Study suggests future sea-level rises may be even higher than predicted

A new study of past sea levels shows that they rose by an average of 1.6 metres every one hundred years the last time the Earth was as warm as it is predicted to be later this century, with levels reaching up to six metres above those seen today. The findings suggest that current predictions of sea-level rises may be too low.

The study by a consortium of scientists from the National Oceanography Centre, Southampton and research centres in Tübingen (Germany), Cambridge and New York, is published this week in the new journal Nature Geoscience.

The rate of future sea level rise is one of the crucial uncertainties in projections of future climate warming. During the last interglacial (124 to 119 thousand years ago), also known as the Eemian or Marine Isotope Stage 5e, the Earth’s climate was warmer than it is today, due to a different configuration of the planet’s orbit around the Sun.

It was also the most recent period in which sea levels reached around six metres (20 feet) above the present, due to melt-back of ice sheets on Greenland and Antarctica. The new results provide the first robust documentation of the rates at which sea level rose to these high positions.

Lead author, Professor Eelco Rohling of the University of Southampton’s School of Ocean and Earth Science, based at the National Oceanography Centre, said: ‘There is currently much debate about how fast future sea level rise might be. Several researchers have made strong theoretical cases that the rates of rise projected from models in the recent IPCC Fourth Assessment are too low. This is because the IPCC estimates mainly concern thermal expansion and surface ice melting, while not quantifying the impact of dynamic ice-sheet processes. Until now, there have been no data that sufficiently constrain the full rate of past sea level rises above the present level.

‘We have exploited a new method for sea level reconstruction, which we have pioneered since 1998, to look at rates of rise during the last interglacial. At that time, Greenland was 3 to 5°C warmer than today, similar to the warming expected 50 to 100 years from now. Our analysis suggests that the accompanying rates of sea level rise due to ice volume loss on Greenland and Antarctica were very high indeed. The average rate of rise of 1.6 metres per century that we find is roughly twice as high as the maximum estimates in the IPCC Fourth Assessment report, and so offers the first potential constraint on the dynamic ice sheet component that was not included in the headline IPCC values.’

The researchers’ findings offer a sound observational basis for recent suggestions about the potential for very high rates of sea-level rise in the near future, which may exceed one metre per century. Current ice-sheet models do not predict rates of change this large, but they do not include many of the dynamic processes already being observed. The new results highlight the need for further development of a better understanding of ice-sheet dynamics in a changing climate.

Earthquake Season in the Himalayan Front

Scientists have long searched for what triggers earthquakes, even suggesting that tides or weather play a role. Recent research spearheaded by Jean-Philippe Avouac, professor of geology and director of the Tectonics Observatory at the California Institute of Technology, shows that in the Himalayan mountains, at least, there is indeed an earthquake season. It’s winter.

For decades, geologists studying earthquakes in the Himalayan range of Nepal had noted that there were far more quakes in the winter than in the summer, but it was difficult to assign a cause. “The seasonal variation in seismicity had been noticed years ago,” says Avouac. Now, over a decade of data from GPS receivers and satellite measurements of land-water storage make it possible to connect the monsoon season with the frequency of earthquakes along the Himalaya front. The analysis also provides key insight into the timescale of earthquake nucleation in the region.

Avouac will present the results of the study on December 12 at the annual meeting of the American Geophysical Union (AGU) in San Francisco. They are also available online through the journal Earth and Planetary Science Letters, and will appear in print early next year.

The world’s tallest mountain range, the Himalaya continues to rise as plate tectonic activity drives India into Eurasia. The compression from this collision results in intense seismic activity along the front of the range. Stress builds continually along faults in the region, until it is released through earthquakes.

Avouac and two collaborators from France and Nepal–Laurent Bollinger and Sudhir Rajaure–began their earthquake seasonality investigation by analyzing a catalog of around 10,000 earthquakes in the Himalaya. They saw that, at all magnitudes above this detection limit, there were twice as many earthquakes during the winter months–December through February–as during the summer. That is, in winter there are up to 150 earthquakes of magnitude three per month, and in summer, around 75. For magnitude four, the winter average is 16 per month, while in summer the rate falls to eight per month. They ran the numbers through a statistical calculation and ruled out the possibility that the seasonal signal was due merely to chance.

“The signal in the seismicity is real; there is no discussion,” Avouac says. “We see this seasonal cycle,” he adds. “We didn’t know where it came from but it is really strong. We’re looking at something that is changing on a yearly basis-the timescale over which stress changes in this region is one year.”

Earlier studies suggested that seasonal variations in atmospheric pressure set off earthquakes, and this had been proposed for seasonal seismicity following the 1992 Landers, California, quake.

