Even with the acceptance of plate tectonics half a century ago, some Earth and space scientists have continued to speculate on Earth's possible expansion or contraction on various scientific grounds.

Now a new NASA study, published recently in Geophysical Research Letters, has essentially laid those speculations to rest. Using a cadre of space measurement tools and a new data calculation technique, the team detected no statistically significant expansion of the solid Earth.

So why should we care if Mother Nature is growing? After all, Earth's shape is constantly changing. Tectonic forces such as earthquakes and volcanoes push mountains higher, while erosion and landslides wear them down. In addition, large-scale climate events like El Nino and La Nina redistribute vast water masses among Earth's ocean, atmosphere and land.

Scientists care because, to put movements of Earth's crust into proper context, they need a frame of reference to evaluate them against. Any significant change in Earth's radius will alter our understanding of our planet's physical processes and is fundamental to the branch of science called geodesy, which seeks to measure Earth's shape and gravity field, and how they change over time.

To make these measurements, the global science community established the International Terrestrial Reference Frame. This reference frame is used for ground navigation and for tracking spacecraft in Earth orbit.

It is also used to monitor many aspects of global climate change,

+ including sea level rise and its sources;

+ imbalances in ice mass at Earth's poles;

+ and the continuing rebound of Earth's surface following the retreat of the massive ice sheets that blanketed much of Earth during the last Ice Age.

But measuring changes in Earth's size hasn't exactly been easy for scientists to quite literally "get their arms around." After all, they can't just wrap a giant tape measure around Earth's belly to get a definitive reading. Fortunately, the field of high-precision space geodesy gives scientists tools they can use to estimate changes in Earth's radius. These include:

Satellite laser ranging - a global observation station network that measures, with millimeter-level precision, the time it takes for ultrashort pulses of light to travel from the ground stations to satellites specially equipped with retroreflectors and back again.

Very-long baseline interferometry - a radio astronomy technology that combines observations of an object made simultaneously by many telescopes to simulate a telescope as big as the maximum distance between the telescopes. Global Positioning System - the U.S.-built space-based global navigation system that provides users around the world with precise location and time information.

Doppler Orbitography and Radiopositioning Integrated by Satellite - a French satellite system used to determine satellite orbits and positioning. Beacons on the ground emit radio signals that are received by satellites. The movement of the satellites causes a frequency shift of the signal that can be observed to determine ground positions and other information.

Scientists use all these techniques to calculate the International Terrestrial Reference Frame. Central to the reference frame is its point of origin: the precise location of the average center of mass of the total Earth system (the combination of the solid Earth and the fluid envelope of ocean, ice and atmosphere that surrounds it, around which all Earth satellites orbit). Scientists currently determine this origin point based on a quarter century of satellite laser ranging data, considered the most accurate space geodetic tool for this purpose.

But the accuracy of the satellite laser ranging data and all existing space geodesy technologies is contaminated, both by the effects of other major Earth processes, and limited ground measurement sites.

Think of it this way: if all of Earth's GPS stations were located in Norway, their data would indicate that Earth is growing, because high-latitude countries like Norway are still rising in elevation in response to the removal of the weight of Ice Age ice sheets. So how can scientists be sure the reference frame is accurate?

Enter an international group of scientists led by Xiaoping Wu of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and including participants from the Institut Geographique National, Champs-sur-Marne in France, and Delft University of Technology in The Netherlands. The team set out to independently evaluate the accuracy of the International Terrestrial Reference Frame and shed new light on the Earth expansion/contraction theory.

The team applied a new data calculation technique to estimate the rate of change in the solid Earth's average radius over time, taking into account the effects of other geophysical processes.

The previously discussed geodetic techniques (satellite laser ranging, very-long baseline interferometry and GPS) were used to obtain data on Earth surface movements from a global network of carefully selected sites.

These data were then combined with measurements of Earth's gravity from NASA's Gravity Recovery and Climate Experiment (GRACE) spacecraft and models of ocean bottom pressure, which help scientists interpret gravity change data over the ocean.

The result? The scientists estimated the average change in Earth's radius to be 0.004 inches (0.1 millimeters) per year, or about the thickness of a human hair, a rate considered statistically insignificant.

"Our study provides an independent confirmation that the solid Earth is not getting larger at present, within current measurement uncertainties," said Wu.

]]> Wed, 08 FEB 2012 08:56:47 AEST Berkeley CA (SPX) Jul 22, 2011 - What spreads the sea floors and moves the continents? What melts iron in the outer core and enables the Earth's magnetic field? Heat. Geologists have used temperature measurements from more than 20,000 boreholes around the world to estimate that some 44 terawatts (44 trillion watts) of heat continually flow from Earth's interior into space. Where does it come from?

Radioactive decay of uranium, thorium, and potassium in Earth's crust and mantle is a principal source, and in 2005 scientists in the KamLAND collaboration, based in Japan, first showed that there was a way to measure the contribution directly. The trick was to catch what KamLAND dubbed geoneutrinos - more precisely, geo-antineutrinos - emitted when radioactive isotopes decay. (KamLAND stands for Kamioka Liquid-scintillator Antineutrino Detector.)

