Relationship between seismic P-wave velocity and the composition of anhydrous igneous and meta-igneous rocks

Author Posting. © American Geophysical Union 2003. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 4 (2003): 1041, doi:10.1029/2002GC000393.This study presents a new approach to quantitatively assess the relationship between the composition and seismic P-wave velocity of anhydrous igneous and meta-igneous rocks. We perform thermodynamic calculations of the equilibrating phase assemblages predicted for all igneous composition space at various pressure and temperature conditions. Seismic velocities for each assemblage are then estimated from mixing theory using laboratory measurements of the elastic parameters for pure mineral phases. The resultant velocities are used to derive a direct relationship between Vp and major element composition valid to ±0.13 km/s for pressure and temperature conditions along a normal crustal geotherm in the depth range of 5–50 km and equilibration pressures ≤12 kbar. Finally, we use the calculated velocities to invert for major element chemistry as a function of P-wave velocity assuming only the in situ temperature and pressure conditions are known. Compiling typical velocity-depth profiles for the middle and lower continental and oceanic crust, we calculate compositional bounds for each of these geologic environments. We find that the acceptable compositional range for the middle (15–30 km) and lower continental (≥35 km) crust is broad, ranging from basaltic to dacitic compositions, and conclude that P-wave velocity measurements alone are insufficient to provide fundamental constraints on the composition of the middle and lower continental crust. However, because major oxides are correlated in igneous rocks, joint constraints on Vp and individual oxides can narrow the range of acceptable crustal compositions. In the case of the lower oceanic crust (≥2 km), observed velocities are 0.2–0.3 km/s lower than velocities calculated based on the average bulk composition of gabbros in drill cores and exposed ophiolite sequences. We attribute this discrepancy to a combination of residual porosity at crustal depths less than ∼10 km and hydrous alteration phases in the lower crust, and suggest caution when inferring mantle melting parameters from observed velocities in the lower oceanic crust.This research was supported by National Science Foundation Grants OCE- 9819666, EAR-9910899, and EAR-0087706 (P.B. Kelemen)

Evaluation of moisture sources for the Central European summer flood of May/June 2013 based on regional climate model simulations

Heavy precipitation affected Central Europe in May/June 2013, triggering damaging floods both on the Danube and the Elbe rivers. Based on a modelling approach with COSMO-CLM, moisture fluxes, backward trajectories, cyclone tracks and precipitation fields are evaluated for the relevant time period 30 May–2 June 2013. We identify potential moisture sources and quantify their contribution to the flood event focusing on the Danube basin through sensitivity experiments: Control simulations are performed with undisturbed ERA-Interim boundary conditions, while multiple sensitivity experiments are driven with modified evaporation characteristics over selected marine and land areas. Two relevant cyclones are identified both in reanalysis and in our simulations, which moved counter-clockwise in a retrograde path from Southeastern Europe over Eastern Europe towards the northern slopes of the Alps. The control simulations represent the synoptic evolution of the event reasonably well. The evolution of the precipitation event in the control simulations shows some differences in terms of its spatial and temporal characteristics compared to observations. The main precipitation event can be separated into two phases concerning the moisture sources. Our modelling results provide evidence that the two main sources contributing to the event were the continental evapotranspiration (moisture recycling; both phases) and the North Atlantic Ocean (first phase only). The Mediterranean Sea played only a minor role as a moisture source. This study confirms the importance of continental moisture recycling for heavy precipitation events over Central Europe during the summer half year

The Cow That Stole Christmas: Framing the First U.S. Mad Cow Crisis

The discovery of bovine spongiform encephalopathy (BSE) in the United States made an impact on the beef industry. Determining how the BSE outbreak was framed by the news media is significant because research indicates that media shape public perceptions. This study examined how several key newspapers framed the 2003 outbreak of BSE in the United States. Determining how the media framed this issue can help communicators ensure bias-free media coverage of similar issues in the future. The study followed established framing analysis categories identified from the literature. There were 149 articles identified in The Washington Post, The Seattle Times, and USA Today for investigation in this study. Findings showed that the BSE issue was framed as an industry crisis and that the tone of the articles and headlines portrayed the beef industry negatively. When compared to the other two newspapers, USA Today framed the issue differently, with economic calamity being the dominant frame. The most heavily cited sources in the articles were government officials. This study recommends that media professionals avoid framing an issue for the public, focusing instead on reporting news in an objective and unbiased manner. Further research is recommended to examine the impact of tone and frame on specific audiences

Service Learning: A Case Study in an Agricultural Communications Course

Academic service-learning can be an effective and successful educational tool across many disciplines. The benefits afforded students and the community they serve are reciprocal in nature, thereby providing service to the community and capitalizing on a real-world learning environment for the students. Agricultural communications programs can offer for service-learning opportunities within the academic arena. The Campaign Planning for Agricultural and Natural Resources course at Oklahoma State University captures the essence of service-learning and provides students with an opportunity to use knowledge gained in previous courses to develop usable communications campaigns for small businesses or organizations. This case study should serve as a starting point for service-learning research in agricultural communications

A regional atmosphere-ocean climate system model (CCLMv5.0clm7-NEMOv3.3-NEMOv3.6) over Europe including three marginal seas: On its stability and performance

The frequency of extreme events has changed, having a direct impact on human lives. Regional climate models help us to predict these regional climate changes. This work presents an atmosphere–ocean coupled regional climate system model (RCSM; with the atmospheric component COSMO-CLM and the ocean component NEMO) over the European domain, including three marginal seas: the Mediterranean, North, and Baltic Sea. To test the model, we evaluate a simulation of more than 100 years (1900–2009) with a spatial grid resolution of about 25 km. The simulation was nested into a coupled global simulation with the model MPI-ESM in a low-resolution configuration, whose ocean temperature and salinity were nudged to the ocean–ice component of the MPI-ESM forced with the NOAA 20th Century Reanalysis (20CR). The evaluation shows the robustness of the RCSM and discusses the added value by the coupled marginal seas over an atmosphere-only simulation. The coupled system is stable for the complete 20th century and provides a better representation of extreme temperatures compared to the atmosphere-only model. The produced long-term dataset will help us to better understand the processes leading to meteorological and climate extremes