Prehistoric global cooling caused by CO2, research finds

Ice in Antarctica suddenly appeared – in geologic terms – about 35 million years ago. For the previous 100 million years the continent had been essentially ice-free.


The question for science has been, why? What triggered glaciers to form at the South Pole?

Matthew Huber, assistant professor of earth and atmospheric sciences at Purdue University, says no evidence of global cooling during the period had been found.

“Previous evidence points paradoxically to a stable climate at the same time this event, one of the biggest climate events in Earth’s history, was happening,” Huber says.

However, in a paper published this week in the journal Science, a team of researchers found evidence of widespread cooling. Additional computer modeling of the cooling suggests that the cooling was caused by a reduction of greenhouse gases in the atmosphere.

Even after the continent of Antarctica had drifted to near its present location, its climate was subtropical. Then, 35.5 million years ago, ice formed on Antarctica in about 100,000 years, which is an “overnight” shift in geological terms.

“Our studies show that just over thirty-five million years ago, ‘poof,’ there was an ice sheet where there had been subtropical temperatures before,” Huber says. “Until now we haven’t had much scientific information about what happened.”

Before the cooling occurred at the end of the Eocene epoch, the Earth was warm and wet, and even the north and south poles experienced subtropical climates. The dinosaurs were long gone from the planet, but there were mammals and many reptiles and amphibians. Then, as the scientists say, poof, this warm wet world, which had existed for millions of years, dramatically changed. Temperatures fell dramatically, many species of mammals as well as most reptiles and amphibians became extinct, and Antarctica was covered in ice and sea levels fell.

History records this as the beginning of the Oligocene epoch, but the cause of the cooling has been the subject of scientific discussion and debate for many years.

The research team found before the event ocean surface temperatures near present-day Antarctica averaged 77 degrees Fahrenheit (25 degrees Celsius).

Mark Pagani, professor of geology and geophysics at Yale University, says the research found that air and ocean surface temperatures dropped as much as 18 degrees Fahrenheit during the transition.

“Previous reconstructions gave no evidence of high-latitude cooling,” Pagani says. “Our data demonstrate a clear temperature drop in both hemispheres during this time.”

The research team determined the temperatures of the Earth millions of years ago by using temperature “proxies,” or clues. In this case, the geologic detectives looked for the presence of biochemical molecules, which were present in plankton that only lived at certain temperatures. The researchers looked for the temperature proxies in seabed cores collected by drilling in deep-ocean sediments and crusts from around the world.

“Before this work we knew little about the climate during the time when this ice sheet was forming,” Huber says.

Once the team identified the global cooling, the next step was to find what caused it.

To find the result, Huber used modern climate modeling tools to look at the prehistoric climate. The models were run on a cluster-type supercomputer on Purdue’s campus.

“That’s what climate models are good for. They can give you plausible reasons for such an event,” Huber says. “We found that the likely culprit was a major drop in greenhouse gases in the atmosphere, especially CO2. From the temperature data and existing proxy records indicating a sharp drop in CO2 near the Eocene-Oligocene boundary, we are establishing a link between the sea surface temperatures and the glaciation of Antarctica.”

Huber says the modeling required an unusually large computing effort. Staff at Information Technology at Purdue assisted in the computing runs.

“My simulations produced 50 terabytes of data, which is about the amount of data you could store in 100 desktop computers. This represented 8,000 years of climate simulation,” Huber says.

The computation required nearly 2 million computing hours over two years on Pete, Purdue’s 664-CPU Linux cluster.

“This required running these simulations for a long time, which would not have been allowed at a national supercomputing center,” Huber says. “Fortunately, we had the resources here on campus, and I was able to use Purdue’s Pete to do the simulation.”

2008 was Earth’s coolest year since 2000

Climatologists at the NASA Goddard Institute for Space Studies (GISS) in New York City have found that 2008 was the coolest year since 2000. The GISS analysis also showed that 2008 is the ninth warmest year since continuous instrumental records were started in 1880.

The ten warmest years on record have all occurred between 1997 and 2008.

