Mantle viscosity, J2 and the nontidal acceleration of Earth rotation

Recent interpretations of laser ranging for the LAGEOS satellite have rather conclusively established that the observed acceleration in the node of its orbit is just that expected to exist as a residual effect of the last deglaciation event which ended about 6000 years ago. The nontidal acceleration of rotation would be rather different than that observed if there were any significant melting of high latitude continental ice masses currently ongoing. The sensitivity of the expected nontidal acceleration to variations of several elements of the radial viscoelastic structure of the planet is explored using a new normal mode method for the computation of viscoelastic relaxation spectra. These calculations establish that the most important sensitivity is to variations in the mantle viscosity profile. Although the predicted nontidal acceleration does depend upon lithospheric thickness and on the elastic component of the radial structure, the dependence on these components of the structure is much weaker than it is upon mantle viscosity. The observed J sub 2 is therefore a particularly useful determinant of radial variations in the latter parameter

Reflecting on reflection: scale extension and a comparison of undergraduate business students in the United States and the United Kingdom

In the Peltier, Hay, and Drago (2005) article entitled “The Reflective Learning Continuum: Reflecting on Reflection,” a reflective learning continuum was conceptualized and tested. This is a follow-up article based on three extensions: (1) determine whether the continuum could be expanded, (2) further validating the continuum using additional schools, and (3) determining whether the continuum could also be applied to undergraduate business education. The findings from a study of U.S. and UK students show that the revised scale is valid and reliable and that U.S. students in the sample universities rated their educational experience higher and were more likely to use reflective thinking practices

Geoscience of Climate and Energy 8. Climate Models: Are They Compatible with Geological Constraints on Earth System Processes?

Models of the global warming process are obliged to include many important small-scale processes that cannot be explicitly represented, given the low spatial and temporal resolution at which the models can be integrated. As the parameterizations of these processes, in terms of the resolved scale fields, must be tuned to permit them to enable the models to fit climate observations from the instrumental era, it is an issue as to whether such models remain robust when they are applied to the prediction of future warming trends. Geological inferences of past climate conditions provide a means by which the robustness of the models may be assessed. In this paper, two examples of such tests are described, both of which demonstrate that a state-of-the-art model is able to accurately simulate past conditions that differ radically from modern. SOMMAIRE Les modèles de processus de réchauffement climatique de la planète doivent intégrer de nombreux et importants processus à petite échelle, lesquels ne peuvent être représentés de façon explicite, étant donné la faible résolution spatiale et temporelle des modèles climatiques. Comme le paramétrage de ces processus, à leur échelle propre, doit être ajusté de manière à permettre aux modèles de correspondre à l'observation du climat de l'aire instrumentale, il faut savoir si de tels modèles peuvent demeurer robustes lorsqu’ils sont utilisés pour prévoir les tendances de réchauffement à venir. Or, les inférences climatiques passées déduites de situations géologiques constituent un moyen de tester la robustesse des modèles. Dans le présent article, deux exemples de ces tests sont décrits, et ceux-ci montrent que les modèles actuels sont capables de reproduire avec précision des conditions climatiques anciennes très différentes des conditions actuelles

Performing Particle Image Velocimetry in a Supersonic Wind Tunnel Using Carbon Dioxide as the Seed Material

Particle image velocimetry (PIV) was performed utilizing clean seed particles generated by injecting liquid carbon dioxide (CO2) directly into an open-circuit blowdown Mach 2.9 supersonic wind tunnel. Rapid atomization and cooling of the liquid CO2 created a preponderance of nearly uniform and well dispersed microscopic dry ice particles which were illuminated using a frequency double Nd:YAG laser. Ample light was scattered from the flow tracers, which provided a strong signal to noise ratio. The particles completely sublimed into an innocuous gas downstream of the test section causing no side effects or problems with wind tunnel operation. A variety of geometries were inspected using PIV. In addition to empty test section characterization, flow aft of a cone and transverse injection through a long shallow cavity was visualized and adaptive cross-correlation vector maps were computed. These vector maps revealed many relevant flow structures pertinent to each test setup. Measured velocities followed the trends expected for each test setup but the vector magnitudes were shifted 3-9% below those predicted by theory. Procedures and information pertinent to liquid CO2 injection are provided to help researchers implement this process in similarly scaled supersonic wind tunnels

An initial intercomparison of atmospheric and oceanic climatology for the ICE-5G and ICE-4G models of LGM paleotopography

This paper investigates the impact of the new ICE-5G paleotopography dataset for Last Glacial Maximum (LGM) conditions on a coupled model simulation of the thermal and dynamical state of the glacial atmosphere and on both land surface and sea surface conditions. The study is based upon coupled climate simulations performed with the ocean–atmosphere–sea ice model of intermediate-complexity Climate de Bilt-coupled large-scale ice–ocean (ECBilt-Clio) model. Four simulations focusing on the Last Glacial Maximum [21 000 calendar years before present (BP)] have been analyzed: a first simulation (LGM-4G) that employed the original ICE-4G ice sheet topography and albedo, and a second simulation (LGM-5G) that employed the newly constructed ice sheet topography, denoted ICE-5G, and its respective albedo. Intercomparison of the results obtained in these experiments demonstrates that the LGM-5G simulation delivers significantly enhanced cooling over Canada compared to the LGM-4G simulation whereas positive temperature anomalies are simulated over southern North America and the northern Atlantic. Moreover, introduction of the ICE-5G topography is shown to lead to a deceleration of the subtropical westerlies and to the development of an intensified ridge over North America, which has a profound effect upon the hydrological cycle. Additionally, two flat ice sheet experiments were carried out to investigate the impact of the ice sheet albedo on global climate. By comparing these experiments with the full LGM simulations, it becomes evident that the climate anomalies between LGM-5G and LGM-4G are mainly driven by changes of the earth’s topography

