Open Access. Powered by Scholars. Published by Universities.®
- Publication
Articles 1 - 14 of 14
Full-Text Articles in Entire DC Network
Influence Of Permafrost Thaw, Microtopography, And Precipitation On Methane Cycling In Northern Peatlands, Clarice Rachelle Perryman
Influence Of Permafrost Thaw, Microtopography, And Precipitation On Methane Cycling In Northern Peatlands, Clarice Rachelle Perryman
Doctoral Dissertations
Northern peatlands are both globally important carbon (C) stores and sources of methane (CH4). The impacts of climate change including warming, changing precipitation and hydrology, shifts in vegetation, and thawing permafrost may increase the vulnerability of the northern peatland C stock, including the amount of C lost to the atmosphere as CH4. Variation in peatland water table depth strongly influences CH4 cycling, as water table levels largely control redox conditions and therefore rates of anaerobic CH4 production (methanogenesis) and aerobic CH4 oxidation (consumption, methanotrophy). As CH4 emissions reflect the balance of methanogenesis and methanotrophy, changes in water table depth due …
Controls On Carbon Gas Fluxes From A Temperate Forest Soil, Natalie A. White, Ruth K. Varner, Clarice R. Perryman
Controls On Carbon Gas Fluxes From A Temperate Forest Soil, Natalie A. White, Ruth K. Varner, Clarice R. Perryman
Honors Theses and Capstones
Forest soils consume atmospheric methane (CH4), serving as a major global CH4 sink that uptake an estimated 22 ± 12 Tg of CH4 per year. Temperature and soil moisture have been identified as key controls of the microbial consumption of CH4 in forest soils. Climate-driven warming and changing moisture regimes may impact forest soils’ role in the carbon cycle, and recent works suggests that forests could become weaker CH₄ sinks. Long-term monitoring sites can capture these changes, leading to better predictions of CH4 exchange between the atmosphere and soils under climate change. This study …
Carbon Emissions From Streams And Rivers: Integrating Methane Emission Pathways And Storm Carbon Dioxide Emissions Into Stream And River Carbon Balances, Andrew Robison
Doctoral Dissertations
River networks play an important role in elemental cycling at watershed, regional, and global scales. They not only serve as pipes that transport elements from land to sea, but also as complex processers that can significantly modify the timing, form, and magnitude of these elemental fluxes. For example, recent studies have shown that river networks contribute significantly to the global carbon cycle by emitting greenhouse gases like carbon dioxide (CO¬2) and methane (CH4) to the atmosphere. However, we currently do not fully understand the controls on GHG emissions from river networks, particularly what drives the variability of emissions across space …
Using Stable Isotopes To Determine Dominant Methane Production Pathways Of Thaw Ponds In A Subarctic Peatland, Kathryn Ann Bennett
Using Stable Isotopes To Determine Dominant Methane Production Pathways Of Thaw Ponds In A Subarctic Peatland, Kathryn Ann Bennett
Master's Theses and Capstones
Arctic and subarctic ecosystems are currently warming faster than any other region of the globe, accelerating seasonal permafrost thaw. As thaw progresses, small water bodies can form due to slumping of the peatland surface. These ponds emit methane (CH4), a strong, radiatively important trace gas, predominantly through ebullition (bubbling). Two different types of methanogenic Archaea present in these systems produce CH4 through their respective production pathways: acetoclastic and hydrogenotrophic methanogenesis. The acetoclastic pathway forms CH4 using CH3COOH, an organic carbon (C) source while hydrogenotrophic methanogenesis uses CO2, an inorganic C source. Stable isotopes can be used to characterize the relative …
Using Stable Isotopes To Determine Dominant Methane Production Pathways Of Thaw Ponds In A Subarctic Peatland, Kathryn Ann Bennett
Using Stable Isotopes To Determine Dominant Methane Production Pathways Of Thaw Ponds In A Subarctic Peatland, Kathryn Ann Bennett
Master's Theses and Capstones
Arctic and subarctic ecosystems are currently warming faster than any other region of the globe, accelerating seasonal permafrost thaw. As thaw progresses, small water bodies can form due to slumping of the peatland surface. These ponds emit methane (CH4), a strong, radiatively important trace gas, predominantly through ebullition (bubbling). Two different types of methanogenic Archaea present in these systems produce CH4 through their respective production pathways: acetoclastic and hydrogenotrophic methanogenesis. The acetoclastic pathway forms CH4 using CH3COOH, an organic carbon (C) source while hydrogenotrophic methanogenesis uses CO2, an inorganic C source. Stable isotopes can be used to characterize the relative …
