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NEWS NOTES | November 1998 |
Rethinking past climate cycles
In the depths of the biosphere
Moving beyond diversity
Celebrating earth science
Cleaning soils with electrodes
The timing of such events is precisely known in the Greenland ice cores, which have been dated with direct counting of annual layering in the ice (warmer climates are wetter and leave behind layers of powdered snow). An ongoing challenge has been to date Antarctic cores just as precisely, which will make it possible to compare them directly to the Greenland cores and determine the cause-and-effect cycle that fuels the climate changes. Antarctic ice cores are harder to date because the rate of snowfall - and hence, the thickness of annual layers - is much smaller in Antarctica.
An American team and a European team both used a dating method that allowed them to place the Antarctic ice cores on the same time scale as the Greenland cores. They dated the ice cores by comparing the global atmospheric concentrations of methane as recorded in ice cores from both continents. The atmosphere is very well mixed, so the global swings in methane concentration that occurred between 12,000 and 50,000 years ago were recorded simultaneously in the ice of both continents, says Eric Steig, lead author for the American team.
But although this dating method has made it possible to draw direct comparisons between Greenland and Antarctic cores, the debate continues. The European team that first used the dating method found that Greenland warming events lagged behind corresponding Antarctic events by more than 1,000 years. At the same time, an American team analyzing an Antarctic ice core closer to the continent's coast has found that the warming at the end of the last glacial period and the Younger Dryas occurred synchronously in Greenland and at their Antarctic site.
Thomas Blunier, of Switzerland's University of Bern, and his colleagues were the first to cross-date isotope records in ice cores from Greenland and Antarctica to within a few centuries by using this methane-comparison method. They published their Antarctic core analysis in the Aug. 20 Nature. They compared isotope records in the Greenland reference core and in the Byrd ice core from Antarctica dating to the last ice age. Blunier's team found that Greenland warming events occurring about 10,000 years and 45,000 years before the present lagged behind similar Antarctic warming events by more than 1,000 years. "This observation contradicts the hypothesis that Antarctic warmings are responses to events in the Northern Hemisphere," they write. "The observed time lag also calls into question a coupling between northern and southern polar regions via the atmosphere, and favors a connection via the ocean."
The ocean could also be responsible for the trend found by the American team, led by Steig, who is currently with the University of Colorado's Institute of Arctic Alpine Research and set to join the University of Pennsylvania this fall. Steig and his colleagues published work in the Oct. 2 Science from analysis of a different Antarctic ice core, contradicting the evidence presented by Blunier's team. Steig's team analyzed methane concentrations in an ice core from the Taylor Dome in Antarctica's western Ross Sea. They compared it to the Greenland Ice Sheet Project 2 (GISP2) core, using the same dating method as Blunier's team. The Taylor Dome core, they write, recorded two prominent Northern Hemisphere events - the rapid warming at the end of the last glacial period and the Younger Dryas sudden cooling event. More importantly, the Taylor Dome corresponds in time with the climate changes recorded in GISP2.
"Differences between the isotope-temperature history from Taylor Dome and those from other Antarctic sites are too large to be attributed to dating errors," Steig and his colleagues write. "Rather, the results indicate that the circum-Antarctic climate response to changes in NADW [North Atlantic Deep Water] formation ... may not be uniform." Steig's team speculates that the difference could arise from the Taylor Dome core's closer proximity to the Ross Sea, which they point out is an area of active wind-driven convection and ocean-atmosphere heat exchange today. "Mechanisms have been proposed that behaviors of the Southern Ocean have been controlled by changes in the North Atlantic," Steig says. It's possible that changing circulation in the North Atlantic caused changing temperatures in the Southern Ocean, which in turn affected climate in some parts of Antarctica, he says. "Taylor Dome may thus record the direct but localized influence of NADW-borne heat on Antarctic climate," they write.
Most importantly, Steig says, the research suggests a rethinking when
debating the global scope of past climate events. It may not be a simple
question of lead or lag - one hemisphere leading or lagging behind the
other in climate change. Around Antarctica, at least, climate changes may
be heterogenous. "It appears that both the warming and cooling around Antarctica
can be consequences of cooling in the Northern Hemisphere," Steig says.
