Digital Commons Network^™

Quantifying Tidewater Glacier-Fjord Environments In The Rapidly Changing Regions Of West And South Greenland, Sydney Baratta

Electronic Theses and Dissertations

The Greenland Ice Sheet has undergone rapid mass loss over the last four decades, primarily through solid and liquid discharge at marine-terminating outlet glaciers. The acceleration of these glaciers is in part due to the increase in temperature of ocean water in contact with the glacier terminus. However, quantifying meltwater injection and heat transport can be challenging due to iceberg abundance, which threatens instrument survival and fjord accessibility. Additionally, acceleration and eventual retreat of tidewater glaciers onto land can change glacier forcing, completely altering fjord water-meltwater dynamics. Here, we couple in situ and remote sensing methods to quantify the upper-layer …

Spatial And Temporal Variability In Snow Properties And Firn Volume Across The Juneau Icefield In Southeast Alaska, Mikaila Mannello

Electronic Theses and Dissertations

Glaciers are important freshwater resources which have far reaching impacts on a range of local to global systems and processes, including ecosystems and societies. As global climate continues to change, the response of glaciers has largely been reductions in ice mass and widespread retreat. A high degree of accumulation and ablation occurs in the near surface which is exposed to the atmosphere. The Juneau Icefield (JIF) has, up until the mid-2010s, historically responded climate change anomalously where its main drainage, Taku Glacier (here forward referred to its native name T’aakú Kwáan Sít’i), has been advancing while all other JIF outlet …

Rheological Bridge Zones: A New Perspective To Explore Strain Localization And Rock Rheological Weakening, He Feng

Electronic Theses and Dissertations

Strain localization, a ubiquitous geological phenomenon, emerges when rock undergoes extensive weakening and accommodates disproportionate deformation. This phenomenon spans from brittle faulting to viscous flow, known as shear zones. Despite its prevalence, discussions on weakening primarily center on highly strained samples, rather than the initial deformation state. This research delves into the evolution of localization and rheology in intact rocks.

Heterogeneous mechanical properties within the lithosphere vary based on mineralogy, microstructure, and environmental conditions. Chapter 2 characterizes microscale structures termed "bridge zones." These zones, observed through optical and electron microscopy, exhibit distinctive morphologies. Comprising fine-grained aggregates, bridge zones link weak …

Kinematic Vorticity And Porphyroclast Rotation In Mylonites Of The Norumbega Fault System: Implications For Paleoviscometry, Hendrik Lenferink

Honors College

Crystallographic and shape preferred orientation (SPO) fabrics that develop in mylonitic shear zones can preserve the mean kinematic vorticity number (Wm) of bulk flow. Microstructural methods exploiting dynamically recrystallized quartz and porphyroclast SPO fabrics typically yield conflicting values of Wm. The Sandhill Corner Mylonite Zone of the Norumbega Fault System, Maine, USA, serves as a case study for investigating this discrepancy; Wm estimates range from 0.90 to 1.00 employing the former method (Method 1) and from 0.3 to 0.6 employing the latter method (Method 2). Using a numerical model, I show how a low-viscosity layer (LVL) surrounding clasts affects their …

A Bi-Hemispheric Perspective On The Last Glacial Maximum And Termination Using 10be Surface-Exposure Chronologies From An Interhemispheric Asia-Zealandia Transect, Peter Strand

Electronic Theses and Dissertations

Late-Pleistocene glacial cycles represent the largest natural changes to Earth’s climate over the past one million years, and yet determining the underlying drivers remains a major mystery in paleoclimate. The observation of generally synchronous glaciation and deglaciation between the polar hemispheres (Mercer, 1984) runs contrary to long-standing ice age theory (e.g. Milankovitch, 1941), and was recently dubbed ‘Mercer’s Paradox’ (Denton et al., 2021). In this thesis I derive regional climate records from mountain glaciers along an interhemispheric Australasian transect, extending from the Mongolian Altai to the Southern Alps of New Zealand, to test the existence of Mercer’s Paradox in the …

The Upper Ocean At The End Of An Ice Age: Using Proxies In Benthic Foraminifera To Investigate Intermediate Water Changes During The Last Glacial Termination, Cassandre R. Stirpe

Electronic Theses and Dissertations

The ocean is an important component of the global climate system and plays a key role as a storage reservoir for heat and carbon. Under glacial conditions, the ocean sequestered carbon from the atmosphere, contributing to a cooler global climate. During the last glacial termination, that carbon was released back into the atmosphere, but the exact timing and mechanisms of this transfer are still not fully understood. This study examines waters from the intermediate depths of the Southern Ocean to gain insight into deglacial processes. Intermediate waters are capable of reacting to climate change on decadal timescales, making them a …

Scaling Up The Relevance Of Land-Sea Connections In Coastal Bacteria Pollution Vulnerability, Bea E. Van Dam

Electronic Theses and Dissertations

Bacteria pollution closures of Maine’s coastal shellfish harvest areas have substantial negative consequences for coastal businesses and communities. Sustainability solutions for Maine’s shellfish harvesting areas and businesses require new types of knowledge and information to protect water quality and public health while avoiding unnecessary fishery closures. Coastal management agencies have interests in tools to support science-based management decision-making related to pollution and sustainability solutions for businesses and communities.

