Digital Commons Network^™

A Synthesis Program: Reducing Uncertainties Of The Terrestrial Biosphere Carbon Cycle At Various Spatio Temporal Scales, Xinyuan Wei

Electronic Theses and Dissertations

The terrestrial biosphere plays an important role in the global carbon cycle, and disturbance fire and climate extreme drought have strong direct and indirect impacts on the carbon fluxes. In addition, the lateral dissolved organic carbon (DOC) flux from soils to inland waters represents an important component of the terrestrial biosphere carbon cycle.

Fires play an important role in the terrestrial biosphere carbon cycle, not only through direct carbon release but also contributing to a potential long-term storage as pyrogenic carbon (PyC). PyC is formed through fires, and because it may resist further biological and chemical degradation, is more stable …

Sulfur And Trace Metal Cycling At Convergent Margins, Jesse B. Walters

Electronic Theses and Dissertations

Subduction zones are the site of long-term chemical exchange between Earth’s surface and interior geochemical reservoirs. Subducting slabs are progressively depleted in volatiles and other mobile elements through dehydration and melting reactions. These elements are then introduced to the mantle wedge and volcanic arc. One consequence of this cycle is that volcanic arcs produce the most oxidized magmas on Earth. Sulfur, which exhibits a range in valence states from S^2- to S⁶⁺, is one of the few elements in the subducting slab capable of oxidizing the arc and mantle wedge. Sulfides in the slab may also act …

Variations In The Southern Hemisphere Westerlies Over The Last 23,000 Years From Lake Records In The Falkland Islands, Meghan M. Spoth

Electronic Theses and Dissertations

The Southern Hemisphere Westerlies (SHW) are an important driver of climate in the mid-latitudes of the Southern Hemisphere. Abrupt latitudinal migration of this coupled atmospheric-oceanic system is thought to be linked to the onset of the Termination at the end of the last ice age and to subsequent climatic variation through the late-glacial period and Holocene. However, the timing and spatial extent of these shifts, as well as variations in wind intensity, are poorly constrained, hindering our understanding of abrupt climate change in the Southern Hemisphere. In addition, future changes in the position and intensity of the SHW are a …

Fostering Climate Change Resilience: A Socio-Ecological Forest Systems Approach, Alyssa R. Soucy

Electronic Theses and Dissertations

As climate change continues to impact socio-ecological systems, those that rely on natural resources are highly sensitive to climatic changes. Maine’s forest industry provides for the economic and social well-being of many residents and is especially vulnerable to climate change impacts. Changes in growing season length and timing, forest health threats imposed by insects and pathogens, extreme weather events, shifting forest composition, and changes in natural disturbance severity and frequency have already begun, and are projected to continue, to impact forest systems in the Northeastern U.S. While climate change presents a threat to forest systems, opportunities also arise due to …

Scientific Assessment Of Climate Change And Its Effects In Maine, Maine Climate Council Scientific And Technical Subcommittee, Ivan Fernandez, Robert Marvinney, Susie Arnold, Linda Bacon, Andrew Barton, Brian Beal, Sean Birkel, Russell Black, Alix Contosta, Amanda Cross, Adam Daigneault, Thomas Danielson, Stephen Dickson, Jeanne Difranco, Susan Elias, Glenn Hodgkins, Brian Hubbell, Joe Kelley, Rick Kersbergen, Glen Koehler, Rebecca Lincoln, William Livingston, Pamela Lombard, Bradfield Lyon, Andrew Pershing, Nichole Price, Jonathan Rubin, Joseph Salisbury, Erin Simons-Legaard, Peter Slovinsky, Robert Steneck, Sally Stockwell, Richard Wahle, Jay Wason, Aaron Weiskittel, Carl Wilson

Climate Change

Climate change has already made its presence known in Maine, from shorter winters and warmer summers with ocean heat waves, to stronger storms, new species showing up in our backyards and the Gulf of Maine, aquatic algal blooms, acidic ocean waters that affect shellfish, and new pests and diseases that harm our iconic forests and fisheries.

