Theses for the College of Natural Sciences & Mathematics

Recent Submissions

  • The distribution of nitric oxide at 150 km

    Stern, Timothy E. (2008-12)
    "The objectives of this thesis are to determine the morphology of nitric oxide at the altitude of 150 km and to determine what drives the observed variability. Those objectives are accomplished by characterizing satellite observations of nitric oxide at that altitude and comparing them with those at 106 km, the altitude of peak density. The global distribution of nitric oxide and its response to geomagnetic activity vary between the two altitudes. At 150 km, nitric oxide is most abundant at high latitudes in the sunlit summer hemisphere, in contrast to nitric oxide at 106 km, which is most abundant at high latitudes in the winter hemisphere. The high-latitude component of nitric oxide at both altitudes is associated with geomagnetic activity, although the primary production mechanisms differ between the two altitudes. At 106 km, high-latitude nitric oxide density enhancements are driven by particle precipitation. At 150 km, nitric oxide at high latitudes is enhanced by increased temperatures arising from Joule heating. Enhancements at 150 km occur more rapidly than those at 106 km. At both altitudes, the response of nitric oxide to geomagnetic activity exhibits a seasonal variation that is attributed to seasonal variations in the production mechanisms"--Leaf iii
  • Balancing the conservation of wildlife habitat with road access for subsistence hunting in Yakutat, Alaska

    Shanley, Colin S.; Pyare, Sanjay; Kofinas, Gary; Hundertmark, Kris (2008-12)
    "This thesis was an interdisciplinary investigation with the goal of balancing the conservation of wildlife habitat with road access for subsistence hunting in Yakutat, Alaska. The problem posed by land managers and subsistence moose hunters revolved around the use of off-highway vehicles (OHVs; e.g. 'four-wheelers') for subsistence moose hunting and the potential disturbance OHVs have on moose. This complex social-ecological problem is becoming an increasingly common management dilemma faced by rural mixed cash-subsistence communities across the Circumpolar North. I addressed this problem in two chapters with a combination of methods from wildlife ecology, landscape modeling, subsistence land-use, and scenario planning. The data used for analysis in Chapter 1 was derived from a three-year moose GPS-collar dataset, remote sensing imagery, and mapped routes. I modeled moose distribution with multi-scale, seasonal and sex-specific resource selection functions in a GIS. The best-fit models suggested female moose were displaced by OHV routes. Male moose were displaced by routes or areas where routes were in close proximity to primary forage. A combined pattern of route avoidance was quantified beyond approximately 1 km of total vehicle travel/km²/day. Chapter 2 describes the application of distribution models from Chapter 1 to a social-ecological assessment of route closures. Meetings with land managers and moose hunters were conducted to identify their respective values and management goals. Then I evaluated the effect of four road closure scenarios on moose habitat and hunting access. A measure of hunting access was evaluated with interviews about hunter land-use patterns, as well as the mapping of harvest areas in a GIS. The results of the scenario evaluation showed the spatial arrangement of routes influenced the total amount of high probability moose habitat and access to preferred harvest areas. A balance in the conservation of wildlife habitat and the maintenance of hunting access may be found in the closure of routes through valuable moose habitat and the spatial arrangement of future routes around valuable moose habitat, within reach of important harvest areas. The results of the analysis and interdisciplinary approach may prove useful to land managers who must evaluate the trade-offs between wildlife habitat conservation and the increasing use of motorized access for contemporary subsistence hunting practices"--Leaf iii
  • Shallow surface thermogenic hydrocarbon migration over western Prudhoe Bay Region, Alaska