Researchers can no longer assume that the relationship is simple.
- K.B.
In addition to gaining new information about seismic and volcanic activity at Papua New Guinea, the scientists studied that area's biosphere, making the two longest profiles into the deep sub-sea floor. They discovered that bacteria remain present in sediment and rock samples as deep as 846 meters into the subsurface. The existence of apparently living microbial material in hard sedimentary rock as old as 15 million years extends the known limit of the biosphere.
"The discovery of the deep bacterial biosphere has changed our perception of life from a surface 'fuzz' on the planet," says co-chief scientist Philippe Huchon of the École Normale Supérieure in Paris. "[This] has profound implications for the biodiversity of our planet, fossil fuel formation, the origins of life on Earth, and the potential for life on other planets."
Subsurface microbes
The same week in which the JOIDES Resolution docked in Sydney,
the Aug. 14 issue of Science published a paper on rock-eating microbes
that live nearly a mile beneath the sea floor. Researchers from Oregon
State University (OSU) and the University of Bergen (Norway) write that
they have discovered evidence of microbial DNA deep within tubes that are
hidden in subsurface fractures. According to Martin Fisk, associate professor
of oceanography at OSU and lead author of the study, microbial fossils
were found in abundant quantities in miles of core samples taken during
various research projects by the ODP in the Pacific, Atlantic, and Indian
oceans.
Fisk and his associates conducted research examining basalts that had been weathered by seawater circulation. "Previous studies of weathering of the quenched glass of ocean basalts have shown intricate weathering patterns that are unlike the weathering ... produced by chemical weathering or experimental alteration of glass," the authors write. Fisk says he became curious about the possibility of life [in the subsurface] after looking at the swirling tracks and trails that were etched into the basalt. The rocks have the basic elements for life, including carbon, phosphorous, and nitrogen - they need only water to complete the formula. Fisk points out that groundwater seeping through the ocean floor could easily provide that.
The scientists say that either bacteria or archea or (although less likely) a new, undocumented chemical process could be providing the tracks that imply microbial activity. Evidence was only found in the glassy outer layer of the basalt, in the first inch of material. Fisk believes the looser chemical structure of the quickly cooled rock makes it easier for microbes to break it down. The microbes were probably carried beneath the sea floor in ocean water, seeping into the basalt and settling in fractures. There they found the necessary ingredients to continue living.
"The microbes would make these little tubes, and inside them were germ-sized bodies," says Fisk. "They are either eating the rock or excreting some kind of acid that is doing it." The researchers now want to attempt to bring up fresh core samples and extract the microbes while they are still alive. Preserving live microbes from rocks found nearly a mile beneath the ocean floor, however, won't be easy, says co-author Stephen Giovannoni, associate professor of microbiology at OSU. Contamination from the drill itself is a potential problem, as is the enormous difference in pressure between the sea floor and the surface.
Fisk suggests that the microbial activity deep beneath the sea floor might be evidence that microbes could live beneath any rocky planet - including Mars or one of Jupiter's moons. The temperatures on these planets shouldn't be a problem, since microbes have been found to exist in extreme conditions on Earth, from super cold to boiling.
Life in extreme environments
Projects to study microorganisms living in extreme environments are
also underway. Oceanographers aboard the National Oceanic and Atmospheric
Administration's ship Ronald H. Brown (see Geotimes, December
1997) spent September preparing to establish a sea-floor observatory at
Axial Volcano, off the coast of Oregon. Studying the heat-loving microorganisms,
called "thermophiles," will help scientists understand the unique relationships
between the microbial biosphere beneath the volcano and volcanic hot springs.
On the Big Island of Hawaii, the Jet Propulsion Laboratory (JPL) is
running an experiment at an undersea volcano. The Lo'ihi Underwater Volcanic
Vent Mission Probe will be looking for life at the volcanic vents. JPL's
Lonne Lane, principal investigator for the experiment, says, "The information
to be gathered from these experiments ... will prepare us for future missions
to difficult places like Antarctica's Lake Vostok and below the surface
of Jupiter's ice-encrusted moon Europa."
- D.W.
