Novel ocean-crust mechanism could affect world’s carbon budget

Bathymetry of a rift segment of the North Guaymas spreading center in the central Gulf of California shows a series of subsurface features. They are interpreted to be shallow sills intruded into the sediment-filled basin up to 50 km from the rift axis (lower left). High-resolution imaging by sidescan sonar revealed nearly 100 potential hydrothermal vent sites (yellow points) believed to result from widespread emplacement of magma over an area 10 times wider than expected at mid-ocean ridges. Deep-sea photographic surveys at some of the sites (red points) found elevated temperatures and methane concentrations in near-bottom waters and vibrant chemosynthetic animal communities (upper right, photo, about 5m across) containing tubeworms, clams, crabs, bacterial mats, and microbially precipitated carbonate deposits. The intrusion of magma into the sediments has the potential to release significant amounts of carbon from the sediments, previously thought to act as a long term carbon repository. (Graphic by S. Adam Soule, Woods Hole Oceanographic Institution)
Bathymetry of a rift segment of the North Guaymas spreading center in the central Gulf of California shows a series of subsurface features. They are interpreted to be shallow sills intruded into the sediment-filled basin up to 50 km from the rift axis (lower left). High-resolution imaging by sidescan sonar revealed nearly 100 potential hydrothermal vent sites (yellow points) believed to result from widespread emplacement of magma over an area 10 times wider than expected at mid-ocean ridges. Deep-sea photographic surveys at some of the sites (red points) found elevated temperatures and methane concentrations in near-bottom waters and vibrant chemosynthetic animal communities (upper right, photo, about 5m across) containing tubeworms, clams, crabs, bacterial mats, and microbially precipitated carbonate deposits. The intrusion of magma into the sediments has the potential to release significant amounts of carbon from the sediments, previously thought to act as a long term carbon repository. (Graphic by S. Adam Soule, Woods Hole Oceanographic Institution)

The Earth is constantly manufacturing new crust, spewing molten magma up along undersea ridges at the boundaries of tectonic plates. The process is critical to the planet’s metabolism, including the cycle of underwater life and the delicate balance of carbon in the ocean and atmosphere.

Now, scientists at the Woods Hole Oceanographic Institution (WHOI) have observed ocean crust forming in an entirely unexpected way-one that may influence those cycles of life and carbon and, in turn, affect the much-discussed future of the world’s climate.

Working at the Guaymas basin in the Gulf of California, WHOI scientists confirmed what they suspected from brief glimpses of the area during previous missions: The inner Earth is injecting swaths of magma called sills as far as 50 kilometers away from the plate boundary, on each side of the ridge -nearly 10 times farther from such an active ocean ridge than had been observed before.

Unlike conventional ocean crust production, where magma bubbles up through volcano-like openings in a narrow (about 5 km-wide) zone at the plate boundary, these recently observed magmatic sills never quite make it to the ocean floor. Rather, they form when magma stops in the thick layers of organic-rich sediment filling the basin and spreads laterally.

Using a sound-wave emitting air gun, side-scan sonar, and ocean-bottom cameras, the scientists determined that the sills are consistently formed at the same shallow depth within the 1-2 km-thick sediment. Normally, when magma erupts at the seafloor, it spreads no farther than 5 km or less from the spreading ridges; any magma found further out than that is usually older material, carried that distance by spreading crust over time and buried deep beneath many years of sedimentation.

The report suggests that rather than escaping through vent openings in the crust confined to the plate boundary, the molten material “intrudes” at numerous points below the sediments up to 50 km from the seafloor ridge, which connects in the north to the San Andreas Fault. This “active, shallow magmatism,” releases nutrient-rich fluids from within the sediments that feed new communities of sea creatures much like those observed around vent sites on deep-water, mid-ocean ridges.

It also releases significant amounts of carbon from sediments, the scientists report in the current issue of the journal Nature Geoscience on Nov. 14. By raising the temperature of the surrounding sediments, the sills produce up to 10 times more CO2 and methane gas than a similar volume of volcanic rocks that spews through a vent onto the seafloor.

The researchers are not sure just how much of these greenhouse gases remain in the sediment and the water, how much they affect the biological communities, and how much CO2 and methane escapes into the atmosphere. But they do know they have observed a novel mechanism in creating ocean crust.

