• On the frontal ablation of Alaska tidewater glaciers

      McNabb, Robert Whitfield; Hock, Regine; Bueler, Edward; Motyka, Roman; Pettit, Erin; Truffer, Martin (2013-08)
      Sea level rise is a major problem that society will face in the coming century. One of the largest unknown components of sea level rise is frontal ablation (the sum of mass loss through calving and subaqueous melting) from glaciers and ice sheets. Using estimates of ice thickness, rates of glacier length change, and glacier velocities, we present a record of frontal ablation over the period 1985-2012 for 20 Alaska tidewater glaciers. We also present a new method for estimating ice thickness by solving the continuity equation between adjacent flowlines. Because of the wealth of data available, we apply this method to Columbia Glacier, Alaska. The mean ice thickness and volume of Columbia Glacier were approximately halved over the period 1957-2007, from 281 m to 143 m, and from 294 km�_ to 134 km�_, respectively. Using bedrock slope and considering how waves of thickness change propagate through the glacier, we conclude that the rapid portion of this tidewater glacier's retreat is likely nearing an end. We present a 64 year record of length change for 50 Alaska tidewater glaciers, over the period 1948-2012. Most (31) glaciers retreated over the period. Examination of the onset of glacier retreats indicates a correlation between high summer sea surface temperature and the triggering of retreat. Finally, we present a 27 year record of surface velocity for 20 Alaska tidewater glaciers derived from Landsat imagery. Surface velocities vary by as much as 80% throughout the year, indicating that using measurements from one time of year may bias estimates of frontal ablation. The total mean rate of frontal ablation for these 20 glaciers over the period 1985-2012 is 16.2 � 6.5 Gt a����_. Extending this to the remaining 30 Alaska tidewater glaciers yields an estimate of frontal ablation of 18.3 � 7.3 Gt a����_, approximately 50% of the climatic mass balance of the region. This indicates the important, non-negligible role frontal ablation can play in regional mass balance, even where tidewater glaciers cover a small fraction of the total area.
    • On the Klein-Gordon equation originating on a curve and applications to the tsunami run-up problem

      Gaines, Jody; Rybkin, Alexei; Bueler, Ed; Nicolsky, Dmitry (2019-05)
      Our goal is to study the linear Klein-Gordon equation in matrix form, with initial conditions originating on a curve. This equation has applications to the Cross-Sectionally Averaged Shallow Water equations, i.e. a system of nonlinear partial differential equations used for modeling tsunami waves within narrow bays, because the general Carrier-Greenspan transform can turn the Cross-Sectionally Averaged Shallow Water equations (for shorelines of constant slope) into a particular form of the matrix Klein-Gordon equation. Thus the matrix Klein-Gordon equation governs the run-up of tsunami waves along shorelines of constant slope. If the narrow bay is U-shaped, the Cross-Sectionally Averaged Shallow Water equations have a known general solution via solving the transformed matrix Klein-Gordon equation. However, the initial conditions for our Klein-Gordon equation are given on a curve. Thus our goal is to solve the matrix Klein-Gordon equation with known conditions given along a curve. Therefore we present a method to extrapolate values on a line from conditions on a curve, via the Taylor formula. Finally, to apply our solution to the Cross-Sectionally Averaged Shallow Water equations, our numerical simulations demonstrate how Gaussian and N-wave profiles affect the run-up of tsunami waves within various U-shaped bays.
    • On the nature and shape of noctilucent cloud particles

      Chao, Jih-Kwin (1965-05)
      The exact theory of the scattering of light from spheres, double-layer spheres, infinite long cylinders and coaxial cylinders is presented here in detail. The theory of scattering from spheres and infinite long cylinders is then applied to the noctilucent Cloud (NCL) problem. The intensity and polarization versus scattering angle, particle size, and wavelength for spherical particle scattering with index of refraction 1.33 (corresponding to ice and stone) were calculated with an IBM 1620 electronic computer and the results are compared with the available experimental data. The experimental data was also compared with the results of Deirmendjian, Clasen, etc., allowing conclusions with regard to the possibility of spherical pure metallic particles. The results indicate that the NLC particles are either stony dust or ice coated stony dust rather than pure metallic in nature. Consideration is given to the possibility of detecting through polarization and spectrographic studies the possible growth of NLC particles resulting from the formation of ice on them. If the NLC become visible only as a result of an increase of the number of particles, then the shape of the polarization versus scattering angle curve will not change, and the intensity versus wavelength curve will not change in shape but only in amplitude. However, if particle growth is responsible for the NLC becoming visible, then the shape of the polarization versus scattering angle curve will change. Careful experimental observations of these quantities should then answer this question about particle growth. A detailed analysis of the NLC particle sampling data obtained in Sweden during 1962 is made. A particle size distribution of the form Nα(diameter)⁻⁴ is required for the sampling data to be consistent with the polarization measurements that have been made.
    • On the physical oceanography of Bristol Bay 1969-1970