Characterization Of A Silty Methane-Hydrate Reservoir In The Gulf Of Mexico: Analysis Of Full Sediment Grain-Size Distributions, Douglas Macleod
Characterization Of A Silty Methane-Hydrate Reservoir In The Gulf Of Mexico: Analysis Of Full Sediment Grain-Size Distributions, Douglas Macleod
Master's Theses and Capstones
Submarine methane-hydrate reservoirs represent an ephemeral reservoir of carbon on Earth that can contain economically important concentrations of methane. Turbidite sands in deepwater marine environments have been targeted by recent research because they contain sufficient primary porosity to host high saturations of methane hydrate within the temperature and pressure window of the gas-hydrate stability zone. Silty turbidite levee deposits, however, also contain sufficient primary porosity to host high saturations of methane hydrate and they may contain more organic carbon than sand to fuel methanogenesis. In this research I used laser diffractometry to measure the full grain-size distribution of 46 bulk …
Investigating The Spatial And Temporal Scale Variability Of Ebullitive Flux From A Subarctic Thaw Pond System, Sophia Burke
Investigating The Spatial And Temporal Scale Variability Of Ebullitive Flux From A Subarctic Thaw Pond System, Sophia Burke
Doctoral Dissertations
Arctic regions are experiencing more rapid warming than other parts of the world, leading to destabilization of carbon (C) that has been sequestered in permafrost, especially in peatlands where the C content of the peat is very high. More frequent incidence of thaw in permafrost peatlands is leading to the development of small thaw ponds that are known to be sources of methane (CH4) to the atmosphere, yet there is a lack in long-term studies of CH4 emission from these formations. This is of concern because CH4 has thirty-two times the global warming potential of carbon dioxide over a one-hundred-year …
Divergent Controls On Stream Greenhouse Gas Concentrations Across A Land Use Gradient, Allison Herreid
Divergent Controls On Stream Greenhouse Gas Concentrations Across A Land Use Gradient, Allison Herreid
Master's Theses and Capstones
Inland waters can be significant sources of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) to the atmosphere. However, considerable uncertainty remains in regional and global estimates of greenhouse gas (GHG) emissions from freshwater ecosystems, particularly streams. Controls on GHG production in fluvial ecosystems, such as water chemistry and sediment characteristics, are also poorly understood. The main objective of this study was to quantify spatial and temporal variability in GHG concentrations in 20 streams across a landscape with considerable variation in land use and land cover. Stream water was consistently supersaturated in CO2, CH4, and N2O, suggesting that small …
Seasonal Methane And Carbon Dioxide Emissions Along A Temperate Fluvial Wetland Dominated River Continuum, Paige Elizabeth Clarizia
Seasonal Methane And Carbon Dioxide Emissions Along A Temperate Fluvial Wetland Dominated River Continuum, Paige Elizabeth Clarizia
Master's Theses and Capstones
Freshwater ecosystems, such as streams and fluvial wetlands, are a subset of global aquatic ecosystems and produce and emit significant amounts of the greenhouse gases (GHG) methane (CH4) and carbon dioxide (CO2) to the atmosphere. In temperate regions, freshwater ecosystems often contain fluvial wetlands, which form the boundary between stream and wetland ecosystems. In fluvial wetlands, oxygen- and nutrient- poor soils are continuously fed by upstream river networks, which have the potential to create ecosystems with enhanced GHG production and emissions. The magnitude and seasonal variability of natural GHG emissions from freshwater fluvial wetlands, though highly understudied, have been suggested …
Assessing The Impact Of Submerged Vegetation On Methane Dynamics In A Discontinuous Permafrost Lake System, Abisko, Sweden, Christopher Daniel Horruitiner
Assessing The Impact Of Submerged Vegetation On Methane Dynamics In A Discontinuous Permafrost Lake System, Abisko, Sweden, Christopher Daniel Horruitiner
Master's Theses and Capstones
Across the Arctic, postglacial lakes contribute a substantial amount of the total atmospheric methane (CH4), and their emissions are predicted to increase. However, there is still much uncertainty as to the contribution of northern water bodies to atmospheric CH4 emissions. This is mainly due to the spatiotemporal variability of the predominant pathway of emission from high latitude lakes: ebullition (bubbling). There are a myriad of factors that affect ebullition fluxes, including solar radiation input and atmospheric pressure, which make it difficult to model the impact on regional emissions. Very few studies have correlated sediment characteristics and submerged vegetation density with …