"As a detector of geoneutrinos, KamLAND has distinct advantages," says Stuart Freedman of the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), which is a major contributor to KamLAND. Freedman, a member of Berkeley Lab's Nuclear Science Division and a professor in the Department of Physics at the University of California at Berkeley, leads U.S. participation.

"KamLAND was specifically designed to study antineutrinos. We are able to discriminate them from background noise and detect them with very high sensitivity."

KamLAND scientists have now published new figures for heat energy from radioactive decay in the journal Nature Geoscience. Based on the improved sensitivity of the KamLAND detector, plus several years' worth of additional data, the new estimate is not merely "consistent" with the predictions of accepted geophysical models but is precise enough to aid in refining those models.

One thing that's at least 97-percent certain is that radioactive decay supplies only about half the Earth's heat. Other sources - primordial heat left over from the planet's formation, and possibly others as well - must account for the rest.

Hunting for neutrinos from deep in the Earth
Antineutrinos are produced not only in the decay of uranium, thorium, and potassium isotopes but in a variety of others, including fission products in nuclear power reactors. In fact, reactor-produced antineutrinos were the first neutrinos to be directly detected (neutrinos and antineutrinos are distinguished from each other by the interactions in which they appear).

Because neutrinos interact only by way of the weak force - and gravity, insignificant except on the scale of the cosmos - they stream through the Earth as if it were transparent. This makes them hard to spot, but on the very rare occasions when an antineutrino collides with a proton inside the KamLAND detector - a sphere filled with a thousand metric tons of scintillating mineral oil - it produces an unmistakable double signal.

The first signal comes when the antineutrino converts the proton to a neutron plus a positron (an anti-electron), which quickly annihilates when it hits an ordinary electron - a process called inverse beta decay. The faint flash of light from the ionizing positron and the annihilation process is picked up by the more than 1,800 photomultiplier tubes within the KamLAND vessel.

A couple of hundred millionths of a second later the neutron from the decay is captured by a proton in the hydrogen-rich fluid and emits a gamma ray, the second signal. This "delayed coincidence" allows antineutrino interactions to be distinguished from background events such as hits from cosmic rays penetrating the kilometer of rock that overlies the detector.

Says Freedman, "It's like looking for a spy in a crowd of people on the street. You can't pick out one spy, but if there's a second spy following the first one around, the signal is still small but it's easy to spot."

KamLAND was originally designed to detect antineutrinos from more than 50 reactors in Japan, some close and some far away, in order to study the phenomenon of neutrino oscillation. Reactors produce electron neutrinos, but as they travel they oscillate into muon neutrinos and tau neutrinos; the three "flavors" are associated with the electron and its heavier cousins.

Being surrounded by nuclear reactors means KamLAND's background events from reactor antineutrinos must also be accounted for in identifying geoneutrino events. This is done by identifying the nuclear-plant antineutrinos by their characteristic energies and other factors, such as their varying rates of production versus the steady arrival of geoneutrinos. Reactor antineutrinos are calculated and subtracted from the total. What's left are the geoneutrinos.

Tracking the heat
All models of the inner Earth depend on indirect evidence. Leading models of the kind known as bulk silicate Earth (BSE) assume that the mantle and crust contain only lithophiles ("rock-loving" elements) and the core contains only siderophiles (elements that "like to be with iron"). Thus all the heat from radioactive decay comes from the crust and mantle - about eight terawatts from uranium 238 (238U), another eight terawatts from thorium 232 (232Th), and four terawatts from potassium 40 (40K).

KamLAND's double-coincidence detection method is insensitive to the low-energy part of the geoneutrino signal from 238U and 232Th and completely insensitive to 40K antineutrinos. Other kinds of radioactive decay are also missed by the detector, but compared to uranium, thorium, and potassium are negligible contributors to Earth's heat.

Additional factors that have to be taken into account include how the radioactive elements are distributed (whether uniformly or concentrated in a "sunken layer" at the core-mantle boundary), variations due to radioactive elements in the local geology (in KamLAND's case, less than 10 percent of the expected flux), antineutrinos from fission products, and how neutrinos oscillate as they travel through the crust and mantle.

Alternate theories were also considered, including the speculative idea that there may be a natural nuclear reactor somewhere deep inside the Earth, where fissile elements have accumulated and initiated a sustained fission reaction.

KamLAND detected 841 candidate antineutrino events between March of 2002 and November of 2009, of which about 730 were reactor events or other background. The rest, about 111, were from radioactive decays of uranium and thorium in the Earth.

These results were combined with data from the Borexino experiment at Gran Sasso in Italy to calculate the contribution of uranium and thorium to Earth's heat production. The answer was about 20 terawatts; based on models, another three terawatts were estimated to come from other isotope decays.

This is more heat energy than the most popular BSE model suggests, but still far less than Earth's total. Says Freedman, "One thing we can say with near certainty is that radioactive decay alone is not enough to account for Earth's heat energy. Whether the rest is primordial heat or comes from some other source is an unanswered question."

Better models are likely to result when many more geoneutrino detectors are located in different places around the globe, including midocean islands where the crust is thin and local concentrations of radioactivity (not to mention nuclear reactors) are at a minimum.