      Myers, Richard L. (1976-08)
      The examination of hydrographic data obtained in Bristol Bay 1969-1970 allowed oceanographic conditions in this region to be described for shorter time periods (several weeks) than previous studies (several months). This data revealed that during early spring Bristol Bay was homogeneous both vertically and horizontally in temperature and vertically in salinity. During late spring, a steep thermocline developed in the offshore regions and was present throughout summer, while the salinity structure remained vertically homogeneous. Salinity and bottom temperature contours tended to follow isobaths and indicated a cyclonic circulation in the bay. Summer surface temperature distributions are characterized by regions of cold water. These regions are believed to be maintained by upwelling of cold bottom water due to a subsurface convergence in the bottom Ekman layer. Data from 1970 showed that low temperature and high salinity water was much more extensive in that year than in 1969. This is attributed to deeper water from outer Bristol Bay surfacing in central Bristol Bay.
    • On the willingness-to-pay for Elodea removal in the Fairbanks North Star Borough

      Kaczmarski, Jesse I.; Little, Joseph; Greenberg, Joshua; Fix, Peter (2018-05)
      The empirical research conducted herein addresses a public need for the funding of a project that would eradicate Elodea in the Fairbanks North Star Borough (FNSB). The eradication project has been outlined and approved by State and Federal agencies and has gathered funding to begin the eradication process. The study aims to develop a mean willingness-to-pay value for survey participants by shifting the funding burden to property tax payers. This body of work includes a primer on Elodea in the borough, an overview of contingent valuation, a parametric approach to willingness-to-pay, and results of the study conducted on Fairbanks property owners. The average willingness-to-pay per survey respondent is $50.32. In addition, 72% of survey respondents voted for the enactment of the program at their proposed cost level. These financial burdens took values of $10, $30, $60, or $120 per year for 4 years to fund the proposed program. A penalized maximum log-likelihood estimation found that the most significant predictors for the likelihood of a yes vote are the respondent's perceived risk to the ecosystem and recreational opportunities. Additionally, the respondents concern for the use of herbicides in the borough to treat the Elodea infestation is highly significant. The high level of prior knowledge throughout the survey indicates that respondents had established view on Elodea prior to the survey.
    • On using numerical sea-ice prediction and indigenous observations to improve operational sea-ice forecasts during spring in the Bering Sea

      Deemer, Gregory Joseph; Bhatt, Uma; Eicken, Hajo; Hutchings, Jennifer; Danielson, Seth (2015-05)
      Impacts of a rapidly changing climate are amplified in the Arctic. The most notorious change has come in the form of record-breaking summertime sea-ice retreat. Larger areas of open water and a prolonged ice-free season create opportunity for some industries, but bring new challenges to indigenous populations that rely on sea-ice cover for subsistence. Observed and projected increases in Arctic maritime activities require accurate sea-ice forecasts on the weather timescale, which are currently lacking. Motivated by emerging needs, this study explores how new modeling developments and local-scale observations can contribute to improving sea-ice forecasts. The Arctic Cap Nowcast/Forecast System, a research sea-ice forecast model developed by the U.S. Navy, is evaluated for forecast skill. Forecasts of ice concentration, thickness, and drift speed produced by the model from April through June 2011 in the Bering Sea have been investigated to determine how the model performs relative to persistence and climatology. Results show that model forecasts can outperform forecasts based on climatology or persistence. However, predictive skill is less consistent during powerful, synoptic-scale events and near the Bering Slope. Forecast case studies in Western Alaska are presented. Community-based observations from recognized indigenous sea-ice experts have been analyzed to gauge the prospect of using local observations in the operational sea-ice monitoring and prediction process. Local observations are discussed in the context of cross-validating model guidance, data sources used in operational ice monitoring, and public sea-ice information products issued by the U.S. National Weather Service. Instrumentation for observing sea-ice and weather at the local scale was supplied to key observers. The instrumentation shows utility in the field and may help translate the context of indigenous observations and provide ground-truth data for use by forecasters.
    • Once upon a time: an anthropological exploration of Gwich'in stories (Man in the moon; The old woman and the brushman)

