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Articles 10891 - 10920 of 59516
Full-Text Articles in Earth Sciences
Earlier Snowmelt May Lead To Late Season Declines In Plant Productivity And Carbon Sequestration In Arctic Tundra Ecosystems, Donatella Zona, Peter M. Lafleur, Koen Hufkens, Barbara Bailey, Beniamino Gioli, George Burba, Jordan P. Goodrich, Anna K. Liljedahl, Eugénie S. Euskirchen, Jennifer D. Watts, Mary Farina, John S. Kimball, Martin Heimann, Mathias Göckede, Martijn Pallandt, Torben R. Christensen, Mikhail Mastepanov, Efrén López-Blanco, Marcin Jackowicz-Korczynski, Albertus J. Dolman, Luca Belelli Marchesini, Roisin Commane, Steven C. Wofsy, Charles E. Miller, David A. Lipson, Josh Hashemi, Kyle A. Arndt, Lars Kutzbach, David Holl, Julia Boike, Christian Wille, Torsten Sachs, Aram Kalhori, Xia Song
Earlier Snowmelt May Lead To Late Season Declines In Plant Productivity And Carbon Sequestration In Arctic Tundra Ecosystems, Donatella Zona, Peter M. Lafleur, Koen Hufkens, Barbara Bailey, Beniamino Gioli, George Burba, Jordan P. Goodrich, Anna K. Liljedahl, Eugénie S. Euskirchen, Jennifer D. Watts, Mary Farina, John S. Kimball, Martin Heimann, Mathias Göckede, Martijn Pallandt, Torben R. Christensen, Mikhail Mastepanov, Efrén López-Blanco, Marcin Jackowicz-Korczynski, Albertus J. Dolman, Luca Belelli Marchesini, Roisin Commane, Steven C. Wofsy, Charles E. Miller, David A. Lipson, Josh Hashemi, Kyle A. Arndt, Lars Kutzbach, David Holl, Julia Boike, Christian Wille, Torsten Sachs, Aram Kalhori, Xia Song
Daugherty Water for Food Global Institute: Faculty Publications
Arctic warming is affecting snow cover and soil hydrology, with consequences for carbon sequestration in tundra ecosystems. The scarcity of observations in the Arctic has limited our understanding of the impact of covarying environmental drivers on the carbon balance of tundra ecosystems. In this study, we address some of these uncertainties through a novel record of 119 site-years of summer data from eddy covariance towers representing dominant tundra vegetation types located on continuous permafrost in the Arctic. Here we found that earlier snowmelt was associated with more tundra net CO2 sequestration and higher gross primary productivity (GPP) only in June …
(R1978) Heated Laminar Vertical Jet Of Psudoplastic Fluids-Against Gravity, Manisha Patel, M. G. Timol
(R1978) Heated Laminar Vertical Jet Of Psudoplastic Fluids-Against Gravity, Manisha Patel, M. G. Timol
Applications and Applied Mathematics: An International Journal (AAM)
A heated laminar jet of Pseudo-plastic fluid flowing vertically upwards from a long narrow slit into a region of the same fluid which is at a rest and at a uniform temperature is considered. The governing non-linear Partial differential equations (PDEs) for the defined flow problem are transformed into non-linear ordinary differential equations using the effective similarity technique-one parameter deductive group theory method. The obtained non-linear coupled Ordinary differential equations are solved and the results are presented by graphs. The effect of the Prandtl number and Grashof number on the velocity and temperature of the jet flow is discussed. Also, …
Predictions And Drivers Of Sub-Reach-Scale Annual Streamflow Permanence For The Upper Missouri River Basin: 1989–2018, Kendra E. Kaiser
Predictions And Drivers Of Sub-Reach-Scale Annual Streamflow Permanence For The Upper Missouri River Basin: 1989–2018, Kendra E. Kaiser
Geosciences Faculty Publications and Presentations
