JOURNAL HIGHLIGHTS(202) 777-7507
hleifert@agu.org
| American Geophysical Union
JOURNAL HIGHLIGHTS |
Contact: Harvey Leifert
(202) 777-7507 hleifert@agu.org |
| 18 December 2003 |
The following highlights summarize research papers in Geophysical Research
Letters (GL), Journal of Geophysical Research-Space Physics (JC),
Journal of Geophysical Research-Solid Earth (JB), Journal of Geophysical Research-Oceans (JC),
and Water Resources Research (WR).
The papers related to these Highlights are printed in the next paper issue of the journal following
their electronic publication.
1. Galileo observes lava spread on Io 1. Galileo observes lava spread on Io Researchers have used images with unprecedented detail of Jupiter's moon Io to determine the surface temperature distribution of the powerful Loki Patera volcano and infer the age and thickness of the new lava's crust. Ashley Davies used newly available data from the Galileo spacecraft's infrared spectrometer to observe lava spreading across the moon's surface at the frequently erupting Loki volcano, whose activity might be indicative of a rare volcanic feature known as a lava lake. Io is the solar system's most volcanically active body and has styles of volcanism similar to those seen on Earth; recent research has suggested that studies of Io's system could provide insight into Earth's ancient volcanic history. Davies based his study on an eruption that resurfaced the floor of the Loki caldera with new lava that flowed forward at nearly 1 kilometer per day and began approximately 80 days before the Galileo observations. Title: Temperature, age and crust thickness distributions of Loki Patera on Io from Galileo NIMS data: Implications for resurfacing mechanism Author:
Source: Geophysical Research Letters (GRL) paper: 10.1029/2003GL018371, 2003
2. Shape of magnetic field determines its properties The configuration of the interplanetary magnetic field (IMF) plays a significant role in the behavior of charged solar particles and their decay near Earth. Sarris and Malandraki analyzed spacecraft observations from two strong electron events, one in which the magnetic field was converging, the other in which it was diverging. The authors found that converging fields contained energetic electrons within a "magnetic bottle" that filled a slowly draining reservoir well beyond Earth's orbit. Conversely, a diverging event recorded by the ACE spacecraft in 2001 allowed electrons to quickly escape from a much smaller bottleneck. The researchers conclude that their study provides the first direct evidence of the correlation between the IMF configuration and the trapping of energetic particles. Title: Dependence of the decay phase of solar energetic electron events on the large-scale IMF structure: ACE observations Authors:
Source: Geophysical Research Letters (GRL) paper: 10.1029/2003GL017921, 2003
3. New method to track underground nuclear tests A method to observe subtle ground movements over time may help scientists remotely detect and precisely locate past and present underground nuclear tests. Vincent et al. analyzed new observations of the surface displacement caused by past underground nuclear tests at the Nevada Test Site using ground-sensing interferometric synthetic aperature radar (InSAR). Their study shows that such testing creates movements in the ground surface that, however small, can be seen by looking at a time series of high-resolution satellite images. The authors suggest that the signals persist for months and even years after an underground detonation and cause various forms of deformation based on the geologic and hydrologic conditions of the test area. The technique could allow researchers a new way to estimate the depth and yield of underground explosions and track nuclear detonations worldwide that do not break the ground surface. Title: New signatures of underground nuclear tests revealed by satellite radar interferometry Authors:
Source: Geophysical Research Letters (GL) paper: 10.1029/2003GL018179, 2003
4. New explanation for Andean mountain range formation A three-dimensional flow model of the South American Andes Mountains indicates that the range's uplift may have been caused by a different mechanism than is currently thought. Yang et al. present model scenarios showing that lateral ground flow contributed to the height and topography of the Andes. Previous research suggested that the range formed from tectonic motion under the South American plate and that magma addition added to the crustal thickness in the region, but had not assessed the possibility that lateral flow contributed to the mountain building. The authors propose, however, that plate motion does not account for the height of the Andean range and that historical flow processes may have caused part of the Earth's crust to creep southward. Such flow could occur concurrently with tectonic motions and might be useful to explain the relatively smooth topography of the Andean mountains. Title: A 3-D geodynamic model of lateral crustal flow during Andean mountain building Authors:
Source: Geophysical Research Letters (GL) paper: 10.1029/2003GL018308, 2003
5. New method to detect sprite halos Researchers have established a strong relationship between ionospheric disturbances and sprite halos, suggesting that new methods could be used to detect the unusual atmospheric flashes. Moore et al. link changes in the amplitude of very low frequency (VLF) waves in the upper atmosphere to the energy released by lightning discharges that create rare luminous events such as sprites, elves, and blue jets. The authors analyzed the low-frequency signatures observed at 13 closely spaced sites in the Midwestern United States during a lightning-producing storm and found that VLF anomalies are associated with electron density changes produced during sprite halos. Their electromagnetic model calculations nearly match the experimental data, which allows them to predict that the sprite halo is the direct cause of the magnetic field changes. The researchers conclude that the newfound discovery could permit scientists a non-optical technique to estimate the global occurrence rate of sprites. Title:Early/fast VLF events produced by electron density changes associated with sprite halos Authors:
Source: Journal of Geophysical Research-Space Physics (JA) paper: 10.1029/2002JA009816, 2003
