Development Of A Decision Support System Webtool For Historic And Future Low Flow Estimation In The Northeast United States With Applications Of Machine Learning For Advancing Physical And Statistical Methodologies, Andrew F. Delsanto

Doctoral Dissertations

Droughts are a global challenge and anthropogenic climate change is expected to increase the frequency and severity of extreme low flow events. A major challenge for resource managers is how best to incorporate future climate change projections into low flow event estimations, especially in ungaged basins. Using both physically based hydrology models and statistical models, this dissertation contributes novel methodologies to three key challenges associated with 7-day, 10-year low flow (7Q10) estimation in the northeast United States. Chapter 2 builds upon statistically based 7Q10 estimation in ungaged basins by comparing multiple machine learning algorithms to classical statistical methodologies. This chapter’s …

Migmatite Formation, Geochronometer Petrogeneisis, And Rare Earth Element Mineralization In The Adirondack Mountains, Ny, Kaitlyn Suarez

Doctoral Dissertations

The Adirondack Mountains in upstate New York contain exposures of complex partially melted rocks, in addition to iron oxide-apatite (IOA) deposits with variable rare earth element (REE) concentrations. Previous workers have suggested that melting occurred during the ca. 1150 Ma Shawinigan and the ca. 1050 Ma Ottawan orogenies. However, there are challenges in determining the timing of melting and the number of partial melt events. Further, tectonic models must be developed to describe the petrogenesis of IOA and REE mineralization. Migmatites are present along Rt. 4/22 near Whitehall, NY. In chapter two, all layers of a single migmatitic rock were …

Sources And Controls Of Carbon Dioxide In Inland Waters At Watershed, Regional, And Continental Scales, Brian Saccardi

Doctoral Dissertations

Inland waters are significant sources of carbon dioxide to the atmosphere, and estimates of emissions are similar in magnitude to those of the carbon dioxide sequestered by the net terrestrial sink. Currently, methods of estimating carbon dioxide emissions are based on statistical approaches and often do not consider landscape attributes such as human development, agriculture, or the hydrologic connectivity of the stream network. The following research addresses these issues in chapter 1 by developing and validating a reactive transport model at the watershed scale, then in chapter 2 by applying the reactive transport model at the continental scale across US …

Benthic Foraminifera As Tools Of Paleoceanography: Three Case Studies From The Late Cretaceous Of The North Pacific Ocean And Western Interior Seaway, And The Miocene-Pleistocene Of The Ross Sea, Antarctica, Serena N. Dameron

Doctoral Dissertations

This dissertation is a widespread compilation of research covering vastly different times and locations. Despite these differences, the use of foraminifera helps to unravel their geologic history, revealing the paleoenvironmental, paleoclimatic, and paleoceanographic conditions of each location. What unites each study is how water mass, food supply and oxygen concentration play a critical role on the microfossil assemblage. This dissertation is broken up into three unique chapters. Chapter 1 reexamines some old ideas of how benthic foraminifera can be used as water mass indicators. A 13-myr record from Shatsky Rise in the paleo-central Pacific Ocean contains several instances water mass …

Geomorphology Of Tidal Wetlands: Impacts Of Extreme And Annual Flood Events To Salt Marsh And Mangrove Systems, Frances R. Griswold

Doctoral Dissertations

Tidal wetlands are vital for buffering coastal settings from the threats of accelerated sea level rise and storms. Understanding the factors that are most influential for the maintenance and recovery of tidal wetlands after extreme events compounded by future accelerated sea level rise is of the utmost importance, yet this knowledge is not well established. Two tidal wetland schemas investigated in this dissertation are mangrove systems in Vieques, Puerto Rico (including robust lagoonal-mangrove forest systems and fringing mangrove forests), and salt marshes in New England. While the climatic forcings, vegetation type, and locations are vastly different for these two tidal …

Size, Timing, And Landscape Impacts Of Glacial Lake Outburst Floods In The Channeled Scabland Of Eastern Washington, Usa, Karin E. Lehnigk

