1. Forest ozone loss may lead to atmospheric aerosols
2. Ozone increases predicted in the 21st century
3. Ancient reflective surface material characterizes lunar magnetic anomalies
4. Ocean water shift led to end of Glacial Maximum
5. Summer snow can predict NAO phase
6. Effects of charged dust on atmospheric turbulence
7. Climate warming melting Arctic sea ice
8. Better estimate for deformation from icy collisions
9. Snow packs not a stable reservoir for mercury
10. Geologic evidence casts doubt on Martian water

Hydrocarbons and other gases normally emitted from pine forests help to destroy tropospheric ozone and may explain the "missing sink" of ozone found in forest ecosystems. Kurpius and Goldstein suggest that organic compounds released by pine forests react with ozone to produce atmospheric aerosols and other ozone-destroying compounds that affect tropospheric chemistry and the climate. Previously, researchers knew that forests act as an ozone sink but were unable to explain what happened to portions of the compound that were not absorbed by tree leaves. The authors propose that the plant emissions are an unrecognized source of naturally emitted reactive compounds and lead to a significant loss of ozone, particularly during warm summer months because of the temperature dependence of the emissions from vegetation.

Title: Gas-phase chemistry dominates O3 loss to a forest, implying a source of aerosols and hydroxyl radicals to the atmosphere

Authors:
Meredith R. Kurpius, Allen H. Goldstein, University of California, Berkeley, California.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016785, 2003

An assessment of international air quality suggests that surface ozone levels will increase globally during the coming century at rates that could adversely affect human health and agricultural conditions. Prather et al. present new maps and seasonal changes of projected ozone increases for the next 100 years. The team of researchers included nearly a dozen models and calculated five scenarios that provided a range of global emission outcomes. All but one of the authors' simulations projected an increase in ozone during the 21st century, ranging from an additional 20 parts per billion to a reduction of four parts per billion under current and possible future pollution conditions. The majority of the projected ozone growth was estimated to occur within and downwind of metropolitan regions in mid-latitude North America, particularly during summer. Increases were also seen over rural areas and in developing regions near India, Southeast Asia and Africa.

Title: Fresh air in the 21st century?

Authors:
Michael Prather, University of California, Irvine, California;
Michael Gauss, Terje Bernsen, Ivar Isaksen, Jostein Sundet, University of Oslo, Oslo, Norway;
Isabelle Bey, Swiss Federal Institute of Technology, Lausanne, Switzerland;
Guy Brasseur, Max Planck Institute for Meteorology, Hamburg, Germany;
Frank Dentener, Joint Research Center, Environmental Institute, Ispra, Italy;
Richard Derwent, David Stevenson, Hadley Centre, UK Met Office, Bracknell, United Kingdom;
Lee Grenfell, Free University, Berlin, Germany;
Didier Hauglustaine, National Scientific Research Center-Atomic Energy Commission, Gif-sur-Yvette, France;
Larry Horowitz, National Oceanic and Atmospheric Administration, Princeton, New Jersey;
Daniel Jacob, Loretta Mickley, Harvard University, Cambridge, Massachusetts;
Mark Lawrence, Rolf von Kuhlmann, Max Planck Institute for Chemistry, Mainz, Germany;
Jean-Francois Muller, Belgian Institute for Space Aeronomy, Brussels, Belgium;
Giovanni Pitari, L'Aquila University, Coppito, L'Aquila, Italy;
Helen Rogers, Matthew Johnson, John Pyle, Kathy Law, Cambridge University, Cambridge, United Kingdom;
Michiel van Weele, Royal Netherlands Meteorological Institute, De Bilt, The Netherlands;
Oliver Wild, Frontier Research System for Global Change, Yokahama, Japan.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016285, 2003

Newly interpreted evidence from a location near the Apollo 16 lunar landing site suggests that the area contains the strongest magnetic anomaly on the near side of the Moon, supporting the hypothesis that ancient reflective materials on the lunar surface often accompany such magnetic anomalies. Richmond et al. used data from the Lunar Prospector spacecraft to estimate that material on the Moon approximately four billion years old was the source of the anomalies, which are likely capable of deflecting ion bombardment from solar winds and partially shielding areas on the lunar surface from impacts. Another theory predicted that the smooth, "weathering" tracks were caused by more recent comet strikes on the Moon. The authors used newly available data from the Prospector's magnetometer to map and model a magnetic anomaly coinciding with a high-albedo [reflection] region of the Descartes Mountains, located within 60 kilometers [40 miles] of the Apollo landing site, and show that the older material found there is probably the source of the anomaly.