      Frey, Monika; Tuttle, Siri; Plattet, Patrick; Koskey, Michael (2015-08)
      This MA thesis research focuses on Gwich'in stories. It seeks to better understand how similar the versions of two stories are when each is parsed into units representing themes within the stories. Drawing in part on Lévi-Strauss's structural study of myth and applying aspects of it to the Gwich'in stories discussed in this research, I will demonstrate that several versions of a story contain identical themes, though levels of detail vary. This occurs when (1) a story is told by the same storyteller at different times, and (2) when a story is told by two or more storytellers. While each version of a particular story may differ in the amount of detail, resulting in shorter and longer versions, my research shows that the main themes of a story are identical even when several storytellers narrate the same story or when the same storyteller tells a story more than once, but several years apart. There is a gap in the academic literature pertaining to Gwich'in stories. Recent projects have been conducted including Gwich'in stories focused on documenting narratives, but no one has investigated whether the content of those tales is actually identical. My research complements these projects by shedding light on a less studied aspect of Gwich'in storytelling.
    • One health toxicology: expanding perspectives and methods to assess environmental contaminants

      Harley, John Robinson; O'Hara, Todd; Dunlap, Kriya; Duffy, Lawrence; Rea, Lorrie (2017-12)
      The discipline of One Health is founded on the principal that environmental health, animal health, and human health are interconnected. Although the field has been largely focused on zoonotic diseases, examining concepts such as toxicology under a One Health lens can offer a more holistic and preventative approach to research and implementation and, in particular, how fish-based diets may be involved with One Health outcomes. Here we present three general case studies that demonstrate new approaches to investigating One Health toxicology. In Chapter One we show how Arctic canids can be used as environmental sentinels for human health. We discuss three separate canid studies; in the first we find that Arctic foxes can act as sentinels of Arctic contaminants due to their foraging plasticity, in the second we examine the use of fish-fed sled dogs as a model for the effects of a fish-based diet on contaminants exposure and gene transcription, and in the third we develop the sled dog as a model for particulate matter air pollution in the Fairbanks North Star Borough. In Chapter Two we utilize the Steller sea lion, a nonmodel organism, as a sentinel for the effects of fish-based diet mercury exposure induced whole-genome changes in gene transcription (RNA-Seq). Using newly developed informatics tools we assemble a de novo transcriptome and examine large scale changes in gene expression related to mercury exposure and other One Health uses. This approach is extremely adaptable and has the potential to be applied across numerous non-model organisms and contaminants. We also applied a microbial mining algorithm to our RNA-Seq data and found evidence for a hemotropic Mycoplasma spp. in one of our samples. In Chapter Three we examine sources of mercury exposure for pregnant women from La Paz, Baja California Sur, Mexico. We found mercury concentrations to be generally low among the examined fish species and staple foods. While typical dietary assessments rely on recall surveys and questionnaires, we found that examining chemical biomarkers of diet including stable isotopes of carbon and nitrogen are critical in dietary risk assessment. Taken together these three investigations offer valuable lessons and techniques which can be applied to the field of One Health toxicology; especially to those fish diet based systems.
    • One large steppe for Russian authorship: Gogol's troika of settings

      Fleharty, Ryan; Carr, Richard; Burleson, Derick; Mamoon, Trina (2011-08)
      This exploration of Gogol's works focuses on the three major setting-related phases of his writing career: the Ukrainian beginnings, his Petersburg tales, and the provincial Russian towns that populated his final works. His choice and execution of settings is correlated to the development of a sophisticated Russian readership clamoring for a national literature, and in attempting to generate one through his works, Gogol joins the other canonical Russian authors by tackling the central problem of 19th century Russian literature: the identity and future of the Russian nation.
    • One woman's land

      Glasoe, Sydney Caroline (2001-05)
      'One woman's land' is an essay collection that explores how place shapes identity and reciprocally how such marked individuals influence their land, family, and community. The essays are memoir and use the author's family farm in northwestern North Dakota as a vehicle to illuminate the dynamics of farming families and their rural communities when the work on which both survive is at once inclusive and a way of life. Each essay remains separate in narrative and structure, but the themes addressed are recursive and reflect upon other sections. The essays remain linked in that they create a social history that seeks to define a rural lifestyle holding an increasingly fragile existence in American identity.
    • Online social media as a social-ecological systems research tool: Facebook and two rural Alaskan communities

