Greenland and Antarctic ice sheet melting, rate unknown

The Greenland and Antarctica ice sheets are melting, but the amounts that will melt and the time it will take are still unknown, according to Richard Alley, Evan Pugh professor of geosciences, Penn State.

In the past, the Greenland ice sheet has grown when its surroundings cooled, shrunk when its surroundings warmed and even disappeared completely when the temperatures became warm enough. If the ice sheet on Greenland melts, sea level will rise about 23 feet, which will inundate portions of nearly all continental shores. However, Antarctica, containing much more water, could add up to another 190 feet to sea level.

“We do not think that we will lose all, or even most, of Antarctica’s ice sheet,” said Alley. “But important losses may have already started and could raise sea level as much or more than melting of Greenland’s ice over hundreds or thousands of years,” Alley told attendees today (Feb 16) at the annual meeting of the American Association for the Advancement of Science.

Warming is expected to cause more precipitation on Greenland and Antarctica, adding snow. Previously, many scientists suggested that this would offset increasing melting. However, recent studies show that the ice sheets on both Greenland and in Antarctica are melting faster than the snow is replacing the mass.

A number of things can contribute to the increased rate of melting in Greenland and Antarctica. Large lakes of water on the ice in Greenland pose a problem. This water, by wedging open a crack or crevasse in the ice, quickly flows through to the bottom, melting the bottom of the ice sheet and causing it to move more rapidly toward the ocean. Observers have seen lakes on the Greenland ice sheet drain at the speed of Niagara Falls.

All ice sheets spread due to their large mass, but friction from the rocks beneath slows the ice’s motion. Water beneath the ice allows the ice to move more rapidly.

“Right now, the center of the Greenland ice sheet is frozen to the rocks,” says Alley. “If the melt water moves inland as the world warms and gets to the bottom, it will thaw the bottom and unstick the ice from the rocks.”

Another contributor to the melting ice sheets is the warming of the ocean. When ice shelves — ice still connected to the ice sheet but floating over water — melt, they also cause the ice sheet to flow faster. In Greenland, the Jakobshavn ice shelf has retreated more than 5 miles since 1992. Rocks and cliffs on the sides of fiords or inlets slow the seaward movement of the ice shelves. If these shelves break up and melt, the ice streams behind them move more rapidly

Ice shelf failures have also occurred on Antarctica where, for example, most of the Larsen B ice shelf disintegrated in March of 2002 and increased the rate of ice stream flow eight times.

“Water temperature is more important than air temperature in melting the ice shelves,” says Alley. “However, both contribute.”

Warmer oceans, caused by general global warming or local events can trigger more breakups of ice shelves and faster flow of ice streams in Antarctica. In Greenland, sustained increase in temperatures of only a few degrees will remove the ice.

Alley believes he knows the direction to go to gain a better understanding of the ice sheets, how they work and the effect they have on climate change. Although those who study ice sheets have long modeled ice sheet behavior, simulations of the whole earth system typically have not included ice sheets along with the atmosphere, oceans and clouds, in their models. Past atmospheric modelers usually treated the ice sheets simply as white mountains.

“They are not white mountains and they need to be modeled,” said Alley. “We need to have them in the models to figure out how the system works.”

Alley notes that a collaboration of government and academic scientists created the atmospheric and ocean models, but collaborations to model the ice are only just being developed.

New monitoring stations detect ‘silent earthquakes’ in Costa Rica

After installing an extensive network of monitoring stations in Costa Rica, researchers have detected slow slip events (also known as “silent earthquakes”) along a major fault zone beneath the Nicoya Peninsula. These findings are helping scientists understand the full spectrum of motions occurring on the fault and may yield new insights into the events that lead to major earthquakes.

A slow slip event involves the same fault motion as an earthquake, but it happens so slowly that the ground does not shake. It can be detected only with networks of modern instruments that use the Global Positioning System (GPS) to measure precisely the movements of the Earth’s crust over time.