Title: Correlation of a strong lunar magnetic anomaly with a high-albedo region of the Descartes mountains

Authors: Nicola Claire Richmond, L. L. Hood, University of Arizona, Tucson, Arizona;
J. S. Halekas, D. L. Mitchell, R. P. Lin, University of California, Berkeley, California;
M. Acuna, NASA Goddard Space Flight Center, Greenbelt, Maryland;
A. B. Binder, Lunar Research Institute, Tucson, Arizona.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016938, 2003

While researchers have speculated that a shift in the global thermohaline [vertical] circulation caused the sudden end of the last Glacial Maximum, they have not been able to explain the exceptional rapidity of the warming. Rossby and Nilsson suggest that a northward shift in the Gulf Stream during glacial times led to the transport of warmer waters into the Nordic Seas, where cold, dense deepwater is produced. Their analysis indicates that the North Atlantic ocean water was already highly saline, which accelerated the production of North Atlantic deepwater. The additional deepwater, in turn, altered the path of the ocean's circulation and contributed to the shift of the Gulf Stream. The authors' model estimates that the shift led to a nearly 10 degree Celsius [20 degrees Fahrenheit] warming over Greenland during a 10-20 year period.

Title: Current switching as the cause of rapid warming at the end of the last Glacial Maximum and younger dryas

Authors:
Thomas Rossby, University of Rhode Island, Narragansett, Rhode Island;
Johan Nilsson, University of Stockholm, Sweden.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL015423, 2003

A new analysis has found that the extent of snow cover in the northernmost sections of North America and Eurasia during summer have a statistically significant inverse relationship with the North Atlantic Oscillation (NAO) during the following winter. The findings by Saunders et al. indicate a possible new way to predict seasonal variations in the NAO with greater accuracy and earlier in the year. Currently, researchers primarily use sea surface temperatures to estimate the upcoming NAO state, which affects atmospheric conditions like temperature and precipitation over the North Atlantic and climactic behavior worldwide. The authors studied the available 30-year snow record for the Northern Hemisphere, finding that the snow extent was a useful predictor of the oscillation's phase in up to 80 percent of winters, and noted that years with exceptionally high (or low) snow cover typically corresponded to a low (or high) NAO index.

Title: Summer snow extent heralding of the winter North Atlantic Oscillation

Authors:
Mark A. Saunders, Budong Qian, Benjamin Lloyd-Hughes, University College London, Holmbury St. Mary, Dorking, Surrey, United Kingdom.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016832, 2003

A computer simulation of the formation of disturbances in the upper atmosphere shows how a unique type of electron turbulence can be produced by charged dust from meteor debris. Scales and Chae studied the evolution of upper atmospheric turbulence, finding that the dust affects the density fluctuations of charged particles deposited in the ionosphere. The fluctuations can also heat the dust and produce unexpected vertically propagating density "waves" that can alter the path of satellite signals passing through the upper atmosphere and hinder the performance of satellite communications and navigation systems. Previous research had looked into similar atmospheric turbulence without the effects from charged dust, but the current work provides the initial evidence that the dust, primarily produced by meteors and particles in high clouds, helps to initiate the disturbances.

Title: Nonlinear evolution of dust waves driven by cross-field electron currents

Authors:
Wayne A. Scales, Gyoo Soo Chae, Virginia Tech University, Blacksburg, Virginia.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016191, 2003

Exceptionally warm conditions through winter and summer, combined with persistent summer storminess, resulted in the 2002 observation of the lowest sea ice cover seen in the Arctic in at least two decades. Serreze et al. suggest that their findings are part of a recently observed downward trend toward less ice cover seen since the beginning of the satellite era in 1979. The authors note that the sea ice losses appear to be related to a larger pattern of Arctic climate change over the past several decades, characterized by widespread warming, melting permafrost, altered precipitation and changes in the atmospheric circulation. Their observations are confirmed by climate model simulations, which predict an additional 20 percent reduction in sea ice cover by the year 2050 as a result of the continued warming during the 21st century.