“There is something different about this ridge,” said geologist S. Adam Soule, a member of the WHOI research team led by fellow geologist Daniel Lizarralde. “Somehow it allows the magma to keep spreading.”

“What we see is something that is surprising to a lot of people,” said Lizarralde. “People are like, ‘How can the magma do that?'” But given the geology of this narrow-rift region, he says, the phenomenon “makes a lot of sense.” Most undersea volcanic areas are able to “focus” magma intrusion up through an opening that is only about 1 or 2 km wide, he says. “Whatever it is that’s different about Guaymas has something to do with controlling these focusing mechanisms.”

Even though it is “different” from conventional sites, Soule suspects the Gulf of California is far from the only place on the planet where this phenomenon is occurring. He says there are “lots of places,” including the Red Sea, with characteristics similar to those of the narrow sea between the Baja Peninsula and the North American continent. In addition to fairly recent sediment deposits, these areas of continental rifting feature coastal ocean upwelling resulting in “high biological productivity and organic-rich sediment,” the researchers report in their study.

Lizarralde, Soule and WHOI colleagues Jeff S. Seewald and Giora Proskurowski detected “thriving animal communities” near the sill areas, Soule said, including tubeworms and bacterial mats. These communities were fostered by the warm water percolating through the sediments to the sea floor, the researchers said.

The findings, Soule added, should be of significant interest to a wide range of scientific disciplines. “For biologists, it is the chemo-synthetic communities at the warm seeps,” he said. “Geologists want to know what they can learn about magmatism and how the ocean crust is built. And for climate scientists, it is critical that we have an accurate characterization of tectonic settings that are sources and sinks of carbon.”

The WHOI study, funded by the National Science Foundation, represents “a start in assessing the contribution of the seafloor spreading process to the global carbon budget,” David Goldberg of the Lamont Doherty Earth Observatory writes in an accompanying News and Views piece in Nature Geoscience. “Sills derived from intrusive volcanism in sedimentary basins have been linked to huge natural methane fluxes in the past.

“Further research concerning the biological uptake from seafloor vents is also needed. But what we know now is that sills such as those observed below the Gulf of California, which naturally vent fluids to the ocean, seem to be carbon sources as they cool. “

Lizarralde says the team has written a proposal to go back and further explore the area with other instruments to get a more accurate picture of the carbon flux at the sediment-ocean interface. “The carbon story still remains unclear,” he says.

Goldberg concurs that “such exploration of the sea floor is critical to assessing its potential as an anthropogenic carbon reservoir as well as to undertaking the Earth’s natural carbon budget.”

Satellites provide up-to-date information on snow cover

This image of Trans-Labrador Highway, located in Canada's province of Newfoundland and Labrador, shows a heavy excavator bucket and a snow plow clearing snow from the road. - Credits: A. Khan, Goverment of Newfoundland and Labrador
This image of Trans-Labrador Highway, located in Canada’s province of Newfoundland and Labrador, shows a heavy excavator bucket and a snow plow clearing snow from the road. – Credits: A. Khan, Goverment of Newfoundland and Labrador

ESA GlobSnow project led by the Finnish Meteorological Institute uses satellites to produce up-to-date information on global snow cover. The new database gives fresh information on the snow situation right after a snowfall. Gathering this information was not possible before when only land-based observations were available.

European Space Agency´s (ESA) GlobSnow project, led by the Finnish Meteorological Institute, can map the extent and volume of snow cover especially on the northern hemisphere. Launched at the beginning of November, the service provides almost real-time data on snow cover and snow depth. The purpose of this service, accessed through the GlobSnow website maintained by the Institute, is to create a global database containing the snow data gathered by satellites.

Global data on snow cover

Snowfall impedes transport but also causes floods in many countries. The seasons affect snow cover the most on the northern hemisphere. The average snow cover in winter extends over an area of 20-40 million square kilometres; in other words, the snow contains as much water as one billion Olympic swimming pools. At the same time, the snow cover is one of the most important factors affecting the global climate, meteorology and water systems. Long distances between observation stations, especially in the sparsely-populated regions of Eurasia and North America, have made it difficult to chart snow and its volume at global level.