The scientists turned to satellite measurements of water levels in the region. Using altimetry data from TOPEX/Poseidon, a satellite launched in 1992 by NASA and the French space agency CNES (Centre National d’Etudes Spatiales), they evaluated the water level in major rivers of the Ganges basin to within a few tens of centimeters. They found that the water level over the whole basin begins its four-meter rise at the onset of the monsoon season in mid-May, reaching a maximum in September, followed by a slow decrease until the next monsoon season.

They combined river level measurements with data from NASA’s GRACE–Gravity Recovery and Climate Experiment–mission, which studies, among other things, groundwater storage on landmasses. The data revealed a strong signal of seasonal variation of water in the basin. Paired with the altimetry data, these measurements paint a complete picture of the hydrologic cycle in the region.

In the Himalaya, monsoon rains swell the rivers of the Ganges basin, increasing the pressure bearing down on the region. As the rains stop, the river water soaks through the ground and the built-up load eases outward, toward the front of the range. This outward redistribution of stress after the rains end leads to horizontal compression in the mountain range later in the year, triggering the wintertime earthquakes.

The final piece connecting winter earthquake frequency to season, and lending insight into the process by which earthquakes nucleate, lay in GPS data. Installation of GPS instruments across the Himalayan front began in 1994, and now they provide a decade’s worth of measurements showing land movement across the region. Instead of looking at vertical motions, which are widely believed to be sensitive to weather and the same forces that cause tides on Earth, the scientists concentrated on horizontal displacements. The lengthy records, analyzed by Pierre Bettinelli during his graduate work at Caltech, show that horizontal motion is continuous in the range front. Stress constantly builds in the region. But just as water levels near their lowest in the adjacent Ganges basin and earthquakes begin their doubletime, horizontal motion reaches its maximum speed.

“We had been staring at [the seasonal signal] for years, and then the satellite data came in and we deployed the GPS network and suddenly it became crystal clear,” says Avouac. “It’s like something you dream of.”

While many scientists have suggested that changing water levels can influence the earthquake cycle, a definitive mechanism had yet to be pinpointed. “There are two main avenues by which people have tried to understand the physics of earthquakes: Earth tides and aftershocks,” says Avouac. With the water level data, he could show that the rate at which stress builds along the rangefront, rather than the absolute level of stress, triggers earthquakes.

Although Earth tides induce stress levels similar to what builds up during seasonal water storage, they only vary over a 12-hour period. The Himalayan signal shows that it is more likely that earthquakes are triggered after stress builds for weeks to months, which matches the timescale of seasonal stress variation in that region.

About other earthquake-prone regions Avouac says, “seasonal variation has been reported in other places, but I don’t know any other place where it is so strong or where the cause of the signal is so obvious.”

Other authors on the paper are Pierre Bettinelli, Mireille Flouzat, and Laurent Bollinger of the Commissariat a l’Énergie Atomique, France; Guillaume Ramillien of the Laboratoire d’Etudes en Géophysique et Océanographie Spatiales, France; and Sudhir Rajaure and Som Sapkota of the National Seismological Centre in Nepal.

Avouac will present details of the group’s findings at AGU on Wednesday, December 12, at 2 p.m., Moscone West room 3018, in session T33F: Earthquake geology, active tectonics, and mountain building in south and east Asia.

Searching for ‘Martians’ in ancient rocks

'The rocks kind of resemble Swiss cheese,' explains Nicola McLoughlin.
‘The rocks kind of resemble Swiss cheese,’ explains Nicola McLoughlin.

They are looking for traces of micro-organisms which literally eat rock. Not just any kind of rock, however: volcanic glass is necessary in order for these tiny organisms to survive.

Such volcanic glass is often found between pillow lava, which are formed when magma comes into contact with water. Pillow lava does not have crystal structures, which means that the microorganisms can manage to “eat” their way through them.

As the microbes eat their way through the glass, they leave behind small cavities shaped like tiny bubbles or pipes.

Searching on the ancient seabed

“The rocks kind of resemble Swiss cheese,” explains Nicola McLoughlin, a post-doc at the University of Bergen. She explains that such microbes are commonly found on the modern seabed around the Mid-Atlantic Ridge. Ms McLoughlin is hunting for ones that may have lived 3.5 billion years ago. In order to study them she needs a seabed which is at least that old.

And that is not easy to find. As a result of the plate tectonics, new seabed is continuously being formed in areas such as the Mid-Atlantic Ridge. But this in turn leads to the older seabed being pushed outwards and destroyed. As a result, the age of the seabed usually does not exceed 170 million years.

“But sometimes processes occur which lead to a part of the seabed being stripped off, and transported up to the continents, so-called ophiolites,” explains Ms McLoughlin.