The presence of year-round surface water in streams (i.e., streamflow permanence) is an important factor for identifying aquatic habitat availability, determining the regulatory status of streams, managing land use change, allocating water resources, and designing scientific studies. However, accurate, high resolution, and dynamic prediction of streamflow permanence that accounts for year-to-year variability at a regional extent is a major gap in modeling capability. Herein, we expand and adapt the U.S. Geological Survey (USGS) PRObability of Streamflow PERmanence (PROSPER) model from its original implementation in the Pacific Northwest (PROSPERPNW) to the upper Missouri River basin (PROSPERUM), a …
The Formation Of The 8˚20’ N Seamount Chain, East Pacific Rise, Dorsey Wanless
The Formation Of The 8˚20’ N Seamount Chain, East Pacific Rise, Dorsey Wanless
Geosciences Faculty Publications and Presentations
Near-axis seamounts provide a unique setting to investigate three-dimensional mantle processes associated with the formation of new oceanic crust and lithosphere. Here, we investigate the characteristics and evolution of the 8˚20’N Seamount Chain, a lineament of seamounts that extends ~ 175 km west of the East Pacific Rise (EPR) axis, just north of the fracture zone of the Siqueiros Transform Fault. Shipboard gravity, magnetic, and bathymetric data acquired in 2016 are utilized to constrain models of seamount emplacement and evolution. Geophysical observations indicate that these seamounts formed during four distinct episodes of volcanism coinciding with changes in regional plate motion …
Modeling Of Population Dynamics In Spatially Continuous And Heterogeneous Environments Using Partial Differential Equations, Ryan T. St. Clair
Modeling Of Population Dynamics In Spatially Continuous And Heterogeneous Environments Using Partial Differential Equations, Ryan T. St. Clair
Masters Theses & Specialist Projects
This thesis provides an expansion of existing reaction diffusion population ecology models into patchy landscapes with greater spatial heterogeneity. The Sturm-Loiville eigenvalue problem for a heterogeneous 3 patch landscape is solved implicitly and the population growth rate and migration dynamics on such a landscape are thoroughly discussed. In addition a system of interface equations is found whose greatest solution is the dominant eigenvalue of an N-patch landscape. The results of this model agree well with previously published results and show the mathematical equivalence of two published approaches for incorporating organism behavior at habitat interfaces. Increased modeling capabilities in heterogeneous environments …
Carbon Cycling And Critical Zone Dynamics In An Urbanized Karst Groundwater System, Amy Hourigan
Carbon Cycling And Critical Zone Dynamics In An Urbanized Karst Groundwater System, Amy Hourigan
Masters Theses & Specialist Projects
Increasing atmospheric CO2 concentrations are correlated to rising global temperatures. Investigating the cumulative global carbon cycling processes is important to understand and quantify the global carbon cycle. By investigating basic geochemical parameters, EpCO2, DIC, and δ13CDIC, at four sites along Lost River Cave (LRC), in Bowling Green, Kentucky, concentrations, fluxes and sources of C dissolved in groundwater were determined. Urban karst groundwater systems, compared to more natural karst landscapes, typically exhibit widespread impervious, heat-absorbing surfaces, urban heat island effects, and increased anthropogenic groundwater inputs and localized CO2 emissions. Carbonate hydrogeochemical …
One Health In Action: Flea Control And Interpretative Education At Badlands National Park, David Eads, Lindsey Buehler, Anne Esbenshade, Jason Fly, Evan Miller, Holly Redmond, Emily Ritter, National Park Service, Sasha Wittmann, Paul Roghair, Eddie Childers
One Health In Action: Flea Control And Interpretative Education At Badlands National Park, David Eads, Lindsey Buehler, Anne Esbenshade, Jason Fly, Evan Miller, Holly Redmond, Emily Ritter, National Park Service, Sasha Wittmann, Paul Roghair, Eddie Childers
United States Geological Survey: Staff Publications
No abstract provided.