Says Freedman, "This is what's called an inverse problem, where you have a lot of information but also a lot of complicated inputs and variables. Sorting those out to arrive at the best explanation among many requires multiple sources of data."

]]> Wed, 08 FEB 2012 08:56:47 AEST Leeds UK (SPX) May 23, 2011 - The inner core of the Earth is simultaneously melting and freezing due to circulation of heat in the overlying rocky mantle, according to new research from the University of Leeds, UC San Diego and the Indian Institute of Technology.

The findings, published tomorrow in Nature, could help us understand how the inner core formed and how the outer core acts as a 'geodynamo', which generates the planet's magnetic field.

"The origins of Earth's magnetic field remain a mystery to scientists," said study co-author Dr Jon Mound from the University of Leeds. "We can't go and collect samples from the centre of the Earth, so we have to rely on surface measurements and computer models to tell us what's happening in the core."

"Our new model provides a fairly simple explanation to some of the measurements that have puzzled scientists for years. It suggests that the whole dynamics of the Earth's core are in some way linked to plate tectonics, which isn't at all obvious from surface observations.

"If our model is verified it's a big step towards understanding how the inner core formed, which in turn helps us understand how the core generates the Earth's magnetic field."

The Earth's inner core is a ball of solid iron about the size of our moon. This ball is surrounded by a highly dynamic outer core of a liquid iron-nickel alloy (and some other, lighter elements), a highly viscous mantle and a solid crust that forms the surface where we live.

Over billions of years, the Earth has cooled from the inside out causing the molten iron core to partly freeze and solidify. The inner core has subsequently been growing at the rate of around 1mm a year as iron crystals freeze and form a solid mass.

The heat given off as the core cools flows from the core to the mantle to the Earth's crust through a process known as convection. Like a pan of water boiling on a stove, convection currents move warm mantle to the surface and send cool mantle back to the core. This escaping heat powers the geodynamo and coupled with the spinning of the Earth generates the magnetic field.

Scientists have recently begun to realise that the inner core may be melting as well as freezing, but there has been much debate about how this is possible when overall the deep Earth is cooling. Now the research team believes they have solved the mystery.

Using a computer model of convection in the outer core, together with seismology data, they show that heat flow at the core-mantle boundary varies depending on the structure of the overlying mantle. In some regions, this variation is large enough to force heat from the mantle back into the core, causing localised melting.

The model shows that beneath the seismically active regions around the Pacific 'Ring of Fire', where tectonic plates are undergoing subduction, the cold remnants of oceanic plates at the bottom of the mantle draw a lot of heat from the core. This extra mantle cooling generates down-streams of cold material that cross the outer core and freeze onto the inner core.

Conversely, in two large regions under Africa and the Pacific where the lowermost mantle is hotter than average, less heat flows out from the core. The outer core below these regions can become warm enough that it will start melting back the solid inner core.

Co-author Dr Binod Sreenivasan from the Indian Institute of Technology said: "If Earth's inner core is melting in places, it can make the dynamics near the inner core-outer core boundary more complex than previously thought.

"On the one hand, we have blobs of light material being constantly released from the boundary where pure iron crystallizes. On the other hand, melting would produce a layer of dense liquid above the boundary. Therefore, the blobs of light elements will rise through this layer before they stir the overlying outer core.

"Interestingly, not all dynamo models produce heat going into the inner core. So the possibility of inner core melting can also place a powerful constraint on the regime in which the Earth's dynamo operates."

Co-author Dr Sebastian Rost from the University of Leeds added: "The standard view has been that the inner core is freezing all over and growing out progressively, but it appears that there are regions where the core is actually melting. The net flow of heat from core to mantle ensures that there's still overall freezing of outer core material and it's still growing over time, but by no means is this a uniform process.

"Our model allows us to explain some seismic measurements which have shown that there is a dense layer of liquid surrounding the inner core. The localised melting theory could also explain other seismic observations, for example why seismic waves from earthquakes travel faster through some parts of the core than others."

]]> Wed, 08 FEB 2012 08:56:47 AEST London (AFP) May 15, 2011 - If alien geologists were to visit our planet 10 million years from now, would they discern a distinct human fingerprint in Earth's accumulating layers of rock and sediment?

Will homo sapiens, in other words, define a geological period in the way dinosaurs -- and their vanishing act -- helped mark the Jurassic and the Cretaceous?

A growing number of scientists, some gathered at a one-day symposium this week at the British Geological Society in London, say "yes".

One among them, chemistry Nobel laureate Paul Crutzen, has even suggested a new name: the Anthropocene.

Whether this "age of man" will be short or long is unknown. But one thing is clear, says Crutzen, who shared his Nobel for unmasking the man-made chemicals eating away at the atmosphere's protective ozone layer.

For the first time in Earth's 4.7 billion year history, a single species has not only radically changed Earth's morphology, chemistry and biology, it is now aware of having done so.

"We broke it, we bought it, we own it," is how Erle Ellis, a professor of geography and ecology at the University of Maryland at Baltimore, put it.

"We don't know what is going to happen in the Anthropocene -- it could be good, even better," he said. "But we need to think differently and globally, to take ownership of the planet."

Dinosaurs were most likely wiped out by a giant meteor that cooled Earth's temperatures below their threshold for survival.