More accurate climate models

The data produced by satellites are used in the forecasting of floods and in climate research. In the coming year, many countries will test application of the new material for making hydrological models and flood forecasts. GlobSnow also provides climate researchers with snow data extending over the past 30 years. Access to satellite data enables researchers to monitor and analyse climatic trends. It has been discovered, for instance, that the snow cover has shrunk globally; this is one indicator of climate change. The database also provides increasingly accurate input data for climate models, thereby further improving the quality and accuracy of climate models.

African dust caused red soil in southern Europe

Spanish and American researchers have conducted a mineralogical and chemical analysis to ascertain the origin of 'terra rossa' soil in the Mediterranean. The results of the study reveal that mineral dust from the African regions of the Sahara and Sahel, which emit between 600 and 700 tonnes of dust a year, brought about the reddish soil in Mediterranean regions such as Mallorca and Sardinia between 12,000 and 25,000 years ago. -  Anna Ávila
Spanish and American researchers have conducted a mineralogical and chemical analysis to ascertain the origin of ‘terra rossa’ soil in the Mediterranean. The results of the study reveal that mineral dust from the African regions of the Sahara and Sahel, which emit between 600 and 700 tonnes of dust a year, brought about the reddish soil in Mediterranean regions such as Mallorca and Sardinia between 12,000 and 25,000 years ago. – Anna Ávila

Spanish and American researchers have conducted a mineralogical and chemical analysis to ascertain the origin of “terra rossa” soil in the Mediterranean. The results of the study reveal that mineral dust from the African regions of the Sahara and Sahel, which emit between 600 and 700 tonnes of dust a year, brought about the reddish soil in Mediterranean regions such as Mallorca and Sardinia between 12,000 and 25,000 years ago.

“The first hint of the relationship between African dust and certain soils in the region of the Mediterranean is their reddish or reddish-brown colour, similar to that of African aerosol filters, caused by their clay content”, co-author of the study and researcher at the Centre for Ecological Research and Forestry Applications (CREAF) at the Universidad Autónoma de Barcelona, Anna Ávila explained to SINC.

The study, which has been published in Quaternary Science Reviews, finds that African mineral dust additions “play an important role” in the origin of the soils (palaeosols) in the Mediterranean region, namely on the island of Mallorca. The results resemble those published regarding the soils on Sardinia, “which indicates the likelihood of Africa being a common source”.

In turn, “African dust explains the origin of the ‘terra rossa’ soils in the Mediterranean region located on top of mother carbonate rock,” Ávila added.

In order to explain the origin of the reddish soils, the researchers considered three hypotheses: the non carbonate residual accumulation theory (soils are derived from the product of non carbonate weathering of the mother carbonate rock), the ascending ‘sesquioxide’ theory (accumulation of iron and aluminium hydroxides following capillary ascent from the bedrock) and the non-native soil accumulation theory (soil is formed by external sources, including airborne contributions).

The first two hypotheses were discarded due to the geochemical composition of the trace elements of red soils and the underlying rock being different. “The hypothesis of non-native (external) contribution was reinforced due to the geochemical value of the land coinciding with that of African dust,” the scientist stated.

However, although the analysis of the soil indicates that African dust is the main contributor to the formation of the palaeosol, “the underlying rock also contributes, probably with residual quartz,” the researcher added.

Origin and Destination of African Dust

“Terra rossa” (red soil in Italian) is located on carbonate rock (with a high content of carbonate) and is spread throughout the Iberian Peninsula, the South of France, the islands in the Mediterranean, Italy and along the coast of the Adriatic Sea, from Slovenia to Greece.
The largest sources of airborne mineral dust can be found in the Sahara and Sahel regions, with emissions of between 600 and 700 tonnes per year. The destination of this dust has recently aroused great interest among the scientific community for various reasons.

Apart from the formation of red soils, African dust has “adverse effects on human health, such as respiratory problems and reduced visibility. It also arouses interest due to its implications where climate change is concerned, with the role that mineral aerosols play in the radiation balance, nutrient deposition and oceanic fertilization”, Ávila explained.

Extreme global warming in the ancient past

The image shows the the scientific drilling ship JOIDES Resolution docked in Hobart, Tasmania. -  John Beck, IODP
The image shows the the scientific drilling ship JOIDES Resolution docked in Hobart, Tasmania. – John Beck, IODP

Variations in atmosphere carbon dioxide around 40 million years ago were tightly coupled to changes in global temperature, according to new findings published in the journal Science. The study was led by scientists at Utrecht University, working with colleagues at the NIOZ Royal Netherlands Institute for Sea Research and the University of Southampton.

