• 60,000 year climate and vegetation history of Southeast Alaska

      Wilcox, Paul S.; Fowell, Sarah; Bigelow, Nancy; Mann, Daniel; Dorale, Jeffrey (2017-08)
      Sedimentological and palynological analyses of lacustrine cores from Baker Island, located in Southeast Alaska's Alexander Archipelago, indicate that glaciers persisted on the island until ~14,500 cal yr. BP. However, the appearance of tree pollen, including Pinus cf. contorta ssp. contorta (shore pine) and Tsuga mertensiana (mountain hemlock) immediately following deglaciation suggests that a forest refugium may have been present on ice-free portions of neighboring islands or the adjacent continental shelf. Sedimentological and palynological analyses indicate a variable climate during the Younger Dryas interval between ~13,000 and ~11,500 cal yr. BP, with a cold and dry onset followed by ameliorating conditions during the latter half of the interval. An eight cm-thick black tephra dated to 13,500 ± 250 cal yr. BP is geochemically distinct from the Mt. Edgecumbe tephra and thus derived from a different volcano. Based on overall thickness, multiple normally graded beds, and grain size, I infer that the black tephra was emplaced by a large strombolian-style paroxysm. Because the dominant wind direction along this coast is from the west, the Addington Volcanic Field on the continental shelf, which would have been subaerially exposed during the eruption, is a potential source. The similarity in timing between this eruption and the Mt. Edgecumbe eruption suggests a shared trigger, possibly a response to unloading as the Cordilleran Ice Sheet retreated. To complement the Baker Island lacustrine record, a speleothem paleoclimate record based on δ¹³C and δ¹⁸O values spanning the interval from ~60,000 yr. BP to ~11,150 yr. BP was recovered from El Capitan Cave on neighboring Prince of Wales Island. More negative δ¹³C values are attributed to predominance of angiosperms in the vegetation above the cave at ~22,000 yr. BP and between ~53,000 and ~46,000 yr. BP while more positive δ¹³C values in speleothem EC-16-5-F indicate the presence of gymnosperms. These data suggest limited or no ice cover above El Capitan Cave for the duration of the record, possibly indicating that this region was a nunatak during glacial periods.
    • An 8 ka record of vegetation cover, fire history and moisture availability from North-Central Mongolia

      Molhoek, Emily (2007-05)
      Analysis of pollen, charcoal, and stable carbon and nitrogen isotopes ([delta]¹³C and [delta]¹⁵N) from a sediment core of Mongolian Lake Terhiyn-Tsagaan show increases in moisture availability coincident with mid- to late Holocene expansion of the Asian monsoon. The lake is freshwater and located in an intermontane depression on the flanks of the Hangai Range of north-central Mongolia. The site lies within the forest-steppe biome ~400 m below tree line. The low C:N of the sediments indicates that organic matter is primarily composed of autochthonous material. Artemisia and Chenopodiaceae pollen are indicators of dry steppe and semi-desert vegetation, whereas Poaceae pollen is more abundant in humid meadow-steppe or forest-steppe assemblages. An aridity index, calculated by dividing Artemisia + Chenopodiaceae by Poaceae pollen, is used to identify changes in moisture availability. High aridity indices and spikes of charcoal influx record relatively humid conditions at the site between 8.0 and 5.5 k years BP. Low charcoal influx rates and peak values of the aridity index between 4.5 and 4.0 k years BP correspond to a documented interval of drought in southern Asia and northern Africa attributed to a weak Asian monsoon. A decrease in charcoal influx since 7.5 k years BP combined with progressive increase in [delta]¹⁵N indicates increasing aridification from the mid-Holocene to nearly the present. Intervals of humidification at Lake Terhiyn-Tsagaan are thus synchronous with the waxing and waning of the Asian monsoon and out of phase with humid intervals recorded at Lake Telmen, approximately 250 km to the northwest. It is possible that the Terhiyn-Tsagaan drainage lies at the northern and/or western edge of the region that received precipitation from an expanded Holocene summer monsoon.
    • A Concept To Assess The Performance Of A Permafrost Model Run Fully Coupled With A Climate Model