      Hum, Richard E.; Koskey, Michael; Taylor, Karen; Brinkman, Todd (2013-12)
      The earth has transitioned into the anthropocene, which is defined by complex environmental change linked to human behavior and requires new tools of analysis in order to understand shifting social-ecological system (SES) dynamics. In this work, I explore taking advantage of widespread online social media participation to develop the tools for doing so. Spatially grounded public exchanges on Facebook are examined with three goals in mind: 1) examine the types of SES content being passed through this communication medium, 2) compare community observations to relevant scientific observations, and 3) define a flexible and reproducible research method for integrating these communications signals into a wide range of SES studies. Facebook activity from two communities in northwest Alaska was studied. Communication patterns were assessed combining content and network analysis methodology. My results indicate that signals are passed through this mode of communication directly addressing the SES topics of subsistence, food security, and human-weather interactions. Data from instrumentally based weather observations are qualitatively aligned with posting frequency and content. A context and community-based research method is defined that uses staged deductive/inductive content analysis, in conjunction with network analysis, to identify emergent local SES relationships.
    • The ontogeny of hypoxic neuroventilation in the brainstem of the developing American bullfrog, Rana catesbeiana

      Buehner, Justin C.; Taylor, Barbara; Drew, Kelly; Harris, Michael; Duffy, Lawrence K. (2008-12)
      Isolated brainstem models have been used twice to examine the hypoxic neuroventilatory response (HnVR) in developing bullfrogs with varying results, leading me to question if the results of these two previous studies were physiologically relevant. Based on in vivo and in vitro observations, I hypothesized that buccal neuroventilation exhibits no ventilatory response to hypoxia in any developmental stage and that lung neuroventilation exhibits a biphasic hypoxic response in late metamorphic tadpoles and a neuroventilatory depression in juvenile bullfrogs and early metamorphic tadpoles. I tested this by using brainstems isolated from intact early and late metamorphic tadpoles and juvenile bullfrogs exposed to 20% O2 saturation in artificial cerebrospinal fluid. Neuroventilatory patterns were recorded from the facial and hypoglossal nerves using suction electrodes and burst frequency, and duration for buccal and lung bursts were examined in all developmental stages. Results confirmed my hypothesis for buccal neuroventilation across development and lung neuroventilation in juveniles, but not my hypothesis about lung neuroventilation in tadpoles. Therefore, the HnVR of developing bullfrogs consists of constant maintenance of neuroventilatory activity in early metamorphic tadpoles, a trend towards a biphasic neuroventilatory response in late metamorphic tadpoles, and ventilatory depression that is mediated centrally in juvenile bullfrogs.
    • Optical observations of critical ionization velocity chemical releases in the ionosphere: The role of collisions

      Hampton, Donald Loyd (1996)
      In recent years researchers have pointed out the importance of collisional processes in ionospheric chemical releases performed to study Alfven's critical ionization velocity effect (CIV). Ionizing collisions, including charge exchange with ambient O$\sp+$ and associative ionization, can not only help initiate CIV, but can also lead to 'contamination' of the ion cloud. Most of the proposed collisions have associated emissions which should be observable with sensitive detectors, but until now have not been attempted since atomic processes had not been considered important. The first four releases of the CRRES satellite were performed to study CIV. The releases were at local dusk over the south Pacific in September, 1990, and were observed from two aircraft with low light level cameras, both filtered and broadband. Ion inventories of the releases show ionization yields (number of ions per number of available neutrals) of 0.02% for Sr, 0.15% for the first Ba release, 0.27% for Ca and 1.48 for the second Ba release. The release clouds were seen to glow quite strongly, below the terminator. The measured light is found to be primarily from line emissions which indicates that it is due to collisional processes in the release cloud. Two measurements were made on the release cloud data; (1) the absolute intensity of the release clouds and (2) the ratio between a broadband intensified CCD (ICCD) and an imaging photon detector filtered for the Ba$\sp+$ 455.4 nm emission line. The measured ratio is compared to the expected ratio for charge exchange collisions, and to electron impact excitation of Ba. The measured ratio is consistent with emissions being from charge exchange collisions. However, when compared to the total intensity of emissions expected from charge exchange, the absolute intensity in the release cloud measured by the ICCD is five times greater. The two measurements are in conflict, and with this limited set of data cannot be fully resolved. The ratio measurement does indicate that any CIV discharge in the Ba releases was extremely weak, and that charge exchange is the dominant collisional process in Ba releases.
    • Optical Remote Sensing Of Snow On Sea Ice: Ground Measurements, Satellite Data Analysis, And Radiative Transfer Modeling