“Understanding the relationship between the Earth’s climate and atmospheric carbon dioxide in the geological past can provide insight into the extent of future global warming expected to result from carbon dioxide emission caused by the activities of humans,” said Dr Steven Bohaty of the University of Southampton’s School of Ocean and Earth Science (SOES) based at the National Oceanography Centre in Southampton.

It has been known for some time that the long-term warmth of the Eocene (~56 to 34 million years ago) was associated with relatively high atmospheric carbon dioxide levels. However, scientists were previously unable to demonstrate tight-coupling between variations in atmospheric carbon dioxide and shorter-term changes in global climate.

To fill this gap in knowledge, the authors of the new study focused on one of the hottest episodes of Earth’s climate history – the Middle Eocene Climatic Optimum (MECO), which occurred around 40 million years ago.

Algae use photosynthesis to harvest the energy of the sun, converting carbon dioxide and water into the organic molecules required for growth. Different isotopes of carbon are incorporated into these molecules depending on the environmental conditions under which algae grow. Ancient climate can therefore be reconstructed by analysing the carbon isotope ratios of molecules preserved in fossilised algae.

The researchers took this approach to reconstruct variations in carbon dioxide levels across the MECO warming event, using fossilised algae preserved in sediment cores extracted from the seafloor near Tasmania, Australia, by the Ocean Drilling Program. They refined their estimates of carbon dioxide levels using information on the past marine ecosystem derived from studying changes in the abundance of different groups of fossil plankton.

Their analysis indicate that MECO carbon dioxide levels must have at least doubled over a period of around 400,000 years. In conjunction with these findings, analysis using two independent molecular proxies for sea surface temperature show that the climate warmed by between 4 and 6 degrees Celsius over the same period.

“We found a close correspondence between carbon dioxide levels and sea surface temperature over the whole period, suggesting that increased amounts of carbon dioxide in the atmosphere played a major role in global warming during the MECO,” said Bohaty.

The researchers consider it likely that elevated atmospheric carbon dioxide levels during the MECO resulted in increased global temperatures, rather than vice versa, arguing that the increase in carbon dioxide played the lead role.

“The change in carbon dioxide 40 million years ago was too large to have been the result of temperature change and associated feedbacks,” said co-lead author Peter Bijl of Utrecht University. “Such a large change in carbon dioxide certainly provides a plausible explanation for the changes in Earth’s temperature.”

The researchers point out that the large increase in atmospheric carbon dioxide indicated by their analysis would have required a natural carbon source capable of injecting vast amounts of carbon into the atmosphere.

The rapid increase in atmospheric carbon dioxide levels around 40 million years ago approximately coincides with the rise of the Himalayas and may be related to the disappearance of an ocean between India and Asia as a result of plate tectonics – the large scale movements of the Earth’s rocky shell (lithosphere). But, as explained by Professor Paul Pearson of Cardiff University in a perspective article accompanying the Science paper, the hunt is now on to discover the exact cause.

Oil will run dry before substitutes roll out

At the current pace of research and development, global oil will run out 90 years before replacement technologies are ready
At the current pace of research and development, global oil will run out 90 years before replacement technologies are ready

At the current pace of research and development, global oil will run out 90 years before replacement technologies are ready, says a new University of California, Davis, study based on stock market expectations.

The forecast was published online Monday (Nov. 8) in the journal Environmental Science & Technology. It is based on the theory that
long-term investors are good predictors of whether and when new energy technologies will become commonplace.

“Our results suggest it will take a long time before renewable replacement fuels can be self-sustaining, at least from a market
perspective,” said study author Debbie Niemeier, a UC Davis professor of civil and environmental engineering.

Niemeier and co-author Nataliya Malyshkina, a UC Davis postdoctoral researcher, set out to create a new tool that would help policymakers
set realistic targets for environmental sustainability and evaluate the progress made toward those goals.

Two key elements of the new theory are market capitalizations (based on stock share prices) and dividends of publicly owned oil companies
and alternative-energy companies. Other analysts have previously used similar equations to predict events in finance, politics and sports.

