Research by scientists affiliated with the Earth Institute at Columbia University

12/13/04

Presented to the American Geophysical Union, December 2004



One of the presentations by Earth Institute scientists involves seismic research in Italy. To understand the subterranean structures that influence earthquakes there, an international team deployed 39 broad-band seismometers in a two-dimensional array extending from the southern Apennines into Calabria. In Campana, researchers placed a seismograph in this crypt, located below the alter of a church.
Click here for a high resolution photograph.

Following are summaries of a few of the papers being presented at the AGU meeting by scientists affiliated with the Earth Institute at Columbia University. For more information about the Earth Institute, please see www.earth.columbia.edu.

Global Poverty
MAPPING POVERTY: THE GEOGRAPHICAL AND BIOPHYSICAL CORRELATES OF HUNGER AND INFANT MORTALITY
It is difficult to design programs to reduce poverty unless you understand where and why that poverty occurs. De Sherbinin and colleagues present recent efforts to integrate global spatial datasets and survey microdata to investigate worldwide drivers of hunger and infant mortality. Data specialists at Columbia's Center for International Earth Science Information Network (CIESIN) are mapping poverty indicators as part of a United Nations-led effort to improve ability to diagnose the causes of poverty and hunger around the world. Alexander M. de Sherbinin, Senior Staff Associate, CIESIN, (adesherbinin@ciesin.columbia.edu, 845-365-8936)

This paper is presented as part of the AGU Special Session on Earth science, human wellbeing, and the alleviation of global poverty. Convened by: John Mutter, Arthur Lerner-Lam, and Daniel Schrag

Paleoclimate
IMPROVED TECHNIQUE TO REVOLUTIONIZE RADIOCARBON DATING
Chiu and Fairbanks present new research that has doubled the timeline over which radiocarbon dating can be performed, and shown a flaw in current radiocarbon dating techniques that has skewed previous fossil dating hundreds to thousands of years in the past. The research shows that a new type of mass sectrometer, combined with an adjustment to the pretreatment and screening of fossil corals, an excellent archive for extending calibration beyond the tree ring records, makes dating much more accurate and precise. Scientists applying radiocarbon dating to their research have since 1998 depended on the radiocarbon calibration curve by Stuiver, which only goes back 20,400 years. "We believe that our doubling of this calibration and significant refinement along with the geophysical and geochemical interpretations will make our new calibration curve the standard for radiocarbon dating," predicts Fairbanks. Richard Fairbanks, Professor, Department of Earth and Environmental Sciences (DEES) (Fairbanks@ldeo.columbia.edu, 845-365-8499), and Clara Chiu, graduate student.

Dr. Fairbanks will also, separately, present a refined model of continental deglaciation, with an accurate new methodology for predicting changes in sea level as a result of changes in land ice volume.

Climate Change
ORIGINS OF ARCTIC SOOT
The fragile Arctic is especially susceptible to the impacts of particles and other pollution. Soot, transported to the Arctic from Asia, Europe, and elsewhere, may affect the radiative balance there, shifting temperature profiles, clouds and precipitation. Absorbing particles, such as black carbon or soot, may accelerate ice and snow melting. Dorothy Koch and James Hansen discuss what global climate models reveal about the origins of black carbon, in the Arctic. Model results suggest a larger contribution of soot and other particles from South Asia to the Arctic than has been inferred in previous Arctic haze studies. hDorothy Koch, Associate Research Scientist, GISS at Columbia, 212-678-5605, DKoch@GISS.nasa.gov; James Hansen, Director, GISS at Columbia, 212-678-5500, JHansen@GISS.nasa.gov.

USING REGIONAL MODELS TO ASSESS POTENTIAL FOR EXTREME CLIMATE CHANGE
Lynn and Rosenzweig discuss exciting progress in the study of climate change and its potential impacts on human society. The team used the circulation pattern from General Circulation Models (GCMs) as background (lateral boundary) conditions to simulate climate change at the regional and local (or city) scale. Results from these models can be used to study human impacts such as health impacts, or future water and energy requirements. The authors' analysis of the modeled data, compared with observational data, suggests that extreme climate change should be considered as a possible outcome of greenhouse forcing on the earth-climate system. Barry H. Lynn, Associate Research Scientist, Center for Climate Systems Research (212-678-5543; bhl7@columbia.edu), Cynthia Rosenzweig, Adjunct Senior Research Scholar GISS at Columbia (212 678 5562; crosenzweig@giss.nasa.gov).

WHAT DO LONG-TERM WARMING TRENDS TELL US ABOUT RECENT CLIMATE CHANGE? A LOOK AT THE DYNAMICS OF 20TH CENTURY CLIMATE TRENDS
Chen and colleagues present analysis of 20th century global climate trends, using long-term records to separate for the first time the human-induced trend from shorter-term variations that are unrelated to climate change. The authors discuss the mechanisms behind climate trends, including the weak warming trend perceived in the Pacific Ocean, and contemplate the atmospheric response to the warming that determines how regional climate is changing in the tropics. Junye Chen, Department of Earth and Environmental Sciences (jc780@columbia.edu, 212-678-5556); Anthony Del Genio, Adjunct Professor, Earth and Environmental Sciences (adelgenio@giss.nasa.gov, 212-678-5588); Barbara Carlson, Physical Scientist, Goddard Institute for Space Studies (bcarlson@giss.nasa.gov, 212-678-5538).