"Being prepared, anticipating, foresight, proaction, not reaction - this is how I believe science should move to meet the challenges of the 21st century," Colwell said. She stressed math and science education and information technology as research priorities for NSF.
She also discussed the emerging concept of biocomplexity. "The myriad forces of a burgeoning world population, coupled with the power of technology, have altered the global environment in ways never before possible," she said. "There is both opportunity and responsibility here for the science community. This is where the concept of biocomplexity takes shape as a research direction." She said biocomplexity goes a step beyond the concept of biodiversity. Scientists need to not only take inventory of Earth's diverse ecosystems, but to find the chemical, biological, and social interactions of Earth's systems, she said. "This is not the work of just the life sciences community. ... It must be of similar concern to the larger science community and to the public. To accomplish this, the science community needs to be more comfortable with dialogue beyond its own inner circles."
Colwell came to NSF from the University of Maryland, where she was president of the Biotechnology Institute and a professor of microbiology. She replaced former NSF director Neal Lane, who is now Assistant to the President and Director of the Office of Science and Technology Policy. Colwell earned her Ph.D. in marine microbiology from the University of Washington and is chairman of the Board of Governors of the American Academy of Microbiology. She is a past president of AAAS and has held numerous advisory positions in the U.S. government, private foundations, and the international community. She also produced a film on marine microbiology called Invisible Seas.
NSF and the geosciences
Asked how the Directorate of Geosciences, the division of NSF that
funds geoscience research, meshes with the concept of biocomplexity, Colwell
said, "I don't see a mismatch there." She added that the ocean sciences
are part of ecology, and that biocomplexity requires input from all the
basic sciences.
The Earth Sciences Division within the Directorate for Geosciences funds research in geology and paleontology, continental dynamics, petrology and geochemistry, hydrologic sciences, instrumentation and facilities, geophysics, and active tectonics (Geotimes, January 1998). The Directorate for Geosciences also includes the Atmospheric Sciences Division and the Ocean Sciences Division. Proposed funding for the directorate for fiscal year 1999 is about $500 million - representing about 13 percent of the total NSF budget request of about $3.8 billion and an 11.5 percent increase over the FY 1998 geosciences budget.
Earth-science funding also comes from the Office of Polar Programs,
created to fund research and maintain research stations in the Arctic and
Antarctic. The FY 1999 budget request allots about $180 million for polar
research programs - a 9.9 percent increase over FY 1998 - and about $62
million for logistical support of Antarctic research.
- K.B.
The first annual Earth Science Week, held Oct. 11-17, celebrated geologists' contributions to society and also highlighted the diversity of earth-science professions. The widespread enthusiasm for the event suggests it also filled a need, says Sam Adams, former AGI president and chair of AGI's 50th Anniversary Committee. Geologists from just about every segment of the profession signed on to promote the celebration in their communities, he says. "The fact that we were able to find something that works for everybody suggests that the need has been enormous. It is a way for us to communicate information and excitement about the earth sciences to the average citizen, and that's exactly what our profession needs."
AGI encouraged volunteers to spread information by the ripple effect, Jackson says, using newspapers, television stations, newsletters, and word-of-mouth to generate enthusiasm in their own communities. After she established an Earth Science Week web site, sent out flyers and press releases, and published announcements in the newsletters of other geoscience societies, the word spread quickly. In museums, libraries, community colleges, universities, and secondary-school classrooms, the earth sciences were examined and the work of earth scientists described.
A matter of recognition
Thirty-six state governors proclaimed Earth Science Week, and Oregon
Sen. Ron Wyden entered the Earth Science Week resolution adopted by the
Association of American State Geologists into the Congressional Record.
That kind of national attention was a larger sign of the recognition geologists
and teachers achieved in their local communities.