“Sophisticated investors tend to put considerable effort into collecting, processing and understanding information relevant to the
future cash flows paid by securities,” said Malyshkina. “As a result, market forecasts of future events, representing consensus predictions
of a large number of investors, tend to be relatively accurate.”

Niemeier said the new study’s findings are a warning that current renewable-fuel targets are not ambitious enough to prevent harm to
society, economic development and natural ecosystems.

“We need stronger policy impetus to push the development of these alternative replacement technologies along,” she said.

Foucault, revisited

Walk into nearly any science museum worth its salt and you’re likely to see a Foucault pendulum, a simple but impressive device for observing the Earth’s rotation. Such pendulums have been around for more than 150 years, and little about how they work remains a mystery today.

The only problem, according to Argentinean researcher Horacio Salva, is that the devices are generally large and unwieldy, making them impractical to install in places where space is at a premium. This limitation was something he and his colleagues at the Centro Atómico Bariloche in Argentina wanted to address.

Now in the American Institute of Physics journal Review of Scientific Instruments, Salva and colleagues report success in what he acknowledges was a fun side project — building two pendulums precisely enough to make measurements of the spinning Earth yet compact enough to fit in a lobby or classroom of just about any science building.

By definition, Foucault pendulums — which are named after the French physicist Léon Foucault who first conceived of one in the middle of the 19th century — count as a simple technology. Generally, a metal orb is suspended by a wire and hung from a height that can be dozens and dozens of feet. The orb is pulled back and released, and as it swings back and forth over the course of a day, it appears to slowly rotate in a circle. In fact what’s observed is the Earth moving underneath the pendulum, which swings back and forth in a fixed plane, like a gyroscope.

Or rather, it’s more accurate to say that pendulums swing in a mostly fixed plane. That’s because, as anyone who pushes a child in a swing can attest, it’s tough to keep a pendulum swinging in a straight line. Over time, due to the vagaries of friction and other forces, a pendulum will start to travel in an ellipse, an effect that can easily garble evidence of the Earth’s rotation, which for generations has been novel enough to astonish when first observed. Here’s the beginning of a February 23, 1908 article in The New York Times describing a Foucault pendulum display in the Big Apple: “Perhaps you were one of the crowd of people who saw the great Foucault pendulum experiment last week at Columbia University. Probably you watched it like the rest with openmouthed wonder.”

The heavier the suspended orb and the longer the wire, the more limited the elliptical drift. Similarly, older children on taller swings tend to fly straighter than younger children in the shorter toddler swings.

Consider the dimensions of an 80-year-old Foucault pendulum on display at Philadelphia’s Franklin Institute: a 180-pound-orb hangs from a wire 85 feet long and swings back and forth once every 10 seconds. The two pendulums built by Salva are kiddie-sized in comparison. In the case of the first, a 27-pound weight swings back and forth on a 16-foot-long piano wire once every 4 and a half seconds. The second pendulum uses the same weight and an even shorter wire. Using a copper ring underneath each orb to damp down the drift, Salva was able to easily observe and measure precession, the technical name for the movement of the Earth relative to the fixed swinging of the pendulums. Indeed his jiggering of the pendulums was able to tune out all but one percent of the elliptical “noise,” at least in the case of his longer pendulum.

Admittedly, says Salva, this new pendulum by no means has the precision necessary to make any groundbreaking new measurements. But the design, he says, is sophisticated enough to be a useful tool for teaching basic physics concepts to physics students and the general public.

“There’s obviously no pressure to do work like this,” said Salva, who in his day job studies far more sophisticated “pendulums” involving the elasticity of various materials. “It’s mostly for fun, though I think it may well help students in the future, too.”

Pointing to one possible application, the paper notes that the device was able to detect earthquakes of medium intensity that took place as far away as 765 km. “Some earthquakes can be seen, because the seismic wave moves the support of the pendulum increasing the ellipse of the moment and changing the precession speed,” said Salva.