The GISS analysis found that the global average surface air temperature was 0.44°C (0.79°F) above the global mean for 1951 to 1980, the baseline period for the study. Most of the world was either near normal or warmer in 2008 than the norm. Eurasia, the Arctic, and the Antarctic Peninsula were exceptionally warm (see figures), while much of the Pacific Ocean was cooler than the long-term average.

The relatively low temperature in the tropical Pacific was due to a strong La Niña that existed in the first half of the year, the research team noted. La Niña and El Niño are opposite phases of a natural oscillation of equatorial Pacific Ocean temperatures over several years. La Niña is the cool phase. The warmer El Niño phase typically follows within a year or two of La Niña.

The temperature in the United States in 2008 was not much different than the 1951-1980 mean, which makes it cooler than all the previous years this decade.

“Given our expectation that the next El Niño will begin this year or in 2010, it still seems likely that a new global surface air temperature record will be set within the next one to two years, despite the moderate cooling effect of reduced solar irradiance,” said James Hansen, director of GISS. The Sun is just passing through solar minimum, the low point in its 10- to 12-year cycle of electromagnetic activity, when it transmits its lowest amount of radiant energy toward Earth.

The GISS analysis of global surface temperature incorporates data from the Global Historical Climatology Network of the National Oceanic and Atmospheric Administration’s National Climate Data Center; the satellite analysis of global sea surface temperature of Richard Reynolds and Thomas Smith of NOAA; and Antarctic records of the international Scientific Committee on Antarctic Research.

“GISS provides the ranking of global temperature for individual years because there is a high demand for it from journalists and the public,” said Hansen. “The rank has scientific significance in some cases, such as when a new record is established. But rank can also be misleading because the difference in temperature between one year and another is often less than the uncertainty in the global average.”

Marine scientists to investigate role of equatorial Pacific ocean in global climate system

In early March, an international team of scientists will set sail aboard the drill ship JOIDES Resolution on the first of two Integrated Ocean Drilling Program (IODP) expeditions to the equatorial Pacific Ocean.

The second expedition will follow immediately afterward in May. Both are grouped into one science program, known as the Pacific Equatorial Age Transect (PEAT).

The results will lead to a clearer understanding of Earth’s climate over the past 55 million years–a vital component to knowing what future course the planet’s climate will take, scientists believe.

“These expeditions focused on climate change come at a critical time,” said Julie Morris, director of the National Science Foundation (NSF)’s Division of Ocean Sciences, which supports IODP. “During the next year, sea-floor drilling related to climate change will happen from pole to pole.”

The PEAT expeditions aim to recover a continuous Cenozoic record (from 65.5 million years ago to the present) of sediments beneath the equatorial Pacific Ocean. Geologists will drill into the crust on the Pacific tectonic plate along the equator.

The first research effort, Expedition 320, is planned for March 5 through May 5, 2009; Expedition 321 will take place from May 5 through July 5, 2009.

Co-chief scientists of Expedition 320 are Heiko Palike of the University of Southampton, U.K., and Hiroshi Nishi of Hokkaido University in Japan; of Expedition 321, Mitch Lyle of Texas A&M University in the U.S., and Isabella Raffi of the Universita “G. D’Annunzio” Campus Universitario in Italy.

Earlier scientific ocean drilling expeditions to the equatorial Pacific yielded discoveries about past climate conditions and the past position of the Pacific tectonic plate relative to the equator.

However, they did not obtain continuous sediment records the two PEAT expeditions will recover seafloor sediment cores with an unbroken record.

“The cores will help us understand how and why productivity in the Pacific changed over time,” said Morris, “and provide information about rapid biological evolution and turnover during times of climatic stress.”

The equatorial Pacific is a major center of solar warming, a region of high productivity, and a primary region for carbon dioxide exchange from the deep ocean to the atmosphere.

It is also the source region for the El Niño-Southern Oscillation phenomenon. The equatorial Pacific also helps maintain global climates, and drives climate change.

Over the last 55 million years, global climate has varied dramatically from extreme warmth to glacial cold. These climate variations have been imprinted on the biogenic-rich sediments that accumulated in the equatorial zone.

Information from the PEAT expeditions will help scientists understand how Earth was able to maintain very warm climates relative to the 20th century, even though solar radiation received at the earth’s surface has remained nearly constant for the last 55 million years.