Susan Schwartz, a professor of Earth and planetary sciences at the University of California, Santa Cruz, leads a team that has installed a permanent network of 13 GPS monitoring stations and 13 seismic stations on Costa Rica’s Nicoya Peninsula.

“At least two slow slip events have occurred beneath the Nicoya Peninsula since 2003,” Schwartz said. “When we recorded the first one in 2003, we had only 3 GPS stations. By 2007, we had 12 GPS stations and over 10 seismic stations, so the event that year was very nicely recorded.”

The National Science Foundation (NSF) has funded the work by Schwartz and others to install monitoring equipment in Costa Rica. Schwartz, who directs UCSC’s Keck Seismological Laboratory, has been working in the region since 1991. At the annual meeting of the American Association for the Advancement of Science (AAAS) in Chicago, she will describe results from the past decade of fault-zone monitoring in Central America.

“The newest discovery is the occurrence of these slow slip events. But there has been a decade of focused effort in this area that has significantly advanced our knowledge of the Central America seismogenic system,” Schwartz said. “Initially, we focused on areas of the fault that are locked up, which slip in an earthquake. The slow slip is occurring in regions that are not strongly locked, and a big question is whether that is loading the locked area, making it more likely to break, or relieving stress on the fault.”

Schwartz said she does not think slow slip events significantly increase the likelihood of a major earthquake on a locked portion of the fault. She noted, however, that scientists are still at an early stage in terms of understanding the implications of different kinds of fault motion and translating that information into earthquake hazard assessments.

Flanked by active tectonic margins on both the Pacific and Caribbean coasts, Costa Rica is one of the most earthquake-prone and volcanically active countries in the world. Just off the west coast is the Middle America Trench, where a section of the seafloor called the Cocos Plate dives beneath Central America, generating powerful earthquakes and feeding a string of active volcanoes. This type of boundary between two converging plates of the Earth’s crust is called a subduction zone–and such zones are notorious for generating the most powerful and destructive earthquakes.

The slow slip phenomenon was first observed at subduction zones where hundreds of GPS and seismic instruments are deployed: the Cascadia fault zone (off the coast of Washington and British Columbia) and Japan’s Nankai Trough. At these and most other subduction zones, the part of the plate boundary where earthquakes originate, called the seismogenic zone, lies beneath the ocean. But in Costa Rica, the seismogenic zone runs right beneath the Nicoya Peninsula.

“It’s a perfect opportunity to study the seismogenic zone using a network of land-based instruments,” Schwartz said.

The 2007 slow slip event in Costa Rica involved movement along the fault equivalent to a magnitude 6.9 earthquake. But it took place over a period of 30 days rather than the 10 seconds typical for an earthquake of that size, and such slow motion does not radiate the seismic energy associated with normal earthquakes. The instruments did pick up seismic tremor, however, which Schwartz likened to a lot of very small earthquakes. Tremor activity is also associated with slow slip events in Japan and Cascadia, but there are some differences in Costa Rica, Schwartz said.

“Costa Rica has a different type of subduction zone from the well-studied ones in Japan and Cascadia,” she said. “One thing that makes it interesting is that the temperature is much cooler at the depth range where slip occurs, and that is helping us work out the role of fluids in generating slow slip.”

Ultimately, the goal of this research is not only a better understanding of subduction zones, but also better assessments of earthquake hazards. Schwartz said her Costa Rican colleagues have been working to educate the population of Nicoya about earthquakes and related hazards. With a growing population along the coast, the region faces a potential tsunami threat as well as the possibility of a major earthquake, she said.

Next generation digital maps are laser sharp

The dynamics of rivers and streams can be more clearly identified using new laser-guided mapping technology, or lidar. This figure shows a segment of Maine's Sheepscot River in a traditional digital topographic contour map (a); a lidar map (b); and the identification of Atlantic salmon spawning habitat (c). Airborne lidar mapping provides far greater resolution and allows researchers to connect the slope of the river with spawning habitat. -  American Geophysical Union
The dynamics of rivers and streams can be more clearly identified using new laser-guided mapping technology, or lidar. This figure shows a segment of Maine’s Sheepscot River in a traditional digital topographic contour map (a); a lidar map (b); and the identification of Atlantic salmon spawning habitat (c). Airborne lidar mapping provides far greater resolution and allows researchers to connect the slope of the river with spawning habitat. – American Geophysical Union

Restoring habitat for spawning species of fish, such as Atlantic salmon, starts with a geological inventory of suitable rivers and streams, and the watershed systems that support them. But the high-tech mapping tools available to geologists and hydrologists have had their limits.