      Zhou, Xiaobing; Li, Shusun; Stamnes, Knut; Sharpton, Buck; Jeffries, Martin O.; Echelmeyer, Keith (2002)
      The successful launch of the Terra satellite on December 18, 1999 opened a new era of earth observation from space. This thesis is motivated by the need for validation and promotion of the use of snow and sea ice products derived from MODIS, one of the main sensors aboard the Terra and Aqua satellites. Three cruises were made in the Southern Ocean, in the Ross, Amundsen and Bellingshausen seas. Measurements of all-wave albedo, spectral albedo, BRDF, snow surface temperature, snow grain size, and snow stratification etc. were carried out on pack ice floes and landfast ice. In situ measurements were also carried out concurrently with MODIS. The effect of snow physical parameters on the radiative quantities such as all-wave albedo, spectral albedo and bidirectional reflectance are studied using statistical techniques and radiative transfer modeling, including single scattering and multiple scattering. The whole thesis consists of six major parts. The first part (chapter 1) is a review of the present research work on the optical remote sensing of snow. The second part (chapter 2) describes the instrumentation and data-collection of ground measurements of all-wave albedo, spectral albedo and bidirectional reflectance distribution function (BRDF) of snow and sea ice in the visible-near-infrared (VNIR) domain in Western Antarctica. The third part (chapter 3) contains a detailed multivariate correlation and regression analysis of the measured radiative quantities with snow physical parameters such as snow density, surface temperature, single and composite grain size and number density. The fourth part (chapter 4) describes the validation of MODIS satellite data acquired concurrently with the ground measurements. The radiances collected by the MODIS sensor are converted to ground snow surface reflectances by removing the atmospheric effect using a radiative transfer algorithm (6S). Ground measured reflectance is corrected for ice concentration at the subpixel level so that the in situ and space-borne measured reflectance data are comparable. The fifth part (chapter 5) investigates the single scattering properties (extinction optical depth, single albedo, and the phase function or asymmetry factor) of snow grains (single or composite), which were calculated using the geometrical optical method. A computer code, GOMsnow, is developed and is tested against benchmark results obtained from an exact Mie scattering code (MIE0) and a Monte Carlo code. The sixth part (chapter 6) describes radiative transfer modeling of spectral albedo using a multi-layer snow model with a multiple scattering algorithm (DISORT). The effect of snow stratification on the spectral albedo is explored. The vertical heterogeneity of the snow grain-size and snow mass density is investigated. It is found that optical remote sensing of snow physical parameters from satellite measurements should take the vertical variation of snow physical parameters into account. The albedo of near-infrared bands is more sensitive to the grain-size at the very top snow layer (<5cm), while the albedo of the visible bands is sensitive to the grain-size of a much thicker snow layer. Snow parameters (grain-size, for instance) retrieved with near-infrared channels only represent the very top snow layer (most probably 1--3 cm). Multi-band measurements from visible to near-infrared have the potential to retrieve the vertical profile of snow parameters up to a snow depth limited by the maximum penetration depth of blue light.
    • Optical spectroscopic observations of sprites, blue jets, and elves: Inferred microphysical processes and their macrophysical implications