An analogous fate could await humans if temperatures climb by five or six degrees Celsius, which climate scientists say could happen within a century.

But dinosaurs thrived for more than 150 million years before a cosmic pebble ended their extraordinary run, while modern humans have only been around for about 200,000 years, a snap of the fingers by comparison.

Another key difference: dinosaurs didn't know what hit them, and played no role in their own demise.

Humans, by contrast, have been the main architects of the enormous changes that are threatening to throw what scientists now call the Earth System out of whack.

Since Crutzen coined the term a decade ago, the Anthropocene has been eagerly adopted by scientists across a broad spectrum of disciplines.

"It triggered the realisation that we were in an entirely new era of planet Earth," said Will Steffen, head of Australian National University's Climate Change Institute.

It also triggered fierce debate.

At one level, the issues are narrow to the point of pedantry -- rock experts quibbling over whether mankind's present and future geological imprint merits recognition by the International Commission on Stratigraphy.

At the same time, however, the concept forces us to ponder whether humanity's outsized impact on the planet could lead to undesired, possibly uncontrollable, outcomes, and what, if anything, humanity should do about it.

That leaves scientists who may be more comfortable classifying rocks than rocking the boat in a tricky position.

-- 'Sculpting the Earth' --

---------------------------

For now, the man in the hot seat is University of Leicester professor Jan Zalasiewicz, who heads the group of geologists tasked with recommending whether the Anthropocene should be added to the 150-odd eons, eras, periods, epochs and ages into which the last 3.6 billion years of Earth's history has been officially divided.

"Jan must recognise the implications for society if his own tribe decides, using classical criteria, that there is not yet enough evidence to formally recognise a new boundary in the geological record," said Bryan Lovell, president of the British Geological Society and a professor at Cambridge.

Evidence of abrupt change -- on a geological time scale -- wrought by human hands would seem to be overwhelming.

The burning of fossil fuels has altered the composition of the atmosphere, pushing the concentration of carbon dioxide to levels unseen at least for 800,000 years, perhaps for three million.

The resulting global warming has itself set in motion other planetary-scale changes: massive melting of the parts of Earth normally covered by ice and snow (aka the cryosphere), and the acidification of the oceans.

Past shifts in the biosphere -- the realm of the living -- show up in sediment and rock, especially mass extinctions that have seen up to 90 percent of all lifeforms disappear within the geological blink of an eye.

There have been five such wipeouts over the last half billion years, and most scientists agree that we have now entered the sixth, with species disappearing at 100 to 1,000 times the so-called "background" rate.

Another key index is the rise of invasive species travelling in a globalised world via ship ballasts, air travel and old-fashioned smuggling.

"The mass homogenisation event" -- finding the same species everywhere -- "will be quite a clear signal in the archaeological record a million years from now," said Zalasiewicz.

Even the planet's outer skin, or lithosphere, has been transformed.

"We are sculpting the surface of the Earth," said James Syvitski, a professor at the University of Colorado, pointing to two centuries of industrial-scale mining, damming, deforestation and agriculture.

Thousands of dams built since the mid-19th century have "completely altered the planet's terrestrial plumbing," he said.

To validate the Anthropocene, all these changes will be measured against the range of variation in our current geological period -- the Holocene epoch -- which began some 12,000 years ago as Earth emerged from the last ice age.

"Human influence on the global environment must push the Earth system well beyond the Holocene envelope of variability," said Steffen.

By one key measure, at least, we already have: the concentration of CO2 in the atmosphere -- measured in parts per million -- remained in a narrow range of 260 to 285 for nearly 12,000 years. Today is stands at 390 ppm, and is sure to rise considerably higher in coming decades.

-- The 'golden spike' --

------------------------

If the hugely complex web of chemical and biological interactions that sustains most life does tip seriously out of kilter, the planet will find a new equilibrium, as it has in the past.

Earth, in other words, will do fine. Humans, on the other hand, may find the transition more than difficult.

"It is a planet that will be much warmer, much stormier, much less biodiverse," said Steffen. "We will need to be very resilient as a species."

In nailing down the Anthropocene, there is also a question of timing. Some scholars favour dating it to the start of agriculture, some 8,000 years ago.

Most, however, favour hammering the "golden spike" in the middle of the 19th century when the steam engine and then fossil fuels kicked off an exponential explosion in population and consumption that is still gathering pace.

Starting around 1950, the "Great Acceleration" has seen dozens of key indicators, plotted on a graph, take off like a rocket: population, damming of rivers, water and fertiliser use, paper consumption, tourism, and vehicles, to name a few.

These, in turn, have sparked correspondingly sharp rises in greenhouse gas concentrations, ozone depletion, great floods, depletion of fisheries, loss of forests, species loss.

The dramatic transformation we have seen so far has been driven mainly by the 20 percent of the world's population living in rich nations.

Crutzen said he hopes that putting a name -- the Anthropocene -- to these changes may help focus humanity's mind on the challenges ahead.

"It could well be a paradigm shift in scientific thinking," he said at the London meeting.

"But it will probably take another 20 years before it is formally accepted."