Climate change: Water reservoir glacier

The researchers investigated the whole river basin region of certain glaciers in the Himalayas, the Andes, the Caucasus Mountains, Siberia, North America and New Zealand. -  Uni  Innsbruck
The researchers investigated the whole river basin region of certain glaciers in the Himalayas, the Andes, the Caucasus Mountains, Siberia, North America and New Zealand. – Uni Innsbruck

Glaciers of large mountain regions contribute, to some extent considerably, to the water supply of certain populated areas. However, in a recent study conducted by Innsbruck glaciologists and climatologists it has been shown that there are important regional differences. The results of the study are published in the scientific journal Proceedings of the National Academy of Sciences (PNAS).

In their recently published study the glaciologists and climatologists, headed by Prof. Georg Kaser and Dr. Ben Marzeion from the Institute of Geography of the University of Innsbruck, have demonstrated that the contribution potential of glaciers to the water supply of populated areas varies regionally. The scientists gathered data on the amount of precipitation on certain glaciers and calculated when the water is discharged and available in populated areas.”There is a big difference in whether the water is discharged in an arid period or in a period, when there usually is a lot of precipitation, e.g. in monsoon regions in Asia,” explains Ben Marzeion. “And there are regions, for instance around the Aral Sea, where precipitation happens in the mountain regions in winter. The glacier melt water runoff in summer is vital for the population living in this area.” The Innsbruck researchers modeled estimates that show human dependence on glacier melt in a certain region. They demonstrate that high-mountain communities are highly dependent on glacier melt water but the population density is usually relatively low in these regions. “The impact is a lot more dramatic in mid latitude river basins, where the population density is a lot higher and glacier melt still contributes to the available water reservoir to a large extent,” the climatologists explain.

Regional differences

The incentive of the study was the widespread discussion about the impact of climate change on water availability in highly populated regions. “In the last few years numbers have been named that do not pass a closer examination,” says glaciologist and climatologist Georg Kaser. “It is an exaggeration when it is claimed that the melting of glaciers endangers the water supply of 2 billion people.” With their study the Innsbruck scientists want to draw attention to the considerable regional differences regarding the problem of future water supply. “By all means, the expected climatic development may have detrimental effects for smaller high-mountain communities.”

The data for the study was obtained from the World Glacier Inventory, global temperature and precipitation data and the Global Digital Elevation Model. The researchers investigated the whole river basin region of certain glaciers in the Himalayas, the Andes, the Caucasus Mountains, Siberia, North America and New Zealand. “In principle, this is a simple research approach, which, nevertheless, provides us with important arguments for a more differentiated discussion in climate research,” says Georg Kaser, who is pleased about the results of the study, which has been published in the renowned scientific journal Proceedings of the National Academy of Sciences (PNAS). “With regard to the next report issued by the Intergovernmental Panel on Climate Change (IPCC), our data can be seen as the basis for regionally more precise estimations and they show that the impact of the expected climate change may be higher in some regions than in others,” says Kaiser.

Volcanic eruptions affect rainfall over Asian monsoon region

This photo shows an 18-kilometer-high plume from one of a series of eruptions in 1991 at Mount Pinatubo. -  USGS
This photo shows an 18-kilometer-high plume from one of a series of eruptions in 1991 at Mount Pinatubo. – USGS

Scientists have long known that large volcanic explosions can affect the weather by spewing particles that block solar energy and cool the air.

Some suspect that extended “volcanic winters” from gigantic eruptions helped kill off dinosaurs and Neanderthals.

In the summer following Indonesia’s 1815 Tambora eruption, frost wrecked crops as far away as New England, and the 1991 blowout of the Philippines’ Mount Pinatubo lowered average global temperatures by 0.7 degrees F–enough to mask the effects of greenhouse gases for a year or so.

Now, in research funded by the National Science Foundation (NSF)’s Division of Atmospheric and Geospace Sciences, scientists have discovered that eruptions also affect rainfall over the Asian monsoon region, where seasonal storms water crops for nearly half of Earth’s population.

Tree-ring researchers at Columbia University’s Lamont-Doherty Earth Observatory (LDEO) showed that big eruptions tend to dry up much of Central Asia, but bring more rain to southeast Asian countries including Vietnam, Laos, Cambodia, Thailand and Myanmar–the opposite of what many climate models predict.

A paper reporting their results appears in an advance online version of the American Geophysical Union (AGU) journal Geophysical Research Letters.

The growth rings of some tree species can be correlated with rainfall. LDEO’s Tree Ring Lab used tree rings from some 300 sites across Asia to measure the effects of 54 volcanic eruptions going back about 800 years.