      Heavner, Matthew James; Sentman, Davis D. (2000)
      During the past decade, several new upper atmospheric phenomena associated with thunderstorms have been discovered. The four main types of optical emissions are now called sprites, blue jets, lves, and halos. Sprites are primarily red and appear between 40--95 km altitude and last between 1--100 ms. The dominant sprite emission is the molecular nitrogen first positive band, a relatively low energy emission also observed in the red lower borders of aurorae. The total optical energy output of a bright sprite is on the order of 50 kJ. Based on spectral observations, the total vibrational and electronic energy deposited in molecular nitrogen and oxygen in the upper atmosphere is 250 MJ-1 GJ. Blue jets last hundreds of milliseconds and span altitudes 15--40 km. Spectral observations of blue jets have not been obtained to date. Elves, the third type of observed optical emissions above thunderstorms, are red emissions at altitudes 75--95 km, lasting one millisecond or less. Elves and halos are similar phenomena, but are distinct based on altitude and duration. Halos typically last 3--6 ms and occur at lower altitudes than elves. This dissertation describes the optical spectrum of sprites obtained by the University of Alaska Fairbanks during summer campaigns of 1995, 1996, and 1998, and its implication to the understanding of the electrodynamics of the middle atmosphere. The single most significant result is the determination that a typical sprite deposits up to one gigajoule into the mesosphere. These forms of electrical energy coupling from tropospheric thunderstorms into the stratosphere, mesosphere, and thermosphere/ionosphere may have critical implications for the global chemistry and energy budgets in these regions.
    • Optimal Inseason Management Of Pink Salmon Given Uncertain Run Sizes And Declining Economic Value

      Su, Zhenming; Adkison, Milo (2001)
      This is a comprehensive study on the fishery and management system (including the inseason stock abundance dynamics, the purse seine fleet dynamics and the inseason management) of pink salmon (Oncorhynchus gorbuscha) in the northern Southeast Alaska inside waters (NSE). Firstly, we presented a hierarchical Bayesian modelling approach (HBM) for estimating salmon escapement abundance and timing from stream count data, which improves estimates in years when data are sparse by "borrowing strength" from counts in other years. We presented a model of escapement and of count data, a hierarchical Bayesian statistical framework, a Gibbs sampling estimation approach for posterior distributions, and model determination techniques. We then applied the HBM to estimating historical escapement parameters for pink salmon returns to Kadashan Creek in Southeast Alaska. Secondly, a simulation study was conducted to compare the performance of the HBM to that of separate maximum likelihood estimation of each year's escapement. We found that the HBM was much better able to estimate escapement parameters in years where few or no counts are made after the peak of escapement. Separate estimates for such years could be wildly inaccurate. However, even a single postpeak count could dramatically improve the estimability of escapement parameters. Third, we defined major stocks and their migratory pathways for the NSE pink salmon. We estimated the escapement timing parameters of these stocks by the HBM. A boxcar migration model was then used to reconstruct the catch and abundance histories for these stocks from 1977 to 1998. Finally, we developed a stochastic simulation model that simulates this fishery and management system. Uncertainties in annual stock size and run timing, fleet dynamics and both preseason and inseason forecasts were accounted for explicitly in this simulation. The simulation model was applied to evaluating four kinds of management strategies with different fishing opening schedules and decision rules. When only flesh quality is concerned, the present and a more aggressive strategy, both of which are adaptive to the run strength of the stocks, are able to provide higher quality fish without compromising the escapement objectives.
    • Optimization of oilfield power distribution through installation of underground transmission lines applied to the Alaskan North Slope

      Mielke, Robert (2004-05)
      An analytical model is developed to evaluate economic feasibility of installing new underground segments to the power transmission system maintained and operated by Greater Prudhoe Bay Central Power Station. Installation of underground segments is considered for intersections of power lines and roadways. Old materials and equipment are abandoned in favor of new technological infrastructure additions to transmission systems. This installation is progressive in its approach; it aims to eliminate superfluous oilfield operations via implementation of technological innovation. Results indicate that installation of underground segments of transmission line is an economically feasible project. Installation sites are chosen that optimize the economics of this investment. Project impact to power reliability, idle rig time, and streamlined rig operations far outweighs the investment associated with this project. Additionally, this project's effect on Prudhoe Bay oil production shows great potential for additional power line burial projects. Hence, it is hoped that this research be considered a pilot project, that future power line burial projects be considered for implementation, and that economic modeling of future projects be accomplished via revision of this work to include comparison of actual vs. predicted economics of this pilot project.
    • Optimizing landbird surveys for detecting population and spatial dynamics