]]> Wed, 08 FEB 2012 08:56:47 AEST Miami FL (SPX) May 05, 2011 - An international team of scientists report on the first observatory experiment to study the dynamic microbial life of an ever-changing environment inside Earth's crust. University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science professor Keir Becker contributed the deep-sea technology required to make long-term scientific observations of life beneath the seafloor.

During the four-year subsurface experiment, the research team deployed the first in situ experimental microbial observatory systems below the flank of the Juan de Fuca Ridge, which is located off the coast of Washington (U.S.) and British Columbia (Canada).

Becker and UM Rosenstiel alumnus Andrew Fisher installed the sub-surface observatory technology known as CORK (Circulation Obviation Retrofit Kit), which seals the sub-surface borehole for undisturbed observations of the natural hydrogeological state and microbial ecosystem inside Earth's crust.

"Similar to a cork in a wine bottle, our technology stops fluids from moving in and out of the drilling hole," said Becker, a UM Rosenstiel School professor of marine geology and geophysics. "Ocean water is blocked from entering the hole and flushing out the natural system."

These natural laboratories allow scientists to investigate the hydrogeology, geochemistry, and microbiology of ocean crust.

A large reservoir of seawater exists in Earth's crust, which is thought to be the largest habitat on Earth.

This seawater aquifer supports a dynamic microbial ecosystem that is known to eat hydrocarbons and natural gas, and may have the genetic potential to store carbon.

Scientists are interested in better understanding the natural processes taking place below the seafloor, which also give rise to economically important ores along the seafloor and may play a role in earthquakes.

"The paper is important since it is the first in-situ experiment to study subsurface microbiology," said Becker, a co-author of the paper.

The new research paper, "Colonization of subsurface microbial observatories deployed in young ocean crust", was published in last month's issue of Multidisciplinary Journal of Microbial Ecology, a publication of the journal Nature.

The paper's co-authors include Becker, Beth Orcutt and Katrina Edwards from the University of Southern California, Wolfgang Bach and Michael Hentscher from University of Bremen in Germany, Andrew Fisher from the University of California Santa Cruz, Brandy Toner from University of Minnesota and C. Geoffrey Wheat from the University of Alaska.

]]> Wed, 08 FEB 2012 08:56:47 AEST Manila (AFP) April 17, 2011 - Philippine authorities said Sunday more people had been evacuated from towns and villages near a volcano island close to the capital amid increasing signs of seismic activity.

The National Disaster Risk Reduction and Management Council said the number evacuated had increased to 1,375 as of Saturday from four towns near Taal volcano, while seismologists recorded 10 volcanic earthquakes overnight.

Water temperatures and gas emissions also increased, seismologists said.

"This large rise in CO2 (carbon dioxide) concentration indicates gas release from the magma at depth," the council said.

It advised the public to stay away from hiking trails on the scenic island because of the possibility of explosions.

"Breathing air with (a) high concentration of gases can be lethal to humans, animals and may even cause damage to vegetation," it added.

The Philippine Institute of Volcanology and Seismology began detecting activity at Taal -- a popular tourist destination -- early this month and on April 9 raised the alert level to the second of five, indicating a state of moderate volcanic unrest.

Taal is one of the most unstable of the country's active volcanoes, with 33 eruptions in recorded history, the last in 1977.

]]> Wed, 08 FEB 2012 08:56:47 AEST Pasadena CA (JPL) Mar 14, 2011 - The latest evidence of the dominant role humans play in changing Earth's climate comes not from observations of Earth's ocean, atmosphere or land surface, but from deep within its molten core.

Scientists have long known that the length of an Earth day - the time it takes for Earth to make one full rotation - fluctuates around a 24-hour average. Over the course of a year, the length of a day varies by about 1 millisecond, getting longer in the winter and shorter in the summer.

These seasonal changes in Earth's length of day are driven by exchanges of energy between the solid Earth and fluid motions of Earth's atmosphere (blowing winds and changes in atmospheric pressure) and its ocean. Scientists can measure these small changes in Earth's rotation using astronomical observations and very precise geodetic techniques.

But the length of an Earth day also fluctuates over much longer timescales, such as interannual (two to 10 years), decadal (approximately 10 years), or those lasting multiple decades or even longer. A dominant longer timescale mode that ranges from 65 to 80 years was observed to change the length of day by approximately 4 milliseconds at the beginning of the 20th century.

These longer fluctuations are too large to be explained by the motions of Earth's atmosphere and ocean. Instead, they're due to the flow of liquid iron within Earth's outer core, where Earth's magnetic field originates. This fluid interacts with Earth's mantle to affect Earth's rotation.

While scientists cannot observe these flows directly, they can deduce their movements by observing Earth's magnetic field at the surface. Previous studies have shown that this flow of liquid iron in Earth's outer core oscillates, in waves of motion that last for decades with timescales that correspond closely to long-duration variations in Earth's length of day.

Still other studies have observed a link between the long-duration variations in Earth's length of day and fluctuations of up to 0.2 degrees Celsius (0.4 degree Fahrenheit) in Earth's long-term global average surface air temperature.