    Sarkar, Sudipta (2008-12)
    "Hydrocarbons leak from petroleum reservoirs to the surface. In continuous permafrost regions like the Alaska North Slope, surface migration of thermogenic hydrocarbons may be hindered by the presence of ground ice. However, suitable permeable migration pathways in the permafrost can exist. Unfrozen sediments at the bottom of the lakes, or open faults can facilitate thermogenic hydrocarbon migration. I studied the nature and distribution of gaseous alkanes (C1 to C6) and helium in the shallow permafrost cores (2 m depth); depth profiles of alkanes (C1 to C7) in the two wells (1500 m deep); and stable isotopes of CH₄ trapped in lake gas bubbles, to trace the presence of thermogenic hydrocarbons and their migration pathways. Geostatistical analysis of the alkane and helium distributions shows that most anomalies occur along northwest-southeast oriented lineaments, roughly corresponding to the trend of the Eileen fault mapped at 2675 m depth, high fault density zones of the Kuparuk Formation, and northwest-southeast trending Sagavanirktok faults mapped at 457 m depth. The anomalies above the Eileen fault can be explained by a fluid-flow model in a dilational jog along a wrench fault. This model agrees with the movements along the Eileen fault"--Leaf iii
  • Non-volcanic tremor in the Alaska/Aleutian subduction zone and its relationship to slow-slip events

    Peterson, Chloe L. (2008-12)
    "We document non-volcanic tremor (NVT) in Southcentral Alaska and the Aleutian Arc in terms of durations and locations. In Southcentral Alaska, we tabulate NVT events occurring during the summer months of each year between 1999 and 2001 to test for a relationship with a slow-slip event that occurred during this time frame. We tabulate NVT events in the Aleutians starting in the summer of 2005 through the summer of 2008. The observed NVT events in both Southcentral Alaska and the Aleutian arc are sequences of emergent pulses with frequencies of 1-10 Hz. The majority of the events have durations ranging from 5-15 minutes. In Southcentral Alaska, the majority of the NVT events locate in the region of the slow-slip event and the quantity of events decreases significantly by the summer of 2001, coinciding with the end of the slow-slip event. Locating NVT events in the Aleutians is problematic due to the linearity and sparse distribution of seismic stations. General locations are established simply by the distribution of volcano seismic networks on which the signal is observed and the strength of that signal. These general locations appear to coincide with regions where the plate interface is locked or is transitioning from creeping to locked. Furthermore, several episodes of NVT in the Aleutians occurring during times of heightened volcanic and seismic activity in the arc, suggesting large regional stress changes possibly caused by undetected slow-slip events"--Leaf iii
  • Determination of the diffusion coefficient for trimethylaluminum in the thermosphere at altitudes 120 to 180 km

    Bhattacharya, Tapas (2009-05)
    "The object of this work is to determine the diffusion coefficient (D) of trimethylaluminum (TMA) in the lower thermosphere as a function of altitude (h). This is done by measuring the dispersion of chemiluminescent TMA that is released in discrete quantities, or puffs, from sounding rockets at altitudes 120 to 180 km. Diffusing TMA, which glows in contact with atmospheric oxygen, is observed with stereoscopic ground-based imaging. Brightness profiles across a puff are found to be Gaussian in shape, with width parameter [sigma](t, h) that increases with age (t) of the puff leading to D = [sigma]² (t, h)/2t, independent of time, which is in good agreement with some past results. For example D = (2.5 ± 0.2) x 10³m²s⁻¹ at an altitude of 128 km for the state of the thermosphere at that time. A constant A links three altitude-dependent terms, the diffusion coefficient, temperature and density, at a particular location of the atmosphere, via D(h) = ATS (h)/n(h). It is determined from this study to be A=(4.42±0.05)x10¹⁸(m·s)⁻¹ for s = 0.75. Using these values for A and s, and temperatures and the densities determined from the MSIS-90 thermospheric model, diffusion coefficients for TMA can be determined at other locations and under different geomagnetic conditions"--Leaf iii
  • Synoptic climatology of the eastern Brooks Range, Alaska: a data legacy of the international geophysical year