A sprightly explanation for UFO sightings?

The appearance of a 'sprite' (about 30 miles high by 30 miles wide), flashing above a distant thunderstorm. The 'sprite' is about 175-250 miles away from the camera. -  ILAN Science Team
The appearance of a ‘sprite’ (about 30 miles high by 30 miles wide), flashing above a distant thunderstorm. The ‘sprite’ is about 175-250 miles away from the camera. – ILAN Science Team

In legend, sprites are trolls, elves and other spirits that dance high above our ozone layer. But scientists at Tel Aviv University have discovered that some very real “sprites” are zipping across the atmosphere as well, providing a possible explanation for those other legendary denizens of the skies, UFOs.

Thunderstorms, says Prof. Colin Price, head of the Geophysics and Planetary Sciences Department at Tel Aviv University, are the catalyst for a newly discovered natural phenomenon he calls “sprites.” He and his colleagues are one of the leading teams in the world studying the phenomenon, and Prof. Price leads the study of “winter sprites” ― those that appear only in the northern hemisphere’s winter months.

“Sprites appear above most thunderstorms,” explains Prof. Price, “but we didn’t see them until recently. They are high in the sky and last for only a fraction of a second.” While there is much debate over the cause or function of these mysterious flashes in the sky, they may, Prof. Price says, explain some bizarre reports of UFO sightings.

An Electrifying Discovery

Sprites are described as flashes high in the atmosphere, between 35 and 80 miles from the ground, much higher than the 7 to 10 miles where regular lightning bolts usually occur.

“Lightning from the thunderstorm excites the electric field above, producing a flash of light called a sprite,” explains Prof. Price. “We now understand that only a specific type of lightning is the trigger that initiates sprites aloft.”

Though sprites have existed for millions of years, they were first discovered and documented only by accident in 1989 when a researcher studying stars was calibrating a camera pointed at the distant atmosphere where sprites occur.

“Sprites, which only occur in conjunction with thunderstorms, never occur on their own, and are cousins to similar natural phenomenon dubbed by atmospheric electricians as ‘elves,’ ‘goblins’ and ‘trolls,'” Prof. Price says. These flashes are so named because they appear to “dance” in the sky, which may explain some UFO sightings.

Candles on a Celestial Birthday Cake

Tel Aviv University’s research team is one of the leading global groups studying the phenomenon. But Prof. Price and his students are now working in collaboration with other Israeli scientists from The Open University and The Hebrew University to take three-dimensional pictures of sprites to gain a better understanding of their structure. Using remote-controlled roof-mounted cameras, the researchers are able to look at the thunderstorms that produce sprites when they are still over the Mediterranean Sea.

From their unique vantage point in Israel, the researchers are leading the world in the study of winter sprites. Prof. Price’s new camera techniques, in particular, have revealed the sprites’ circular structures, which are much like those of candles on a birthday cake. Using triangulation, Prof. Price and his team have also been able to calculate the dimensions of the sprites’ features. “The candles in the sprites are up to 15 miles high, with the cluster of candles 45 miles wide — it looks like a huge birthday celebration!”

Because of their high altitude, sprites may also have an impact on the chemistry of the Earth’s ozone layer. “Since they are relatively infrequent, the global impact is likely small,” says Prof. Price. “But we’re researching that now.”

Billions of years ago, microbes were key in developing modern nitrogen cycle

As the world marks the 200th anniversary of Charles Darwin’s birth, there is much focus on evolution in animals and plants. But new research shows that for the countless billions of tiniest creatures – microbes – large-scale evolution was completed 2.5 billion years ago.

“For microbes, it appears that almost all of their major evolution took place before we have any record of them, way back in the dark mists of prehistory,” said Roger Buick, a University of Washington paleontologist and astrobiologist.

All living organisms need nitrogen, a basic component of amino acids and proteins. But for atmospheric nitrogen to be usable, it must be “fixed,” or converted to a biologically useful form. Some microbes turn atmospheric nitrogen into ammonia, a form in which the nitrogen can be easily absorbed by other organisms.

But the new research shows that about 2.5 billion years ago some microbes evolved that could carry the process a step further, adding oxygen to the ammonia to produce nitrate, which also can be used by organisms. That was the beginning of what today is known as the aerobic nitrogen cycle.