Controversial finds

In South Africa and Australia, signs of such “rock eating” microorganisms have been found in seabed which is approximately 3.5 billion years old.

“These finds are controversial since it is practically speaking often impossible to find traces of organic material in rocks that are so old. However, we have observed that many of the same tubular or pipe structures that we find after modern rock eating microorganisms are present,” explains Ms McLoughlin.

Even though the rock has been periodically subject to high pressures and temperatures for billions of years, the cavities are preserved intact because they have been filled up with different materials after they arose. When geologists date the age of the material which has filled the pipe-shaped cavities, and the surrounding volcanic glass, they find a discrepancy.

Radiometric dating

For example, in one of the places she has been searching for such ancient micro-biotic life, North Pilbara, the former seabed is in fact 3.5 billion years old. However, the materials which filled the cavities are “only” 2.9 billion years old.

“The fact that the cavities are filled with materials is what makes it possible for us to find these traces such a long time afterwards,” says Ms McLoughlin of the Centre for geo-biosphere research.

The results of the research conducted by Ms McLoughlin and her colleagues are of interest to those who are searching for life in completely different places. Places like Mars for example.

Need to perfect our methods here on the Earth first

The reason for this is that there is a great deal of volcanic rock on Mars. If there was once water on Mars, and if it is possible to find pillow lava there similar to that which exists here on Earth, then conditions may be right for discovering traces of microbial life.

“But first we must perfect our own methods and thoroughly test the criteria that form the basis for our claim that we have found such structures on the terrestrial seabed. Until we can trust our results from here on the Earth, we cannot use our methods on another planet,” emphasises Ms McLoughlin. In the exploration of this phenomenon, she has teamed up with Ingunn Thorseth, Harald Furnes and Neil Banerjee.

Tracking Earth Changes with Satellite Images

Satellite Imagery
Satellite Imagery

For the past two decades, radar images from satellites have dominated the field of geophysical monitoring for natural hazards like earthquakes, volcanoes, or landslides. These images reveal small perturbations precisely, but large changes from events like big earthquake ruptures or fast-moving glaciers remained difficult to assess from afar, until now.

Sebastien Leprince, a graduate student in electrical engineering at the California Institute of Technology, working under the supervision of geology professor and director of Caltech’s Tectonics Observatory (TO), Jean-Philippe Avouac, wrote software that correlates any two optical images taken by satellite. It has proved extremely reliable in tracking large-scale changes on Earth’s surface, like earthquake ruptures, the mechanics of “slow” landslides, or defining the fastest-moving sections of glaciers that, due to global warming, have recently increased their pace.

Leprince will describe his software and results of many of its applications on December 14 at the annual meeting of the American Geophysical Union (AGU) in San Francisco. His research will also be featured in the January 1 issue of Eos, AGU’s weekly newspaper.

When the technique called InSAR, which uses radar images to reveal details about ground displacement, was introduced, it was quickly embraced. No longer did geoscientists have to rely solely on measurements made by troupes of field geologists or by ground-based devices that might not have been optimally placed. But, says Leprince, “InSAR is physically limited: it’s good for small displacements but not for large ones. The radar resolution isn’t enough to look at deformation with a large gradient.”

Using optical images to complement the radar-based InSAR technique seemed like a natural step. When Leprince began grappling with the idea in 2003, he found several baby steps had been taken. “Satellite image correlation was not a science yet, it was more like an art,” he says. The first attempts, reported in 1991, were inconclusive but promising. Since then, several teams of scientists had worked on the problem independently. Some had even developed it well enough to monitor glacier flow.

The major obstacle Leprince faced in developing optical image correlation software was that there were several steps involved but no one knew in which order to take them. “Errors came from everywhere, but where exactly?” he noted. “And we found at least one major flaw in each step.”

Three of the four main steps involve correcting geometric distortions innate to taking pictures from space and projecting them onto a surface. The first step matches coordinates of the satellite image with coordinates on the ground. “This is not new, but the approximations being made were not okay,” says Leprince. The second step describes the satellite’s position in its orbit at the time it took the photo. This is just like in everyday life–you need to know how your camera was oriented when you show off a photo you snapped. In the next step, which Leprince says people never knew they were doing wrong, the image is correctly wrapped onto topography. Finally, the images are precisely combined-or coregistered-in order to measure surface displacements accurately.

“What is important is that we identified the steps and took each one independently and did an error analysis for each step to see how errors propagated,” says Leprince. His program, which he calls COSI-Corr and which was packaged by the TO’s software engineer Francois Ayoub for official release this year, takes all of these steps automatically in just a few hours of processing time. “You start the program, you go home, you have a nice weekend on the beach, and it’s done.”