Doctoral Dissertations

Extreme floods have dramatically altered landscapes on Earth and Mars through bedrock erosion, sediment deposition, and canyon formation. The Channeled Scabland of the Columbia Plateau in eastern Washington, USA, is perhaps the most striking example of such a landscape, where outburst floods from an ice-dammed glacial Lake Missoula eroded immense canyons and transported large volumes of sediment during the late Pleistocene. Despite advances in numerical modeling and geochemical exposure dating methods, it has remained a challenge to untangle the complex interactions between floodwater, bedrock, and glacial ice to link the size of a flood with its impact on the landscape. …

Remote Sensing Of High Latitude Rivers: Approaches, Insights, And Future Ramifications, Merritt E. Harlan

Doctoral Dissertations

High latitude rivers across the pan-Arctic domain are changing due to changes in climate and positive Arctic feedback loops. Understanding and contextualizing these changes is challenging due to a lack of data and methods for estimating and modeling river discharge, and mapping rivers. Remote sensing, and the availability of satellite imagery can provide ways to overcome these challenges. Through combining various forms of fieldwork, modeling, deep learning, and remote sensing, we contribute methodologies and knowledge to three key challenges associated with better understanding high latitude rivers. In the first chapter, we combine field data that can be rapidly deployed with …

Antarctic Ice Sheet Stability During Warm Periods: Integrating Numerical Modeling With Geologic Data, Anna Ruth W. Halberstadt

Doctoral Dissertations

Sea level rise is one of the major social and environmental challenges that threatens modern civilization, yet the response of polar ice sheets to future warming is deeply uncertain. Mass loss from the Antarctic Ice Sheet is projected to dominate global sea level rise in the near future, but how much, and when, remains a key unknown. The challenges associated with projecting Antarctica’s future sea level contribution are derived from a knowledge gap of physical ice sheet processes in a world warmer than today, and a lack of understanding of climatic thresholds that drive potentially irreversible retreat. Future and even …

Perceptions Of Historical Climate Change And Park Policy: The Impact On The Fremont Cottonwood In Zion National Park, Kathleen Kavarra Corr

Doctoral Dissertations

Despite its “natural” appearance and the Organic Act 1916 mandate for preservation of the natural environment in National Parks, the Virgin River as it flows through Zion National Park’s Zion Canyon was transformed through massive flood control re-engineering projects in the 1930s. The armoring of the river has had significant impacts on riparian vegetation, particularly on the stands of native Fremont Cottonwood trees that once filled the narrow valley. What was the motivation for this massive flood control project carried out in an arid region with less than 15 inches of rain per year? This dissertation explores the motivations which …

Improving The Hydrological Analysis Of Groundwater Flow Paths By Integrating Geochemical And Physical Characteristics Of A Highly Fractured Aquifer System To Create Sustainable Use Of Groundwater In A Climate With Projected Drying Trends., Marsha K. Allen

Doctoral Dissertations

Improving the hydrological analysis of groundwater flow paths by integrating geochemical and physical characteristics of a highly fractured aquifer system to create sustainable use of groundwater in a climate with projected drying trends. Precipitation over Caribbean islands has decreased steadily since the 1950's, which has led to severe drought conditions. The most recent Pan-Caribbean Drought occurred from 2013 to 2016. Climate models predict that drying trends are expected to continue and become more severe over time as precipitation decreases and temperatures rise. In addition, evaporation rates on these islands are expected to increase by ~15-17%, contributing to the drought. Though …

Fundamental Controls On The Water Cycle In Arid Environments: A Mechanistic Framework For Spatiotemporal Connectivity Between Hydroclimate And Groundwaters In The Dry Andes, Brendan J. Moran

Doctoral Dissertations

There remain many persistent uncertainties regarding fundamental aspects of natural water cycles in arid mountainous regions, the Dry Andes of South America represents one of the most extreme examples of these environments on the Planet. Deep water tables (>100 meters), long groundwater transit times and distances (>100 years, 10-100 kilometers), limited and infrequent rainfall, remote and difficult to access terrain, and complex salar/evaporite hydrogeology common in these environments make reliable monitoring of these hydrological systems particularly difficult. As a result, major gaps remain in our understanding of critical aspects of the water cycle such as recharge and evaporation …

Magnitude And Rates Of Agriculturally-Induced Soil Erosion In The Midwestern United States, Evan Thaler