      Paimazumder, Debasish (2009)
      Soil-temperatures simulated by the fully coupled Community Climate System Model LCM version 3.0 (CCSM3) are evaluated using three gridded Russian soil-temperature climatologies (1951-1980, 1961-1990, and 1971-2000) to assess the performance of permafrost and/or soil simulations. CCSM3 captures the annual phase of the soil-temperature cycle well, but not the amplitude. It provides slightly too high (low) soil-temperatures in winter (summer) with a better performance in summer than winter. In winter, soil-temperature biases reach up to 6 K. Simulated near-surface air temperatures agree well with the near-surface air temperatures from reanalysis data. Discrepancies in CCSM3-simulated near-surface air temperatures significantly correlate with discrepancies in CCSM3-simulated soil-temperatures, i.e. contribute to discrepancy in soil-temperature simulation. Evaluation of cloud-fraction by means of the International Satellite Cloud Climatology project data reveals that errors in simulated cloud fraction explain some of the soil-temperature discrepancies in summer. Evaluation by means of the Global Precipitation Climatology Centre data identifies inaccurately-simulated precipitation as a contributor to underestimating summer soil-temperatures. Comparison to snow-depth observations shows that overestimating snow-depth leads to winter soil-temperature overestimation. Sensitivity studies reveal that uncertainty in mineral-soil composition notably contributes to discrepancies between CCSM3-simulated and observed soil-temperature climatology while differences between the assumed vegetation in CCSM3 and the actual vegetation in nature marginally contribute to the discrepancies in soil-temperature. Out of the 6 K bias in CCSM3 soil-temperature simulation, about 2.5 K of the bias may result from the incorrect simulation of the observed forcing and about 2 K of the bias may be explained by uncertainties due network density in winter. This means that about 1.5 K winter-bias may result from measurement errors and/or model deficiencies. Overall, the performance of a permafrost/soil model fully coupled with a climate model depends partly on the permafrost/soil model itself, the accuracy of the forcing data and design of observational network.
    • A Mechanism For Current Sheet Thinning In The Growth Phase Of Magnetospheric Substorms

      Hall, Fred, Iv; Otto, Antonius (2006)
      The thinning of the near-Earth current sheet during the growth phase of magnetospheric substorms is a fundamental problem of space physics. It is a characteristic of the slow, steady evolution of the magnetosphere during the growth phase, during which the bulk kinetic energy of the solar wind is transformed into and stored as magnetic field energy in the magnetotail lobes. The thin near-Earth current sheet at the end of the growth phase provides the conditions for the onset of the expansion phase, and is fundamentally important to understand the physical mechanism for the onset of the rapid evolution during which the stored energy is released. I propose that current sheet thinning occurs because of the evacuation of a 'magnetic flux reservoir' in the near-Earth magnetotail by convection to replace magnetic flux that is eroded on the dayside by magnetic reconnection. My hypothesis is able to predict basic properties of current sheet thinning, such as the location, temporal evolution, and dynamics of this process. I examined this new mechanism both conceptually and quantitatively. My conceptual considerations enabled the prediction of the location and duration of current sheet thinning. This location is largely independent of the detailed state of the magnetosphere. I examined this mechanism quantitatively through the use of a three-dimensional ideal MHD simulation. I was able to predict the duration of the growth phase by considering the time needed to deplete our proposed 'magnetic flux reservoir.' The simulation demonstrates the global increase of the current density in this reservoir, despite the removal of magnetic flux---which one would otherwise expect to lead to a decrease of current---as well as even greater local amplifications of the current density. The simulation results are even more significant because the model does not include other effects of the real magnetosphere that contribute to a further increase of the tail current. The increase in current density and thinning are found to be consistent with the amount of flux removed from the system. In addition, I have found a new explanation for the very thin bifurcated current sheets that have been reported in recent publications.
    • A Search For Thermospheric Composition Perturbations Due To Vertical Winds

      Krynicki, Matthew P.; Conde, Mark (2006)
      The thermosphere is generally in hydrostatic equilibrium, with winds blowing horizontally along stratified constant-pressure surfaces, driven by the dayside-to-nightside pressure gradient. A marked change in this paradigm resulted after Spencer et al. [1976] reported vertical wind measurements of 80 m·s-1 from analyses of AE-C satellite data. It is now established that the thermosphere routinely supports large-magnitude (~30-150 m·s-1) vertical winds at auroral latitudes. These vertical winds represent significant departure from hydrostatic and diffusive equilibrium, altering locally---and potentially globally---the thermosphere's and ionosphere's composition, chemistry, thermodynamics and energy budget. Because of their localized nature, large-magnitude vertical wind effects are not entirely known. This thesis presents ground-based Fabry-Perot Spectrometer OI(630.0)-nm observations of upper-thermospheric vertical winds obtained at Inuvik, NT, Canada and Poker Flat, AK. The wind measurements are compared with vertical displacement estimates at ~104 km2 horizontal spatial scales determined from a new modification to the electron transport code of Lummerzheim and Lilensten [1994] as applied to FUV-wavelength observations by POLAR spacecraft's Ultraviolet Imager [Torr et al. , 1995]. The modification, referred to as the column shift, simulates vertical wind effects such as neutral transport and disruption of diffusive equilibrium by vertically displacing the Hedin [1991] MSIS-90 [O2]/[N2] and [O]/([N2]+[O2]) mixing ratios and subsequently redistributing the O, O2, and N 2 densities used in the transport code. Column shift estimates are inferred from comparisons of UVI OI(135.6)-nm auroral observations to their corresponding modeled emission. The modeled OI(135.6)-nm brightness is determined from the modeled thermospheric response to electron precipitation and estimations of the energy flux and characteristic energy of the precipitation, which are inferred from UVI-observed Lyman-Birge-Hopfield N2 emissions in two wavelength ranges. Two-dimensional column shift maps identify the spatial morphology of thermospheric composition perturbations associated with auroral forms relative to the model thermosphere. Case-study examples and statistical analyses of the column shift data sets indicate that column shifts can be attributed to vertical winds. Unanticipated limitations associated with modeling of the OI(135.6)-nm auroral emission make absolute column shift estimates indeterminate. Insufficient knowledge of thermospheric air-parcel time histories hinders interpretations of point-to-point time series comparisons between column shifts and vertical winds.
    • A temperature only formulation for ice sheets