Flood Hazard And Risk Analyses In The Republic Of Panama: A Case Study From The Juan Diaz River Watershed In Panama City, Virgilio De Jesus Quintero
Flood Hazard And Risk Analyses In The Republic Of Panama: A Case Study From The Juan Diaz River Watershed In Panama City, Virgilio De Jesus Quintero
Graduate Theses and Dissertations
Flooding is the natural hazard with most occurrences in Panama. Its frequency and magnitude have increased over the years. This dissertation analyzes Panama’s flood activity in order to better understand flood hazards, the current evolution of Panamanian perceptions of flood risk, and the incorporation of indigenous knowledge used to mitigate flood hazards. The first chapter developed a baseline of past and current flood inventory in Panama, which required the use of flood historical data, thematic cartography, and Geographic Information Science (GIS). This chapter shows Panama has experienced floods in varying degrees. Through the spatial and temporal distribution of floods from …
A Framework For Assessing The 4th Rank Dispersivity Tensor Under Anisotropic Axial Symmetries, Xiang Fan
A Framework For Assessing The 4th Rank Dispersivity Tensor Under Anisotropic Axial Symmetries, Xiang Fan
Dissertations
Multi-dimensional expansion of the advection-dispersion equation necessitated the representation of dispersivity as a 4th rank tensor. This tensorial form of dispersivity has 81 terms in three-dimensions with a maximum of 36 independent terms that may be used to describe Fickian spreading of a dissolved contaminant plume according to intrinsic properties of a porous medium. The complexity of the 4th rank tensor has led to the common practice of simplifying the tensor to only 2 or 3 independent terms by assuming isotropic conditions, although isotropic porous media are uncommon in nature as many natural geologic systems exhibit pronounced anisotropy. A broad …
Investigating The Frictional Properties Of Organic Matter And Pore Structure Of Organic-Rich Shales With Atomic Force Microscopy And Scanning Electron Microscopy, Farnood Sobhbidari
Investigating The Frictional Properties Of Organic Matter And Pore Structure Of Organic-Rich Shales With Atomic Force Microscopy And Scanning Electron Microscopy, Farnood Sobhbidari
Earth & Environmental Sciences Dissertations - Archive
Understanding geomechanical properties of shales, such as stiffness properties and fracture toughness, is important in different areas of petroleum industry-related activities including fracturing efficiency, petroleum flow to the wellbores, and induced seismicity. Nanoscale to microscale experiments on shale samples require a much smaller sample compared to macroscale experiments. This is a major advantage because irregularly-shaped drill cuttings from shales can be used for experimental analyses, such as nanoindentation or atomic force microscopy (AFM). However, a characterization of mechanical properties at the nano- to micro-scale is a relatively new addition to classical geomechanical experiments on shales, and there is still lack …
Late Pleistocene Piedmont Records In The Grand Staircase Region, Southern Utah, Alexander K. Short
Late Pleistocene Piedmont Records In The Grand Staircase Region, Southern Utah, Alexander K. Short
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Today the climate in the southwestern United States is arid, characterized by desert landscapes and habitats, periods of drought, and arroyo streams that frequently fill with, and erode, through fine riverbed sediments. A series of cliffs and benches rising from the Grand Canyon to the southern plateaus of Utah, known as the Grand Staircase - home to Kodachrome Basin State Park, Bryce Canyon, are a classical example of this environment as we know it today. However, a record spanning the past 300 thousand years is preserved on the steps of the staircase indicating periods in the past where the climate …
