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Articles 1 - 8 of 8
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Manganese Bioavailability Drives Organic Matter Transformations Across Oxic-Anoxic Interfaces Via Biotic And Abiotic Pathways, Nathan A. Chin
Manganese Bioavailability Drives Organic Matter Transformations Across Oxic-Anoxic Interfaces Via Biotic And Abiotic Pathways, Nathan A. Chin
Masters Theses
Soil organic matter decomposition is a critical process that affects nutrient cycling, CO2 emissions, and carbon storage in terrestrial environments. Recent evidence suggests reactive manganese (Mn) phases, potent oxidants that depolymerize compounds like lignocellulose in soil organic matter, act as critical drivers of organic matter decomposition in soil and sediment environments. Furthermore, oxic-anoxic interfaces (OAIs) have been shown to be crucial hotspots for the formation of reactive Mn(III) species and associated organic matter degradation. However, the extent to which microbially mediated Mn(III) formation and subsequently Mn(III)-driven organic matter oxidation depends on Mn availability remains largely unknown. Additionally, the relative …
Size, Timing, And Landscape Impacts Of Glacial Lake Outburst Floods In The Channeled Scabland Of Eastern Washington, Usa, Karin E. Lehnigk
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. …
Pre-Agricultural Soil Erosion Rates In The Midwestern U.S., Caroline Lauth Quarrier
Pre-Agricultural Soil Erosion Rates In The Midwestern U.S., Caroline Lauth Quarrier
Masters Theses
Soil erosion undermines agricultural productivity, limiting the lifespan of civilizations. For agriculture to be sustainable, soil erosion rates must be low enough to maintain fertile soil, as was present in many agricultural landscapes prior to the initiation of farming. However, there have been few measurements of long-term pre-agricultural erosion rates in major agricultural landscapes. We quantified geological erosion rates in the Midwestern U.S., one of the world’s most productive agricultural areas. We sampled soil profiles from 14 native prairies and measured concentrations of the cosmogenic nuclide 10Be and chemically immobile elements to calculate physical erosion rates. We used the erosion …
Remote Sensing Of High Latitude Rivers: Approaches, Insights, And Future Ramifications, Merritt E. Harlan
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
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
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 …