The microbes that accomplished that feat are on the last, or terminal, branches of the bacteria and archaea domains of the so-called tree of life, and they are the only microbes capable of carrying out the step of adding oxygen to ammonia.

The fact that they are on those terminal branches indicates that large-scale evolution of bacteria and archaea was complete about 2.5 billion years ago, Buick said.

“Countless bacteria and archaea species have evolved since then, but the major branches have held,” said Buick, a UW professor of Earth and space sciences.

He is the corresponding author of the research, which appears in the Feb. 20 edition of Science. Lead author is Jessica Garvin, a UW Earth and space sciences graduate student. Other authors are Ariel Anbar and Gail Arnold of Arizona State University and Alan Jay Kaufman of the University of Maryland. The work was funded by NASA and the National Science Foundation.

The scientists examined material from a half-mile-deep core drilled in the Pilbara region of northwest Australia. They looked specifically at a section of shale from 300 to 650 feet deep, deposited 2.5 billion years ago, and found telltale isotope signatures created in the process of denitrification, the removal of oxygen from nitrate.

If denitrification was occurring, then nitrification – the addition of oxygen to ammonia to form nitrate – also must have been taking place, Buick said. That makes the find the earliest solid evidence for the beginning of the aerobic nitrogen cycle.

“What this shale deposit has done is record the onset of the modern nitrogen cycle,” he said. “This was a life-giving nutrient then and remains so today. That’s why you put nitrogen fertilizer on your tomato plants, for example.”

The discovery gives clues about when and how the Earth’s atmosphere became oxygen rich, Buick believes.

Geochemical examination of stratigraphic samples from the core indicates that atmospheric oxygen rose in a temporary “whiff” about 2.5 billion years ago. The whiff lasted long enough to be recorded in the nitrogen isotope record, then oxygen dropped back to very low levels before the atmosphere became permanently oxygenated about 2.3 billion years ago.

It is unclear why the oxygen level declined following the temporary increase. It could have been that the oxygen was depleted rapidly as it reacted with chemicals and minerals that had not been exposed to oxygen previously, Buick said. Or something could have halted the photosynthesis that produced the oxygen in the first place.

But it seems clear, he said, that the tiniest creatures played a crucial role in completing the nitrogen cycle that life depends on today.

“All microbes are amazing chemists compared to us. We’re really very boring, metabolically,” Buick said.

“To understand early evolution of life, we have to know how organisms were nourished and how they evolved. This work helps us on both of those counts,” he said.

Scientists find black gold amidst overlooked data

About half of the oil in the ocean bubbles up naturally from the seafloor, with Earth giving it up freely like it was of no value. Likewise, NASA satellites collect thousands of images and 1.5 terrabytes of data every year, but some of it gets passed over because no one thinks there is a use for it.

Scientists recently found black gold bubbling up from an otherwise undistinguished mass of ocean imagery. Chuanmin Hu, an optical oceanographer at the University of South Florida, St. Petersburg, and colleagues from the National Oceanic and Atmospheric Administration (NOAA) and the University of Massachusetts-Dartmouth (UMass), found that they could detect oil seeping naturally from the seafloor of the Gulf of Mexico by examining streaks amid the reflected sunlight on the ocean’s surface.

Most researchers usually discard such “sun glint” data as if they were over-exposed photos from a camera. “Significant sun glint is sometimes thought of as trash, particularly when you are looking for biomass and chlorophyll,” said Hu. “But in this case, we found treasure.”

The new technique could provide a more timely and cost-effective means to survey the ocean for oil seeps, to monitor oil slicks, and to differentiate human-induced spills from seeps.

Oil decreases the roughness of the ocean surface. Depending on the angles of the camera and of the light reflection, oil creates contrasting swaths that can show up in airborne images as either lighter or darker than the surrounding waters.

The detection and monitoring of oil spills and seeps by satellite is not new. Visible, infrared, microwave, and radar sensors have all been used, with synthetic aperture radar (SAR) being the most popular and reliable method in recent years according to the study authors. SAR imagery can be very expensive, the authors note, and timely, repeat coverage is not always possible, particularly in tropical regions.