The paper describing the software Leprince developed appeared in the June 2007 issue of the journal IEEE Transactions on Geoscience and Remote Sensing. COSI-Corr can now combine any images taken by different satellite imagers from different incidence views. For example, to analyze displacement from the 1999 Hector Mine earthquake near Twenty-Nine Palms in California, Leprince correlated a SPOT 4 image with an ASTER image. This had never been done before. It takes only a few hours to process.

Using his technique, Leprince has precisely measured offset from several notable recent earthquakes, including 2005 Kashmir, Pakistan; 2002 Denali, Alaska; 1999 Hector Mine and Chi Chi, Taiwan; and 1992 Landers, California. In the case of earthquakes, the image correlation technique can be used to map in detail all fault ruptures and to measure displacements both along and across the fault. Uncertainties, typically within centimeters for 10-15-meter-resolution images, are extremely low.

The day after Leprince released his software through the TO website, he was contacted by a geologist in Canada asking how the technique could be used to study glacier flow. Radar images cannot analyze glaciers because they move too fast and ice melting poses a problem. “The tectonic application was pretty well set up and we’d tested it thoroughly,” says Leprince. “So we extended it to glaciology.” And then to other studies as well.

What’s tricky about studying glacier flow is that not only has their pace picked up in recent years due to climate change, but glaciers have a natural yearly cycle of ice gain and loss. The two signals can be discerned with cross-correlation of optical imagery. Leprince’s method was used to study Mer de Glace glacier in the Alps, which flows at around 90 meters per year. The optical images provide a full view of the ice flow field, pinpointing exactly where the glacier is moving fastest. The same approach was taken with a landslide above the Alpine town of Barcelonnette in eastern France. Benchmarks had been planted to monitor the landslide’s flow, and Leprince’s correlation methods showed that all 38 of them missed the fastest-moving region. While the landslide is moving slow now, the town will be threatened when the landslide detaches and descends rapidly.

There are many more applications for correlating optical images to monitor Earth surface changes. Caltech geologists and their collaborators began to apply it to studying dunes, which radars cannot image, after they were contacted by labs in Egypt who need information on dune migration for urban planning.

“Radar interferometry is a huge technique, but you can only measure half of the world with it. Now we can measure the other half with this technique,” comments Leprince. “The biggest thing is what’s to come.”

Evolution Tied to Earth Movement

Kibo Summit of Kilimanjaro
Kibo Summit of Kilimanjaro

Scientists long have focused on how climate and vegetation allowed human ancestors to evolve in Africa. Now, University of Utah geologists are calling renewed attention to the idea that ground movements formed mountains and valleys, creating environments that favored the emergence of humanity.

“Tectonics [movement of Earth’s crust] was ultimately responsible for the evolution of humankind,” Royhan and Nahid Gani of the university’s Energy and Geoscience Institute write in the January, 2008, issue of Geotimes, published by the American Geological Institute.

They argue that the accelerated uplift of mountains and highlands stretching from Ethiopia to South Africa blocked much ocean moisture, converting lush tropical forests into an arid patchwork of woodlands and savannah grasslands that gradually favored human ancestors who came down from the trees and started walking on two feet – an energy-efficient way to search larger areas for food in an arid environment.

In their Geotimes article, the Ganis – a husband-and-wife research team who met in college in their native Bangladesh – describe this 3,700-mile-long stretch of highlands and mountains as “the Wall of Africa.” It parallels the famed East African Rift valley, where many fossils of human ancestors were found.

“Because of the crustal movement or tectonism in East Africa, the landscape drastically changed over the last 7 million years,” says Royhan Gani (pronounced rye-hawn Go-knee), a research assistant professor of civil and environmental engineering. “That landscape controlled climate on a local to regional scale. That climate change spurred human ancestors to evolve from apes.”

Hominins – the new scientific word for humans (Homo) and their ancestors (including Ardipithecus, Paranthropus and Australopithecus) – split from apes on the evolutionary tree roughly 7 million to 4 million years ago. Royhan Gani says the earliest undisputed hominin was Ardipithecus ramidus 4.4 million years ago. The earliest Homo arose 2.5 million years ago, and our species, Homo sapiens, almost 200,000 years ago.

Tectonics – movements of Earth’s crust, including its ever-shifting tectonic plates and the creation of mountains, valleys and ocean basins – has been discussed since at least 1983 as an influence on human evolution.

But Royhan Gani says much previous discussion of how climate affected human evolution involves global climate changes, such as those caused by cyclic changes in Earth’s orbit around the sun, and not local and regional climate changes caused by East Africa’s rising landscape.