      Gillispie, Lyman; Bueler, Edward; Allman, Elizabeth; Maxwell, David (2014-05)
      Temperature plays an important role in the dynamics of large flowing ice masses like glaciers and ice sheets. Because of this role many models for ice sheets model temperature in some form. One type of model for polythermal glaciers (glaciers which contain both ice below, and at the pressure-melting temperature) explicitly separates the ice into distinct cold and temperate regimes, and tracks the interface between them as a surface. Other models track the enthalpy (internal energy) across both domains, with temperature being a function of enthalpy. We present an alternative mathematical formulation for polythermal glaciers and ice-sheets, in the form of a variational inequality for the temperature field only. Using the calculus of variations, we establish some sufficient conditions under which our formulation is well-posed. We then present some numerical approximations of solutions obtained via the Finite Element Method.
    • Acacia constricta gains novel benefits from ants while minimizing potential conflicts

      Nicklen, E. Fleur (2006-08)
      The sum of costs and benefits in an interspecific interaction determines whether the relationship is mutualistic, neutral, or antagonistic. We investigate novel benefits Acacia constricta may gain from ant visitors and how A. constricta may minimize potential costs of ant visitation. A. constricta attracts ants onto its foliage and encourages nesting at its base with extrafloral nectaries. Plants with basal nests have significantly greater soil nutrients and produce twice as many seeds as plants lacking basal nests (Wagner 1997). Along side these benefits, however, ants can interfere with plant reproduction. This study tests whether augmented soil nutrients increase A. constricta's defenses and ant attractants. We further test mechanisms A. constricta may have to reduce the potential costs of ants to reproduction. We found that increased soil nutrients elevated defense mechanisms in A. constricta and increased extrafloral nectary number, suggesting ants that provide plants with nutrients may indirectly increase plant defense as well as participate in a feed back cycle where ants increase soil nutrients allowing plants to increase ant attractants. In addition, plants have at least two mechanisms to keeps ants separated from flowers, minimizing ant costs to reproduction.
    • Acclimation and migration potential of a boreal forest tree, balsam poplar (Populus balsamifera L.) in a changing climate

      Robertson, Amanda L.; Olson, Mattew; Takebayashi, Naoki; Wolf, Diane E.; Chapin, Stuart F. III (2012-12)
      In the North American boreal forest, 21st century climate change is projected to result in longer growing seasons, increased forest productivity, and northward expansions or shifts in species ranges. These projected impacts are largely based on observations across natural temperature gradients, e.g., latitude or altitude, or correlations between current species' distributions and modern climate envelopes. These approaches, although valuable, do not consider biological capacities important in a species' ability to cope with novel environments through physiological or phenological acclimation. Within a single species, adaptation to local environments may cause some populations to respond differently to climate change than others. Acclimation (phenotypic plasticity) is often treated as a separate phenomenon from local adaptation, but the latter may determine the range of acclimation responses or thresholds. To more accurately predict how boreal tree species will respond to a directionally changing climate, it is necessary to experimentally examine the effects of warming on the growth and physiology of individual species and how those effects differ across a species' range. This research investigated how tree growth responses to increasing temperature are influenced by differences in adaptation and acclimation across the latitudinal range of the North American boreal forest tree, Populus balsamifera L. (balsam poplar). Warming experiments, both in the greenhouse and in the field, indicated that growth of balsam poplar trees from a broad latitudinal gradient responds positively to increased growing temperatures, with increases in height growth ranging from 27-69 % in response to 3-8 °C average warming. Genotypes from southern populations grew consistently taller in both field and greenhouse experiments. The field experiment enabled investigation into the effects of warming and source latitude on balsam poplar phenology; both experimentally warmed and southern individuals grew larger and exhibited longer growing seasons (more days of active growth). Lastly, I describe a theoretical/methodological framework for exploring the role of epigenetics in acclimation (plasticity) and adaptation to changing environments. The results from these experiments are integrated with information on adaptive gradients in balsam poplar to predict both the in situ responses of balsam poplar to increased temperatures, and the potential for northward range shifts in the species.
    • The acetylcholine binding protein of Lymnaea stagnalis as a biosensor and model for ligand gated ion channel proteins