Using imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA’s Terra and Aqua satellites, Hu and colleagues assert, is far cheaper because the data is collected daily and provided freely by NASA, without the need for special observation requests. And the polar orbits of Terra and Aqua allow images of oil slicks to be collected several times per week in tropical regions and perhaps several times a day at higher latitudes.
The description of the new technique was published in January in Geophysical Research Letters.

Hu actually happened upon the oil imagery while looking for signs of harmful algal blooms-commonly referred to as “red tide”-in the western Gulf of Mexico. Examining MODIS images, he kept noticing streaks across the sun glint reflections. After conferring with study co-authors Xiaofeng Li and William Pichel of NOAA and Frank Muller-Karger of UMass, Hu became aware that the streaks could be oil from natural seeps on the seafloor.

Hu and colleagues then defined a geographic area of the western Gulf and obtained MODIS images for the month of May for nine consecutive years (2000 to 2008) from NASA’s Goddard Space Flight Center, Greenbelt, Md. The team reviewed more than 200 images containing sun glint, and found more than 50 with extensive oil slicks.

Exactly how much oil naturally seeps out of the seafloor is unknown, and most estimates are very crude because there has never been a proper global survey made for the public record. Researchers identified the natural seepage rate as a critical unanswered question when the National Academy of Sciences compiled its third Oil in the Sea report in 2003.

“This capacity for detecting oil in the ocean has great potential, not just for oil seeps but for responding to oil spills,” said Chris Reddy, a marine chemist at the Woods Hole Oceanographic Institution in Massachusetts. “Scientists might be able to use this to forensically study old spills, to watch how new ones evolve in real time, and to rule out a spill when there is none. Ultimately, this could lead to a better use of our public resources.”

The technique could be useful for detecting and monitoring oil spills from ships and other platforms, though Hu emphasized that the spills must be large enough (at least hundreds of meters or feet) to be visible in the MODIS imagery. If there is suspicion of a large human-caused spill, for instance, researchers would be able to review ocean imagery to see if the slick was present before the alleged spill, indicating a natural seepage. On the other hand, MODIS satellite imagery collected on a regular basis could help coastal managers track and mitigate the effects of large accidental spills.

The new method is not perfect, as cloud cover or a lack of sun glint can limit its use. Hu and colleagues suggest it may be best used as a complement to SAR, which penetrates cloud cover and can be tilted to get the necessary imaging angle.

“If you can get an image on a two- to three-day time frame and anywhere on the globe, that’s pretty spectacular,” said Reddy. “The first few days are critical to tracking oil in the ocean, so it helps to be able to use technology in real time to make informed decisions about cleanup.”

Erosion rates double along portion of Alaska’s coast

Skyrocketing coastal erosion occurred in Alaska between 2002 and 2007 along a 64 kilometer (40 mile) stretch of the Beaufort Sea, a new study finds. The surge of erosion in recent years, averaging more than double historical rates, is threatening coastal towns and destroying Alaskan cultural relics.

Average annual erosion rates along this segment of the Beaufort Sea, which lies North of Alaska, had already climbed from about 6.1 m (20 ft) per year between the mid-1950s and late-1970s, to 8.5 m (28 ft.) per year between the late-1970s and early 2000s, the study’s authors note. The most recent erosion rates reached an average of 14 meters (45 feet) per year during the 2002-2007 period, reported Benjamin Jones, a geologist with the U.S Geological Survey in Anchorage, and his colleagues on February 14 in Geophysical Research Letters, a journal of the American Geophysical Union (AGU).

Changing arctic conditions may have caused these recent shifts in the rate and pattern of land loss along this coastline segment, the authors propose. The changes include declining sea ice extent, increasing summertime sea-surface temperature, rising sea level, and increases in storm power and corresponding wave action.

“These factors may be leading to a new era in ocean-land interactions that seem to be repositioning and reshaping the Arctic coastline,” Jones and his colleagues write. The authors also documented sections of Beaufort Sea coastline that eroded more than 24 m (80 ft.) during 2007.

The researchers caution that the recent patterns documented in their study may not be representative of the overall Arctic. However, they may well forecast the future pattern of coastline erosion in the region.