The data came from LDEO’s new 1,000-year tree-ring atlas of Asian weather, which has produced evidence of long, devastating droughts.

“We might think of the solid Earth and the atmosphere as two different things, but everything in the system is interconnected,” said Kevin Anchukaitis, the paper’s lead author. “Volcanoes can be important players in climate over time.”

Large explosive eruptions send up sulfur compounds that turn into tiny sulfate particles high in the atmosphere, where they deflect solar radiation.

The resulting cooling on Earth’s surface can last for months or years.

Not all eruptions have that effect, however. For instance, the continuing eruption of Indonesia’s Merapi this fall has killed dozens, but this latest episode is probably not big enough by itself to effect large-scale weather changes, scientists believe.

As for rainfall, in the simplest models, lowered temperatures decrease evaporation of water from the surface to the air. Less water vapor translates to less rain.

But matters are greatly complicated by atmospheric circulation patterns, cyclic changes in temperatures over the oceans, and the shapes of land masses.

Until now, most climate models incorporating changes in the sun and the atmosphere have predicted that volcanic explosions would disrupt the monsoon by bringing less rain to southeast Asia–but the researchers found the opposite.

They studied several eruptions, including one in 1258 from an unknown tropical site, thought to be the largest of the last millennium; the 1600-1601 eruption of Peru’s Huaynaputina; Tambora in 1815; the 1883 explosion of Indonesia’s Krakatau; Mexico’s El Chichón in 1982; and Pinatubo.

Tree rings showed that huge swaths of southern China, Mongolia and surrounding areas consistently dried up in the year or two following big events, while mainland southeast Asia received increased rain.

The researchers believe there are many possible factors involved.

“The data only recently became available to test the models,” said Rosanne D’Arrigo, one of the paper’s co-authors. “There’s a lot of work to be done to understand how all these different forces interact.”

In some episodes pinpointed by the study, it appears that strong cycles of the El Niño-Southern Oscillation, which drives temperatures over the Pacific and Indian Oceans and is thought to strongly affect the Asian monsoon, might have counteracted eruptions, lessening their drying or moistening effects. p>

But it could work the other way, too, said Anchukaitis; if atmospheric dynamics and volcanic eruptions come together with the right timing, they could reinforce one another–with drastic results.

“Then you get flooding or drought, and neither flooding nor drought is good for the people living in those regions,” he said.

Ultimately, said Anchukaitis, such studies should help scientists refine models of how natural and man-made forces might act together to shift weather patterns–a vital question for all areas of the world.

Earth’s climate change 20,000 years ago reversed the circulation of the Atlantic Ocean

The Atlantic Ocean circulation (termed meridional overturning circulation, MOC) is an important component of the climate system. Warm currents, such as the Gulf Stream, transport energy from the tropics to the subpolar North Atlantic and influence regional weather and climate patterns. Once they arrive in the North the currents cool, their waters sink and with them they transfer carbon from the atmosphere to the abyss. These processes are important for climate but the way the Atlantic MOC responds to climate change is not well known yet.

An international team of investigators under the leadership of two researchers from the UAB now demonstrates the response of the Atlantic MOC to climate change in the past. The new research results will be published on 4 November 2010 in the international front-line journal NATURE. The research project was led by Rainer Zahn (ICREA researcher) and Pere Masque, both of the UAB at the Institut de Ciència i Tecnologia Ambientals (ICTA) and Department of Physics. With collaborators at the universities of Seville, Oxford and Cardiff (UK) they investigated the distribution of isotopes in the Atlantic Ocean that are generated from the natural decay of uranium in seawater and are distributed with the flow of deep waters across the Atlantic basin. The young investigator Cesar Negre studied the natural abundance of these isotopes in the seafloor sediments 2.5 km deep in the South Atlantic and achieved a PhD degree in the Environmental Science and Technology doctoral program at ICTA.