Doctoral Dissertations

Fertile, agricultural productive soils are essential for producing food for a growing global population. Soil erosion diminishes soil quality, threatens food security by decreasing crop productivity, and degrades ecosystem health through increased rates of sedimentation and runoff. Despite decades and thousands of soil erosion studies, robust scalable methods for estimating the magnitude and rates of soil erosion have been elusive. In this dissertation, we develop a remote sensing method for quantifying the areal extent of historical loss in an agricultural landscape and provide a method for estimating the total thickness of soil loss and rates of historical soil loss in …

Advances In Assessing Flood Hazard And Sediment Dynamics At The Coast, Hannah Baranes

Doctoral Dissertations

Earth’s coastlines are shaped by geophysical and human dynamism. Waves, tides, currents, and sea level change reconfigure coastal environments on hourly to centennial timescales, and the coast is experiencing the fastest economic and population growth rates in the world. This coexistence of a dynamic environment and human development makes coastal communities uniquely vulnerable to natural hazards. Climate change is expected to exacerbate flooding and erosion hazards in the future; thus, it is critical that we understand the underlying physical drivers of coastal change. The overarching goal of this dissertation is to improve the mechanistic understanding and quantification of dynamic processes …

Seismic Characteristics Of The Eastern North American Crust And Upper Mantle: The Formation And Evolution Of Continental Lithosphere, Cong Li

Doctoral Dissertations

The impact of past tectonic events on formation and modification of continental lithosphere over the course of Earth’s history remains as an open question of fundamental importance. Physical properties of continental crust and mantle lithosphere, such as their age, thickness, composition, temperature, and velocity, contain crucial information for informing this question. Eastern North America provides at least two complete records of supercontinent assembly and breakup over the past 1.3 Ga, serving as a natural laboratory for our understanding of continental lithosphere evolution and for integrating geologic and geophysical observations. In this thesis, I have investigated the seismic properties of crust …

Physiological Constraints, Mechanisms, And Mineral Transformations Of Iron Reduction In Hyperthermophilic Crenarchaea, Srishti Kashyap

Doctoral Dissertations

Dissimilatory iron reduction by hyperthermophilic archaea occurs in many geothermal environments and typically relies on microbe-mineral interactions that transform various iron oxide minerals. However, the kinds of iron oxides that can be used, growth rates, extent of iron reduction, and the mineral transformations that occur due to this metabolism are poorly understood. This dissertation improves our fundamental understanding of the physiological mechanisms and mineral transformations of hyperthermophilic iron reduction using two model crenarchaea, Pyrodictium delaneyi and Pyrobaculum islandicum. Using growth yields and metabolite production rates, we demonstrated that a broad range of Fe(III) (oxyhydr)oxides of variable thermodynamic stability was …

Implications And Significance Of Partial Melting On The Tectonic History Of The Eastern Adirondack Mountains, Claire Rose Pless

Doctoral Dissertations

The eastern Adirondack Mountains contain abundant exposures of high-grade metamorphic rocks. These exposures are interpreted to be a window into the mid/deep crust of an ancient, large, hot, long-duration orogen, allowing the Adirondack Mountains to be used as an analogue to the deep processes of modern orogens. Currently interpreted thermo-tectonic events in the eastern Adirondack Mountains include the ca. 1245-1220 Ma Elzevirian orogeny, the ca. 1190-1150 Ma Shawinigan orogeny, emplacement of the ca. 1150 Ma AMCG igneous suite, the ca. 1090-1050 Ma Ottawan orogeny, and a ca. 1050-1020 Ma extensional collapse phase. This dissertation focuses on six migmatite domains within …

3-D Shear Wave Velocity Structures Of The Crust And Upper Mantle Beneath Cascadia And New Zealand From Full-Wave Ambient Noise Tomography, Sampath Rathnayaka Mudiyanselage

Doctoral Dissertations

The (de)hydration process and the amount of hydrated sediment carried by the downgoing oceanic plate play a key role in the subduction dynamics. The deformation and (de)hydration of the downgoing tectonic plates, as well as the seismic, tsunami, volcanic hazards, in Cascadia and the New Zealand regions are not fully understood, partly due to a lack of combined studies of onshore and offshore data. In order to address these questions, we developed a 3-D high-resolution shear wave velocity model beneath Cascadia, the North and the South Islands of New Zealand, extending from offshore to onshore, with the use of full-wave …

