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Tip Sheet

For immediate use

Dec. 7, 2006 -- No. 587

Climate change, Earth and oceans
focus of UNC-Chapel Hill at AGU

CHAPEL HILL -- Researchers from the University of North Carolina at Chapel Hill will present findings on a variety of earth science topics at the 2006 annual fall meeting of the American Geophysical Union (AGU). The meeting runs Monday (Dec. 11) through Dec. 15 at the Moscone Convention Center in San Francisco, Calif. Highlights from UNC-Chapel Hill researchers include:

The following is a chronological list of presentations and detailed session information.

Impacts of land use and inter-annual climate variability on nitrogen export characteristics
9 a.m. PT, Monday, Dec. 11
Abstract number: H11J-05
Catherine Shields, master's student, Department of Geography
cat_shields@unc.edu

The spread of urban areas into former farm and forest areas (sprawl) is producing a mosaic of different residential, remnant farm and forest and commercial land uses. Nutrients, including nitrogen and phosphorus, flow from these areas into receiving freshwater and marine environments. The nutrients contribute to water quality degradation and affect resources such as drinking water, fisheries and recreation areas. Understanding nutrient transport includes generating long-term measurements of water flow and quality from a number of watersheds in the Baltimore area, and analyzing the variations in the amount and timing of nutrient loading into aquatic ecosystems. The results have important implications for stream restoration methods intended to reduce nutrient contamination from these areas.
Related study: http://www.unc.edu/news/archives/sep05/band090205.htm

The interpretation of energy and energy fluxes of nonlinear internal waves:
an example from Massachusetts Bay

1:40 p.m. PT, Monday, Dec. 11
Abstract number: OS13A-1543
Alberto Scotti, assistant professor, department of marine sciences
ascotti@unc.edu

Freak waves are the stuff of legends among seafarers. Less well known, but much more widespread, are giant waves that propagate internally within the ocean. Their effect on the sea surface is small, albeit detectable from satellites. However, within the water column they have a strong influence on the dispersal of plankton and pollutants, and affect how the ocean mixes itself. "When it comes to assessing how much energy these waves transport, the old theory just does not add up," Scotti said. Scotti and his colleagues developed a new theory to asses the amount of energy transported by these waves and applied the model to waves observed in Massachusetts Bay.

A Tale of Two Limpets (Patella vulgata and Patella stellaeformis): Evaluating a New Proxy
for Late Holocene Climate Change in Coastal Areas

8 a.m. PT, Tuesday, Dec. 12
Abstract number: PP21C-1698
Donna Surge, assistant professor, department of geological sciences
donna64@unc.edu

Surge reports on the first phase of a project to reconstruct climate change using chemical variation in limpet shells from Viking-age deposits in the United Kingdom. The shells were used for fishing; discards accumulated as shell middens. The age of these middens range from the ninth to fourteenth centuries, spanning the height and demise of Viking exploration. This time span corresponds to the Medieval Warm Period and Little Ice Age climate intervals. The first phase of the project involves developing proxies (tracers) of seawater temperature using modern shells. These proxies will allow the researchers to ultimately decipher the climate archives preserved in Viking shells as chemical (oxygen isotope) variations.

Growth and interaction of active faults within a nascent shear zone, central Mojave Desert, California
8 a.m. PT, Tuesday, Dec. 12
Abstract Number: T21B-0403
Michael Oskin, assistant professor, department of geological sciences
oskin@email.unc.edu

Complex plate boundary fault systems, such as California's San Andreas, are constantly changing through the growth and interaction of active, earthquake-producing faults. Understanding the processes underlying fault growth and interaction is important for understanding triggering of earthquakes from transfer of stress from nearby faults. In the Eastern California shear zone -- a portion of the Pacific-North America plate boundary east of the San Andreas fault -- a complex network of interacting faults takes up to 20 percent of total plate motion. Some faults within this network formed very recently in the geologic past, probably within the last 1 million years. Measurements along the Calico fault reveal both fault slip rate and total fault displacement vary along its length as it interacts with other faults.

Climate Variability, Melt-Flow Acceleration, and Ice Quakes at the Western Slope
of the Greenland Ice Sheet

10:20 a.m. PT, Tuesday, Dec. 12
Abstract number: U22A-01
Jose Rial, professor, department of geological sciences
jar@email.unc.edu

Measurements of seismic activity in Greenland's ice sheet indicate the activity is related to the ice sheet's probable fragmentation due to global warming. Project SMOGIS (Seismic Monitoring of Greenland's Ice Sheet), a collaboration between UNC-Chapel Hill and the University of Colorado at Boulder, has detected intense microearthquake activity throughout the region close to the Jacobshavn glacier, one of the world's fastest moving glaciers. The seismic activity is clearly related to glacial sliding (at the base of the ice sheet) and crevassing, or large fractures expanding under the increased warming. "The area we are inspecting could be seen as belonging to the buttresses of a giant cathedral, which is the Greenland ice sheet," Rial said. "If the buttresses fail, the entire cathedral could collapse, perhaps in just a few years. This may be part of what has been called abrupt climate change."

Incremental Growth and Consolidation of the Half Dome Granodiorite, Tuolumne Intrusive Suite
12:05 p.m. PT, Tuesday, Dec. 12
Abstract number: V22A-08
Drew Coleman, associate professor, department of geological sciences
dcoleman@unc.edu

Coleman and his colleagues are examining magmas that freeze in place before they erupt in an effort to better understand the rates that magmas are added under volcanoes. The work is aimed at evaluating the record of magma additions under volcanoes, with a focus on understanding the links between the underground rock record, the periodic eruption of volcanoes and the potential for super-volcano eruptions.