6. Unique view of submarine volcanic eruption An instrument designed to monitor underwater volcanoes accidentally became trapped in a submarine lava flow, providing researchers a serendipitous view into the dynamics of seafloor eruptions. William W. Chadwick, Jr. reports on measurements from a seafloor instrument that survived being overrun by lava during a 1998 eruption in the northeast Pacific. The data recovered from the instrument after the incident provide new insights into the formation of lava "pillars," tall, narrow pipes of solidified lava found only underwater. Such pillars are relatively common in submarine lava flows but little was known about their formation, since their evolution had never been directly observed. Chadwick notes that the during the pillar's formation, the monitoring instrument was lifted upward approximately 3 meters [10 feet] and was set back down within two and a half hours as the lava flow inflated and drained. The new information show for the first time how fast the lava pillars for during a submarine volcanic eruption. Title: Quantitative constraints on the growth of submarine lava pillars from a monitoring instrument that was caught in a lava flow Author:
Source: Journal of Geophysical Research-Solid Earth (JB) paper:
10.1029/2003JB002422, 2003
7. Newly released sea ice data improves analysis A recently released sea ice index containing data spanning more than 20 years of Arctic ice cover during the late 20th century has provided a new source of information on the Northern Hemisphere's changing polar ice cover. Partington et al. suggest that the new high-quality records, released in late 2000 by the U.S. National Ice Center, provide a useful comparison to existing sea ice indices in the Arctic that have shown significant reductions in the polar ice cover and ice thickness. The authors show that the new ice charts, taken from military and commercial satellites to guide shipping through the region, address deficiencies in existing microwave observations that are known to underestimate summer ice cover. The dataset reveals the delayed response of the sea ice cover to large-scale atmospheric conditions, both in winter and summer, and is one of a number of new data sources that can help researchers better understand the sea ice changes resulting from human causes and natural climate variations. Title: The late twentieth century Northern Hemisphere sea-ice record from US National Ice Center ice charts Authors:
Source: Journal of Geophysical Research-Oceans (JC) paper: 10.1029/2002JC001623, 2003
8. Maintaining freshwater needs in coastal areas The results from a new analytical model can help water managers maintain the freshwater needs for residents and tourists of congested coastal areas. Aristotelis Mantoglou presents a method to determine the optimal standards for pumping freshwater from coastal aquifers that avoids problems from saltwater intrusion into the regional water supplies. His research provides proxies for several of the hydraulic processes used to govern pumping in the aquifers, which he suggests are simpler, yet equally accurate, as existing methods and can provide a reasonable water management solution to coastal areas and islands. Current methods to measure the flow in coastal aquifers are complicated by the density variations and complexities of mixing among fresh and saltwater. Mantoglou suggests that new water management techniques are needed to provide potable water to residents in many coastal areas where a growing population and increasing municipal needs have strained the freshwater requirements. Title: Pumping management of coastal aquifers using analytical models of saltwater intrusion Author:
Source: Water Resources Research (WR) paper: 10.1029/2002WR001891, 2003
9. New method to improve soil moisture measurements A new analytical method may allow researchers to estimate surface soil moisture directly from rainfall data. Pan et al. derived a diagnostic equation that does not require estimates for the initial condition of soil moisture and additional details that are not always readily available. The authors used soil moisture data collected during three field experiments and found that their method provided a close correlation to actual moisture conditions in the uppermost several meters of land that is available for plant growth. The new technique uses information from the land surface characteristics and soil properties instead of using existing algorithms that include complicated water diffusion measurements to forecast the water loss after a rainfall and predict the soil saturation. They suggest that their technique can improve the quantity of soil moisture measures worldwide and therefore increase the accuracy of hydrologic and water balance predictions. Title: An analytical method for predicting surface soil moisture from rainfall observations Authors:
Source: Water Resources Research (WR) paper: 10.1029/2003WR002142, 2003
10. Pine needle cover can mitigate soil erosion after forest fires Pine needles spread over the soil (needle cast) have been shown to limit soil runoff in areas scorched by forest fires. Pannkuk and Robichaud analyzed the erosion suppression ability of two needle types on two types of soil. The authors used varying percentages of needle coverage from Douglas fir and Ponderosa pine trees and simulated streaming water and rainfall on bare soil. They found that Douglas fir needles, which are shorter than Ponderosa needles, reduce erosion by more than 80 percent compared to no cover. However, the longer, curved Ponderosa needles tend to interlock and are more likely to form small dams that block water and help reduce channels of erosion by approximately 60 percent. Although there is limited research on using surface cover to reduce erosion after a fire, the researchers note that needle cast can significantly reduce soil erosion. They conclude that areas with low to moderate burn damage may have ample needle cast and may not need any additional treatment. [Note: See also AGU Press Release 03-30: www.agu.org/sci_soc/prrl/prrl0330.html] Title: Effectiveness of needle cast at reducing erosion after forest fires Authors:
Source: Water Resources Research (WR) paper: 10.1029/2003WR002318, 2003 *****
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