      Harms-Smyth, Abraham Edward (2008-12)
      The structural similarity of the Acetylcholine Binding Protein (AChBP) from Lymnaea stagnalis to the extracellular ligand binding domain of Ligand Gated Ion Channel (LGIC) receptors suggests that the AChBP could be used to mimic cys-loop ligand-gated ion channel (LGIC) receptors. An LGIC mimic could be used as a sensor molecule in a range of biotechnology applications including high throughput drug screening as well as in vivo and in vitro sensing of biologically active compounds. It could also be used as a lead molecule for engineering novel proteins with binding characteristics similar to non-acetylcholine receptor LGIC's. The soluble AChBP is easily expressed and purified and can be produced in reasonably large amounts. This thesis explores the potential for using the AChBP and related proteins as biosensors by evaluating their action on three key medium and high throughput systems: Scintillation Proximity Assay (SPA), Surface Plasmon Resonance (SPR), and Microcantilevers (MC). As a preliminary step to developing a 5-HT₃R-ligand binding protein, by altering the ligand specificity of the AChBP, the interaction of 5-HT₃R ligands with the AChBP is also evaluated. The work presented in this thesis contributes to improved methods of drug design and testing, and to a better understanding of LGIC structure.
    • Active Tectonics In Southern Alaska And The Role Of The Yakutat Block Constrained By Gps Measurements

      Elliott, Julie; Freymueller, Jeff (2011)
      GPS data from southern Alaska and the northern Canadian Cordillera have helped redefine the region's tectonic landscape. Instead of a comparatively simple interaction between the Pacific and North American plates, with relative motion accommodated on a single boundary fault, the margin is made up of a number of small blocks and deformation zones with relative motion distributed across a variety of structures. Much of this complexity can be attributed to the Yakutat block, an allochthonous terrane that has been colliding with southern Alaska since the Miocene. This thesis presents GPS data from across the region and uses it to constrain a tectonic model for the Yakutat block collision and its effects on southern Alaska and eastern Canada. The Yakutat block itself moves NNW at a rate of 50 mm/yr. Along its eastern edge, the Yakutat block is fragmenting into small crustal slivers. Part of the strain from the collision is transferred east of the Fairweather -- Queen Charlotte fault system, causing the region inboard of the Fairweather fault to undergo a distinct clockwise rotation into the northern Canadian Cordillera. About 5% of the relative motion is transferred even further east, causing small northeasterly motions well into the northern Cordillera. Further north, the GPS data and model results indicate that the current deformation front between the Yakutat block and southern Alaska runs along the western side of the Malaspina Glacier. The majority of the ~37 mm/yr of relative convergence is accommodated along a narrow band of thrust faults concentrated in the southeastern part of the St. Elias orogen. Near the Bering Glacier, the tectonic regime abruptly changes as crustal thrust faults give way to subduction of the Yakutat block beneath the western St. Elias orogen and Prince William Sound. This change aligns with the Gulf of Alaska shear zone, implying that the Pacific plate is fragmenting in response to the Yakutat collision. The Bering Glacier region is undergoing internal deformation and may represent the final stage of accretion of the Yakutat block sedimentary layers. Further west, modeled block motions suggest the crust is laterally escaping along the Aleutian forearc.
    • Addressing feasibility of using microdialysis to monitor adenosine in Arctic ground squirrel (Spermophilus parryii)