Now, lasers beamed from planes overhead are adding greater clarity to mapping streams and rivers and interpreting how well these bodies of water can help maintain or expand fish stocks, according to a new study.

“It’s kind of like going from your backyard telescope to the Hubble telescope,” says Boston College Geologist Noah P. Snyder. “Restoring fish habitat is just one example. For the fisherman, backpacker, forester, land use planner or developer – anyone who uses map data – this new technology is the next revolution in mapping.”

Airborne laser elevation (or lidar) surveys provide a 10-fold improvement in the precision with which topographical features are measured, Snyder reports in the current edition of Eos, the weekly journal of the American Geophysical Union.

Lidar represents the latest technology to improve digital topographical maps – known as digital elevation models, or DEMs. Pulsing laser beams released by a lidar device from a plane overhead bounce off of rocks, trees, soil, even water, and send signals back to the device, which makes topographical calculations based on the time it takes the laser signal to return at the speed of light.

Hundreds of beams produce a dynamic topographical picture, Snyder says. In the case of streams and rivers, the technology means that channel features such as water surface, bank edges, floodplains, even the slope of a stream, can be measured, he reports in the journal.

In addition, lidar provides new types of data about the vegetation that covers a particular watershed, such as the height and density of the tree canopy, Snyder says.

“We can look at much finer scale features in streams using a remote mapping technique, as opposed to field work over the entire lengths of streams,” says Snyder, chairman of the steering committee of the National Center for Airborne Laser Mapping. “Digitally, we can now connect topographical features to habitat characteristics or the habitat that needs to be restored.”

That means geologists and other earth scientists will be able to digitally search large swaths of lidar-mapped territory for a particular feature of interest – like salmon habitat or particularly steep sections of streams – then narrow down likely candidates for field study.

“I don’t think this will replace field investigations, but it will allow us to better focus our field investigations,” says Snyder, an expert in river geology, with a particular focus on restoration.

DEM technology, which digitized topographical maps in the early 1990s, led to breakthroughs in research ranging from the relationship between hillside and stream processes to the response of rivers to climate change. But the technology did reveal some limits, such as difficult profiling relatively smooth landscapes.

Traditional DEMs offer a resolution that provides one measure of elevation value for every 10-square meters of ground. Lidar mapping offers one measure of elevation value for each square meter, reports Snyder, whose research was funded by the National Science Foundation.

The amount of land currently mapped using lidar is gradually expanding. The state of Connecticut is the only stated entirely mapped via lidar. Pennsylvania has embarked on a lidar mapping project. Researchers, government agencies and private companies are increasingly using the technology to speed the creation of the next generation of maps, Snyder says.

Aerosols and their part in our rainfall

This is CSIRO atmosphere expert Dr. Leon Rotstayn. -  Photo by: Bruce Miller
This is CSIRO atmosphere expert Dr. Leon Rotstayn. – Photo by: Bruce Miller

“We have identified that the extensive pollution haze emanating from Asia may be re-shaping rainfall patterns in northern Australia but we wonder what impact natural and human-generated aerosols are having across the rest of the country,” Dr Rotstayn said.

Aerosols are fine particles suspended in the atmosphere. Sources of human-generated aerosols include industry, motor vehicles and vegetation burning. Natural sources include volcanoes, dust storms and ocean plankton. Human-generated aerosols have long been known to exert a cooling effect on climate. This has partly masked the warming effect of increasing greenhouse gases. As aerosol pollution is predicted to decrease over the next few decades, unmasking of the greenhouse effect may lead to accelerated global warming.