A Force from within the Earth

The geological or tectonic forces shaping Africa begin deep in the Earth, where a “superplume” of hot and molten rock has swelled upward for at least the past 45 million years. This superplume and its branching smaller plumes help push apart the African and Arabian tectonic plates of Earth’s crust, forming the Red Sea, Gulf of Aden and the Great Rift Valley that stretches from Syria to southern Africa.

As part of this process, Africa is being split apart along the East African Rift, a valley bounded by elevated “shoulders” a few tens of miles wide and sitting atop “domes” a few hundreds of miles wide and caused by upward bulging of the plume.

The East African Rift runs about 3,700 miles from the Ethiopian Plateau south-southwest to South Africa’s Karoo Plateau. It is up to 370 miles wide and includes mountains reaching a maximum elevation of about 19,340 feet at Mount Kilimanjaro.

The rift “is characterized by volcanic peaks, plateaus, valleys and large basins and freshwater lakes,” including sites where many fossils of early humans and their ancestors have been found, says Nahid Gani (pronounced nah-heed go-knee), a research scientist. There was some uplift in East Africa as early as 40 million years ago, but “most of these topographic features developed between 7 million and 2 million years ago.”

A Wall Rises and New Species Evolve

“Although the Wall of Africa started to form around 30 million years ago, recent studies show most of the uplift occurred between 7 million and 2 million years ago, just about when hominins split off from African apes, developed bipedalism and evolved bigger brains,” the Ganis write.

“Nature built this wall, and then humans could evolve, walk tall and think big,” says Royhan Gani. “Is there any characteristic feature of the wall that drove human evolution?”

The answer, he believes, is the variable landscape and vegetation resulting from uplift of the Wall of Africa, which created “a topographic barrier to moisture, mostly from the Indian Ocean” and dried the climate. He says that contrary to those who cite global climate cycles, the climate changes in East Africa were local and resulted from the uplift of different parts of the wall at different times.

Royhan Gani says the change from forests to a patchwork of woodland and open savannah did not happen everywhere in East Africa at the same time, and the changes also happened in East Africa later than elsewhere in the world.

The Ganis studied the roughly 300-mile-by-300-mile Ethiopian Plateau – the most prominent part of the Wall of Africa. Previous research indicated the plateau reached its present average elevation of 8,200 feet 25 million years ago. The Ganis analyzed rates at which the Blue Nile River cut down into the Ethiopian Plateau, creating a canyon that rivals North America’s Grand Canyon. They released those findings in the September 2007 issue of GSA Today, published by the Geological Society of America.

The conclusion: There were periods of low-to-moderate incision and uplift between 29 million and 10 million years ago, and again between 10 million and 6 million years ago, but the most rapid uplift of the Ethiopian Plateau (by some 3,200 vertical feet) happened 6 million to 3 million years ago.

The Geotimes paper says other research has shown the Kenyan part of the wall rose mostly between 7 million and 2 million years ago, mountains in Tanganyika and Malawi were uplifted mainly between 5 million and 2 million years ago, and the wall’s southernmost end gained most of its elevation during the past 5 million years.

“Clearly, the Wall of Africa grew to be a prominent elevated feature over the last 7 million years, thereby playing a prominent role in East African aridification by wringing moisture out of monsoonal air moving across the region,” the Ganis write.

That period coincides with evolution of human ancestors in the area.

Royhan Gani says the earliest undisputed evidence of true bipedalism (as opposed to knuckle-dragging by apes) is 4.1 million years ago in Australopithecus anamensis, but some believe the trait existed as early as 6 million to 7 million years ago.

The Ganis speculate that the shaping of varied landscapes by tectonic forces – lake basins, valleys, mountains, grasslands, woodlands – “could also be responsible, at a later stage, for hominins developing a bigger brain as a way to cope with these extremely variable and changing landscapes” in which they had to find food and survive predators.

For now, Royhan Gani acknowledges the lack of more precise timeframes makes it difficult to link specific tectonic events to the development of upright walking, bigger brains and other key steps in human evolution.

“But it all happened within the right time period,” he says. “Now we need to nail it down.”

Ancient Flood Disrupted Ocean Circulation And Triggered Climate Cooling

As the giant North American ice sheets melted an enormous pool of freshwater, many times larger than all of the Great Lakes, formed behind them. About 8400 years ago this pool of freshwater burst free and flooded the North Atlantic. About the same time, a sharp century long cold spell is observed around the North Atlantic and other areas. Researchers have often speculated that the cooling was the result of changes in ocean circulation triggered by this freshwater flood. The sudden addition of so much freshwater would have curtailed (suppressed) the sinking of deep water in the North Atlantic and as a consequence less warm water would be pulled north in the Gulf stream.