      Chi, Bongchu (2005-12)
      Both hibernation and anapyrexia are important physiological adaptations. In addition, there is a strong relationship between survival rate and hypothermia during metabolic trauma. Evidence shows that adenosine might be one of the mediators, both of hibernation and anapyrexia. Adenosine is an inhibitory neuromodulator that suppresses neuronal activity when energy stores are low. This inhibitory activity makes adenosine a good candidate for neuroprotection via the suppression of neural activity during metabolic trauma. The main objective of this study was to investigate the feasibility of using microdialysis to monitor extracellular adenosine in the brains of Arctic ground squirrels (AGS), Spermophilus parryii, throughout hibernation. To investigate this feasibility, the basal level of adenosine concentration in AGS was collected using an in vivo microdialysis method. Samples then were analyzed by high performance liquid chromatography (HPLC). Also, the effects of adding an adenosine transporter inhibitor, S-(p-Nitrobenzyl)-6-thioinosine (NBTI), on extracellular adenosine concentration and body temperature (Tb) of AGS were observed. The results of this study indicate that it is not feasible to observe extracellular adenosine concentrations in AGS during hibernation using these techniques.
    • Air quality degradation in Alaska wilderness areas due to emission changes

      Tran, Trang T.; Cahill, Catherine; Webley, Peter; Newby, Gregory; Simpson, William (2013-08)
      The increasing trends in aerosol concentrations observed by the Interagency Monitoring of Protected Visual Environments (IMPROVE) network in the wilderness areas along the Gulf of Alaska during low insolation periods and in Denali National Park and Preserve (Denali NP) during high insolation periods have raised the concerns about air quality degradation and visibility impairment in these pristine areas. This dissertation aims to investigate the reason for those observed increases in aerosol concentrations in Alaska wilderness areas by performing a series of simulation sets with the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). These simulation sets use the same meteorological conditions but change the emission scenarios. The model evaluation analysis showed that WRF-Chem performed well in simulating meteorological conditions over Alaska and the North Pacific under both low and high insolation conditions. Performance skill-scores of the WRF-Chem model in simulating aerosol concentrations for the coastal monitoring sites along the Gulf of Alaska were consistent with state-of-the-science air-quality model performance. During low insolation periods, domestic and international ship emissions were the most important contributors to aerosol concentrations in the coastal regions along the Gulf of Alaska. The increases/decreases in ship emissions led to subsequent increases/decreases in aerosol concentrations in the coastal areas along the Gulf of Alaska during low insolation periods. During high insolation periods, in Interior Alaska, the contributions of local wildfire emissions to aerosol concentrations were notable even during the weak Alaska fire activity scenario. Under the strong Alaska fire activity scenario, local wildfire emissions were the dominant source of aerosols in Interior Alaska. The increases in Alaskan wildfire emissions led to significant increases in aerosol concentrations in Interior Alaska. During both low and high insolation periods, Japanese anthropogenic and Siberian wildfire emissions were not important contributors to total aerosol concentrations in all regions of Alaska. Overall in the wilderness areas along the Gulf of Alaska, the increases in aerosol concentrations observed during low insolation periods stemmed from increases in domestic and international ship emissions in the North Pacific. In contrast, the increases in aerosol concentrations observed at Denali NP during high insolation periods stemmed from increases in Alaskan wildfire emissions.
    • Alaska Shorefast Ice: Interfacing Geophysics With Local Sea Ice Knowledge And Use

      Druckenmiller, Matthew L.; Eicken, Hajo (2011)
      This thesis interfaces geophysical techniques with local and traditional knowledge (LTK) of indigenous ice experts to track and evaluate coastal sea ice conditions over annual and inter-annual timescales. A novel approach is presented for consulting LTK alongside a systematic study of where, when, and how the community of Barrow, Alaska uses the ice cover. The goal of this research is to improve our understanding of and abilities to monitor the processes that govern the state and dynamics of shorefast sea ice in the Chukchi Sea and use of ice by the community. Shorefast ice stability and community strategies for safe hunting provide a framework for data collection and knowledge sharing that reveals how nuanced observations by Inupiat ice experts relate to identifying hazards. In particular, shorefast ice break-out events represent a significant threat to the lives of hunters. Fault tree analysis (FTA) is used to combine local and time-specific observations of ice conditions by both geophysical instruments and local experts, and to evaluate how ice features, atmospheric and oceanic forces, and local to regional processes interact to cause break-out events. Each year, the Barrow community builds trails across shorefast ice for use during the spring whaling season. In collaboration with hunters, a systematic multi-year survey (2007--2011) was performed to map these trails and measure ice thickness along them. Relationships between ice conditions and hunter strategies that guide trail placement and risk assessment are explored. In addition, trail surveys provide a meaningful and consistent approach to monitoring the thickness distribution of shorefast ice, while establishing a baseline for assessing future environmental change and potential impacts to the community. Coastal communities in the region have proven highly adaptive in their ability to safely and successfully hunt from sea ice over the last 30 years as significant changes have been observed in the ice zone north of Alaska. This research further illustrates how Barrow's whaling community copes with year-to-year variability and significant intra-seasonal changes in ice conditions. Hence, arctic communities that have coped with such short-term variability may be more adaptive to future environmental change than communities located in less dynamic environments.
    • Alpine thermal dynamics and associated constraints on the behavior of mountain goats in Southeast Alaska