The study shows that the ocean circulation was very different in the past and that there was a period when the flow of deep waters in the Atlantic was reversed. This happened when the climate of the North Atlantic region was substantially colder and deep convection was weakened. At that time the balance of seawater density between the North and South Atlantic was shifted in such a way that deep water convection was stronger in the South Polar Ocean. Recent computer models simulate a reversal of the deep Atlantic circulation under such conditions while it is only now with the new data generated by UAB scientists and their colleagues from Seville and the UK that the details of the circulation reversal become apparent. This situation occurred during the ice age 20,000 years ago. Although this was far back in time the results are relevant for our climate today and in the near future. The new study shows that the Atlantic MOC in the past was very sensitive to changes in the salt balance of Atlantic Ocean currents. Similar changes in seawater salt concentration are expected to occur in the North Atlantic in the course of climate warming over the next 100 years. Therefore the data to be published in Nature offer the climate modelling community the opportunity to calibrate their models and improve their capacity to predict reliably future ocean and climate changes.

Water flowing through ice sheets accelerates warming, could speed up ice flow

Standing melt water in Greenland crevasses can carry warmth to the ice sheet's interior, accelerating the thermal response of the ice sheet to climate change. -  Image courtesy Konrad Steffen, CIRES
Standing melt water in Greenland crevasses can carry warmth to the ice sheet’s interior, accelerating the thermal response of the ice sheet to climate change. – Image courtesy Konrad Steffen, CIRES

Melt water flowing through ice sheets via crevasses, fractures and large drains called moulins can carry warmth into ice sheet interiors, greatly accelerating the thermal response of an ice sheet to climate change, according to a new study involving the University of Colorado at Boulder.

The new study showed ice sheets like the Greenland Ice Sheet can respond to such warming on the order of decades rather than the centuries projected by conventional thermal models. Ice flows more readily as it warms, so a warming climate can increase ice flows on ice sheets much faster than previously thought, said the study authors.

“We are finding that once such water flow is initiated through a new section of ice sheet, it can warm rather significantly and quickly, sometimes in just 10 years, ” said lead author Thomas Phillips, a research scientist with Cooperative Institute for Research in Environmental Sciences. CIRES is a joint institute between CU-Boulder and the National Oceanic and Atmospheric Administration.

Phillips, along with CU-Boulder civil, environmental and architectural engineering Professor Harihar Rajaram and CIRES Director Konrad Steffen described their results in a paper published online this week in Geophysical Research Letters.

Conventional thermal models of ice sheets do not factor in the presence of water within the ice sheet as a warming agent, but instead use models that primarily consider ice-sheet heating by warmer air on the ice sheet surface. In water’s absence, ice warms slowly in response to the increased surface temperatures from climate change, often requiring centuries to millennia to happen.

But the Greenland ice sheet is not one solid, smooth mass of ice. As the ice flows towards the coast, grating on bedrock, crevasses and new fractures form in the upper 100 feet of the ice sheet. Melt water flowing through these openings can create “ice caves” and networks of “pipes” that can carry water through the ice and spreading warmth, the authors concluded.

To quantify the influence of melt water, the scientists modeled what would happen to the ice sheet temperature if water flowed through it for eight weeks every summer — about the length of the active melt season. The result was a significantly faster-than-expected increase in ice sheet warming, which could take place on the order of years to decades depending on the spacing of crevasses and other “pipes” that bring warmer water into the ice sheet in summer.

“The key difference between our model and previous models is that we include heat exchange between water flowing through the ice sheet and the ice,” said Rajaram.

Several factors contributed to the warming and resulting acceleration of ice flow, including the fact that flowing water into the ice sheets can stay in liquid form even through the winter, slowing seasonal cooling. In addition, warmer ice sheets are more susceptible to increases of water flow, including the basal lubrication of ice that allows ice to flow more readily on bedrock.

A third factor is melt water cascading downward into the ice, which warms the surrounding ice. In this process the water can refreeze, creating additional cracks in the more vulnerable warm ice, according to the study.

Taken together, the interactions between water, temperature, and ice velocity spell even more rapid changes to ice sheets in a changing climate than currently anticipated, the authors concluded. After comparing observed temperature profiles from Greenland with the new model described in the paper, the authors concluded the observations were unexplainable unless they accounted for warming.

“The fact that the ice temperatures warm rather quickly is really the key piece that’s been overlooked in models currently being used to determine how Greenland responds to climate warming,” Steffen said. “However, this process is not the ‘death knell’ for the ice sheet. Even under such conditions, it would still take thousands of years for the Greenland ice sheet to disappear, Steffen said.