“This segment of coastline has historically eroded at some of the highest rates in the circum-Arctic, so the changes occurring on this open-ocean coast might not be occurring in other Arctic coastal settings,” says Jones. But Arctic climate change is leading to rapid and complex environmental responses in both terrestrial and marine ecosystems in ways that will almost certainly affect the rate and pattern of coastline erosion in the Arctic, the authors write.

Interestingly, there were no westerly storm events during the summer of 2007, traditionally believed to be the drivers of coastal erosion in this region the Arctic. However, 2007 did boast the minimum arctic sea-ice extent and the warmest ocean temperatures on record.

“The recent trends toward warming sea-surface temperatures and rising sea-level may act to weaken the permafrost-dominated coastline by helping more quickly thaw ice-rich coastal bluffs and may potentially explain the disproportionate increase in erosion along ice-rich coastal bluffs relative to ice-poor coastal bluffs that we documented in our study,” Jones says. “Any increases in already rapid rates of coastal retreat will have further ramifications on Arctic landscapes – including losses in freshwater and terrestrial wildlife habitats, in subsistence grounds for local communities, and in disappearing cultural sites, as well as adversely impacting coastal villages and towns. In addition, oil test wells are threatened.”

Jones and his coauthors verified in another recent study the disappearance of cultural and historical sites along the same stretch of the Beaufort Sea. Those sites include Esook, a turn-of-the-century trading post now buried in the sea and Kolovik (Qalluvik), an abandoned Inupiaq village site that may soon be lost. At another site, near Lonely, Alaska, Jones snapped a picture of a wooden whaling boat that had rested on a bluff overhanging the ocean for nearly a century. A few months later the boat had washed away to sea. The study was published in the journal Arctic.

Global effort to extract more oil and gas

A University of Adelaide petroleum geologist is spearheading an international project to extract more oil and gas from the ground, potentially saving companies billions of dollars.

Associate Professor Bruce Ainsworth from the Australian School of Petroleum (ASP) is a principal investigator of the WAVE Consortium, an industry-sponsored global group that hopes to improve the average extraction rate of 60% from oil and gas fields.

“Petroleum companies are generally leaving about 40% of the oil behind due to a number of factors,” Dr Ainsworth says.

“A large proportion of the remaining hydrocarbon reserves are contained in rocks deposited in marginal and shallow marine environments. When they were laid down these deposits were influenced by waves, tides and river currents that together determine the geometries of our shorelines,” he says.

The consortium’s aim is to study these influences in order to better predict the distribution of oil and gas in the earth’s subsurface and to more efficiently extract it from hydrocarbon reservoirs.

Eight petroleum companies from around the world – in Australia, Austria, Canada, Egypt, New Zealand, Norway, The Netherlands and the United States – have provided $820,000 for the first phase of the project, which involves the study of ancient and modern coastal systems.

The University of Adelaide has employed two postdoctoral researchers, Dr Rachel Nanson and Dr Ivar Midtkandal, who together with Dr Ainsworth and Dr Boyan Vakarelov, a lecturer and co-investigator at ASP, will investigate the wave, tidal and fluvial processes that affect the shoreline.

Dr Nanson is in the final stages of a study to determine which of the three processes were responsible for generating Australia’s present-day coastline, while Dr Midtkandal will be working in western Canada, examining ancient geological systems to help develop models that can be applied to oilfields.

Another Canadian-based researcher is studying the traces that animals left in the sediments over millions of years ago.

“Animals only live in certain environments so their traces can give us a better idea of where these sediments were actually deposited and what the predominant influences on the coastlines were,” Dr Ainsworth says.

Dr Ainsworth has 17 years’ experience in the field of petroleum geology and worked in The Netherlands, Canada, Thailand, New Zealand and Western Australia before taking up a research and teaching post at the University of Adelaide in 2007.

“We hope to attract sufficient funding to take the project to the next level,” he says.

Cardiac fibrillation of the climate

In the current issue of the Scientific Journal Nature Geoscience a group of Norwegian, Swiss and German geoscientists prove that before the set-in of the Holocene very rapid climate changes already existed. The transition from the stable cold period took place about 12 150 to 11 700 years ago with very rapid fluctations up to the temperatur-threshold at which the Holocene began.