      Frederick, Jeffrey Hébert; Hundertmark, Kris; Pyare, Sanjay; Brinkman, Todd; White, Kevin (2015-08)
      Alpine Caprinae, including mountain goats (Oreamnos americanus), have been described to be sensitive to temperature changes within their summer range and consequently may be forced to select habitats that allow for the maintenance of a stable core temperature on warm days. Survival may be inhibited if warm ambient temperatures cause mountain goats to reduce time foraging or if too much time is spent on thermoregulatory habitat selection. I investigated mountain goat behavioral activity budgets across alpine temperature gradients in Southeast Alaska using focal animal sampling and scan sampling techniques. I tested the effects of temperature on mountain goat activity and mountain goat elevation. Coupled with the behavioral investigations, I simultaneously monitored elevational temperature gradients using an array of passive thermistors. By monitoring hourly temperatures and deriving near-surface lapse rates, I demonstrate the utility of downscaled, region-specific temperature-elevation profiles for ecological applications rather than making inferences based on broad spatial models. Except in winter, lapse rates within the study area were between -0.3°C 100m⁻¹ and -0.4°C 100m⁻¹, and were not inclusive of the global mean environmental lapse rate (-0.65°C 100m⁻¹). Mountain goats within the study area demonstrated behavioral conservation of their activity budgets by altering their orientation through space and time, rather than incurring thermal and/or nutritional deficits. In addition, the animals took advantage of cooler temperatures at high elevations to bolster thermoneutrality. I highlight the need for behavioral ecology research that links physiological mechanisms and mammalian life history in an effort to predict the fate of a sentinel wildlife species as it copes with a changing environment. Indeed, such indicator species are invaluable to understanding the dynamics of change in ecosystem structure, function, and phenology. Given current warming trends and projections of changing climate regimes being more pronounced at higher latitudes, there is a marked need to better understand thermoregulatory constraints on faunal behavior and the effect of changing landscapes on the distributions and survival of wildlife populations in Alaska.
    • An Analysis Of Using Semi-Permeable Membrane Devices To Assess Persistent Organic Pollutants In Ambient Air Of Alaska

      Wu, Ted Hsin-Yeh; Cahill, Catherine (2006)
      A region of concern for persistent organic pollutants (POPS) contamination is the Arctic, because of POPs' ability to migrate long distances through the atmosphere toward cold regions, condense out of the atmosphere in those region, deposit in sensitive arctic ecosystems and bioaccumulate in Arctic species. Thus, monitoring of POP concentrations in the Arctic is necessary. However, traditional active air monitoring techniques for POPs may not be feasible in the Arctic, because of logistics and cost. While these issues may be overcome using passive air sampling devices, questions arise about the interpretation of the contaminant concentrations detected using the passive air samplers. In this dissertation semi-permeable membrane devices (SPMDs) containing triolein were characterized and evaluated for use in sampling the ambient air of Alaska for three classes of POPS (organochlorines [OCs], polychlorinated biphenyls [PCBs] and polyaromatic hydrocarbons [PAHs]). In addition, a SPMD-based sampling campaign for POPS was conducted simultaneously at five sites in Alaska during a one-year period. The POP concentrations obtained from the SPMDs were examined to determine the spatial and seasonal variability at the locations. POP concentrations detected in SPMDs were influenced by exposure to sunlight, concentrations of particulate-bound contaminants and changes in temperature. PAH concentrations in a SPMD mounted in a sunlight-blocking deployment unit were higher than in a SPMD exposed to sunlight (P = 0.007). PCB concentrations in SPMD exposed to filtered and non-filtered air were significantly different (P < 0.0001). Derived PAH air concentrations measured using SPMD were within a factor of approximately 7 of those obtained from an air sampler in Barrow, Alaska. The field study showed three distinct groups of samples. Barrow was separated from the sub-Arctic samples and a Homer sample (September-December) was distinct from the sub-Arctic samples. The separations suggest different air masses are being sampled by SPMDs. Lower concentrations of total POPs were measured at the coastal sites than the Interior sites.
    • An Interdisciplinary Computational Study Of Magnetosphere-Ionsphere Coupling And Its Visual And Thermal Impact In The Auroral Region