Prior research into land-sea connections has demonstrated uses of geographic information and statistical methods to facilitate management and science communication. Research in Maine has focused on identification and comparison of attributes influencing …

Investigating Mercer's Paradox: A 10be Chronology Of Moraines Deposited During The Last Glaciation At Soda Lake, Wind River Range, Wyoming, U.S.A., Lauren M. Woods

Electronic Theses and Dissertations

Here I use geomorphic mapping and ¹⁰Be surface-exposure dating to address the paradox that lies within the general understanding of the mechanisms driving ice-age climate and glacial cycles. The long-standing and widely accepted Murphy-Milankovitch hypothesis suggests glacial cycles are controlled by the local intensity of summer-time insolation. By this hypothesis, glacier maxima should be achieved at times of low insolation intensity and asynchronously between the polar hemispheres, a pattern which is inconsistent with the glacial geomorphic record. The ¹⁰Be chronology I have constructed of moraines at Soda Lake, Wind River Range, Wyoming, U.S.A. shows nine glacial advances to …

Stratigraphic Architecture Of Pozuelo Mounds As Revealed By Earth Resistivity Tomography, Caeli Connolly

Honors College

This study is a geoarchaeological analysis using earth resistance tomography (ERT) surveys of two of four mounds at Pozuelo (Formative Period, cal yr 3000 BP) in the Chincha Valley of coastal, southern Peru. Layers identified in the subsurface were to determine the presence or absence of regional continuity between the mounds. This effort is part of a larger investigation examining the paleoenvironmental setting of the site, and its influence on site location and use. Ten earth resistance tomography profiles were collected using an ABEM Terrameter LS2 and 81 pin array. These profiles were then topographically corrected using topographic survey data …

Lethal And Sublethal Effects Of Beauveria Bassiana On Maine Ticks Across Soil Ph, Alexander Mahar

Honors College

Ticks are obligate parasite arthropods that are becoming increasingly common in northern regions of the United States. Ticks such as the black-legged tick (Ixodes scapularis) and the American dog tick (Dermacentor variabilis) are vectors for pathogens that cause a wide range of diseases, and as these ticks increase their exposure to humans, the diseases they transmit become more prevalent. This upward trend in cases of tick-borne illnesses has necessitated the pursuit of tick control methods that can be used across the diverse environments that are present in tick habitat ranges. One such control method is the fungal biological control, Beauveria …

Assessing College Students' Understanding Of Geologic Timescales, Ethan Couture

Honors College

Geologic timescales are central to many concepts in the natural sciences, including evolution, climate change and plate tectonics. However, geologic time scales can be challenging to appreciate, especially for those who have not had exposure to such topics previously. During primary and secondary education (K-12) students are provided with foundational information about geology that is then further developed in specialized classes in college. Yet most students are not getting this foundation, which could arguably lead to deficits in their post-secondary education. Despite the importance of these concepts, especially for those interested in careers associated with geologic timescales, there have been …

Modeling Franconia Ridge, New Hampshire Using Structure From Motion And Developing New Techniques For Fracture Detection, Dane Johnson

Honors College

Bedrock fracture density is an important characteristic of bedrock that determines its structural formation, the potential for groundwater or fluid flow, and the capacity of erosion for exposed features. In the case of the Franconia Range, there are two primary bedrock lithologies that we wish to analyze. In this research, we conduct the first structural analysis and quantification of the bedrock fracture density of this region using Structure from Motion modeling and machine learning algorithms. Additionally, the algorithms were supplemented to be useful in determining fracture density in the subsurface geology of Ground-Penetrating-Radar (GPR) radargrams. The products of this work …

The Surprising Oceanography Of The Gulf Of Maine, Nicholas R. Record, Benjamin Tupper, Johnathan Evanilla, Kyle Oliveira, Camille Ross, Logan Ngai, Karen Stamieszkin

Maine Policy Review

The oceanography of the Gulf of Maine has changed in ways that have not been seen previously but that are likely to be more common in the future–changes like extreme rapid warming and declines in primary productivity. The changing oceanography has underpinned surprising losses in commercial stocks and endangered species. Because of the rapid rate of change, some have viewed the Gulf of Maine as a window into the ocean’s future, with the idea that lessons learned can be applied in places that have yet to experience similar rapid changes. We can examine the dynamics, origin, and implications of surprising …