Nanoindentation Characterization Of Elastic Properties Of Shales And Swelling Clay Minerals, Shengmin Luo

Doctoral Dissertations

Oil and gas shales are a class of multiscale, multiphase, hybrid inorganic-organic sedimentary rocks that consist of a generally uniform, preferentially oriented clay matrix with randomly embedded silt and sand particles as solid inclusions. A thorough understanding of the mechanical properties of shales is crucial for the exploration and production of oil and gas in the unconventional shale reservoirs, but it can be a challenging task due to their nature of compositional heterogeneity and microstructural anisotropy. In efforts to better characterize the mechanical properties of shales across different length scales and to fundamentally understand the laws of upscaling from individual …

Modeling The Pleistocene History Of The Greenland Ice Sheet, Benjamin Andrew Keisling

Doctoral Dissertations

One of the most profound and immediate consequences of anthropogenic climate change is sea level rise, which in large part is driven by the melting of polar ice sheets. The Greenland Ice Sheet (GrIS) contains enough ice to raise global sea level by ~7 meters. Fluctuations of the GrIS in response to past climate change provide an opportunity to better understanding the stability of the ice sheet during periods of climatic change. In this thesis, we use numerical ice-sheet models to understand the causes and consequences of past fluctuations of the Greenland ice sheet. In Chapters 3 and 4, we …

Petrogenesis Of Basaltic Lavas In Iceland And The Springerville Volcanic Field, U.S.A.: The Influence Of Tectonic Setting, Depth Of Melting And Volatiles, Marissa Mnich

Doctoral Dissertations

Icelandic basalts were long thought to be low in water (e.g. Gunnarsson et al., 1998), but more recent studies suggest that hotspots, like the Iceland mantle plume, may be a source of hydrous basaltic melts (Nichols et al., 2002). To explore a possible link between location, volatile concentration and resulting petrogenetic implications, samples were collected from eleven volcanic centers throughout Iceland. Water concentrations were measured in melt inclusions and phenocrysts using Fourier transform infrared (FTIR) spectroscopy. Results for a subset of samples indicate variable water in melt inclusions ranging from approximately 50 ppm to over 3000 ppm. Samples from southwestern …

Numerical Modeling Of Deformation Within Restraining Bends And The Implications For The Seismic Hazard Of The San Gorgonio Pass Region, Southern California, Jennifer Hatch

Doctoral Dissertations

Assessment of seismic hazards in southern California may be improved with more accurate characterization of active geometry, stress state, and slip rates along the active San Andreas fault strands within the San Gorgonio Pass region. For example, on-going debate centers on the activity and geometry of the Mill Creek and Mission Creek strands. Calculated misfits of model slip rates to geologic slip rates for six alternative active fault configuration models through the San Gorgonio Pass reveal two best-fitting models, both of which fit many but not all available geologic slip rates. Disagreement between the model and geologic slip rates indicate …

Middle To Late Pleistocene Paleoenvironmental Reconstructions From Lake El'gygytgyn, Arctic Russia, Mary Helen Habicht

Doctoral Dissertations

Climate change is a major issue challenging the world today. Our global society faces rising temperatures, variable weather patterns, and rising sea level among other associated issues. Our action (or inaction) to address current changes will have serious ramifications for life on our planet in the coming centuries and millennia. In order to provide context for these present and future changes, we can utilize the paleo record to understand the natural variability of Earth’s climate system. One region of the world is changing more rapidly than the global average. Over recent decades, the Arctic has experienced warmer temperatures, reduced sea …

Sorption Temperature And And The Stability Of Iron-Bound Soil Organic Matter, Michael L. Nguyen

Doctoral Dissertations

The preservation of soil organic matter (SOM) is an important control on the global cycling of carbon. Long-term preservation of SOM has important implications on soil fertility and climate regulation. Minerals, such as iron oxides, can react with SOM and serve as a preservation mechanism for SOM. Globally, iron oxide-SOM interactions form a “rusty carbon sink” which protects up to 22% of organic carbon in marine sediments. Climate changes, such as warming, may alter the size or efficacy of the “rusty carbon sink.” The effects of temperature, SOM composition, and mineral particle size on the formation and stability of iron …

Wildfires In The Northeastern United States: Evaluating Fire Occurrence And Risk In The Past, Present, And Future, Daniel R. Miller