Assessing The Impact Of Submerged Vegetation On Methane Dynamics In A Discontinuous Permafrost Lake System, Abisko, Sweden, Christopher Daniel Horruitiner
Assessing The Impact Of Submerged Vegetation On Methane Dynamics In A Discontinuous Permafrost Lake System, Abisko, Sweden, Christopher Daniel Horruitiner
Master's Theses and Capstones
Across the Arctic, postglacial lakes contribute a substantial amount of the total atmospheric methane (CH4), and their emissions are predicted to increase. However, there is still much uncertainty as to the contribution of northern water bodies to atmospheric CH4 emissions. This is mainly due to the spatiotemporal variability of the predominant pathway of emission from high latitude lakes: ebullition (bubbling). There are a myriad of factors that affect ebullition fluxes, including solar radiation input and atmospheric pressure, which make it difficult to model the impact on regional emissions. Very few studies have correlated sediment characteristics and submerged vegetation density with …
Broadband Acoustic Measurements Of A Controlled Seep With Multiple Gases For Verification Of Flux Estimates Through Bubble Dissolution And Target Strength Models, Kevin Michael Rychert
Broadband Acoustic Measurements Of A Controlled Seep With Multiple Gases For Verification Of Flux Estimates Through Bubble Dissolution And Target Strength Models, Kevin Michael Rychert
Master's Theses and Capstones
To verify existing models for conversion of acoustic target strength to estimates of the total volume of methane gas released from the seafloor through the water column, a synthetic seep system was designed and fabricated. This system creates individual bubbles of the sizes most commonly found in gaseous methane seeps, <1 to 5mm radii, which can be released at any interval at depths up to 200m. The synthetic seep system was deployed off the coast of New Hampshire adjacent to the Isles of Shoals to a depth of 55m. Acoustic backscatter from 16-24kHz was collected by steaming over the synthetic seep multiple times with a suite of broadband splitbeam sonar systems. Each iteration ensonified a predetermined and calibrated bubble size created by the system at depth. These data represent a direct field measurement which was used to test models describing bubble evolution and acoustic scattering during the ascent through the water column for bubbles of different sizes and gasses. Validating these models directly tests the ability of broadband sonar systems to estimate the transport of gas from the seabed to the ocean and atmosphere. Acoustic data from 2.35mm radii argon bubbles, and 2.45mm radii nitrogen bubbles are consistent with bubble evolution and target strength models which validates spherical approximations made in both the mass transfer and acoustic scattering assumptions. Based on the similar uncertainty values for these bubble sizes, these data add confidence to the claims of previous studies which use similar methods for methane flux approximations.
Tracking Sulfur Diagenesis In Methane Rich Marine Sediments On The Cascadia Margin: Comparing Sulfur Isotopes Of Bulk Sediment And Chromium Reducible Sulfur, Sarah Chaviva Turner
Tracking Sulfur Diagenesis In Methane Rich Marine Sediments On The Cascadia Margin: Comparing Sulfur Isotopes Of Bulk Sediment And Chromium Reducible Sulfur, Sarah Chaviva Turner
Master's Theses and Capstones
Methane gas is produced in anoxic marine sediments by methanogenic bacteria and can be ephemerally stored in gas hydrate deposits, escape to the seafloor at methane seeps, and/or be consumed at depth by the anaerobic oxidation of methane (AOM). One way to examine changes in methane flux in cold seep environments through time is to identify past positions of the sulfate methane transition zone (SMTZ) where AOM results in sulfate and methane consumption and bicarbonate and hydrogen sulfide production, often resulting in the precipitation of authigenic carbonates and iron sulfides. One method to identify paleo-positons of the SMTZ is through …
Characterizing And Quantifying Marine Methane Gas Seeps Using Acoustic Observations And Bubble Dissolution Models, Liam Pillsbury
Characterizing And Quantifying Marine Methane Gas Seeps Using Acoustic Observations And Bubble Dissolution Models, Liam Pillsbury
Master's Theses and Capstones
A method for characterizing and quantifying marine methane gas seeps along the U.S. Western Atlantic Margin was developed and applied to 70 free-gas seeps observed by the R/V Okeanos Explorer in 2012 and 2013, in water depths ranging from 300-2000 meters. Acoustic backscatter from an 18 kHz split-beam echo sounder and a 30 kHz multi-beam echo sounder provided information on the height to which the gas seeps rose from the seafloor. Profiles of the depth-dependent target strength and scattering strength were compared to models of the evolution of rising bubbles to help constrain the ultimate fate of the methane gas. …