However, in an address tomorrow to the International Conference on Southern Hemisphere Meteorology and Oceanography in Melbourne, Dr Rotstayn said aerosols are much more than a “negative greenhouse gas” because they can actively force changes in winds and ocean currents by altering the distribution of solar heating at the earth’s surface.

“Recent climate modelling at CSIRO shows that there may be important effects on Australian climate due to aerosol pollution from the Northern Hemisphere. These include an increase of rainfall in north-western Australia, and an increase of air pressure over southern Australia, which may have contributed to less rainfall there.

“New simulations with the CSIRO climate model also show big improvements in the simulation of El Niño and the associated natural rainfall variability over eastern Australia, when natural and human-generated aerosols are included in the model. Natural aerosol includes Australian dust, which may be the key factor that improved our simulation. A realistic simulation of natural rainfall variability is essential if a climate model is to be used to improve our understanding of Australian rainfall changes.

Dr Rotstayn said that further research into how aerosols are influencing climate and rainfall patterns across Australia is critical to scientists’ ability to more accurately predict the longer-term effects of climate change.

“It is crucial to quantify the relative roles of different drivers of recent Australian rainfall changes. A rainfall decline attributed to natural variability will be a passing phenomenon, and changes forced by human-generated aerosols are likely to be more short-term than changes forced by increasing greenhouse gases. The implications for decision makers will be very different, depending on whether the drivers are long-term or short-term,” Dr Rotstayn said.

Beneath the surface

It was the geological collision between India and Asia millions of years ago that created one of the world’s most distinctive places: The area around Lake Baikal in Siberia, which contains 20 per cent of the world’s fresh water reserves and a unique display of plant- and wildlife.

That is the conclusion reached by two Danish researchers from the University of Copenhagen, Professor Hans Thybo and PhD Christoffer Nielsen, after many seismic examinations, including blowing up tons of dynamite, and five years work of analyzing the data.

In the middle of Siberia lies the 2000km long Baikal Rift Zone, where, over the last 35 million years, a gigantic crack in the Earth’s crust has developed. In the middle of this rift zone lies the world’s deepest lake, Lake Baikal, which is almost 1700m deep. Due to Lake Baikal’s isolated location, far from the world’s oceans the microbial and animal life found here has undergone a unique evolution over the last 30 million years. The Baikal Rift Zone, or fracture zone, is also special because it is located 3000km away from the nearest tectonic plate boundary. Therefore, it has been difficult, until now, to explain the origin of the Baikal Rift Zone using commonly accepted geological premises and methods.

However, two Danish researchers from the University of Copenhagen in collaboration with Eastern European colleagues, have succeeded in uncovering what happened, and what is still happening, under the surface of one of the most special and distinctive areas on Earth. More than that; the results from the experiment in Siberia have lead to a new understanding of, and model for, the formation of and activity in rift zones, which are found in locations around the globe, including between the continents.

Lots of dynamite

In Siberia the Danish research team lead a seismic experiment known as BEST (Baikal Explosion Seismic Transects) carried out around Lake Baikal. The experiment included setting off of tons of dynamite so the scientists could follow the sound waves from the explosion as they travelled through the ground, using them to determine the structure of the Earth’s crust and the upper mantle and thus gain an understanding of the processes driving the rift zone’s development.

The fieldwork at Lake Baikal was carried out in 2003-2004 with financial support from the Carlsberg Foundation and the Danish Natural Science Research Council and in collaboration with geologists and geophysicists from the Russian Academy of Science’s Siberian departments and the Polish Academy of Science. Since then the scientists have spent 5 years interpreting the huge amount of data they collected and have ended up with sensational seismic results related to the general formation of, and activity in, rift zones around the world.