The health of Maine people is also being affected by climate change, from high heat index days driving increased emergency room visits to the ravages of Lyme and other vector-borne diseases. And our economy is feeling the effects, too — with farmers trying to …

Distribution Of First Row Transition Elements In Eclogites, Natalie Harmon

Honors College

Surficial materials are recycled back into the deep Earth at subduction zones. The oxidation state of subducted materials affects the oxidation state of major geochemical reservoirs in the Earth, such as the mantle and the crust. First row transition elements (FRTEs), such as V and Sc, are highly redox sensitive and thus have the potential to track important redox processes in subduction zones. In this project, concentrations of FRTEs in garnet, omphacite, and rutile were determined for a global suite of oceanic eclogites, which represent exhumed subducted materials. Data were collected by LA-ICP-MS using an ESI NWR193UC laser ablation system …

A Groundwater Flow Model To Aid In Water Resource Management For The Carraipia Basin In The Coastal Semi-Arid Region Of La Guajira State (Colombia), Efren D. Gomez Arevalo

Electronic Theses and Dissertations

About 160,000 inhabitants live in the 1,600 square kilometers Carraipia River Basin located in northeastern Colombia and northwestern Venezuela. Historically, water has been supplied to the inhabitants in this arid coastal region by shallow dug wells. Water supplied by these wells is frequently of poor quality due to high concentrations of total dissolved solids (TDS). Recently, due to the increasing demand for water, numerous deep wells have been drilled in the region to supply water to rural and urban areas from deep aquifers. Colombian agencies seek more quantitative information on groundwater resources, driven by increasingly severe water shortages over the …

Harold B. "Bud" Rollins (1 February 1939-9 January 2017), Daniel H. Sandweiss

Andean Past

This is an appreciation of the life and work of invertebrate paleontologist. Harold B. Rollins emphasizing his contributions to our understanding of ENSO.

Estimating Bedrock Fracture Density Of The Juneau Icefield, Ak, To Inform Glacial Erosion Models, Colby Rand

Honors College

Understanding glacial erosion rates is important because debris eroded by a glacier can impact glacier flow speeds, protect tidewater glaciers from rapid retreat, and impact the productivity of marine ecosystems. Traditionally, glacial erosion models rely on a rock’s inherent “erodibility”, typically presented as a constant, to predict how much debris will be eroded by the glacier. However, the erodibility of bedrock varies spatially as a function of its fracture density, fracture orientation, and lithology, so the notion of applying a constant erodibility term to a whole field site does not fully capture the actual bedrock dynamics of the system. In …

The Microstructural Heterogeneity Of Ice In Jarvis Glacier, Alaska, Renée Clavette

Honors College

Glacier ice behaves as a viscous fluid, where flow is controlled by a number of external and internal processes. One crucial, yet sometimes overlooked, factor is ice microstructure. Studies have shown that ice crystal (grain) size, shape, and orientation influence the viscous strength of ice, and therefore its resistance to flow and deformation. Glacier flow is also impacted by friction at the bed and lateral margins. The magnitude of flow resistance due to the lateral margins is not well quantified. The goal of this overall project is to evaluate how heterogeneous optical properties of ice are that are influenced by …

An Algorithm To Estimate Suspended Particulate Matter Concentrations And Associated Uncertainties From Remote Sensing Reflectance In Coastal Environments, Juliana Tavora

Electronic Theses and Dissertations

Suspended Particulate Matter (SPM) is a major constituent in coastal waters, involved in processes such as light attenuation, pollutant propagation, and waterways blockage. The spatial distribution of SPM is an indicator of deposition and erosion patterns in estuaries and coastal zones and a necessary input to estimate the material fluxes from the land through rivers to the sea. In-situ methods to estimate SPM provide limited spatial data in comparison to the coverage that can be obtained remotely. Ocean color remote sensing complements field measurements by providing estimates of the spatial distributions of surface SPM concentration in natural waters, with high …