    March, Jennifer R. (2009-12)
    "Data from three International Geophysical Year (1957-1958) expeditions and one International Hydrological Decade National Science Foundation project (1969-1972) to the eastern Alaska North Slope have been rescued and made available in digital form: Chamberlain Glacier, Lake Peters, and McCall Glacier. Comparisons between these sites and US and Canadian Weather Service stations within 500km of McCall Glacier were conducted to determine the broad temperature climatology of the region. McCall Glacier is generally a swing site, and the climatology of the region often was linked most closely to the Beaufort Sea coast, though on some occasions, was more closely related to the Mackenzie River Delta and on other occasions, to the Interior. These early data represent an important addition to the Arctic data legacy by allowing a more complete climate record to be developed that focuses on a region demonstrably sensitive to climate change and yet lacking in data. Key words: glacier, meteorology, International Geophysical Year, Alaska, McCall Glacier, Brooks Range, data rescue"--Leaf iii
  • Theoretical and experimental investigations of resonance fluorescence lidar for measurements of N₂ in the auroral atmosphere

    Light, Agatha S. (2009-12)
    "In this thesis, a series of experimental and theoretical studies of the resonance fluorescence lidar system at Poker Flat Research Range (located in Chatanika, Alaska) for use in obtaining measurements of aurorally produced molecular nitrogen ions (N₂) are presented. Obtaining measurements of N₂ is made challenging by both the operational performance of the resonance lidar system and the high degree of geophysical variability inherent in the aurora. Analyses are conducted of measurements obtained by the operational sodium and iron resonance lidar systems to verify the lidar system performance. To increase the strength and quality of the lidar measurements, the telescope in the lidar receiver system was upgraded from a 0.6 in Newtonian telescope to a Cassegrain telescope with a 1.02 m diameter primary mirror. Lidar measurements from the system operating with this telescope are presented and compared to previous measurements to confirm an improvement to the overall operation. A spectroscopic analysis of the laser dye used in the previous development of the molecular nitrogen resonance lidar system is conducted to determine the cause of decreased lidar system performance at the operational wavelength relevant for studies of N₂. A total of ten laser dyes are tested in the dye laser system. Based upon the performance of these dyes in the resonance lidar system, it is concluded that successful measurements of the strongest emission band in N⁺₂ are unlikely due the transmittance of the diffraction grating at the relevant wavelength and low system efficiency in the dye laser. Therefore, the resonance lidar system is being developed to obtain measurements of the second strongest band of emissions in N⁺₂ . To assess the capabilities of this system to obtain statistically significant measurements of aurorally produced N⁺₂, the expected resonance lidar signal is simulated by modifying an existing model. It is found that to obtain N⁺₂ resonance lidar measurements of reasonable strength with the current operational system, the data would be obtained at high resolution and post integrated over selected temporal and spatial ranges"--Leaf iii
  • Ecological linkages between headwater streams and riparian and downstream habitats in the eastern Cascade Range, Washington, USA

    Green, Elizabeth C. (2009-12)
    "I examined how headwater streams are ecologically linked with the terrestrial environment and upstream waters. I examined relationships between fish (rainbow and cutthroat trout), invertebrates, and habitat in 15 headwater streams in two ecoregions (wet, dry) and timber harvest scenarios (logged, unlogged) in the Wenatchee River sub-basin in the eastern Cascade Mountain Range, Washington state, USA. Fish biomass, density, and size were not related to ecoregion or to logging history. Invertebrate drift manipulations in 13 streams influenced fish movement (fish moved downstream in sites that were not supplemented with food) and diet (fish consumed less prey when drifting invertebrates were removed), but not fish growth or abundance. This study demonstrated that fish utilize drifting prey originating from upstream fishless waters, and that they are not able to compensate for the loss of this food. Headwater forest management may affect fish populations by altering prey resources where fish are food-limited"--Leaf iv
  • In defense of quaking aspen (Populus tremuloides): the distribution and roles of phenolic glycosides and extrafloral nectaries within and among trees