The sensational results from Siberia now form the basis for a new model for understanding the formation of rift zones on a global plan. The results from Lake Baikal show that the 40-50km wide crack in the Earth’s crust is around 10km deep. All previous models of rift processes have assumed that the bottom of the Earth’s crust would have a corresponding bulge. However to the researchers’ great surprise it turned out that the bottom of the crust is flat across Lake Baikal. The two scientists explain this phenomenon by a greater thinning of the crust than expected but at the same time also by an intrusion of magma (liquid rock from the Earth’s mantle) into the bottom part of the crust layer. The volume of the magma corresponds to the thinning of the crust.

The research group has therefore reinterpreted data from a number of other rift zones around the globe, including from the East African rift in Kenya where Karen Blixen had her African farm and from an older rift zone in the Ukraine. In both places the researchers see the same phenomenon found in Siberia. This is an important reason for the Danish researcher’s new results.

Rift zones can divide continents

Rift formation is a fundamental process of plate tectonics, which can, given time, split a continent in two. Up until 60 million years ago, what is currently Europe and North America was one large continent. The northern Atlantic appeared when a rift zone developed between what is now Norway and Greenland. The rifting process continued and ca 55 million years ago a new ocean arose.

Rift zones are also important for oil exploration as many oil rich areas have arisen as a result of rift processes. This is true, for example, of the area around the Central Graben in the North Sea which is a former rift zone whose development halted. The Central Graben is the location where the countries bordering the North Sea obtain most of their oil. It is therefore important to understand the processes that lead to rift formation, as it may give us an opportunity to pump more oil up from underground.

Sea level rise could be worse than anticipated

If global warming some day causes the West Antarctic Ice Sheet to collapse, as many experts believe it could, the resulting sea level rise in much of the United States and other parts of the world would be significantly higher than is currently projected, a new study concludes.

The catastrophic increase in sea level, already projected to average between 16 and 17 feet around the world, would be almost 21 feet in such places as Washington, D.C., scientists say, putting it largely underwater. Many coastal areas would be devastated. Much of Southern Florida would disappear.

The report will be published Friday in the journal Science, by researchers from Oregon State University and the University of Toronto. The research was funded by the National Science Foundation and other agencies from the U.S. and Canada.

“We aren’t suggesting that a collapse of the West Antarctic Ice Sheet is imminent,” said Peter Clark, a professor of geosciences at Oregon State University. “But these findings do suggest that if you are planning for sea level rise, you had better plan a little higher.”

The Intergovernmental Panel on Climate Change has estimated that a collapse of this ice sheet would raise sea levels around the world by about 16.5 feet, on average, and that figure is still widely used. However, that theoretical average does not consider several key forces, such as gravity, changes in the Earth’s rotation or a rebound of the land on which the massive glacier now rests, scientists say in the new study.

Right now, this ice sheet has a huge mass, towering more than 6,000 feet above sea level over a large section of Antarctica. This mass is sufficient to exert a substantial gravitational attraction, researchers say, pulling water toward it – much as the gravitational forces of the sun and moon cause the constant movement of water on Earth commonly known as tides.

“A study was done more than 30 years ago pointing out this gravitational effect, but for some reason it became virtually ignored,” Clark said. “People forgot about it when developing their sea level projections for the future.”

And aside from incorporating the gravitational effect, the new study adds further wrinkles to the calculation – the weight of the ice forcing down the land mass on which it sits, and also affecting the orientation of the Earth’s spin. When the ice is removed, it appears the underlying land would rebound, and the Earth’s axis of rotation defined by the North and South Pole would actually shift about one-third of a mile, also affecting the sea level at various points.

When these forces are all taken into calculation, the sea level anywhere near Antarctica would actually fall, the report concludes, while many other areas, mostly in the Northern Hemisphere, would go up.

If the West Antarctic Ice Sheet completely melted, the East Coast of North America would experience sea levels more than four feet higher than had been previously predicted – almost 21 feet – and the West Coast, as well as Miami, Fla., would be about a foot higher than that. Most of Europe would have seas about 18 feet higher.

“If this did happen, there would also be many other impacts that go far beyond sea level increase, including much higher rates of coastal erosion, greater damage from major storm events, problems with ground water salinization, and other issues,” Clark said. “And there could be correlated impacts on other glaciers and ice sheets in coastal areas that could tend to destabilize them as well.”