Secular sea level change in the Russian sector of the Arctic Ocean

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C03042, doi:10.1029/2003JC002007.Sea level is a natural integral indicator of climate variability. It reflects changes in practically all dynamic and thermodynamic processes of terrestrial, oceanic, atmospheric, and cryospheric origin. The use of estimates of sea level rise as an indicator of climate change therefore incurs the difficulty that the inferred sea level change is the net result of many individual effects of environmental forcing. Since some of these effects may offset others, the cause of the sea level response to climate change remains somewhat uncertain. This paper is focused on an attempt to provide first-order answers to two questions, namely, what is the rate of sea level change in the Arctic Ocean, and furthermore, what is the role of each of the individual contributing factors to observed Arctic Ocean sea level change? In seeking answers to these questions we have discovered that during the period 1954–1989 the observed sea level over the Russian sector of the Arctic Ocean is rising at a rate of approximately 0.123 cm yr−1 and that after correction for the process of glacial isostatic adjustment this rate is approximately 0.185 cm yr−1. There are two major causes of this rise. The first is associated with the steric effect of ocean expansion. This effect is responsible for a contribution of approximately 0.064 cm yr−1 to the total rate of rise (35%). The second most important factor is related to the ongoing decrease of sea level atmospheric pressure over the Arctic Ocean, which contributes 0.056 cm yr−1, or approximately 30% of the net positive sea level trend. A third contribution to the sea level increase involves wind action and the increase of cyclonic winds over the Arctic Ocean, which leads to sea level rise at a rate of 0.018 cm yr−1 or approximately 10% of the total. The combined effect of the sea level rise due to an increase of river runoff and the sea level fall due to a negative trend in precipitation minus evaporation over the ocean is close to 0. For the Russian sector of the Arctic Ocean it therefore appears that approximately 25% of the trend of 0.185 cm yr−1, a contribution of 0.048 cm yr−1, may be due to the effect of increasing Arctic Ocean mass.This material is based upon work supported by the National Science Foundation under grant 0136432

Using Sales Competition Videos in a Principles of Marketing Class to Improve Interest in a Sales Career

Purpose of the Study: This study describes an easily conducted teaching innovation to enhance introductory marketing students’ perception of sales and selling. Sales jobs are plentiful; yet, many marketing students do not pursue sales courses or sales careers. Our purpose is to describe a classroom intervention that improves students’ intent to pursue a sales career. Method/Design and Sample: This study tests the classroom inclusion of an actual student sales competition video from the National Collegiate Sales Competition (NCSC) to provide visual as well as verbal learning stimuli. Following a 45 minute lecture on sales, students were exposed to the 20-minute final round winning NCSC video. During the video, the instructor stopped the video 12 times to relate specific aspects of the video role-play to the lecture. Students completed a pre- and post-intervention survey of the Intent to Pursue Sales Career Scale (ITPSC). Results: Results show that the educational intervention positively impacted students’ perceptions of a sales career, salespeople, salesperson ethics, sales knowledge, and intent to pursue a sales career. The largest student perception increases were within the sales knowledge dimension. Value to Marketing Educators: Graduates with degrees in marketing, business, and other areas often begin their careers in entry level sales positions. Sales skills are transferable and have utility in marketing and other careers. Instructional innovations designed to enhance student interest in a selling career, and that also advance sales training, have tremendous value. The use of an exemplar video from a sales competition is an easy way to accomplish these goals

Radiative effects of ozone on the climate of a Snowball Earth

Some geochemical and geological evidence has been interpreted to suggest that the concentration of atmospheric oxygen was only 1–10 % of the present level in the time interval from 750 to 580 million years ago when several nearly global glaciations or Snowball Earth events occurred. This low concentration of oxygen would have been accompanied by a lower ozone concentration than exists at present. Since ozone is a greenhouse gas, this change in ozone concentration would alter surface temperature, and thereby could have an important influence on the climate of the Snowball Earth. Previous works that have focused either on initiation or deglaciation of the proposed Snowball Earth has not taken the radiative effects of ozone changes into account. We address this issue herein by performing a series of simulations using an atmospheric general circulation model with various ozone concentrations. <br><br> Our simulation results demonstrate that, as ozone concentration is uniformly reduced from 100 % to 50 %, surface temperature decreases by approximately 0.8 K at the Equator, with the largest decreases located in the middle latitudes reaching as high as 2.5 K. When ozone concentration is reduced and its vertical and horizontal distribution is simultaneously modulated, surface temperature decreases by 0.4–1.0 K at the Equator and by 4–7 K in polar regions. These results here have uncertainties, depending on model parameterizations of cloud, surface snow albedo, and relevant feedback processes, while they are qualitatively consistent with radiative-convective model results that do not involve such parameterizations and feedbacks. These results suggest that ozone variations could have had a moderate impact on the climate during the Neoproterozoic glaciations