Bedrock Geology Map Of The Naomi Peak 7.5' Quadangle, Cache County, Utah And Novel Age Constraints On Its Cambrian Strata, Hannah R. Cothren
Bedrock Geology Map Of The Naomi Peak 7.5' Quadangle, Cache County, Utah And Novel Age Constraints On Its Cambrian Strata, Hannah R. Cothren
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Geologists use various “rock-clocks” in order to interpret the timing and tempo of events in Earth’s history. These include global geochemical events in the oceans (chemostratigraphy), the evolution of certain fossil species (trilobite biostratigraphy), and the radiogenic decay of uranium to lead in certain mineral such as zircon (U-Pb geochronology). Integrating these methods in the stratigraphic record in one location can provide a well-constrained timeline for a select part of the Geologic, or Deep Time, record. This technique is especially important in the Cambrian Period (538.8 to 486.9 million years; Ma), which sets the stage for life today with the …
Ancient Marine Sediment Dna Reveals Diatom Transition In Antarctica, Linda Armbrecht, Michael E. Weber, Maureen E. Raymo, Victoria L. Peck, Trevor Williams, Jonathan Warnock, Yuji Kato, Iván Hernández-Almeida, Frida Hoem, Brendan Reilly, Sidney Hemming, Ian Bailey, Yasmina M. Martos, Marcus Gutjahr, Vincent Percuoco, Claire Allen, Stefanie Brachfeld, Fabricio G. Cardillo, Zhiheng Du, Gerson Fauth, Chris Fogwill, Marga Garcia, Anna Glüder, Michelle Guitard, Ji Hwan Hwang, Mutsumi Iizuka, Bridget Kenlee, Suzanne O’Connell, Lara F. Pérez, Thomas A. Ronge, Osamu Seki, Lisa Tauxe
Ancient Marine Sediment Dna Reveals Diatom Transition In Antarctica, Linda Armbrecht, Michael E. Weber, Maureen E. Raymo, Victoria L. Peck, Trevor Williams, Jonathan Warnock, Yuji Kato, Iván Hernández-Almeida, Frida Hoem, Brendan Reilly, Sidney Hemming, Ian Bailey, Yasmina M. Martos, Marcus Gutjahr, Vincent Percuoco, Claire Allen, Stefanie Brachfeld, Fabricio G. Cardillo, Zhiheng Du, Gerson Fauth, Chris Fogwill, Marga Garcia, Anna Glüder, Michelle Guitard, Ji Hwan Hwang, Mutsumi Iizuka, Bridget Kenlee, Suzanne O’Connell, Lara F. Pérez, Thomas A. Ronge, Osamu Seki, Lisa Tauxe
Department of Earth and Environmental Studies Faculty Scholarship and Creative Works
Antarctica is one of the most vulnerable regions to climate change on Earth and studying the past and present responses of this polar marine ecosystem to environmental change is a matter of urgency. Sedimentary ancient DNA (sedaDNA) analysis can provide such insights into past ecosystem-wide changes. Here we present authenticated (through extensive contamination control and sedaDNA damage analysis) metagenomic marine eukaryote sedaDNA from the Scotia Sea region acquired during IODP Expedition 382. We also provide a marine eukaryote sedaDNA record of ~1 Mio. years and diatom and chlorophyte sedaDNA dating back to ~540 ka (using taxonomic marker genes SSU, LSU, …
A Comprehensive Analysis Of The Evolution Of Coastal Flooding In Texas And Louisiana For Application In Risk Assessment, Joshua Pulcinella
A Comprehensive Analysis Of The Evolution Of Coastal Flooding In Texas And Louisiana For Application In Risk Assessment, Joshua Pulcinella
Earth & Environmental Sciences Dissertations - Archive
Coastal communities of the northern Gulf of Mexico have historically been at risk of flooding from tropical cyclone induced storm surge and extreme precipitation. Relative sea level rise resulting from a combination of increasing global mean sea level and regional subsidence presents an escalating threat that requires a comprehensive assessment of changing flood risks for the area. This study examines how coastal flooding events are changing and focuses on the future risks to communities and infrastructure in Texas and Louisiana. Utilizing historic tide gauge observations, tropical cyclone records, and associated storm tide data, the frequency, duration, and magnitude of events …