It’s still unclear, Clark said, when or if a breakup of the West Antarctic Ice Sheet might occur, or how fast it could happen. It may not happen for hundreds of years, he said, and even then it may not melt in its entirety. Research should continue to better understand the forces at work, he said.

“However, these same effects apply to any amount of melting that may occur from West Antarctica,” Clark said. “So many coastal areas need to plan for greater sea level rise than they may have expected.”

A significant part of the concern is that much of the base of this huge ice mass actually sits below sea level, forced down to the bedrock by the sheer weight of the ice above it. Its edges flow out into floating ice shelves, including the huge Ross Ice Shelf and Ronne Ice Shelf. This topography makes it “inherently unstable,” Clark said.

“There is widespread concern that the West Antarctic Ice Sheet, which is characterized by extensive marine-based sectors, may be prone to collapse in a warming world,” the researchers wrote in their report.

Scientists uncover a dramatic rise in sea level and its broad ramifications

Scientists have found proof in Bermuda that the planet’s sea level was once more than 21 meters (70 feet) higher about 400,000 years ago than it is now. Their findings were published in the journal Quaternary Science Reviews Wednesday, Feb. 4.

Storrs Olson, research zoologist at the Smithsonian’s National Museum of Natural History, and geologist Paul Hearty of the Bald Head Island Conservancy discovered sedimentary and fossil evidence in the walls of a limestone quarry in Bermuda that documents a rise in sea level during an interglacial period of the Middle Pleistocene in excess of 21 meters above its current level. Hearty and colleagues had published preliminary evidence of such a sea-level rise nearly a decade ago, which was met with skepticism among geologists. This marine fossil evidence now provides unequivocal evidence of the timing and extent of this event.

The nature of the sediments and fossil accumulation found by Olson and Hearty was not compatible with the deposits left by a tsunami but rather with the gradual, yet relatively rapid, increase in the volume of the planet’s ocean caused by melting ice sheets.

A rise in sea level to such a height would have ramifications well beyond geology and climate modeling. For the organisms of coastal areas, and particularly for low islands and archipelagos, such a rise would have been catastrophic. The Florida peninsula, for example, would have been reduced to a relatively small archipelago along the higher parts of its central ridge.

“We have only to look at Bermuda to begin to assess the impact for terrestrial organisms or seabirds dependant on dry land for nesting sites,” said Olson. “This group of islands in the Atlantic was so compromised as a nesting site for seabirds that at least one species of shearwater became extinct as well as the short-tailed albatross, marking the end of all resident albatrosses in the North Atlantic.”

Determining the timing and extent of this global rise in sea level is not only important for interpreting the influence that it may have had on biogeographical patterns and extinctions of organisms on islands and low-lying continental coastal areas, it is also critical for anticipating the possible effects of future climate change. This particular interglacial period is considered by some scientists to be a suitable comparison to our current interglacial period. With future carbon dioxide levels possibly rising higher than any time in the past million years, it is important to consider the potential effects on polar ice sheets.

Biogeographers, conservationists and many others in the biological sciences must take these findings into consideration, Olson urged. “These findings are incredibly important and have major relevance because of their potential predictive value since this sea-level rise took place during the interglacial period most similar to the present one now in progress. So it is essential that the full extent and duration of this event be more widely recognized and acknowledged.”

Sea-level rise around North America upon collapse of Antarctic ice sheet to be higher than expected

University of Toronto geophysicists have shown that should the West Antarctic Ice Sheet collapse and melt in a warming world – as many scientists are concerned it will – it is the coastlines of North America and of nations in the southern Indian Ocean that will face the greatest threats from rising sea levels.

“There is widespread concern that the West Antarctic Ice Sheet may be prone to collapse, resulting in a rise in global sea levels,” says geophysicist Jerry X. Mitrovica, who, along with physics graduate student Natalya Gomez and Oregon State University geoscientist Peter Clark, are the authors of a new study to be published in the February 6 issue of Science magazine. “We’ve been able to calculate that not only will the rise in sea levels at most coastal sites be significantly higher than previously expected, but that the sea-level change will be highly variable around the globe,” adds Gomez.