So how might all three of these variables - Earth's rotation, movements in Earth's core (formally known as the core angular momentum) and global surface air temperature - be related? That's what researchers Jean Dickey and Steven Marcus of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and colleague Olivier de Viron of the Universite Paris Diderot and Institut de Physique du Globe de Paris in France, set out to discover in a first-of-its-kind study.

The scientists mapped existing data from a model of fluid movements within Earth's core and data on yearly averaged length-of-day observations against two time series of observed annual global average surface temperature: one from NASA's Goddard Institute of Space Studies in New York that extends back to 1880, and another from the United Kingdom's Met Office that extends back to 1860.

Since total air temperature is composed of two components - temperature changes that occur naturally and those caused by human activities - the researchers used results from computer climate models of Earth's atmosphere and ocean to account for temperature changes due to human activities. These human-produced temperature changes were then subtracted from the total observed temperature records to generate corrected temperature records.

The researchers found that the uncorrected temperature data correlated strongly with data on movements of Earth's core and Earth's length of day until about 1930. They then began to diverge substantially: that is, global surface air temperatures continued to increase, but without corresponding changes in Earth's length of day or movements of Earth's core.

This divergence corresponds with a well-documented, robust global warming trend that has been widely attributed to increased levels of human-produced greenhouse gases.

But an examination of the corrected temperature record yielded a different result: the corrected temperature record remained strongly correlated with both Earth's length of day and movements of Earth's core throughout the entire temperature data series. The researchers performed robust tests to confirm the statistical significance of their results.

"Our research demonstrates that, for the past 160 years, decadal and longer-period changes in atmospheric temperature correspond to changes in Earth's length of day if we remove the very significant effect of atmospheric warming attributed to the buildup of greenhouse gases due to mankind's enterprise," said Dickey.

"Our study implies that human influences on climate during the past 80 years mask the natural balance that exists among Earth's rotation, the core angular momentum and the temperature at Earth's surface."

So what mechanism is driving these correlations? Dickey said scientists aren't sure yet, but she offered some hypotheses.

Since scientists know air temperature can't affect movements of Earth's core or Earth's length of day to the extent observed, one possibility is the movements of Earth's core might disturb Earth's magnetic shielding of charged-particle (i.e., cosmic ray) fluxes that have been hypothesized to affect the formation of clouds. This could affect how much of the sun's energy is reflected back to space and how much is absorbed by our planet.

Other possibilities are that some other core process could be having a more indirect effect on climate, or that an external (e.g. solar) process affects the core and climate simultaneously.

Regardless of the eventual connections to be established between the solid Earth and climate, Dickey said the solid Earth's impacts on climate are still dwarfed by the much larger effects of human-produced greenhouse gases. "The solid Earth plays a role, but the ultimate solution to addressing climate change remains in our hands," she concluded.

]]> Wed, 08 FEB 2012 08:56:47 AEST Gloucester Point VA (SPX) Mar 09, 2011 - An international team of researchers including professor Emmett Duffy of the Virginia Institute of Marine Science has published a comprehensive new analysis showing that loss of plant biodiversity disrupts the fundamental services that ecosystems provide to humanity.

Plant communities-threatened by development, invasive species, climate change, and other factors-provide humans with food, help purify water supplies, generate oxygen, and supply raw materials for building, clothing, paper, and other products.

The 9-member research team, led by professor Brad Cardinale of the University of Michigan, analyzed the results of 574 field and laboratory studies-conducted across 5 continents during the last 2 decades-that measured the changes in productivity resulting from loss of plants species.

This type of "meta-analysis" allows researchers to move beyond their own individual or collaborative studies to get a much more reliable global picture. Their study appears in the March special biodiversity issue of the American Journal of Botany.

"The idea that declining diversity compromises the functioning of ecosystems was controversial for many years," says Duffy, a marine ecologist who has studied the effects of biodiversity loss in seagrass beds.

"This paper should be the final nail in the coffin of that controversy. It's the most rigorous and comprehensive analysis yet, and it clearly shows that extinction of plant species compromises the productivity that supports Earth's ecosystems."

The team's analysis shows that plant communities with many different species are nearly 1.5 times more productive than those with only one species (such as a cornfield or carefully tended lawn), and ongoing research finds even stronger benefits of diversity when the various other important natural services of ecosystems are considered. Diverse communities are also more efficient at capturing nutrients, light, and other limiting resources.

The analysis also suggests, based on laboratory studies of algae, that diverse plant communities generate oxygen-and take-up carbon dioxide-more than twice as fast as plant monocultures.

The team's findings are consistent for plant communities both on land and in fresh- and saltwater, suggesting that plant biodiversity is of general and fundamental importance to the functioning of the Earth's entire biosphere.

Duffy, Loretta and Lewis Glucksman Professor of Marine Science at VIMS, says the team's findings are important locally because estuaries like Chesapeake Bay are naturally low in plant diversity, making them especially vulnerable to ecological surprises resulting from loss of species.

"Salt marshes and seagrass beds depend largely on one or a few species of plants that create the habitat structure," says Duffy. "When such species are lost, low diversity means there is often no one else to take their place and the effects can ripple out through the community of animals, potentially up to fishery species."