    Young, Brian D.; Wagner, Diane; Wolf, Diana; Doak, Patricia; Clausen, Thomas (2009-05)
    "I studied the concentrations of phenolic glycosides (PGs) from leaves with and without extrafloral nectaries (EFNs) in Populus tremuloides during an outbreak of the aspen leaf miner, Phyllocnistis populiella, in interior Alaska. P. populiella feeds on the contents of epidermal cells from both top (adaxial) and bottom (abaxial) surfaces of P. tremuloides leaves. The objective of this study was to assess the association of chemical and biotic defenses in P. tremuloides and their interaction with the insect herbivore P. populiella. The concentration of PGs (salicortin and tremulacin) was approximately 70% greater in leaves bearing EFNs than in those without EFNs from short trees (<2.5 m); leaves with and without EFNs did not differ significantly in PG concentration for tall trees (5-8 m). Leaf mining caused the induction of the foliar PGs following eight days of mining. There was no difference in the ability of leaves with and without EFNs to induce PGs in response to mining. The extent of mining damage was significantly and negatively related to the PG concentration, whereas EFNs were not related to the extent of mining. At the site level, I found no evidence for a tradeoff between these two putative forms of defense in P. tremuloides"--Leaf iii
  • Lessons from the river: identifying factors that influence the comprehension of genetics research in a Yup'ik Eskimo community

    McGlone West, Kathleen; Boyer, Bert; Fryer-Edwards, Kelly; Hopper, Kim (2009-05)
    "The Center for Alaska Native Health Research (CANHR) follows a Community-Based Participatory Research (CBPR) approach to study genetic, nutritional, behavioral and cultural protective factors for obesity and Type 2 diabetes in Yup'ik Eskimo communities. As a multidisciplinary center, investigators have returned results of many of their research projects to participants and participating communities. However, traditionally, genetics research results are only returned to participants under specific conditions, which are not necessarily compatible with a CBPR approach. I ask how CANHR can improve its dissemination efforts, especially in the area of genetics research. I identify factors that influence how community members receive and understand health information, including genetics information. This study uses a grounded theory approach to qualitatively analyze interviews and focus group discussions with Yup'ik community members, identify themes and construct a theoretical narrative. The primary factors that emerged include communication pathways (ways in which information is transmitted in the community); health beliefs (what people already know and believe about health); and social location (a person's role in the community). I examine each of these through the framework of a river metaphor to provide recommendations for improving CANHR's dissemination efforts with the communities, including genetics research results"--Leaf iii
  • Holocene vegetation and climate change at Canyon Lake, Copper River basin, Alaska

    Shimer, Grant (2009-05)
    "The regional vegetation response to Holocene warming and the recession of glacial Lake Atria is recorded by environmental proxies in cores from Canyon Lake, near the northern limit of the Copper River Basin. Pollen, spores, plant macrofossils, and stable isotope analyses of C, N and H indicate that conditions in the northern margins stabilized fairly quickly following the recession of Lake Atria around 10740 cal yr BP. The development of a shallow lake ecosystem surrounded by Betula (birch) shrub-tundra was followed by the migration of Picea (spruce) and Alnus (alder) into the Copper River Basin around 9800 cal yr BP and the eventual development of the Picea-dominated boreal forest that persists to this day. The stable isotope record indicates that lake systems are more sensitive to neoglacial cooling, Medieval warming, and the Little Ice Age than the surrounding boreal forest during the middle to late Holocene. The magnitude and severity of these events may have been limited in the Copper River Basin, but climate and vegetation change may have had significant effects on the available resources to the human populations of the region"--Leaf iii
  • Investigation of the impact of ship emissions on atmospheric composition and deposition into remote, coastal landscapes of Southwest Alaska