“Scientists are particularly worried about the ice sheet because it is largely marine-based, which means that the bedrock underneath most of the ice sits under sea level,” says Mitrovica, director of the Earth Systems Evolution Program at the Canadian Institute for Advanced Research. “The West Antarctic is fringed by ice shelves which act to stabilize the ice sheet – these shelves are sensitive to global warming, and if they break up, the ice sheet will have a lot less impediment to collapse.” This concern was reinforced further in a recent study led by Eric Steig of the University of Washington that showed that the entire region is indeed warming.

“The typical estimate of the sea-level change is five metres, a value arrived at by taking the total volume of the West Antarctic Ice Sheet, converting it to water and spreading it evenly across the oceans, says Mitrovica. “However, this estimate is far too simplified because it ignores three significant effects:

1. when an ice sheet melts, its gravitational pull on the ocean is reduced and water moves away from it. The net effect is that the sea level actually falls within 2,000 km of a melting ice sheet, and rises progressively further away from it. If the West Antarctic Ice Sheet collapses, sea level will fall close to the Antarctic and will rise much more than the expected estimate in the northern hemisphere because of this gravitational effect;

2. the depression in the Antarctic bedrock that currently sits under the weight of the ice sheet will become filled with water if the ice sheet collapses. However, the size of this hole will shrink as the region rebounds after the ice disappears, pushing some of the water out into the ocean, and this effect will further contribute to the sea-level rise;

3. the melting of the West Antarctic Ice Sheet will actually cause the Earth’s rotation axis to shift rather dramatically – approximately 500 metres from its present position if the entire ice sheet melts. This shift will move water from the southern Atlantic and Pacific oceans northward toward North America and into the southern Indian Ocean.

“The net effect of all of these processes is that if the West Antarctic Ice Sheet collapses, the rise in sea levels around many coastal regions will be as much as 25 per cent more than expected, for a total of between six and seven metres if the whole ice sheet melts,” says Mitrovica. “That’s a lot of additional water, particularly around such highly populated areas as Washington, D.C., New York City, and the California coastline.” Digital animation of what various sea-level rise scenarios might look like for up to six metres is at www.cresis.ku.edu/research/data/sea_level_rise.

“There is still some important debate as to how much ice would actually disappear if the West Antarctic Ice sheet collapses – some fraction of the ice sheet may remain quite stable,” he says. “But, whatever happens, our work shows that the sea-level rise that would occur at many populated coastal sites would be much larger than one would estimate by simply distributing the meltwater evenly. Any careful assessment of the sea-level hazard associated with the loss of major ice reservoirs must, of course, account for the sea-level fingerprint of other sources of meltwater, namely Greenland, the East Antarctic and mountain glaciers. The most important lesson is that scientists and policy makers should focus on projections that avoid simplistic assumptions.”

Ancient geologic escape hatches mistaken for tube worms

Tubeworms have been around for millions of years and the fossil record is rich with their distinctive imprints. But a discovery made by U of C scientists found that what previous researchers had labeled as tubeworms in a formation near Denver, Colorado, are actually 70 million-year-old escape hatches for methane.

Tubeworms, or siboglinids, look like long lipstick tubes and have been observed in warm and cold environments on the ocean floor, as well as in whale carcasses and decomposing organic-rich cargoes in sunken ships. Ecosystems teeming with tubeworm colonies were discovered at hydrothermal vents in the Galapagos Ridge in 1977 and at cold seeps at the base of the Florida Escarpment in 1984. As a result of these modern sightings, a number of fossil examples of tubeworms were subsequently identified in the rock record. One of these localities, found south of Denver, Colorado, was recently re-examined by U of C scientists.

In an area approximately one and a half times the size of the City of Calgary, scientists discovered that what was previously identified as fossilized tubeworms were actually fossilized tubular escape hatches for methane, a major constituent of natural gas.