In addition to analyzing the general effects of biodiversity loss, the team also sought to determine the specific fraction of plant species needed to maintain the effective functioning of a particular ecosystem-important information for resource managers with limited human and financial resources to manage forests, marine reserves, and other protected areas on land and sea. The results of this effort were mixed, and the team's ongoing research is tackling this question.

Data from the study did suggest, however, that biodiversity loss may follow a "tipping-point" model wherein some fraction of species can be lost with minimal change to ecological processes, followed by a sharp drop in ecosystem function as species loss continues.

Biodiversity loss in the real world
Recognizing that their findings mostly rest on analysis of short-term experiments (generally a few days, weeks, or months) in relatively small settings, the researchers also attempted to determine how diversity effects "scale-up" to longer time scales, bigger areas, or both. The authors note that these are the real-world scales "at which species extinctions actually matter and at which conservation and management efforts take place."

The team's findings suggest that scale does indeed matter, and that small laboratory and field experiments typically underestimate the effects of biodiversity loss. In the researchers' own words, "Data are generally consistent with the idea that the strength of diversity effects are stronger in experiments that run longer, and in experiments performed at larger spatial scales."

Duffy is now further testing this scaling issue with a 3-year grant from the U.S. National Science Foundation. He is using the grant to establish a global experimental network for studying how nutrient pollution and changes in biodiversity impact seagrass beds.

The future of biodiversity studies
The American Journal of Botany study also identifies the additional information needed to better understand biodiversity loss and its effects. Important frontiers include additional studies of how small-scale diversity experiments scale-up to real ecosystems; how biodiversity loss compares to and interacts with other environmental stressors such as climate change, invasive species, low-oxygen dead zones, ocean acidification, and water pollution; and how species-level diversity compares in importance with diversity at other levels such as genetic and functional (e.g., herbivore, grazer, or carnivore)

Cardinale says information from these types of studies will put scientists "in a position to calculate the number of species needed to support the variety of processes required to sustain life in real ecosystems." He adds, "And we don't mean 'need' in an ethical or an aesthetic way. We mean an actual concrete number of species required to sustain basic life-support processes."

Study co-author Jarrett Byrnes, of the National Center for Ecological Analyses and Synthesis, says "Species extinction is happening now, and it's happening quickly. And unfortunately, our resources are limited. This means we're going to have to prioritize our conservation efforts, and to do that, scientists have to start providing concrete answers about the numbers and types of species that are needed to sustain human life. If we don't produce these estimates quickly, then we risk crossing a threshold that we can't come back from."

]]> Wed, 08 FEB 2012 08:56:47 AEST Washington DC (SPX) Feb 25, 2011 - People who want to eat healthy and live sustainably have a new way to measure their impact on the environment: a Web-based tool that calculates an individual's "nitrogen footprint." The device was created by University of Virginia environmental scientist James N. Galloway; Allison Leach, a staff research assistant at U.Va.; and colleagues from the Netherlands and the University of Maryland.

The calculator is a project of the International Nitrogen Initiative, a global network of scientists who share research and data on the nitrogen dilemma. The project was announced at the annual meeting of the American Association for the Advancement of Science in Washington.

What's the nitrogen dilemma? Though some residents of the Chesapeake Bay and Gulf of Mexico likely are familiar with it, it's unknown to most Americans outside the agricultural world. For the last 30 years, Galloway and other leading scientists have been noting fish kills in coastal areas, threats to human health as a result of air and water pollution, and changes to global biodiversity and climate. This tool is one of their attempts to foster more understanding of nitrogen's role in our lives.

"Nitrogen, as any farmer knows, is essential to plant life," said Galloway, associate dean for the sciences in the College of Arts and Sciences at U.Va. and the Sidman P. Poole Professor of Environmental Sciences. "But the widespread use of synthetic nitrogen fertilizer to boost crop production has resulted in excess nitrogen coming off farms - essentially adding unwanted, unneeded fertilizer to our natural systems, with disastrous results. The combustion of fossil fuels adds even more nitrogen to our environment. It's a largely untold story."

Scientists are calling nitrogen pollution a major environmental problem that includes significant damage to air and water quality in places such as the Chesapeake Bay, where the federal government has dedicated hundreds of millions of dollars to reducing nitrogen runoff from farms and industry. Similarly, nitrogen runoff from Midwestern farms that ultimately flows into the Gulf of Mexico is largely responsible for toxic algal blooms that have suffocated coastal waters, leading to hypoxic zones, resulting in the loss of fish and shellfish.

To raise awareness, Galloway, a pioneering nitrogen scientist, organized a global team of experts to develop the footprint calculator as an educational tool - one he and his colleagues hope will both raise the profile of the nitrogen issue and galvanize people into action. By measuring what and how much you eat, as well as other factors like how you travel, the calculator shows your impact on the nitrogen cycle.

The website also makes recommendations for how to lessen your "nitrogen footprint." They are similar to other sustainable living choices: reduce airplane travel, choose renewable energy and eat less meat, particularly beef (since cattle consume massive quantities of farmed feed, which requires much fertilizer). Professors and lecturers are already using the tool in classrooms to teach students how one individual can alter - and help restore - a natural nitrogen cycle.