"Earth Science Week gave us the vehicle to create publicity and communication and education [programs] for something I've been wanting to do for many years," says Walt Schmidt, state geologist of Florida. Because Earth Science Week was sponsored by the American Geological Institute, Schmidt says, it had the visibility and credibility he needed to win an Earth Science Week proclamation from Governor Lawton Chiles, to obtain funding from the Florida Department of Environmental Protection for an Earth Science Week symposium at Tallahassee's convention center, and to use the Wakulla Springs State Park for a public education day. Schmidt used the events to emphasize how the solid Earth and Earth's systems create ecosystems and affect water resources. "We focused on the surface environment and how the surface of Earth must be understood in order to understand groundwater - and the word was interconnectedness." He hopes this year's celebration will become an annual one in Florida, staged at a different water basin and in a different community each year.
At the Austin Community College in Austin, Texas, associate professor Robert Blodgett mobilized all his resources to draw public and media attention to both the earth sciences and the college. "It was something that raised visibility of geologists in the city," he says. "People are aware of what geologists do and how they get their information." Earth Science Week also helped Blodgett establish communication links between secondary-school earth-science teachers in central Texas and professors at the community college - a link that didn't exist before he organized the events. Volunteer geologists visited classrooms, serving as "a catalyst for getting people together to do things," he says.
Celebrations from the The Earth & Mineral Sciences Museum at Pennsylvania State University to a former quarry in Hamburg, N.Y, to the Exploratorium Museum in San Francisco and to a street festival in Washington, D.C., made Earth Science Week a national event.
"I don't want to see the first annual [Earth Science Week] be the last,"
says Robert Cowdery, chairman for the Kansas Geological Society's public
relations committee and past president of the society. The Kansas Geological
Society invited astronaut James Reilly (see p. 14), a former exploration
geologist, to speak to earth scientists in Wichita. "It takes funding,
and it takes somebody [being] interested," Cowdery says. "And it takes
someone in every state."
- K.B.
The problem of soil contamination is acute, and current techniques don't work in all situations, says Krishna Reddy, assistant professor of civil engineering at UIC, and one of several engineers pursuing soil remediation. "I asked, what are the mechanisms that prevent us from totally removing contaminants, and how can we counter those hindering mechanisms," he says. In his research, Reddy discovered that soil chemistry and synergistic effects between different elements of the mix of contaminants could limit the usefulness of electrokinetics. His recent experiments show possibilities for overcoming the problems.
Electrokinetics works on the principle that opposite electric charges attract. Engineers at contaminated sites, which are typically about football-field size, drill an array of wells into the soil, place electrodes or wires inside, and connect the electrodes to a small direct-current source. These procedures set up an electric field between pairs of electrodes, pulling positively charged pollutants toward the negative electrode (cathode), and negatively charged pollutants toward the positive electrode (anode). It can take years for pollutants to migrate through the soil, but eventually they concentrate around the wells and can be pumped out or excavated from a small area.
There are three other mechanisms at work: an electrical potential applied to the soil causes the pore water to move (electro-osmosis); chemical constituents move in response to chemical concentration gradients (diffusion); and water and the associated dissolved chemical constituents move in response to hydraulic gradients (hydraulic flow). Electrokinetic soil decontamination can be used to clean up many of the estimated 200,000 sites around the country, including former dumping grounds used by the electroplating industries, underground storage tanks at gasoline stations, weapons laboratories, and civilian sites.
Reddy devised an approach using so-called purging solutions. The engineers apply water-soluble chemicals around the cathodes to correct soil acidity problems and withdraw the pollutants. This process can be repeated at the anodes until all types of contaminants are removed. Reddy is also studying ways to decontaminate organically polluted soils.
"It's hard enough to remove metals, but for organics, a further problem is that they don't dissolve in water," says An Li, assistant professor of environmental and occupational health sciences at UIC. She is working with Reddy on the problem of remediating soils contaminated with organic compounds such as polychlorinated biphenyls. The organics can't be carried through the soil in standard electrokinetics, Li explains.
The trick, she says, is to add a co-solvent to the water that will enhance the solubility of the organic compounds. If she and Reddy can find the appropriate co-solvent, says Li, the organic compounds will dissolve and move along with the water, making it possible to remediate low-permeability soils, like clay.
"Electrokinetics has advantages over other approaches," Reddy says.
"You're not excavating and disposing of the soil on a large scale so it's
safe, and you don't disturb the site operations." Reddy and Li presented
their research results at the annual meeting of the American Chemical Society
in August.
- D.W.
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