      Styers, John; Newby, Greg (2012)
      A three-dimensional, three-fluid simulation (ions, electrons, and neutrals) was explicitly parallelized, facilitating the study of small-scale magnetospheric-ionospheric (M-I) coupling processes. The model has ionization and recombination, self-consistently (semi-empirically) determined collision frequencies, and a height resolved ionosphere. Inclusion of ion inertial terms in the momentum equation enables the propagation of Alfven waves. Investigation at small scales required large system domains, and thus fast parallel computers. The model was explicitly parallelized---enabling investigations of M-I coupling processes on very small temporal and spatial scales. The generation, reflection, and propagation of Alfven waves is of importance to the understanding of M-1 coupling processes---it is, in fact, the primary means of communication of physical processes in the coupled system. Alfvenic reflections were modeled for two different boundary conditions, and it was shown that the deformation of the current layer was Alfvenic in character. Visualizations of the data obtained appear to be consistent with the visual characteristics of actual discrete aurora in nature. The model reproduces qualitatively, and semi-quantitatively, in a self-consistent manner, some the behaviors of the formation and time-evolution of discrete arcs. These include the narrowness of arcs; electric fields extending parallel outward from the arcs; and fast (plasma) flows in the region of discrete arcs. Large-scale models---due to inevitable limitations of computational resources---need to make large-scale averages of computed properties. In regions of active small-scale structure, significant under-representation of the Joule heating occurs. It has been shown that the under-representation of the Joule heating in the region of active aurora can be as large as a factor of 8. This work includes a computer-based study of a quantitative approximation of this underrepresentation of the Joule heating by global, large-scale models and experimental observations.
    • Analysis and interpretation of volcano deformation in Alaska: Studies from Okmok and Mt. Veniaminof volcanoes

      Fournier, Thomas J.; Freymueller, Jeffrey; Larsen, Jessica; Cervelli, Peter; Christensen, Douglas; McNutt, Stephen (2008-12)
      Four studies focus on the deformation at Okmok Volcano, the Alaska Peninsula and Mt. Veniaminof. The main focus of the thesis is the volcano deformation at Okmok Volcano and Mt. Veniaminof, but also includes an investigation of the tectonic related compression of the Alaska Peninsula. The complete data set of GPS observations at Okmok Volcano are investigated with the Unscented Kalman Filter time series analysis method. The technique is shown to be useful for inverting geodetic data for time dependent non-linear model parameters. The GPS record at Okmok from 2000 to mid 2007 shows distinct inflation pulses which have several months duration. The inflation is interpreted as magma accumulation in a shallow reservoir under the caldera center and approximately 2.5km below sea level. The location determined for the magma reservoir agrees with estimates determined by other geodetic techniques. Smaller deflation signals in the Okmok record appear following the inflation pulses. A degassing model is proposed to explain the deflation. Petrologic observations from lava erupted in 1997 provide an estimate for the volatile content of the magma. The solution model VolatileCalc is used to determine the amount of volatiles in the gas phase. Degassing can explain the deflation, but only under certain circumstances. The magma chamber must have a radius between ~1and 2km and the intruding magma must have less than approximately 500ppm CO2. At Mt. Veniaminof the deformation signal is dominated by compression caused by the convergence of the Pacific and North American Plates. A subduction model is created to account for the site velocities. A network of GPS benchmarks along the Alaska Peninsula is used to infer the amount of coupling along the mega-thrust. A transition from high to low coupling near the Shumagin Islands has important implications for the seismogenic potential of this section of the fault. The Shumagin segment likely ruptures in more frequent smaller magnitude quakes. The tectonic study provides a useful backdrop to examine the volcano deformation at Mt. Veniaminof. After being corrected for tectonic motion the sites velocities indicate inflation at the volcano. The deformation is interpreted as pressurization occurring beneath the volcano associated with eruptive activity in 2005.
    • Analysis of composition and chronology of dome emplacement at Black Peak Volcano, Alaska utilizing aster remote sensing data and field-based studies

      Adleman, Jennifer Nicole (2005-05)
      Black Peak volcano is a 3̃.5km-diameter caldera located on the Alaska Peninsula that formed 4̃,600 years ago in an eruption that excavated>km³ of material. The caldera floor is occupied by at least a dozen overlapping dacitic to andesitic lava domes and flows. Examination of XRF results and observations of the domes in and around the caldera reveals a range of 57-65wt% SiO₂ and variations in amphibole content. Evidence for magma mixing includes vesicular enclaves and geochemical trends that indicate involvement of a more mafic magma into a dacitic reservoir. The purpose of this study is to investigate if, and how, these differences in composition and mineralogy are detectable in satellite emissivity and TIR data (ASTER) and compare the results to ground-based field observations to discern changes in the mineralogical and chemical properties of the domes. This study incorporates the use of decorrelation-stretch image processing techniques and the deconvolution of laboratory emissivity spectra to assess the viability of discriminating variations in the lithologies observed at Black Peak volcano. Compositional results from XRD and electron microprobe analyses are comparable to those obtained through deconvolution processing. Surfaces of <10% amphibole and SiO₂ of 60-65wt% and those that correspond to>1̲0% and <61 wt% SiO₂ are distinguishable in the ASTER data.
    • Analysis Of Methods For Solar Wind Propagation From Lagrangian Point L1 To Earth