In a new study in Science (published online in Science Express 6 December) Kleiven and co workers confirm that the deep ocean was disturbed in just the way previous workers had speculated. Using a marine core from south of Greenland, which monitors the southward flowing deep waters formed in the North Atlantic they show that there is a sudden disruption in the deep circulation pattern at the time of the flood outburst.

Just at the time of the flood, the chemical properties of the deep ocean shift suddenly to values not observed at any other time in the last 10,000 years. The chemical changes suggest that at the site south of Greenland, the new deep waters formed in the North were completely replaced by older deepwater coming from the south.

This suggests that deep waters from the North Atlantic were too shallow or weak to influence this site for about century following the flood outburst after which time the deep ocean snapped back to its near modern state. This is what researchers had predicted and what computers have simulated the ocean needed to have done in order to help bring about the cold spell.

Kleiven et al., strengthen the connection between the deep ocean changes and the climate anomaly by showing that the sharp cooling at their location falls within the century long disruption in deep circulation. If the cooling had fallen outside the period of disrupted circulation, the role of the ocean and related heat transport could have been ruled out as the major driver of the cooling.

Perhaps even more importantly, they show that deep circulation is altered over just a few decades or less demonstrating that the the deep ocean changes fast enough to drive the sudden jump in climate seen at this and other times in the past.

There is no modern or future equivalent source for freshwater to cause a mega flood like that which occurred 8400 years ago. Yet, the fact that these deep ocean changes clearly occur on timescales rapidly enough to impact human societies underscores the importance of determining just how much freshwater is needed to bring about such dramatic changes—given the concerns that melting of the Greenland Ice Sheet may accelerate as the globe warms.

Engineering researchers capture optical ‘rogue waves’

Maritime folklore tells tales of giant “rogue waves” that can appear and disappear without warning in the open ocean. Also known as “freak waves,” these ominous monsters have been described by mariners for ages and have even appeared prominently in many legendary literary works, from Homer’s “Odyssey” to “Robinson Crusoe.”

Once dismissed by scientists as fanciful sailors’ stories akin to sea monsters and uncharted inlands, recent observations have shown that they are a real phenomenon, capable of destroying even large modern ships. However, this mysterious phenomenon has continued to elude researchers, as man-made rogue waves have not been reported in scientific literature — in water or in any other medium.

Now, researchers at the UCLA Henry Samueli School of Engineering and Applied Science have succeeded in creating and capturing rogue waves. In their experiments, they have discovered optical rogue waves — freak, brief pulses of intense light analogous to the infamous oceanic monsters — propagating through optical fiber. Their findings appear in the Dec. 13 issue of the journal Nature.

“Optical rogue waves bear a close connection to their oceanic cousins,” said lead investigator Daniel Solli, a UCLA Engineering researcher. “Optical experiments may help to resolve the mystery of oceanic rogue waves, which are very difficult to study directly.”

It is thought that rogue waves are a nonlinear, perhaps chaotic, phenomenon, able to develop suddenly from seemingly innocuous normal waves. While the study of rogue waves has focused on oceanic systems and water-based models, light waves traveling in optical fibers obey very similar mathematics to water waves traveling in the open ocean, making it easier to study them in a laboratory environment.

Still, detecting a rogue wave is like finding a needle in a haystack. The wave is a solitary event that occurs rarely, and, to make matters worse, the timing of its occurrence is entirely random. But using a novel detection method they developed, the UCLA research group was able to not only capture optical rogue waves but to measure their statistical properties as well.

They found that, similar to freak waves in the ocean, optical rogue waves obey “L-shaped” statistics – a type of distribution in which the heights of most waves are tightly clustered around a small value but where large outliers also occur. While these occurrences are rare, their probability is much larger than predicted by conventional (so-called normal or Gaussian) statistics.

“This discovery is the first observation of man-made rogue waves reported in scientific literature, but its implications go beyond just physics,” said Bahram Jalali, UCLA professor of electrical engineering and the research group leader. “For example, rare but extreme events, popularly known as “black swans,” also occur in financial markets with spectacular consequences. Our observations may help develop mathematical models that can identify the conditions that lead to such events.”

Co-authors on the Nature paper include UCLA Engineering researchers Claus Ropers and Prakash Koonath.

The research was funded by the Defense Advanced Research Projects Agency (DARPA), the central research and development organization for the U.S. Department of Defense.

Peat moves from the bog to the generating station

Biofuel made of peat and wood could replace coal at the Atikokan Generating Station in northwestern Ontario. Photo courtesy of Mike Waddington.
Biofuel made of peat and wood could replace coal at the Atikokan Generating Station in northwestern Ontario. Photo courtesy of Mike Waddington.

