Browsing by Subject "Earth sciences"
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Item Open Access A formal Anthropocene is compatible with but distinct from its diachronous anthropogenic counterparts: a response to W.F. Ruddiman’s ‘three flaws in defining a formal Anthropocene’(Progress in Physical Geography, 2019-06-01) Zalasiewicz, J; Waters, CN; Head, MJ; Poirier, C; Summerhayes, CP; Leinfelder, R; Grinevald, J; Steffen, W; Syvitski, J; Haff, P; McNeill, JR; Wagreich, M; Fairchild, IJ; Richter, DD; Vidas, D; Williams, M; Barnosky, AD; Cearreta, A© The Author(s) 2019. We analyse the ‘three flaws’ to potentially defining a formal Anthropocene geological time unit as advanced by Ruddiman (2018). (1) We recognize a long record of pre-industrial human impacts, but note that these increased in relative magnitude slowly and were strongly time-transgressive by comparison with the extraordinarily rapid, novel and near-globally synchronous changes of post-industrial time. (2) The rules of stratigraphic nomenclature do not ‘reject’ pre-industrial anthropogenic signals – these have long been a key characteristic and distinguishing feature of the Holocene. (3) In contrast to the contention that classical chronostratigraphy is now widely ignored by scientists, it remains vital and widely used in unambiguously defining geological time units and is an indispensable part of the Earth sciences. A mounting body of evidence indicates that the Anthropocene, considered as a precisely defined geological time unit that begins in the mid-20th century, is sharply distinct from the Holocene.Item Open Access A Time Series Regression Analysis of Future Climate(2012-04-23) Rudulph, JakeCurrent approaches to climate modeling, including environmental simulation, may not be able to generate actionable results for a few decades yet. Over the last 50 years, methods attempting to capture and predict states of the climate system have flourished and diversified. However, many such models are subject to errors and uncertainty arising from parameterization problems, the obligate characterization of poorly understood phenomena, and high capacity requirements stemming from the incredible computing power needed. As the window for meaningful actions towards altering the climate change trajectory closes, we should consider the use of simple methods that generally predict the conditions of the future climate. For my analysis, I developed a time-series regression analysis of land surface trends in precipitation and near-surface temperature. For each global 0.5º land surface grid, values for 1901-2009 baseline means were calculated, and 2050 values were predicted using time series regression models for each of four historical data subsets. Average predicted warming across the subsets range from 0.89 ºC to 5.8 ºC above the baseline, with high northern latitudes predicted to experience the most warming. Precipitation is predicted to follow the “wet getting wetter, dry getting dryer” paradigm, with average predicted changes across the subsets ranging from 3.2% to 26% above the baseline.Item Open Access Investigating Linkages Between Engineering and Petrophysical Properties of Unconsolidated Geomaterials and Their Geoelectrical Parameters(2011) Owusu-Nimo, FrederickThe need for an improved ability to "see into the earth" has resulted in the use of geophysical techniques, especially the electrical resistivity method, in engineering and environmental investigations. The major challenge in the use of electrical resistivity measurements however is the interpretation of the electrical response. This is due to the lack of adequate understanding of the relationships between the physical factors controlling the engineering behavior of geomaterials (earth materials) and their measurable electrical parameters. This research work therefore sets out to investigate the linkages between engineering and petrophysical properties of geomaterials and their geoelectrical parameters. This goal is achieved through the development of laboratory equipments and the conduction of both laboratory and field studies. The laboratory experiments involve the measurement of the complex resistivity responses of natural and artificial soil samples under varying effective stress conditions. The field study involves the characterization of subsurface fracture parameters from field electrical measurements in complex fractured terrains at selected farming communities in Ghana.
The results from this study improve on our knowledge and understanding of the influence of fundamental engineering properties of geomaterials on their electrical responses. It results will aid in the interpretation of field electrical measurements and provide a means for engineering properties of geomaterials to be estimated from measurable electrical parameters. It will also contribute towards using non-invasive electrical measurements to locate weak zones in the subsurface, assess and monitor the stability conditions of soil units and assist in the environmental impact assessment of anthropogenic activities on groundwater resources in complex fractured terrain.