AGU Journal highlights -- Sept. 18, 2006

September 18, 2006

1. Plasmaspheric drainage plumes can affect down auroral activity

Gas ionized by solar radiation, called plasma, is trapped within the layers of the magnetosphere by Earth's magnetic field lines. This layer, called the plasmasphere, can expand during prolonged intervals of geomagnetic quiet, filling out to geosynchronous orbit and beyond. A subsequent increase in magnetospheric convection will strip away the outer plasmasphere, forming a drainage plume of dense, cold plasma. To study the effects of these drainage plumes, Borovsky and Denton analyzed data from plasma detectors on satellites circling in geosynchronous orbit, and compared that with statistical analyses of solar wind/magnetospheric coupling data matched with several geomagnetic indices. They found that plasmaspheric drainage plumes flow into an area called the dayside reconnection site, where magnetic field lines from the Sun connect, break, and reconnect with Earth's field lines, transferring energy. This flow of plasma overloads the dayside reconnection site, reducing the coupling of the solar wind to Earth's magnetosphere and influencing the strength of auroral activity and geomagnetic storms, phenomena of particular interest to the general public, because of their capacity to disrupt electric power grids and affect communication and navigation satellites.

Title: The effect of plasmaspheric drainage plumes on solar-wind/magnetosphere coupling

Authors: Joseph E. Borovsky: Los Alamos National Laboratory, Los Alamos, New Mexico, U.S.A.; Michal H. Denton: School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom; now at Department of Communications Systems, Lancaster University, Lancaster, United Kingdom.

Source: Geophysical Research Letters (GRL) paper 10.1029/2006GL026519, 2006

2. Due to increased air conditioning needs, carbon emissions will increase as climate changes

Observed atmospheric carbon dioxide increases are expected to continue, leading to continued increases in near-surface air temperatures. As temperatures change, so too will the amount of energy required for heating and cooling buildings, with fossil fuel emissions increasing as a result. Hadley et al. melded the results of detailed climate and energy economics models, running simulations for the United States through year 2025 for a low (1.2 degrees Celsius) [2.2 degrees Fahrenheit] and a high (3.4 degrees Celsius) [6.1 degrees Fahrenheit] temperature response to carbon dioxide doubling. They found that energy for heating in the low temperature change scenario is relatively consistent in the end years of the simulation, but continues to decline in the high temperature change scenario, making projected net energy use in the latter actually slightly lower than former by 2025. In northern regions, the net energy requirements are lower due to climate warming, but southern and western regions of the U.S. will experience increases in energy use as air conditioning needs increase with rising temperatures. As a whole, increases in carbon emissions from higher air conditioning needs more than offset decreases in carbon emissions from reduced heating needs.

Title: Responses of energy use to climate change: A climate modeling study

Authors: Stanton W. Hadley, David J. Erickson III, Jose Luis Hernandez, and T. J. Blasing: Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A.; Christine T. Broniak: Oregon State University, Oregon, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2006GL026652, 2006

3. Remote wind forcing contributed to the recovery of the California Current in summer 2005

Seasonal water properties on the continental shelves of the California Current System are controlled by ocean basin-scale flow from the north or south and the ability of winds to raise this water to the surface. In 2005, the spring onset of persistent winds favorable to upwelling was later than usual in the northern California Current System, delaying the delivery of inorganic nutrients to the upper waters of the coastal ocean. Hickey et el. illustrate the evolution of temperature, salinity, nitrate, and chlorophyll prior to and after the onset of these winds, including recovery to "typical" conditions. Warm, nutrient- and chlorophyll-depleted surface conditions were observed from Vancouver Island to central Oregon and extended to depths greater than 500 meters [2,000 feet]. Return to typical conditions was more rapid than suggested by local winds, but consistent with temporal changes in upwelling-favorable winds off northern California, suggesting that both local and remote forcing played a role in recovery.

Title: Evolution of chemical, biological, and physical water properties in the Northern California Current in 2005: Remote or local forcing?

Authors:B. Hickey and A. MacFadyen: School of Oceanography, University of Washington, Seattle, Washington, U.S.A.;

W. Cochlan: Romberg Tiburon Center for Environmental Studies, San Francisco State University, San Francisco, California, U.S.A.; R. Kudela and K. Bruland: Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, California, U.S.A.;C. Trick: Department of Biology, University of Western Ontario, London, Ontario, Canada.