For hundreds of years, peat has been used in Ireland, Sweden, Finland, Estonia, Belarus and Russia as a fuel source for thermal generating stations. Now Peat Resources Ltd. is looking at replacing the coal that fuels the province’s Atikokan Generating Station in northwestern Ontario with peat and wood.

Mike Waddington, associate professor in the Department of Geography & Earth Sciences at McMaster University, is leading the team that will assess the environmental impacts of using the new biofuel. He says Canada is a virtual peat paradise.

Canada has the world’s second-largest supply of peat; most of it around the Hudson and James Bay Lowlands and in Northern Ontario.

Says Waddington: “There are about 113 million hectares of peat in Canada — about 11 per cent of the country’s land — and if peat does become the preferred fuel of Atikokan’s Generating Station then it would use only a very small portion, about 100 hectares a year, of our total resource.”

Waddington’s first job is to determine the environmental impacts of the proposal. The greenhouse gas emissions, changes to water quantity and quality after the peat is removed from the peatlands; the rehabilitation of the peatlands, the return of process water to the peatlands, and the mercury relationships in the peatlands, all need to be explored, he says.

The process of harvesting peat for fuel involves removing the top layer of the peat, about 30 centimetres deep, and extracting from the deeper and older peat, material that is several thousand years old. Peat is a slowly renewing biofuel, says Waddington, and studies in Europe suggest it takes between 300 and 1,000 years to renew.

In Scandinavia, Ireland and Russia, peat was harvested using a dry technique that meant draining the wetlands prior to removing the peat. This method raised environmental concerns about water quality and flash flooding.

“We know how to restore dry harvest peatlands,” says Waddington, “however, with Peat Resources Ltd., we’ll be using an innovative wet harvest approach in which the peat is pumped to the processing facility through a pipeline. Once the peat is removed, the water that was removed from the peat extraction will be returned from the processing facility to the peatland.”

The proposed peat biofuel project is not the only water and peat-related energy concern in Canada.

“We’re already encountering some potential issues that will need to be hashed out,” says Waddington. “For instance, the Alberta oil sands are located under peatlands, and the hydroelectric reservoirs around James Bay region in Quebec are flooded peatlands. The question arises: Do you intrude on one resource to make room for another? It’s a tricky question.”

With 15 years experience in peatland restoration, Waddington will also be focused on how to remediate the peatlands and return them to as close to their pre-extraction state as possible. Blueberries, cranberries and wild rice are possible crops that could thrive in former peatlands.

The research for this project is being funded by the Ontario Centre of Excellence and Peat Resources Ltd.

Greenland Melt Accelerating

An iceberg calved from a glacier floats in the Jacobshavn fjord in southwest Greenland. A new CU-Boulder study indicates Greenland continues to lose ice mass, and the rate of loss is accelerating.
An iceberg calved from a glacier floats in the Jacobshavn fjord in southwest Greenland. A new CU-Boulder study indicates Greenland continues to lose ice mass, and the rate of loss is accelerating.

The 2007 melt extent on the Greenland ice sheet broke the 2005 summer melt record by 10 percent, making it the largest ever recorded there since satellite measurements began in 1979, according to a University of Colorado at Boulder climate scientist.

The melting increased by about 30 percent for the western part of Greenland from 1979 to 2006, with record melt years in 1987, 1991, 1998, 2002, 2005 and 2007, said CU-Boulder Professor Konrad Steffen, director of the Cooperative Institute for Research in Environmental Sciences. Air temperatures on the Greenland ice sheet have increased by about 7 degrees Fahrenheit since 1991, primarily a result of the build-up of greenhouse gases in Earth’s atmosphere, according to scientists.

Steffen gave a presentation on his research at the fall meeting of the American Geophysical Union held in San Francisco from Dec. 10 to Dec. 14. His team used data from the Defense Meteorology Satellite Program’s Special Sensor Microwave Imager aboard several military and weather satellites to chart the area of melt, including rapid thinning and acceleration of ice into the ocean at Greenland’s margins.

Steffen maintains an extensive climate-monitoring network of 22 stations on the Greenland ice sheet known as the Greenland Climate Network, transmitting hourly data via satellites to CU-Boulder to study ice-sheet processes.

Although Greenland has been thickening at higher elevations due to increases in snowfall, the gain is more than offset by an accelerating mass loss, primarily from rapidly thinning and accelerating outlet glaciers, Steffen said. “The amount of ice lost by Greenland over the last year is the equivalent of two times all the ice in the Alps, or a layer of water more than one-half mile deep covering Washington, D.C.”