    Porter, Stacy E. (2009-05)
    "Every summer season, the Gulf of Alaska experiences an influx of shipping traffic, yet ship emissions are only modestly regulated allowing for substantial amounts of pollutants to be released. These pollutants can be transformed and transported affecting atmospheric composition and deposition of contaminants in even remote landscapes. The fully coupled Weather Research and Forecasting meteorology and chemistry transport model, WRFChem, is used to simulate physical and chemical processes such as transport, transformation, and deposition. Model simulations for a tourist season are performed without and with the inclusion of a ship emission inventory developed for this study. Ship emissions are shown to significantly increase both primary and secondary pollutant concentrations in the Gulf of Alaska causing reduced visibility and contributing greatly to accumulated deposition into coastal ecosystems. Complex topography also plays a role in regions most affected by ship emissions including Prince William Sound and the Kenai Peninsula. Meteorological conditions govern the temporal evolution of air quality and deposition throughout the season. Evaluation of WRFChem with meteorological observations reveals that it well captures the synoptic situation during the season. WRFChem underestimates aerosol concentrations, but aerosol monitoring sites are sparse within the Gulf of Alaska and may not accurately reflect overall performance"--Leaf iii
  • Ecology and evolution of truffle fungi : the diversity of fungi associated with northern flying squirrels

    Bruner, Benjamin Luke (2009-05)
    "This thesis explores the ecology of truffle fungi, a diverse assemblage of symbiotic mycorrhizal fungi that extend microscopic hyphae throughout forest floors, forming networks of foraging mycelium capable of transporting water, vitamins, minerals, and other nutrients to the roots of plants. Plant sugars are used for energy and as raw material for the creation of complex reproductive structures and vast water and nutrient gathering infrastructures essential to the survival of most plants. Truffle fungi are defined here by their ability to form mycorrhiza and produce truffles: hypogeous sporocarps that are excavated and consumed by animals ranging from squirrels to humans, resulting in the long-distance transport of spores. In Chapter 1, I compile and synthesize published information on the evolution and ecology of truffle fungi. In Chapter 2, I describe molecular techniques used to extract, amplify, and characterize fungal DNA from the scat of an endemic island population of northern flying squirrels, Glaucomys sabrinus griseifrons, which specialize in the consumption of truffles. Statistical analysis of RFLP data from clones of fungal DNA indicates much higher levels of fungal diversity in G. s. griseifrons scat than expected. I argue that the estimated numbers of fungi associated with G. s. griseifrons represent a baseline of diversity for fungi associated with mainland populations of Glaucomys sabrinus"--Leaf iii
  • Terrestrial arthropod biodiversity on the Kenai National Wildlife Refuge, Alaska

    Bowser, Matthew L. (2009-05)
    "Elucidating the causes of observed patterns of living diversity remains a central goal of ecology. To understand patterns of terrestrial arthropod diversity on Kenai National Wildlife Refuge (KENWR), arthropods were collected by sweep net on 255 100m2 plots systematically distributed at 4.8km intervals across KENWR. I calculated three indices of diversity for 90 families conveying information on richness and evenness for each site. Using Bayesian Model Averaging, I found all indices were strongly influenced by site productivity, local climate, time of sampling arid plant species richness. Physiographic variables were less important than climate for determining arthropod distributions. Because many species are expected to alter their distributions in response to accelerated climate change, I assessed the use of occupancy models for monitoring those shifts on KENWR. I compared rotating panel and periodic census sampling designs using Monte-Carlo simulations given a range of occupancy and detectability values. Both designs estimated detectability within single visits and provided reasonable precision and accuracy on occupancy estimates of species with detection probabilities> 0.5, but the rotating panel design was preferred because it yielded information at shorter time intervals. I recommended adding sites sampled in consecutive seasons to better estimate local extinction and colonization rates"--Leaf iii
  • Platinum group element enriched hydrothermal magnetite of the Union Bay Alaska-type ultramafic intrusion, Southeast Alaska

