooled sea surface temperatures in the central Pacific Ocean and warmed the coast of western North America, bringing long-range changes to the northern hemisphere.

After this climate shift waned, an era of frequent El Ninos and rising global temperatures began.

Understanding the mechanisms driving such climate variability is difficult because unraveling causal connections that lead to chaotic climate behavior is complicated.

To simplify this, Tsonis et al. investigate the collective behavior of known climate cycles such as the Pacific Decadal Oscillation, the North Atlantic Oscillation, the El Nino/Southern Oscillation, and the North Pacific Oscillation.

By studying the last 100 years of these cycles' patterns, they find that the systems synchronized several times.

Further, in cases where the synchronous state was followed by an increase in the coupling strength among the cycles, the synchronous state was destroyed. Then. a new climate state emerged, associated with global temperature changes and El Nino/Southern Oscillation variability.

The authors show that this mechanism explains all global temperature tendency changes and El Nino variability in the 20th century.

Title: A new dynamical mechanism for major climate shifts

Authors: Anastasios A. Tsonis, Kyle Swanson, and Sergey Kravtsov: Atmospheric Sciences Group, Department of Mathematical Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030288, 2007

Note: This story has been adapted from a news release issued by American Geophysical Union.

This is an article in ScienceDaily

Global Warming

More than a mile beneath the Atlantic's surface, roughly halfway between New York and Portugal, seawater rushing through the narrow gullies of an underwater mountain range much as winds gust between a city's tall buildings is generating one of the most turbulent areas ever observed in the deep ocean.

In fact, the turbulence packs an energy wallop equal to about five million watts -- comparable to output from a small nuclear reactor, according to a landmark study led by Florida State University researcher Louis St. Laurent and described in the August 9 edition of the journal Nature.

The study -- an international collaboration of scientists from the United States and France -- documents for the first time the turbulent conditions in an undersea mountain range known as the Mid-Atlantic Ridge. It provides never-before-seen evidence that deep water turbulence swirling in the small passageways of such mountains is generating much of the mixing of warm and cold waters in the Atlantic Ocean.

Better understanding of the mechanisms of mixing is crucial, says St. Laurent, an assistant professor of physical oceanography at FSU and the study's co-principal investigator, because mixing produces the overall balance of water temperatures that helps control the strength of the Gulf Stream -- the strong, warm ocean current that starts in the Gulf of Mexico, flows along the U.S. east coast to Canada and on to Europe, and plays a crucial climate role.

"Oceanographers are working hard to understand how processes in the ocean help to keep the Earth's climate stable," St. Laurent said. "We are aware that the climate is warming, but we don't yet fully understand how the changes will affect society. Our work will result in better models for predicting how the ocean will affect the climate in the future and a better understanding of sea-level rise, weather patterns such as El Nino, and the impact of these events on fisheries."

St. Laurent compared the flow of seawater through underwater gullies in the Mid-Atlantic Ridge to the wind, so familiar to hikers, that blows through mountain passages on land.

"That wind creates a condition known as turbulence, which can blow the hat from your head," St. Laurent said. "In the ocean, turbulence is produced when water flows quickly though oceanic passages. The turbulence stirs the almost freezing-water near the bottom with warmer water that is closer to the surface much as you would mix cream into coffee by stirring it with a spoon.

"We know that the mixing of warm surface water with very cold deep water is one of several factors that influence the Earth's climate," he said. "The mixing we observed and measured for our study allows the warmth at the surface of the ocean to 'diffuse' deep into the sea. The overall balance between warm and cold water in the Atlantic helps control the strength of the Gulf Stream, which moves heat away from the Earth's equator toward regions that receive much less heating from the sun's rays."

St. Laurent's co-principal investigator and co-author was Andreas M. Thurnherr, a former postdoctoral researcher in the FSU oceanography department and now a scientist at Columbia University. The field study took place in August 2006 during a three-week expedition aboard a French research vessel to a location close to the Azores, volcanic islands 2,000 miles east of the U.S. and west of Europe that comprise an above-sea portion of the mostly submerged Mid-Atlantic Ridge.

To measure the energy generated by the extraordinarily intense turbulence more than a mile below the ocean's surface, St. Laurent and crew used a custom-made instrument called the "turbulence profiler," outfitted with special sensors.

"The turbulence profiler measured the output using 'watts,' the same unit of measurement as printed on light bulbs," St. Laurent said. "In the undersea mountain passage where we intentionally looked, we found turbulence levels as large as one-10th watt per cubic meter of seawater. This is a huge amount of energy when you add all the seawater in the passage, equal to around five million watts, which is comparable to output from a nuclear reactor."

Article: "Overflow Mixing of Lower Thermocline Water on the Crest of the Mid-Atlantic Ridge"

Note: This story has been adapted from a news release issued by Florida State University.

This is an article from the site ScienceDaily