• An analysis of volcanic ash plume movement and dispersion within the North Pacific

      Papp, Kenneth R.; Dean, Kenneson; Sharpton, Virgil; Dehn, Jonathan; Schneider, David (2002-08)
      This study analyzes the movement and dispersion of airborne volcanic ash within the North Pacific region by simulating volcanic plumes from 22 volcanoes using the PUFF ash-tracking model. The model is run hourly using archived wind field data between 1994-2001 and the results are analyzed with statistical and GIS software. Maps and statistics are generated revealing the distribution of simulated airborned ash particles at 6 and 24 hr intervals, constraining the likely direcion and distance a volcanic ash cloud may propagate from a given volcano. The results indicate wind field charactistics during and after an eruption may have a larger effect on volcanic cloud growth rate than the eruption dynamics. Wind field and statistical analyses show North Pacific ash cloud distribution is strongly affected by the intensity, migration, and location of the Polar jet stream and associated cyclones. Although often used operationally during an eruption crisis, the PUFF model can also be used as an effective research tool and provide airborne ash hazard mitigation for towns, airports, and air traffic within the North Pacific region.
    • Analyzing tree distribution and abundance in Yukon-Charley Rivers National Preserve: developing geostatistical Bayesian models with count data

      Winder, Samantha; Short, Margaret; Roland, Carl; Goddard, Scott; McIntyre, Julie (2018-05)
      Species distribution models (SDMs) describe the relationship between where a species occurs and underlying environmental conditions. For this project, I created SDMs for the five tree species that occur in Yukon-Charley Rivers National Preserve (YUCH) in order to gain insight into which environmental covariates are important for each species, and what effect each environmental condition has on that species' expected occurrence or abundance. I discuss some of the issues involved in creating SDMs, including whether or not to incorporate spatially explicit error terms, and if so, how to do so with generalized linear models (GLMs, which have discrete responses). I ran a total of 10 distinct geostatistical SDMs using Markov Chain Monte Carlo (Bayesian methods), and discuss the results here. I also compare these results from YUCH with results from a similar analysis conducted in Denali National Park and Preserve (DNPP).
    • Anisotropy in the Alaska subduction zone: shear-wave splitting observations from local and teleseismic earthquakes

      Richards, Cole; Tape, Carl; West, Michael; Freymueller, Jeffrey (2020-05)
      Shear-wave splitting observations can provide insight to mantle flow due to the link between the deformation of mantle rocks and their direction dependent seismic wave velocities. We identify shear-wave anisotropy in the Cook Inlet segment of the Alaska subduction zone by analyzing splitting parameters of S phases from local intraslab earthquakes between 50 and 200 km depths and SKS waves from teleseismic events. These earthquakes were recorded from 2015-2017 (local S) and 2007-2017 (SKS) by stations from SALMON (Southern Alaska Lithosphere and Mantle Observation Network), TA (EarthScope Transportable Array), MOOS (Multidisciplinary Observations Of Subduction), AVO (Alaska Volcano Observatory), and the permanent network. Automatic phase picking (dbshear) of 12095 local earthquakes (Ml ≥ 1.5) recorded at 84 stations yielded 678 high-quality splitting measurements (filtered 0.2-1 Hz). Teleseismic SKS phases recorded at 112 stations with 26,143 event-station pairs resulted in 360 high-quality SKS splitting measurements (filtered 0.02-1 Hz and 0.01-1 Hz). Measurements for both datasets were made using the SC91 minimum eigenvalue method with software package MFAST. We compare local S and SKS splitting patterns both from previous studies and our own analysis and find that they are most similar in the far forearc, at the Kenai Peninsula, below which there is no mantle wedge. Anisotropy in the subducting Pacific lithosphere and subslab asthenosphere is likely here as both S and SKS display plate convergence fast directions and SKS measurements exhibit delay times too long (∼2 s) to be explained solely by lithospheric anisotropy. Large splitting delay times (∼0.5 s) for local measurements that mainly sample slab further indicate that the Pacific slab lithosphere contains significant anisotropy. We also observe anisotropy in the mantle wedge indicated by an increase in delay time as focal depth increases for stations with ray paths dominantly sampling wedge. These measurements display trench-perpendicular and plate convergence fast directions consistent with 2D corner flow in the mantle wedge. Both datasets show trench-parallel splitting directions in select areas of the arc/forearc that overlie parts of the mantle wedge and nose. B-type olivine in the mantle nose, subslab asthenospheric flow, flow around the slab edge, and anisotropy in the Pacific lithosphere all could be invoked to explain this pattern. While we are unable to distill the anisotropy to a single responsible structure, the sharp transition in the local S data splitting pattern from trench-perpendicular in the backarc to trench-parallel across the arc suggests B-type olivine in the mantle nose. For an overall model, we favor 2D corner flow of A-type olivine in the mantle wedge induced by downdip motion of the slab, B-type olivine in the nose, and plate convergence parallel anisotropy in the subslab asthenosphere and subducting Pacific lithosphere to explain the observed splitting patterns. It is clear that the subducting slab's structure and motion are the dominant influence on anisotropy and mantle flow regimes here. The differences in local S and SKS splitting results motivate further study on frequency dependence of splitting measurements and emphasize the need for a better understanding of which earth structures are responsible for the observed splitting patterns globally. This study constitutes the first comprehensive local splitting study in Alaska and refutes the common interpretation of along arc flow in the mantle wedge proposed by many previous splitting studies in Alaska.
    • An anomalous process of fast ionization of a barium shaped charge release