    Van Treeck, Christopher Jared (2009-08)
    "The Union Bay Alaskan-type Complex represents a completely different type of platinum group element (PGE) concentration from the classic Alaskan-type Complex PGE mineralization model, with PGEs localized in vein/veinlet magnetite, commonly within the olivine + pyroxene portions of the body. PGE concentrations of 18 g/t occur in magnetite veins and pods which cross magmatic layering and have an irregular morphology in both outcrop and thin section. Fe-Ti oxide geothermometry indicates that this mineralization formed at temperatures between 675-475°C. A variation in the amount of ilmenite and Mg-Al spinel exsolution in magnetite correlates with temperature estimates, lower temperature magnetite has less exsolution. Magnetite veins with a formation temperature of less than 600°C are surrounded by an alteration envelope of hydrous silicates that vary with temperature and contain appreciable amounts of Cl. Interaction of a PGE-Fe-Cl rich fluid with clinopyroxene and olivine increased the fluids pH and decreased PGE and Fe solubility depositing a PGE enriched magnetite within the wehrlite and clinopyroxenite of the Union Bay Alaskan-type complex. Potentially this fluid remobilized the PGE from disseminated euhedral magnetite of the peripheral units to form PGE enriched magnetite veins in the near-central portion of the complex"--Leaf iii
  • Cellulose degrading microorganisms in Alaskan boreal forest soil

    Stone, Kelsie Marie Engen; Leigh, Mary Beth; Taylor, D. Lee; Valentine, David (2009-08)
    "Cellulose is the most abundant organic compound on earth, and has been studied intensely. This thesis includes a review of previous studies and literature compiled on cellulose degradation and its significance to biofuel production. It also reports a study designed to advance knowledge of cellulose degrading bacteria and fungi in Alaskan boreal forest soil. This was accomplished using stable isotope probing (SIP) in soil microcosms and community analyses of organisms colonizing in situ buried Birch Tongue Depressors (BTDs). We identified which organisms incorporated a 13C cellulose label into their genomic material, finding degradation to be dominated by fungi. Fungi from the genera Sebacina, Geopyxis and Geomyces were the most prevalent in fungal ITS clone libraries. The most abundant bacterial cellulose utilizers were members of the order Sphingobacteriales, along with several unclassified Bacteria; the well-known cellulose degrader Cellvibrio was present, but found less frequently. The microbial community colonizing BTDs shared some taxa in common with bacterial SIP results, but differed from fungi identified with SIP. Using SIP, we identified a variety of soil microorganisms active in utilization of carbon from cellulose. These findings are significant for understanding fundamental ecosystem carbon cycling and may have application to cellulosic biofuel production technologies"--Leaf iii
  • Tectonic geomorphology of the Chukchi borderland: constraint for tectonic reconstruction models

    Brumley, Kelley (2009-08)
    "The Chukchi Borderland is a region of extended continental crust within the Amerasia Basin and is bounded on one side by oceanic crust of the Canada Basin. Because of its central location within the basin, tectonic models for the reconstruction of the Arctic Ocean, must include the Chukchi Borderland although there is no consensus about its pre-rift location or kinematic development. In recent years bathymetric data have been collected that can offer constraint on the tectonic evolution of the Amerasia Basin by providing details about the geomorphology of the intra-basinal ridges allowing comparison of bathymetric features to those in other ocean basins. Bathymetric information in conjunction with multi-channel seismic and chirp sub-bottom profiler data show the location and strike of inferred faults used to determine rift directions which then provide constraint on tectonic reconstructions. The central Amerasia Basin, which includes the Chukchi Borderland, Mendeleev Ridge and south central Alpha Ridge, has experienced significant extension in generally the same direction and probably during one event. This type of plate boundary scale extension requires the development of accommodation faulting or transfer zones that facilitate the amalgamation of long fault segments. Features consistent with this type of faulting are observed throughout the Chukchi Borderland. There is no evidence of compression along the Northwind Ridge nor is there any indication of a strike-slip boundary within the Northern Chukchi Borderland as some tectonic models suggest. Whichever model is preferred, the geomorphology of the intra-basinal ridges must be taken into account and used as constraint for the reconstruction of the Amerasia Basin"--Leaf iii
  • Character and controls of fold-and-thrust deformation from pre-orogenic to foreland basin deposits: an example from the Gilead creek region of the Northeastern Brooks Range, Alaska