      Jensen, Poul F.; Bristow, William; Newman, David; Nielsen, Hans; Otto, Antonius; Smith, Roger (2013)
      The Lagrangian point L1 is situated about 1.5 million kilometers sunwards from Earth and provides a unique orbiting point for satellites, placing them constantly upstream in the solar wind, allowing for prediction of solar wind conditions impacting Earth's magnetosphere. Short-term forecasting of geomagnetic activity requires extrapolation of solar wind data from L1 to Earth (typical propagation time around 1 hour), as does any research in interactions between the solar wind and the magnetosphere during intervals when no Earth-orbiting satellites are in the solar wind. To accurately predict propagation delays it is necessary to take the geometry of incoming solar wind structures into account. Estimating the orientation of solar wind structures currently has to be done using single satellite measurements, which will likely remain the case for another decade or more, making it important to optimize single satellite techniques for solar wind propagation. In this study a comprehensive analysis of 8 different single satellite propagation methods was performed, each involving several variable parameters. 4 of these used electric field calculations and had not previously been tested for solar wind propagation. Large amounts of data were propagated from a satellite near L1 to target satellites near Earth for comparison to measured data, using specific test scores to evaluate relative performance between methods and parameter values. Electric field methods worked well for continuous data but did not predict arrival time of discontinuities (abrupt transitions) as accurately as methods based on magnetic field data, one of which delivered the best results on all accounts. This method had also been found to give best results in a previous study, but optimal parameter values were significantly different with the larger data set used here. Propagating 6,926 discontinuities it was found that on average they arrive about 30 seconds later than predicted (about 1% of the propagation time). Barring a systematic error in velocity data or delay calculations the offset suggests an asymmetry in the geometry of solar wind structures. While this idea is physically plausible it was not unambiguously supported by the data.
    • Analysis Of Model And Observation Data For The Development Of A Public Pm2.5 Air-Quality Advisories Tool (Aquat)

      Tran, Huy Nguyen Quang; Molders, Nicole; Bhatt, Uma; Cahill, Catherine F.; Grell, Georg A.; Kramm, Gerhard (2012)
      An air-quality advisory tool (AQuAT) that combines mobile measurements of particulate matter less than or equal to 2.5mum in diameter (PM2.5) with air-quality simulations performed with the Alaska adapted version of the Community Multiscale Air Quality (CMAQ) model was developed to interpolate PM2.5-measurements into unmonitored neighborhoods in Fairbanks, Alaska. AQuAT was developed as traditional interpolation methods of interpolating the mobile measurements were unsuccessful. Such a spatially differentiated air-quality advisory is highly desired in Fairbanks due to health concerns of PM2.5, and the need to improve the quality of life. The accuracy of AQuAT depends on the accuracy of the air-quality simulations used for its database. Evaluation of these simulations showed that they captured the observed relationships between PM2.5-concentrations and major meteorological fields (e.g., wind-speed, temperature, and surface-inversions) well. Skill scores for simulated PM2.5-concentrations fell in the range of modern models. The AQuAT database can include information on the nonlinear impacts of various emission sources on PM2.5-concentrations. This benefit was illustrated by investigating the impacts of emissions from point sources, uncertified wood-burning devices, and traffic on the distribution of PM 2.5-concentrations in the neighborhoods. Sensitivity studies on the effects of wood-burning device changeouts on the PM2.5-concentrations suggested that the emission inventory should be updated as soon as possible to capture recent changes in the emission situation in response to the changeout program. The performance of AQuAT was evaluated with PM2.5-measurements from mobile and stationary sites, and with simulated PM2.5-concentrations of winter 2010/2011 which were assumed to be "grand-truth" data. These evaluations showed that AQuAT captured the magnitudes and temporal evolutions of the PM 2.5-measurements and the "grand-truth" data well. The inclusion of wind-speed, wind-direction, and temperature in AQuAT did not improve its accuracy. This result may be explained by the fact that the relationships between meteorology and PM2.5-concentrations were already captured by the database. AQuAT allows quick spatial interpolation after the mobile measurements were made and provides error bars. It also allows for any route within the area for which a database of simulated concentrations exists. It was shown that AQuAT can be easily transferred for applications in other regions.