Title: A record minimum Arctic sea ice extent and area in 2002

Authors:
Mark C. Serreze, T. A. Scambos, F. Fetterer, J. Stroeve, K. Knowles, R. G. Barry, T. M. Haran, National Snow and Ice Data Center, University of Colorado, Boulder, Colorado;
J. A. Maslanik, C. Fowler, S. Drobot, Department of Aerospace Engineering Sciences, University of Colorado, Boulder, Colorado.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016406, 2003

A new study can help predict the effects from collisions of icy bodies such as comets and the satellites of the outer planets of the solar system. Current estimates rely on data collected at 263 Kelvin [-10 degrees Celsius; 10 degrees Fahrenheit], whereas ice temperatures on Mars are approximately 200 Kelvin [-70 degrees Celsius; -100 degrees Fahrenheit] and dip to 40 Kelvin [-200 degrees Celsius; -400 degrees Fahrenheit] on Pluto. Stewart and Ahrens measured the dynamic deformation of ice, known as the shock Hugoniot, to calculate the effects of the pressure during an impact onto or between icy planetary surfaces. The researchers extended the shock measurements on ice from 263 Kelvin [-10 degrees Celsius; 10 degrees Fahrenheit] to 100 Kelvin  [-200 degrees Celsius; -300 degrees Fahrenheit], which can provide a more realistic assessment of collisions on a wide range of planetary bodies. They defined a new ice shock Hugoniot and derived the criteria for melting ice from the pressure shock due to a collision. The authors conclude that there is significant melting during collisions on icy bodies throughout the cold outer solar system.

Title: Shock Hugoniot of H2O ice

Authors:
Sarah T. Stewart, Thomas J. Ahrens, California Institute of Technology, Pasadena, California.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016798, 2003

More than 40 percent of mercury in remote, untouched snow can be transferred back into the environment within a day because of the effects from sunlight, according to Lalonde et al. The authors suggest that their experiment disproves the notion that snow is a stable reservoir for mercury in the winter that would release the toxic metal into the aquatic and terrestrial systems only in spring when the snow melts and when the seasonal pulse of mercury accumulation would cause health concerns due to its bioaccumulation in plants and animals. The researchers confirm their previous study, which found that sunlight initiates a photochemical reaction that promotes gaseous mercury emissions from snow packs in suburban environments. They conclude that the unexpected mercury emissions could affect analyses that use snow and ice core samples to estimate the history of the chemical's distribution worldwide.

Title: Photo-induced Hg(II) reduction in snow from the remote and temperate Experimental Lakes Area (Ontario, Canada)

Authors:
Janick D. Lalonde, Marc Amyot, National Institute for Earth Science Research, University of Quebec, Quebec, Canada, and University of Montreal, Quebec, Canada;
Jean-Christian Auclair, Marie-Renee Doyon, National Institute for Earth Science Research, University of Quebec, Quebec, Canada.

Source: Source: Journal of Geophysical Research-Atmospheres (JGR-D) paper 10.1029/2001JD001534, 2003

A geologic analysis of more than 1,000 Martian gullies concludes that liquid water was not important in their formation. Allan H. Treiman suggests that the gullies formed without water, as massive landslides and flows of sand or soil. Trieman shows that the geology around the gullies appears to be inconsistent with published ideas about how liquid water or carbon dioxide flows could arise near the planet's surface. He notes the broad distribution of gullies on steep slopes across the Martian surface, regardless of the slope's origin, location or surrounding geology, and notes that such scattering is not consistent with the highly specific circumstances needed for gully formation. His analysis suggests that the features of the gullies agree with wind circulation patterns on Mars, leading him to conclude that the gullies are likely formed by wind-blown dust deposited at the bottom of hills and land formations, similar to the way snow avalanches build up along mountainsides on Earth.

Title: Geologic settings of Martian gullies: Implications for their origins

Author:
Allan H. Treiman, Lunar and Planetary Institute, Houston, Texas.

Source: Source: Journal of Geophysical Research-Planets (JGR-E) paper: 10.1029/2002JE001900, 2003
 

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