The Jacobshavn Glacier on the west coast of the ice sheet, a major Greenland outlet glacier draining roughly 8 percent of the ice sheet, has sped up nearly twofold in the last decade, he said. Nearby glaciers showed an increase in flow velocities of up to 50 percent during the summer melt period as a result of melt water draining to the ice-sheet bed, he said.

“The more lubrication there is under the ice, the faster that ice moves to the coast,” said Steffen. “Those glaciers with floating ice ‘tongues’ also will increase in iceberg production.”

Greenland is about one-fourth the size of the United States, and about 80 percent of its surface area is covered by the massive ice sheet. Greenland hosts about one-twentieth of the world’s ice — the equivalent of about 21 feet of global sea rise. The current contribution of Greenland ice melt to global sea levels is about 0.5 millimeters annually.

The most sensitive regions for future, rapid change in Greenland’s ice volume are dynamic outlet glaciers like Jacobshavn, which has a deep channel reaching far inland, he said. “Inclusion of the dynamic processes of these glaciers in models will likely demonstrate that the 2007 Intergovernmental Panel on Climate Change assessment underestimated sea-level projections for the end of the 21st century,” Steffen said.

Helicopter surveys indicate there has been an increase in cylindrical, vertical shafts in Greenland’s ice known as moulins, which drain melt water from surface ponds down to bedrock, he said. Moulins, which resemble huge tunnels in the ice and may run vertically for several hundred feet, switch back and forth from vertical to horizontal as they descend toward the bottom of the ice sheet, he said.

“These melt-water drains seem to allow the ice sheet to respond more rapidly than expected to temperature spikes at the beginning of the annual warm season,” Steffen said. “In recent years the melting has begun earlier than normal.”

Steffen and his team have been using a rotating laser and a sophisticated digital camera and high-definition camera system provided by NASA’s Jet Propulsion Laboratory to map the volume and geometry of moulins on the Greenland ice sheet to a depth of more than 1,500 feet. “We know the number of moulins is increasing,” said Steffen. “The bigger question is how much water is reaching the bed of the ice sheet, and how quickly it gets there.”

Steffen said the ice loss trend in Greenland is somewhat similar to the trend of Arctic sea ice in recent decades. In October, CU-Boulder’s National Snow and Ice Data Center reported the 2007 Arctic sea-ice extent had plummeted to the lowest levels since satellite measurements began in 1979 and was 39 percent below the long-term average tracked from 1979 to 2007.

CIRES is a joint institute of CU-Boulder and the National Oceanic and Atmospheric Administration.

Water, water everywhere but is it sustainable?

Professor Malcolm Cox
Professor Malcolm Cox

While Brisbane is flush with underground water stores, more needs to be known about refill times to aquifers and the environmental effects of large-scale freshwater extraction to ensure their sustainable use.

Internationally recognised groundwater expert, UNESCO Professor Yongxin Xu is visiting Queensland University of Technology’s Institute for Sustainable Resources on Thursday to speak about the links between surface water and groundwater systems and how to model them.

QUT hydrogeologist Associate Professor Malcolm Cox said Professor Xu had developed models to assess the effect of changing rainfall patterns on the ability of groundwater systems to recharge.

He said Professor Xu’s work had many aspects that could be applied to South- East Queensland conditions to help understand how climate change was affecting our groundwater supplies.

“SEQ has a great variation in groundwater systems which need intensive study before it can be used with confidence as a long-term, sustainable resource,” Professor Cox said.

“Unlike Sydney, which is within a large basin of groundwater, we have groundwater stored in many different rock types with varying porosity and rates of recharge (refill times). Some of the SEQ groundwater may be thousands of years old, some might be only a few weeks.”

He urged caution in utilising South-East Queensland’s subsurface water supplies without fully understanding recharge times, how aquifer systems were linked and how they were connected to the surface.

“For example, The Lockyer Valley, which produces 30 per cent of Brisbane’s vegetables, has used its alluvial groundwater intensively for irrigation,” Professor Cox said.

“The alluvium (river gravel and sand) is not being recharged because rainfall has dropped. Normally it recharges very quickly from rainfall on mountains round the Valley.

Professor Cox said not enough was known about the environmental impact of extracting a lot of freshwater from the ground, especially in coastal areas.

“Stradbroke and Bribie islands, for example, are totally reliant on rainfall recharge for their groundwater supplies therefore groundwater extraction must be carefully monitored.”

Professor Cox said that in both these areas groundwater use must also consider potential problems such as the intrusion of saltwater to replace the fresh groundwater and the effects on ecosystems that rely on groundwater.

He said the Institute for Sustainable Resources had a key focus on water resources and was supporting a number of groundwater research projects in the region.