“It is the first time that evidence of a natural ancient geologic conduit system has been discovered where gas, water and solids were all being vented at once,” says Federico Krause, the lead author of the paper which is co-authored by Selim Sayegh, an adjunct professor in geoscience, Jesse Clark, a former undergraduate student, and Renee Perez, research associate in the Department of Chemical and Petroleum Engineering. The paper is published in this month’s edition of Palaios.

The discovery was made possible thanks to the Stable Isotope Laboratory of the Department of Physics and Astronomy and the electronic microprobe housed in the Department of Geoscience. Stable isotopes and chemical elements maps demonstrated that not only methane gas bubbles were being expelled but that solid particles that had adhered to the bubbles were also being ejected from the fossil vents.

Although the results may be surprising, the ramifications are even more so.

The fact that methane gas can escape from a thick shale seafloor may demonstrate that there needs to be more research done on the integrity of geologic seals in petroleum reservoirs earmarked for CO2 injection,” says Krause who is a professor in the Department of Geoscience at the University of Calgary. “It shows that under different geologic circumstances gases that are present in underground formations can indeed seep out, and all the effort expended in trying to remove CO2 from our atmosphere would be lost.”

In addition, there are vast volumes of methane gas naturally trapped beneath the seafloor in the form of gas hydrates. If these hydrates were to be destabilized, methane bubbles could release large quantities of microparticles to the ocean bottom. This release would cloud up the deep ocean and the effect would be akin to fouling up the atmosphere with a dense smog. Given that the ocean bottom is one of the last frontiers of petroleum exploration, further research will be needed to properly plan for the location of production and containment facilities on the seafloor. Installation of these facilities has the potential to destabilize underlying hydrates.

“These 70-million-year-old tubular escape hatches south of Denver, Colorado, provide a glimpse to processes that are occurring in the ocean bottoms at present,” says Krause. “While finding tubeworms would have been satisfying, uncovering tubular gas vents has been much more exciting.”

China monsoon rainfall prediction and Pacific surface-subsurface sea temperature anomalies

The Monsoon and Environment Research Group of Peking University submitted a report to Chinese Science Bulletin, recently, showed that regional summer monsoon rainfall in China can be predicted by 1-2 seasons ahead by using the signals of the sea surface temperature anomaly (SSTA) and the subsurface temperature anomaly (STA) in the central equatorial Pacific (CEP). Several new facts have been revealed as follows.

(1)The strongest center of SSTA along the equatorial Pacific has migrated westward from the eastern equatorial Pacific (EEP, NINO3 region) to the CEP (NINO3.4 or NINO4 region) in the last half century. Regular inter-annual oscillations or variation frequency of SSTA in the equatorial Pacific are modulated by intensive La Niña events for about decadal interval. The winter phase-lock feature for warming events is commonly found at different intervals but warming places are also modulated by intensive La Niña events. The positive SSTA along the equatorial zone results from exposing positive STA which appears about 3 months earlier than SSTA. This is a precursory signal for indicating the future warming or cooling event in the equatorial Pacific.

(2)The subtropical summer monsoon rainfall in China has had a long-term rising trend for the last two decades. The long-term increasing trend is still continued in the central China (Huaihe) region but a deducing trend has been observed since 1998 in southern regions. A typical biennial oscillation of summer rainfall anomaly has been found in central China and biennial oscillation of SSTA has also been observed in the CEP since the early 21st century.

(3)Since the beginning of the 21st century, three warm events in winter occurring in the CEP have been accompanied with more summer rainfall in central China and less summer rainfall in southern China. The warm SSTA indicated that the winter phase-lock SSTA had a determined relationship with the summer rainfall anomalies in central China and southern China respectively. This relationship shows that the more summer rainfall in central China follows the winter-spring warm water in the CEP while the more summer rainfall in southern China may follow the winter-spring cool water in recent years. A cold water event was observed in 2008 so that the more summer rainfall has been successfully predicted in southern China.