      Xin, Wei; Swift, D. W.; Smith, R. W.; Kan, J. R. (1987-12)
      Fast ionization in excess of the photo-ionization rate appears to only occur when the barium shaped charge release is along the magnetic field direction. This thesis investigates the hypothesis that rapid ionization is caused by electrons heated in an ion cyclotron wave excited by the field-aligned streaming of barium ions through the ambient ionospheric plasma. The seed population of barium ions is assumed to be due to photo-ionization. The number density of barium ions due to photo-ionization is calculated. The plasma dispersion relation is derived based on the assumption of collisionless plasma. The excitation of barium ion cyclotron waves due to the interpenetrating of barium ions through the ambient plasma is investigated. It is proposed that the electrons are heated by the Doppler shifted waves via Landau damping. The Doppler shift is caused by an ambipolar electric field generated by the finite divergence of the injected barium neutrals.
    • Applicability of synthetic aperture radar for investigating river breakup on the Kuparuk River, Northern Alaska

      Floyd, Angelica L. (2012-12)
      A combined use of remote sensing techniques and field measurements is a pragmatic approach to study Arctic hydrology, given the vastness, complexity, and logistical challenges posed by most Arctic watersheds. This study investigates the use of synthetic aperture radar (SAR) to define spring breakup of the Kuparuk River on the North Slope of Alaska. A time series (years 2001-2010) of SAR images was assembled at the river mouth on the Arctic Coastal Plain. A statistical analysis was used and was limited to three variables: image brightness, variance in brightness over the river length, and a rank order analysis accomplished by segmenting the river and ranking segments in order of relative brightness. Variance was the only reliable breakup indicator of the three tested. A shorter one year temporal stack was assembled at the river's headwaters for a visual interpretation, which had limited success. Results from both analyses were calibrated with in-situ stream gauge data. River ice breakup is a highly complex process which may be defined differently by the remote sensing community and hydrologists, due to the sensitive nature of SAR, which may indicate surficial changes on the river before any discharge is recorded.
    • An application of an integrated population model: estimating population size of the Fortymile caribou herd using limited data

      Inokuma, Megumi; Short, Margaret; Barry, Ron; Goddard, Scott (2017-05)
      An Integrated Population Model (IPM) was employed to estimate the population size of the Fortymile Caribou herd (FCH), utilizing multiple types of biological data. Current population size estimates of the FCH are made by the Alaska Department of Fish and Game (ADF&G) using an aerial photo census technique. Taking aerial photos for the counts requires certain environmental conditions, such as the existence of swarms of mosquitoes that drive the majority of caribou to wide open spaces, as well as favorable weather conditions, which allow low-altitude flying in mid-June. These conditions have not been met in recent years so there is no count estimate for those years. IPMs are considered as alternative methods to estimate a population size. IPMs contain three components: a stochastic component that explains the relationship between biological information and population size; demographic models that derive parameters from independently conducted surveys; and a link between IPM estimates and observed-count estimates. In this paper, we combine census count data, parturition data, calf and female adults survival data, and sex composition data, all of which were collected by ADF&G between 1990 and 2016. During this time period, there were 13 years - including two five-consecutive-year periods - for which no photo census count estimates were available. We estimate the missing counts and the associated uncertainty using a Bayesian IPM. Our case study shows that IPMs are capable of estimating a population size for years with missing count data when we have other biological data. We suggest that sensitivity analyses be done to learn the relationship between amount of data and the accuracy of the estimates.
    • An application of Bayesian variable selection to international economic data