Seismic Mapping
EARTHQUAKES IN ITALY: THE CAT/SCAN SEISMIC EXPERIMENT
To understand the subterranean structures that influence earthquakes in Italy, an international team has deployed 39 broad-band seismometers in a two-dimensional array extending from the southern Apennines into Calabria. Calabria is the toe of Italy, and part of the most seismically active belt in Italy. The international project, supported by the National Science Foundation, is known as the Calabrian-Apennine-Tyrrhenian/ Subduction-Collision-Accretion Network (CAT/SCAN). In a series of AGU presentations, members of the team discuss their preliminary findings on what is driving active structures below the earth's surface. Michael Steckler, Doherty Senior Scientist, steckler@ldeo.columbia.edu, 845-365-8479, Art Lerner-Lam, Director, Center for Hazards and Risk Research, Earth Institute at Columbia (lerner@ldeo.columbia.edu, 845-365-8356), Leonardo Seeber, Doherty Senior Research Scientist, LDEO, (nano@ldeo.columbia.edu, 845-365-8385), and Deirdre Commins, Postdoctoral Research Fellow, LDEO (dcommins@ldeo.columbia.edu, 845-365-8580).

SEISMICITY AND FAULT STRUCTURE IN CA: IMPROVED DATA AND IMAGING
Felix Waldhauser, David Schaff, and colleagues present research aimed at increasing understanding of seismicity and fault structures throughout Northern California. The research team used the previously known techniques of waveform cross correlation to improve seismic arrival time measurements, and multiple event location techniques to reduce model errors. They applied these techniques on a massive scale to all 250,000 events recorded in the NCSN catalog of Northern California. The authors comment on and present results from ongoing efforts, based on these newly adjusted data, to produce more accurate and detailed images of fault structures in Northern California and their correlation with the local geology. Felix Waldhauser, Doherty Associate Research Scientist, LDEO (felixw@ldeo.columbia.edu, 845-365-8538).

Dr. Waldhauser with colleages Bill Ellsworth and David Oppenheimer of the US Geological Survey, will also be discussing research on the recent Parkfield M6 earthquake in Central California that occurred on September 28, 2004.

Oceanography
THE HOW AND WHY OF OCEAN FLOOR GAS BLOWOUT STRUCTURES
Along the U.S. Atlantic margin are sites where giant methane gas explosions have occurred, and other places that are actively emitting methane as well as fluid from under the seafloor. Oceanographers from the Lamont Doherty Earth Observatory and elsewhere conducted surveys of these structures aboard the R/V Cape Hatteras in July, 2004. These surveys provided the data for several Earth Institute scientists to take a closer look at these large-scale gas blowout features. In several presentations, scientists discuss new discoveries based on data collected during the July voyage, such as correlations between the blowouts, methane gas emissions, and marine life, and links between fluid expulsion and slope stability. Jeffrey Weissel, Doherty Senior Scholar, LDEO (845-365-8818, jweissel@ldeo.columbia.edu).

OCEAN MIXING IN UNDERSEA CANYONS NEAR A MID-OCEAN RIDGE
Ocean circulation depends on dense water sinking, balanced by more buoyant water rising elsewhere. The authors of this study discuss their finding that a large portion of this mixing occurs in underwater canyons as water flows across sills within the canyons. In previous studies it has been suggested that the enhanced mixing is primarily caused by breaking internal waves forced by tidal flows, but now it appears that sill-related mixing in canyons seems to be at least as important as tidal mixing. Andreas Thurnherr, Doherty Associate Research Scientist (845-365-8816, ant@ldeo.columbia.edu)

HELIUM ISOTOPES AND THE STUDY OF OCEAN CIRCULATION
Helium isotopes have been used to study global ocean circulation since the 1960's, but new research has provided more detailed information on the distribution of helium isotopes, as well as their sources and sinks in the ocean. This information can now be applied to construct global fields of helium isotopes and to extract unique information on the circulation patterns at different depth levels in the ocean, as well as on local and regional processes such as ventilation of water masses in deep water formation regions. Additionally, the data sets are now sufficiently large to be useful for validation of Ocean General Circulation Models (OGCM's). Peter Schlosser, Associate Director, The Earth Institute at Columbia University (212-854-0306, schlosser@ldeo.columbia.edu).

Arsenic
TRYING TO PREVENT ARSENIC FROM LEACHING OUT OF LANDFILLS
Two papers from Lamont Doherty Earth Observatory scientists examine how a landfill in Maine causes release of naturally-occurring arsenic from sediment into groundwater, and efforts to prevent this groundwater from seeping out of this landfill. When several methods of removing the arsenic failed, the researchers came up with another idea: sequestration of arsenic through the formation of solid phase sulfides under sulfate-reducing conditions. This technique was tested in the laboratory, with promising results. Over ten days, roughly 70 to 80% of the dissolved arsenic and more than 99% of the dissolved iron was removed from solution. The prospects are promising for preventing high arsenic groundwater plumes at this and similarly affected landfill sites. Alison Keimowitz, Graduate Research Fellow, ark@ldeo.columbia.edu, 845-365-8793

ARSENIC VARIATION OVER TIME IN BANGLADESH AQUIFERS
A team of Earth Institute researchers has been looking at the geology of shallow aquifers in Bangladesh as part of a five-year study aimed at preventing people in rural Bangladesh from suffering as a result of ingesting arsenic in their well water. Tens of millions of people in South Asia are affected by this problem. The spatial variation of arsenic in the Bangladesh study area has been fairly well understood (it varies even within small areas), but the current study addresses variation from single sources over time. The study site consisted of six nests of monitoring wells installed in an area where the hydrology and geochemistry had been carefully studied The study shows that the wells studied did not display any discernable arsenic pattern linked to seasonal water table fluctuations. This suggests that once an aquifer is found to be safe for drinking, it will stay safe throughout the year. R.K. Dhar with Martin Stute, Adjunct Research Scientist, LDEO martins@ldeo.columbia.edu 845-365-8704.

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