"Solving the nitrogen dilemma is a major challenge of our time," Leach said. "By calculating our individual impact, and taking small steps to reduce it, we can all play a part - and send a strong message to our nation's leaders that we want this issue taken seriously."

This new footprint calculator is the first in a series of research tools, known as N-Print, which Galloway and his team are developing to connect the production of nitrogen with the policies used to manage it. The team is currently creating a similar calculator for farmers and other nitrogen users, as well as a tool for policymakers that will provide regional nitrogen emission ceilings, which will show how much nitrogen can be released in these regions without major negative environmental impact.

"There are readily available solutions to reducing nitrogen pollution," Galloway said. "By connecting consumers, producers and policymakers, we can solve it."

Chemical fertilizer use and combustion engines are the main sources of nitrogen pollution. Scientists who are recording dramatic changes to ecosystems from the U.S. to China say the disruption of the naturally occurring cycle of nitrogen through ecosystems due to human activity leads the list of global tipping points and have named it a top threat to global biodiversity. It contributes to human health problems, water pollution, ozone layer depletion, smog, climate change and coastal dead zones. Nitrous oxide, created mostly from grain and meat production, is also a greenhouse gas 300 times more potent than carbon dioxide.

This project is supported by the Agouron Institute, the U.S. Environmental Protection Agency, U.Va., and the Energy Research Center of the Netherlands.

]]> Wed, 08 FEB 2012 08:56:47 AEST Woods Hole MA (SPX) Feb 08, 2011 - They were called the Eighth Wonder of the World. Until the late 19th century, New Zealand's Pink and White Terraces along Lake Rotomahana on the North Island, attracted tourists from around the world, interested in seeing the beautiful natural formations created by a large geothermal system.

But the eruption of Mt. Tarawera on June 10, 1886, buried the terraces in sediment and caused the lake basin to enlarge, engulfing the land where the terraces stood. For more than a century, people have speculated whether any part of the Pink and White Terraces survived the eruption.

This week, scientists from New Zealand's GNS Science, one of several government laboratories, in collaboration with engineers and scientists from Woods Hole Oceanographic Institution (WHOI) and colleagues from Lamont-Doherty Earth Observatory of Columbia University and NOAA-PMEL, located portions of the long-lost Pink Terraces.

The research team, using autonomous underwater vehicles (AUVs) to map the bottom of Lake Rotomahana, are certain they have found the lower portions of the Pink Terraces on the lake floor. Project leader Cornel de Ronde, of GNS Science, said the team was elated by the discovery.

"The first sidescan sonar image gave a hint of a terraced structure so we scanned the area twice more and we are now 95 percent certain we are seeing the bottom two tiers of the Pink Terraces," de Ronde said.

Side-scan sonar and bathymetric data collected by two REMUS 100 AUVs clearly show crescent-shaped terraced structures in about 60 meters of water where the Pink Terraces were located prior to 1886. They are covered by a brownish lake sediment.

The free-swimming REMUS vehicles were developed by WHOI with funding from the US Navy and were operated by Amy Kukulya and Robin Littlefield of the WHOI Oceanographic Systems Laboratory (OSL) who travelled to New Zealand for the expedition.

Dan Fornari, a scientist with the WHOI Geology and Geophysics department, helped lead the expedition and, along with Marshall Swartz of the WHOI Physical Oceanography department, developed the underwater camera system used in the lake.

After detecting areas of interest with the AUV's sonar systems, the team used the underwater camera system, developed with funds from the U.S. National Science Foundation, to capture images of the lake floor where they were able to photograph some of the stepped terrace edges.

Dr. de Ronde said the rest of the Pink Terraces were either destroyed during the eruption, or are still concealed under thick sediment not able to be penetrated by high-frequency AUV sonars.

The scientists found no sign of the larger White Terraces in the part of the lake that matched their location prior to 1886. The two terraces, part of a very large on-land geothermal system, were separated by several hundred meters prior to the eruption.

There are very few examples of large land-based geothermal systems that have been torn apart by an eruption and become inundated in this way. Scientists hope the data collected during this expedition will help them better understand how geothermal systems respond to disruptions of this kind.

"It was very gratifying to take the tools and knowledge we've developed for ocean research and apply them to work in the lake, especially for a scientific project with so much Maori cultural significance."

In 2009, WHOI signed a memorandum of understanding with GNS and New Zealand's National Institute for Water and Atmospheric Research (NIWA) to expand research and technology development collaborations across the scientific disciplines in the southwest Pacific and within New Zealand territorial waters.

In addition to the work in Lake Rotomahana, the organizations are also collaborating on deep ocean research on the Kermadec Seamounts north of New Zealand's North Island using the Sentry AUV and TowCam deep-sea imaging system.

"We hope the success in Lake Rotomahana is the first of many scientific collaborations in this part of the world where there are many interesting research problems to investigate."

The project was a collaboration involving GNS Science, Woods Hole Oceanographic Institution in Massachusetts, Lamont-Doherty Earth Observatory at Columbia University in New York, the National Oceanic and Atmospheric Administration in Seattle, and the University of Waikato.

After this week's discovery, de Ronde paid tribute to colleagues from WHOI, saying "This result would not have been possible without the team from Woods Hole Oceanographic Institution and their American colleagues. Their contribution has been huge."

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