Mgrre_Thinsections_Mgrre-129_9, Mgrre
Mgrre_Thinsections_Mgrre-129_10, Mgrre
Mgrre_Thinsections_Mgrre-129_13, Mgrre
Statistical Analysis Of Aquifer Hydraulic Properties By A Continuous Pumping Tomography Test: Application To The Boise Hydrogeophysical Research Site, Kan Bun Cheng, Gedeon Dagan, Warren Barrash, Michael Cardiff, Avinoam Rabinovich
Statistical Analysis Of Aquifer Hydraulic Properties By A Continuous Pumping Tomography Test: Application To The Boise Hydrogeophysical Research Site, Kan Bun Cheng, Gedeon Dagan, Warren Barrash, Michael Cardiff, Avinoam Rabinovich
Geosciences Faculty Publications and Presentations
Characterizing aquifer heterogeneity is paramount for accurate flow and transport modeling. In this work, we present a new approach for statistical analysis of hydraulic properties in continuous pumping tomography tests of a phreatic aquifer. The method entails determining equivalent hydraulic conductivity (Keq), specific storage (Ss,eq), and specific yield (Sy,eq) at many locations in the field and then calculating statistical moments of the equivalent properties, assuming they are random space variables. Equivalent properties are defined as the ones pertinent to a homogeneous aquifer for which the head time …
Computational And Experimental Investigations Of Alkali Cation Interactions At The Rutile – Water Interface, Isaac Johnston
Computational And Experimental Investigations Of Alkali Cation Interactions At The Rutile – Water Interface, Isaac Johnston
All Dissertations
Overall, the objective of this dissertation was to investigate the degree of sorption for the alkali cations on rutile to ascertain the impact of different cation properties, such as ion size and charge density, on sorption mechanics as well as probe how the ion may alter the surface – aqueous interface. Initial molecular dynamic simulations and batch experiments showed minimal surface sorption for any alkali cation at relatively low concentrations while simultaneously suggesting the enthalpy of deprotonation shifts slightly in the presence of the alkali cations at different ionic strengths. The cations are likely causing small reorientations of the near-surface …
Mgrre_Thinsections_Mgrre-129_1, Mgrre
Mgrre_Thinsections_Mgrre-129_4, Mgrre
Mgrre_Thinsections_Mgrre-129_3, Mgrre
Mgrre_Thinsections_Mgrre-129_11, Mgrre
Mgrre_Thinsections_Mgrre-129_12, Mgrre
Mgrre_Thinsections_Mgrre-129_8, Mgrre
Antiphased Dust Deposition And Productivity In The Antarctic Zone Over 1.5 Million Years, Michael E. Weber, Ian Bailey, Sidney R. Hemming, Yasmina M. Martos, Brendan T. Reilly, Thomas A. Ronge, Stefanie Brachfeld, Trevor Williams, Maureen Raymo, Simon T. Belt, Lukas Smik, Hendrik Vogel, Victoria L. Peck, Linda Armbrecht, Alix Cage, Fabricio G. Cardillo, Zhiheng Du, Gerson Fauth, Christopher J. Fogwill, Marga Garcia, Marlo Garnsworthy, Anna Glüder, Michelle Guitard, Marcus Gutjahr, Iván Hernández-Almeida, Frida S. Hoem, Ji Hwan Hwang, Mutsumi Iizuka, Yuji Kato, Bridget Kenlee, Suzanne Oconnell, Lara F. Pérez
Antiphased Dust Deposition And Productivity In The Antarctic Zone Over 1.5 Million Years, Michael E. Weber, Ian Bailey, Sidney R. Hemming, Yasmina M. Martos, Brendan T. Reilly, Thomas A. Ronge, Stefanie Brachfeld, Trevor Williams, Maureen Raymo, Simon T. Belt, Lukas Smik, Hendrik Vogel, Victoria L. Peck, Linda Armbrecht, Alix Cage, Fabricio G. Cardillo, Zhiheng Du, Gerson Fauth, Christopher J. Fogwill, Marga Garcia, Marlo Garnsworthy, Anna Glüder, Michelle Guitard, Marcus Gutjahr, Iván Hernández-Almeida, Frida S. Hoem, Ji Hwan Hwang, Mutsumi Iizuka, Yuji Kato, Bridget Kenlee, Suzanne Oconnell, Lara F. Pérez
Department of Earth and Environmental Studies Faculty Scholarship and Creative Works
The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust …
Impact Of Eocene-Oligocene Antarctic Glaciation On The Paleoceanography Of The Weddell Sea, Victoria Hojnacki, Allison Lepp, Josie Horowitz Castaldo, Abbey States, Xiaona Li, Sandra Passchier