For this study, a group of scientists around J. Bakke, University of Bergen, examined sediments from Lake Kråkenes in Southwest Norway. These micro-layered lake deposits constitute a particularly suitable geological archive, with which scientists are able to analyse the climate volatility. The geochemical determination of titanium in sediments shows that during this phase significant short-term fluctuations in the titanium concentrations in the lake are detectable.

“We ascribe this to the short-term fluctuations in watermelt runoff from the inland glacier which feeds this lake”, explains Professor Gerald Haug from the DFG Leibniz Center for Earth Surface Process and Climate Studies at the University of Potsdam and the ETH Zürich, who carried out the analysis together with his colleague, Peter Dulkski, from the GFZ German Research Centre for Geosciences. “The fluctuating glacialmelt is a result of the intermittent advancement of the Gulf Stream and the resulting successive retreat of the sea-ice coverage.”

This process is closely linked with an equally high-frequence change in the westwind system and the therewith connected heat transport to Europe. This cardiac fibrillation of the climate is reflected again, as shown, in the fast-varying meltwater runoff into the examined lake, which at this point in time actually lay at the most climate-sensitive location of Europe, namely there where the Gulf Stream and the sea-ice coverage transformed.

Locations of strain, slip identified in major earthquake fault

Deep-sea drilling into one of the most active earthquake zones on the planet is providing the first direct look at the geophysical fault properties underlying some of the world’s largest earthquakes and tsunamis.

The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is the first geologic study of the underwater subduction zone faults that give rise to the massive earthquakes known to seismologists as mega-thrust earthquakes.

“The fundamental goal is to sample and monitor this major earthquake-generating zone in order to understand the basic mechanics of faulting, the basic physics and friction,” says Harold Tobin, University of Wisconsin-Madison geologist and co-chief scientist of the project.

Tobin will present results from the first stage of the project Sunday, Feb. 15, at the 2009 American Association for the Advancement of Science meeting in Chicago.

Subduction zone faults extend miles below the seafloor and the active earthquake-producing regions – the seismogenic zones – are buried deep in the Earth’s crust. The NanTroSEIZE project, an international collaboration overseen by the Integrated Ocean Drilling Program, is using cutting-edge deep-water drilling technology to reach these fault zones for the first time.

“If we want to understand the physics of how the faults really work, we have to go to those faults in the ocean,” Tobin explains. “Scientific drilling is the main way we know anything at all about the geology of the two-thirds of the Earth that is submerged.”

The decade-long project, to be completed in four stages, will use boreholes, rock samples, and long-term in situ monitoring of a fault in the Nankai Trough, an earthquake zone off the coast of Japan with a history of powerful temblors, to understand the basic fault properties that lead to earthquakes and tsunamis. The project is currently is its second year.

Subduction zone faults angle upward as one of the giant tectonic plates comprising Earth’s surface slides below another. Tremendous friction between the plates builds until the system faults and the accumulated energy drives the upper plate forward, creating powerful seismic waves that make the crust shake and can produce a tsunami. But although both shallow and deep parts of the fault slip, only the deep regions produce earthquakes.

During the first stage of the project, the team found evidence of extensive rock deformation and a highly concentrated slip zone even in shallow regions that do not generate earthquakes. One rock core from a shallow part of the fault contains a narrow band of finely ground “rock flour” revealing a fault zone between the upper and lower plates that is only about two millimeters thick – roughly the thickness of a quarter.

Above deeper portions of the fault, the team discovered layers of displaced rock and evidence of prolonged seismic activity that suggest a region known as the megasplay fault is likely responsible for the largest tsunami-generating plate slips.

“A fundamental goal was to understand how the faults at depth connect up toward the Earth’s surface, and we feel that we’ve discovered the fault zone that’s the main culprit,” Tobin says.

The next stage of drilling will commence this May, with plans to drill additional boreholes into the plate above deep regions of the fault zone. In addition to collecting cores for comparison to those from shallower parts of the fault, the scientists will install sensors in these holes to set up a deep-sea observatory monitoring physical stresses, movement, temperature and pressure.