Doctoral Dissertations

Climate change is one of the most complex and challenging issues facing the world today. A changing climate will affect humankind in many ways and alter our physical environment, presenting ethical challenges in how we respond. The impact of climate change will likely be exacerbated in heavily populated regions of the planet, such as the Northeastern United States (NEUS). The NEUS is comprised of complex, sprawling urban centers and rural regions, both of which are vital to the economic and cultural character of the region. Furthermore, both urban and rural areas in the NEUS contain communities that have been historically …

Evaluation Of The Erodibility Of Soft Clays And The Influence Of Biopolymers, Pamela Judge

Doctoral Dissertations

Erosion of silts and clays is less well understood than erosion of sands. Further, current and anticipated climate change impacts along coastlines compel consideration of new approaches to coastal protection measures; seawalls and breakwaters designs now include natural and nature-based measures. The first research topic consists of the Adaptive Gradients Framework which was a theoretically-informed facilitation tool. The framework was intended to aid a collaborative and interdisciplinary decision-making process to encourage inclusion of natural and nature-based measures in coastal protection planning and design. This research is the culmination of a series of workshops and fieldtrips executed by the Sustainable Adaptive …

Estimation Of Cdom In Inland Waters Via Water Bio-Optical Properties Using A Remote Sensing Approach, Jiwei Li

Doctoral Dissertations

Monitoring of Colored dissolved organic matter (CDOM) in inland waters provides important information for tracing carbon cycle at the land-water interface and studying aquatic ecosystem. Remote sensing estimation of CDOM in the inland waters offers an alternative approach to field samplings in examining CDOM spatial-temporal dynamics. However, CDOM retrieval is a challenge due to the lack of algorithm for resolving bottom effect in shallow inland waters. Moreover, an effective approach based on multi-spectral, high spatial resolution and global coverage satellite images is in urgent need. To resolve these challenges, shallow water bio-optical properties (SBOP) algorithm was developed to overcome bottom …

Modeling Deformation Behavior And Strength Characteristics Of Sand-Silt Mixtures: A Micromechanical Approach, Mehrashk Meidani

Doctoral Dissertations

This dissertation is comprised of six chapters. In the first chapter the motivation of this research, which was modeling the deformation behavior and strength characteristics of soils under internal erosion, is briefly explained. In the second chapter a micromechanis-based stress-strain model developed for prediction of sand-silt mixtures behavior is presented. The components of the micromechanics-based model are described and undrained behavior of six different types of sand-silt mixtures is predicted for several samples with different fines contents. The need for a more comprehensive compression model for sand-silt mixtures is identified at the end of this chapter. This desired compression model …

Eccentricity Modulation Of Precessional Variation In The Earth’S Climate Response To Astronomical Forcing: A Solution To The 41-Kyr Mystery, Rajarshi Roychowdhury

Doctoral Dissertations

The 41,000-year variability of Earth’s glacial cycles during the late Pliocene-early Pleistocene is usually attributed to variations in Earth’s obliquity (axial tilt). However, a satisfactory explanation for the lack of precessional variation in marine d¹⁸O records, a proxy for ocean temperature and ice-volume, remains contested. Here, a physically based climate model is used to show that the climatic effect of precession is muted in global isotope records due to two different mechanisms, with each dominating as a function of eccentricity. At low eccentricities (e0.019), the time-integrated summer insolation and number of positive degree-days impacting ice sheets varies at …

Arctic And North Atlantic Paleo-Environmental Reconstructions From Lake Sediments, Gregory A. De Wet

Doctoral Dissertations

ABSTRACT

A New Paradigm For Predicting Fracture Growth, Interaction And Linkage: Faulting In Numerical And Physical Experiments With Work Optimization, Jessica Mcbeck

Doctoral Dissertations

This dissertation predicts fracture propagation and interaction within the framework of work optimization. With this approach, fractures are predicted to propagate along the path that optimizes work. This dissertation includes three projects that predict fracture growth using work optimization in varying tectonic environments. The projects build on work completed during my M.S. at UMass, which includes the development of the fracture modeling tool Growth by Optimization of Work (GROW) [McBeck et al., 2016]. GROW simulates fracture propagation, interaction and linkage by iteratively searching for fracture propagation paths that maximize the change in external work done on the system …