Impact Of Eocene-Oligocene Antarctic Glaciation On The Paleoceanography Of The Weddell Sea, Victoria Hojnacki, Allison Lepp, Josie Horowitz Castaldo, Abbey States, Xiaona Li, Sandra Passchier
Department of Earth and Environmental Studies Faculty Scholarship and Creative Works
The Eocene-Oligocene Transition (EOT) at ∼34 Ma marked a climatic shift from greenhouse to icehouse conditions, toward long-lasting lower global temperatures and a continental ice sheet in the Antarctic. We report on sedimentological and inorganic geochemical results across the EOT at Ocean Drilling Program (ODP) Site 696 in the Weddell Sea, within the Antarctic limb of the Atlantic circulation. The geochemical composition of detrital, authigenic and biogenic marine sediment components, and sortable silt proxies demonstrate the impact of ice growth on high latitude water masses. Sortable silt grain size and Zr/Rb ratios attest to a period of vigorous circulation at …
Phosphate Mineralogy And Paragenesis Of The Fletcher Pegmatite, North Groton, New Hampshire, Susanna T. Kreinik
Phosphate Mineralogy And Paragenesis Of The Fletcher Pegmatite, North Groton, New Hampshire, Susanna T. Kreinik
LSU New Orleans Theses and Dissertations
Investigation of phosphate assemblages selectively collected at the Fletcher Mine pegmatite, North Groton, New Hampshire, yielded eighteen discrete secondary phosphate species. Secondary phases were formed via metasomatic (high temperature) and hydrothermal (low temperature) alteration of primary triphylite and fluorapatite. Mineral associations bear proximal phases known to occur under contrasting conditions, both oxidizing and reducing, suggesting the formation of microenvironments during concomitant mineral generation. Late-stage hydrothermal fluids provide ions taken up in low temperature secondary phases with calcium and magnesium most prevalent in these suites. High iron to manganese ratios in analyzed specimens establish the relative evolution of the pegmatite host. …
The North Platte River Valley: The Intersectionality Between Water Quality And People, Anni Poetzl
The North Platte River Valley: The Intersectionality Between Water Quality And People, Anni Poetzl
School of Natural Resources: Dissertations, Theses, and Student Research
The North Platte River (NPR) Valley of western Nebraska is a semi-arid watershed with row crop production, livestock production, and urban land use activity and has a population of diverse stakeholders. These land use activities contribute to the enrichment of surface waters, such as streams, which can affect human and ecosystem health, as well as economic development and recreational activities. The project objectives are to: (1) quantify the movement of dissolved inorganic nutrients from the land within the NPR Valley to the NPR via tributaries and canals, (2) identify spatiotemporal variability of nutrient limitation of periphyton growth within the NPR, …
Human And Hydrologic Influences On Nebraska's Endangered Rainwater Basin Wetlands, Sarah Thompson
Human And Hydrologic Influences On Nebraska's Endangered Rainwater Basin Wetlands, Sarah Thompson
Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research
Over half of wetlands in North America have been lost or degraded. Rainwater Basin (RWB) wetlands, located in south-central Nebraska, are a primary example of such loss; an estimated 90% have been destroyed by land conversion for agriculture. Remaining RWB wetlands are often embedded in row-crop fields, where they are threatened by altered surface water runoff flow, drainage features, and excess sediment inputs. Efforts at the state and federal level have been made to preserve this wetland complex due to the critical stopover habitat these wetlands provide for migratory birds. Land managers work to maintain sufficient water levels during migratory …