      Mizel, Jeremy D.; Lindberg, Mark; Breed, Greg; Powell, Abby; Schmidt, Joshua (2017-12)
      Landbird populations are undergoing concurrent changes in population size, spatial distribution, and phenology. The sensitivity of landbird monitoring programs to detect and distinguish these varied processes is of critical importance. Consequently, these efforts require inference methods that are efficient and fully leverage information about spatial, population, and phenological dynamics. The development of efficient inference methods can be addressed in part through a thorough understanding of how the data are actually generated, the application of sampling methods that attempt to maximize encounter probability, and the tailoring of sampling methods to maximize sensitivity to specific inference objectives. Chapter one of this dissertation is concerned with accommodating temporary emigration in spatial distance sampling models. Model-based distance sampling is commonly used to understand spatial variation in the density of wildlife species. The standard approach is to assume that individuals are distributed uniformly in space and model spatial variation in abundance using plot-level effects. Thinned point process models for surveys of unmarked populations (spatial distance sampling) frame the sampling process in terms of the individual encounter in space and, consequently, are expected to offer greater sensitivity for understanding spatial processes. However, existing spatial distance sampling approaches are conditioned on the assumption that all individuals are present and available for sampling. Temporary emigration of individuals can therefore result in biased estimates of abundance. Herein, I extend spatial distance sampling models to accommodate temporary emigration. A simulation study indicated more precise and less biased estimation under the spatial distance sampling model compared to models that assume a uniform distribution of individuals and assess spatial variation in abundance using plot-level effects. An applied example involving two arctic-breeding passerines indicated considerably stronger inference under the spatial distance sampling model than standard distance sampling models. Chapter two is concerned with the capacity of subarctic passerines to adjust their arrival timing to relatively extreme variation in spring conditions. I assessed interannual variation in passerine arrival timing in Denali National Park, Alaska from 1995-2015, a period that included both the warmest and coldest recorded mean spring temperatures for the park. Neotropical-Nearctic migrants varied in terms of the flexibility of their arrival timing, but generally showed plastic phenologies, suggesting resilience under extreme spring conditions. In comparison, Nearctic-Nearctic migrants showed similar or greater plasticity in arrival timing. A majority of species showed synchronous-asynchronous fluctuation in arrival (i.e., synchronous arrival in some years, asynchronous in others) in combination with various levels of the mean response (i.e., early, average, and late arrival), suggesting the presence of interactions between environmental conditions at multiple scales and inter-individual variation. Overall, these findings suggest that monitoring of the mean-variance relationship may lead to a deeper understanding of the factors shaping phenological responses. Chapter three is concerned with developing efficient inference methods for inventorying and monitoring cliff-nesting raptor populations. In nest occupancy studies of cliff-nesting raptors, the standard approach is to allocate a level of survey effort that is assumed to ensure that the occupancy state is known with certainty. However, allocating effort in this manner is inefficient, particularly at landscape scales, constraining our capacity for effective management of these species. To increase survey efficiency and expand the spatial inference of these studies, I developed two versions of a multi-state, time-removal model, one for long-term monitoring studies and another for population inventories or single-season surveys in which there is no prior knowledge of nest locations. For long-term monitoring of species with alternative nests, I formulated a version of the model that accounts for state uncertainty at the territory-level caused by a failure to observe all nests within a territory. Simulation studies indicated generally low to moderate relative bias under the monitoring and inventory models. In addition, I applied the monitoring model to a long-term study of golden eagles (Aquila chrysaetos) in Alaska and demonstrate that the maximum effort spent on any nesting territory could be reduced by up to almost 90% of that recommended by standard protocols.
    • Order reduction and eigenstructure assignment for nonsmooth vibrating systems: a nonlinear normal modes approach

      Lu, Rongdong (2002-08)
      Two related problems are addressed in this thesis. The first one is for order reduction of conservative vibrating systems with piecewise linear nonsmooth nonlinearities of arbitrary dimension. Linear-based, PMM-based and LELSM-based order reduction transformations are applied. The technique is applied to multi-degree-of-freedom systems with nonsmooth clearance, deadzone, bang-bang, and saturation nonlinearities. The resulting approximate frequencies are compared with those obtained from numerical simulations. The second technique is eigenstructure assignment of n-degree-of-freedom conservative vibrating systems with nonsmooth nonlinearities. Three distinct control strategies which utilize methods for approximating the NNM frequencies and mode shapes are employed. First, PMM for approximating NNM frequencies is used to determine n constant actuator gains for eigenvalue placement. Second, an approximate single-degree-of-freedom reduced model is found with one actuator gain for the mode to be controlled. The third strategy allows the frequencies and mode shapes (eigenstructure) to be placed by using a full n x n matrix of actuator gains and employing LELSM for approximating NNM frequencies and mode shapes.