Source: Geophysical Research Letters (GRL) paper 10.1029/2006GL026782, 2006

4. Anomalous physical and biological spring conditions in the waters off Oregon in 2005

Over the continental shelf off Oregon, winter conditions are characterized by high coastal sea level, warm water temperatures, and northward seasonal currents within the California Current System. By contrast, spring and summer conditions are characterized by low coastal sea level, southward-moving current jets, and upwelling of deep, cold subsurface waters to the surface. Past studies have shown that the transition between these regimes occurs rapidly, usually sometime in mid-April. However, Kosro et al. observed that in 2005, the transition to spring conditions came about 50 days later than average off Newport, Oregon. There was a further delay before spring biological conditions began; subsurface cool water critical for productivity upwelled and penetrated into an anomalously stratified surface layer another 50 days later in mid-July. The warm anomaly in sea surface temperature, which provided the surface cap, was observed at mid-shelf locations from Washington state to central California during these delays. The authors note that others have reported the impacts of these delays on plankton, bivalves, fish, and seabird populations.

Title: The physical vs. the biological spring transition: 2005

Authors: P. Michael Kosro, R. Kipp Shearman, and Stephen D. Pierce: College of Oceanic & Atmospheric Sciences, Oregon State University, Corvallis, Oregon, U.S.A.; William T. Peterson: National Marine Fisheries Service, Northwest Fisheries Science Center, Hatfield Marine Science Center, Newport, Oregon, U.S.A.; Barbara M. Hickey: School of Oceanography, University of Washington, Seattle, Washington, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2006GL027072, 2006

5. The effecting of UV scattering on sulfur dioxide emission rate measurements

The sulfur dioxide emission rate, an important indicator of volcanic activity, is monitored at major volcanoes by the UV spectrometer system, which measures the absorption of the Sun's ultraviolet light by sulfur dioxide molecules, to calculate the amount of sulfur dioxide along the light path based on the absorption intensity. However, ultraviolet scattering between volcanic plumes and the measurement instrument introduces a significant error into absorption intensity calculations, causing the sulfur dioxide emission rate to be underestimated. In order to clarify this effect on ultraviolet scattering, Mori et al. set up stationary measurement instruments at three different locations in the proximity of volcanic plume on the Aso volcano in Japan. Through measurements of sulfur dioxide emissions rates from these stations, the authors were able to quantify the variation of ultraviolet absorbance for various ultraviolet wavelength ranges as a function of distance from the plume. The authors expect that similar efforts to reflect this variation at other volcanic monitoring sites will lead to improved calculations of sulfur dioxide emissions rates and a better understanding of volcanic hazards.

Title: Effect of UV scattering on SO2 emission rate measurements

Authors: Takehiko Mori, Kohei Kazahaya, and Michiko Ohwada: Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan; Toshiya Mori: Laboratory for Earthquake Chemistry, Graduate School of Science, University of Tokyo, Bunkyo, Tokyo, Japan; Jun'ichi Hirabayashi: Volcanic Fluid Research Center, Tokyo Institute of Technology, Meguro, Tokyo, Japan; Shin Yoshikawa: Aso Volcanological Laboratory, Graduate School of Science, Kyoto University, Minamiaso, Kumamoto, Japan.

Source: Geophysical Research Letters (GRL) paper 10.1029/2006GL026285, 2006

6. Perennial sea ice in the Arctic Ocean has reduced rapidly

Recent observations have indicated more rapid decreases in sea ice cover compared to the summer ice reduction rate of 7.8 percent per decade since the 1970s. A diminished ice cover may profoundly impact the Arctic environment, commerce, resource development, and marine operations. Nghiem et al. monitored sea ice over the Arctic Ocean using scatterometer data acquired from NASA's QuikSCAT satellite. Between 2004 and 2005, they found that the extent of perennial sea ice (ice that persists from year to year) in the eastern Arctic Ocean (0-180 degrees East) decreased by nearly one half, while the western Arctic Ocean (1-180 degrees West) had a slight gain in ice extent. These changes in perennial ice extent resulted in a net decrease of 720,000 square kilometers [280,000 square miles], about the size of Texas. Data collected in April 2006 showed that perennial ice extent in the eastern Arctic Ocean had depleted by 70 percent compared to satellite observations in October 2005. The authors note that as sea ice cover continued to reduce, the surrounding ocean would absorb more solar radiation, further accelerating ice melt.

[Note: See also AGU Press Release 06-32 at]

Title: Depletion of perennial sea ice in the East Arctic Ocean

Authors: S. V. Nghiem, Y. Chao, G. Neumann, and P. Li: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, U.S.A.;

D. K. Perovich: U.S. Army Cold Region Research and Engineering Laboratory, Hanover, New Hampshire, U.S.A.;

T. Street and P. Clemente-Colón: National Ice Center, Washington, D.C., U.S.A.;

Source: Geophysical Research Letters (GRL) paper 10.1029/2006GL027198, 2006
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American Geophysical Union

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