    Speeter, Garrett (2010-12)
    "The character of structures in the Gilead Creek region is influenced by the mechanical stratigraphy in the area. Shortening is distributed throughout the mechanical stratigraphy along detachments in the incompetent Kayak, Kavik, Kingak, and Hue Shales. Detachment intervals separate competent Lisburne Group, Echooka Formation, Ledge Sandstone/Shublik Formation, Gilead sandstone, and moderately competent Seabee Formation from each other and allow the competent units to fold at distinct wavelengths according to their mechanical properties. Thick, competent units tend to form long-wavelength folds. Thin, competent units form relatively short-wavelength folds. Thin, competent units that are structurally bound to a thicker, structurally more dominant unit, adhere to the structural style of the dominant unit unless there is some detachment between them. Strain is distributed through shale intervals in the moderately competent units, allowing short-wavelength folds in the thin competent beds. The dominant trend of structures in the area is northeast overprinted on east. East-trending structures formed during the ~60 Ma event that formed the main axis of the Brooks Range and its foothills. Northeast-trending structures formed during the formation of the northeastern Brooks Range dated at ~45 Ma, ~35 Ma, and ~27 Ma, manifest locally by the compressional uplift of the Echooka anticlinorium southeast of Gilead Creek"--Leaf iii.
  • North Atlantic air-sea interactions driven by atmospheric and oceanic stochastic forcing in a simple box model

    Legatt, Rebecca Anne (2010-12)
    "North Atlantic (NA) variability has wide-spread implications locally and globally. This study investigates mechanisms driving NA variability using a simple box model incorporating time evolution of interacting upper ocean temperature anomalies, horizontal (Gyre) and vertical (meridional overturning circulation, or MOC) circulation, driven by surface air temperature, wind, and Labrador Sea temperature forcings. Simulated upper ocean responses to external atmospheric forcing result in solutions with redder spectra than solutions by white noise atmospheric forcing, implying that the ocean acts as a low-pass filter to this external forcing. Simulated ocean dynamic response may be viewed as a response to a cumulative atmospheric forcing over an interval defined by system damping properties. A strong anti-correlation links simulated MOC and Gyre circulation intensity suggesting a mechanism, in which system heat balance is maintained via communication between the dynamic components, (e.g. excess of heat supply from a stronger Gyre circulation would be balanced by lack of heat from a weaker MOC circulation and vise versa). Wind was the dominant forcing for NA upper ocean temperature anomalies and the intensity of MOC and Gyre circulations. Further investigations of NA variability mechanisms are important as they have serious implications on global heat transport"--Leaf iii.
  • Relating deep magmatic processes to eruptive behavior at arc volcanoes through an analysis of deep seismicity

    George, Ophelia A. (2010-12)
    "In this thesis, the seismicity at depths greater than 15 km beneath two sets of volcanic centers, the Klyuchevskoy Volcanic Group (KVG), Russia and Mount Spurr, Alaska is examined. In both regions, a pulsing pattern of deep seismicity is observed with many cycles following eruptive activity or periods of unrest. The bulk of the seismicity beneath the KVG is comprised of long-period events many of which share a similar appearance. Cross correlation of the waveforms for events occurring between 12/24/2007 and 12/31/2008 show a number of event families occurring over long time spans. New relative locations for these families which better constrain their spatial extent are derived. The pulsing pattern of seismicity seen here is in close keeping with the expected cyclic nature of melt segregation which occurs as melt leaves the site of generation and ascends to shallower levels. Based on evidence in the data, a model is proposed whereby melt segregation on the time scales necessary to facilitate eruptions is attributable to a pressure response in the deep system induced by the removal of material in the shallow chamber during an eruptive cycle"--Leaf iii.

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