Impact of In-Channel Geomorphic Structures on Surface-Subsurface Exchange
of Water and Heat in Streams

1:40 p.m. PT, Tuesday, Dec. 12
Abstract number: B23A-1063
Erich Hester, doctoral student in ecology, department of geography
ethester@email.unc.edu

In-stream structures -- logs that fall across the stream, collect sediment and leaves, and back up water -- affect the exchange of water between the stream and groundwater beneath it. This exchange is important ecologically for many reasons. For instance, it helps reduce peak summer water temperatures, which in some cases have been or will be elevated to unhealthy levels (for certain stream organisms) due to human activities such as cutting of streamside forests and climate change.

Hester demonstrates how basic dimensions of these in-stream structures and various aspects of their setting impact the amount of water exchanged. His research sets the stage for determining how much summer cooling the structures can accomplish. The results will help improve stream restoration practice in many areas, particularly in mitigating human-induced elevated summer temperatures.

Internal oscillations of the thermohaline circulation and the Dansgaard-Oeschger events
of the last ice age

1:40 p.m. PT, Tuesday, Dec. 12
Abstract number: PP23C-1768
Max (Ming) Yang, doctoral student, department of geological sciences
myang@email.unc.edu;
Jose Rial, professor, department of geological sciences
jar@email.unc.edu

Paleoclimate records show that abrupt climate changes happened repeatedly during the past 100,000 years. Regional temperature increases of up to 15 degrees Celsius may have occurred in just a few decades or even a few years around North America and Europe.

Yang research suggests that the cyclical nature of past abrupt climate change events are caused by a free oscillation of oceanic thermohaline circulation. The study further shows that this oscillation is thermally driven, most likely by varying solar radiation caused by the cyclical changes of earth's orbital around the sun, (the Milankovitch cycles). Two independent model simulations support this idea and demonstrate that the timing of past climate changes is indeed linked to varying solar radiation. Because astronomical changes are readily predicable, it is in principle possible to anticipate long-term (centennial to millennial), large-amplitude abrupt climate change events in the future, Yang said.

What Plutons Have to Say About Big Eruptions
1:40 p.m. PT, Tuesday, Dec. 12
Abstract number: V23G-05
Allen Glazner, professor, department of geological sciences
afg@unc.edu

Most big plutons, like those in California's Yosemite National Park, are generally thought to be the residues of big eruptions - the stuff left behind after the more-liquid magma high in the magma chamber erupts. However, several lines of geochemical data suggest this isn't true -- that supereruptions tend to empty the magma chamber. Glazner and his colleagues contend that such eruptions are significantly less common in Earth history than the plutonic record suggests. No such eruptions since civilization began; the last supereruption was Toba, 73,000 years ago in Indonesia, and DNA studies suggest that it just about wiped out the human race.

Glazner will also discuss the intriguing observation that really big clusters of calderas tend to occur in really dry places, and that climate (mainly precipitation) may have a big influence on whether huge magma chambers ever form at all.

BLAM (Benthic Light Availability Model): A Proposed Model of Hydrogeomorphic Controls on Light in Rivers
1:40 p.m. PT, Tuesday, Dec. 12
Abstract number: H23B-1499
Jason Julian, doctoral student, department of geography
jjulian@unc.edu

Sunlight is the primary energy source of river ecosystems. Despite the importance of sunlight to river ecosystems, light studies in rivers have been mostly neglected because of difficulties in light measurement in rivers and the high degree of variation of light availability along the river and with different flow conditions. Julian proposes a model that predicts the amount of light available in rivers after all shading, both from trees and the water itself, has been taken into account. This model can be used to investigate behavioral patterns of flora and fauna in rivers, aid in river restoration design, and determine water quality standards.

Geologic fault slip rates support transitory, elevated geodetic strain accumulation across
the Mojave Desert, Eastern California shear zone

1:40 p.m. PT, Thursday, Dec. 14
Abstract number: G43B-0992
Michael Oskin, assistant professor, department of geological sciences
oskin@email.unc.edu

GPS technology for measuring relative motion across faults has revolutionized near-term seismic hazard studies -- research that aims to calculate the probability of an earthquake occurring in future decades. It is generally assumed that GPS measurements can be extrapolated across thousands of years to predict both short-term and long-term fault behavior. However, in the Eastern California shear zone, the short-term relative motion measured by GPS is twice as fast as the long-term motion, which was measured with geologic markers tens of thousands of years old. This change in rate coincides with a recent cluster of earthquake activity in the shear zone, and could indicate a feedback relationship between earthquake activity and loading rates. The increase in earthquake activity may have increased relative motion temporarily across the shear zone, Oskin said. Recognizing discrepancies between short-term and long-term rates can lead to better understanding of near-term earthquake hazards.

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For more information and a complete list of abstracts from the American Geophysical Union, visit: http://www.agu.org/meetings/fm06/

Note: Between Dec. 11 and Dec. 15, media should call the AGU press room at (415) 348-4440 for assistance on-site.

News Services contact: Becky Oskin, (919) 962-8596 (office), (919) 218-7835 (cell) or becky_oskin@unc.edu