      Tian, Xiang; Goddard, Scott; Barry, Ron; Short, Margaret; McIntyre, Julie (2017-06)
      GDP plays an important role in people's lives. For example, when GDP increases, the unemployment rate will frequently decrease. In this project, we will use four different Bayesian variable selection methods to verify economic theory regarding important predictors to GDP. The four methods are: g-prior variable selection with credible intervals, local empirical Bayes with credible intervals, variable selection by indicator function, and hyper-g prior variable selection. Also, we will use four measures to compare the results of the various Bayesian variable selection methods: AIC, BIC, Adjusted-R squared and cross-validation.
    • The application of cavity ring-down spectroscopy to determine nitrate radical concentrations in the atmosphere

      Dick, Eric Michael (2002-05)
      The nitrate radical, NO₃, is a potent atmospheric oxidant. Current NO₃ measurement methods average NO₃ concentrations over several kilometer pathlengths. Recent modeling studies predict that NO₃'s distribution is vertically inhomogenous, causing previous NO₃ observations to not be representative of its atmospheric chemistry. In-situ measurements offer a test of these modeling predictions and a better understanding of NO₃ chemistry. In this thesis, we describe construction of an instrument capable of detecting NO₃ in-situ. This sensor is based upon cavity ring-down spectroscopy. Our initial work demonstrated that CRDS could sensitively detect NO₃. We then built and tested a field prototype during June 2001, successfully detecting NO₃ in the field. CRDS observations were compared to path averaged NO₃ observations. Similar time behavior of both signals indicated that the techniques were observing NO₃. A consistent difference in signal levels indicated that the two techniques were not sampling a homogeneous air mass.
    • Application of environmental DNA-based occurrence data in modeling wood frog (Rana sylvatica) distribution in Interior Alaska

      Spangler, Mark A.; López, J. Andrés; Huettmann, Falk (2017)
      Knowledge of wood frog distribution in Alaska is incomplete due to insufficient baseline occurrence data. A short season of activity and difficult access to remote areas restrict implementation of consistent monitoring efforts. Detecting the presence of species in aquatic landscapes using environmental DNA (eDNA) assays is increasingly applied as a monitoring method in wildlife surveys. However, uncertainties regarding the technique’s sensitivity to environmental variables and human error have thus far prevented its widespread adoption in studies of species distribution. Predictive models built on machine learning algorithms can help provide precise descriptions of species distribution using eDNA occurrence data, but they will require ground-truthing efforts to confirm accuracy in under-sampled landscapes. Here we assess the ability of wood frog eDNA occurrence data to inform species distribution models under five criteria for data use. We sampled 60 wetlands for eDNA in the Fairbanks North Star Borough during summer 2015. Samples were processed using a species-specific quantitative PCR assay. Wood frog presence at each site was inferred from the PCR results. This data was used to construct four different wood frog distribution models. From each model we produced a predictive distribution map encompassing the Fairbanks North Star Borough. We assess the performance of each model using available wood frog presence data. Our highest performing model achieves moderate predictive accuracy (Area Under the Curve = 0.74). Weak signals in eDNA occurrence data are important in revealing species presence at low abundance, but strict lab hygiene, quality control practices, and detailed metadata are needed to retain confidence in the results. We show a powerful new way to study wood frog distribution by combining eDNA occurrence data with machine learning techniques. Wider implementation of eDNA surveys and increased availability of high resolution GIS data will help to refine these models.
    • The application of synthesized transition metal compounds as paint additives for the preparation of a self-decontaminating coating

      Giles, Spencer Lawrence; Rasley, Brian; Green, Thomas; Wynne, James (2011-08)
      The synthesis of transition metal compounds has been performed to create reactive additives that can be incorporated into commercial grade paints for the purpose of developing a continuous self-decontaminating coating. The coatings were designed to allow for the decontamination of persistent chemical warfare agents: sulfur mustard and organophosphate nerve agents. Since the persistence of these chemicals on surfaces due to their low volatility and long hydrolysis half lives could possibly lead to involuntary exposures, a continuous self-decontaminating coating would provide an alternative approach to eliminate residual chemical warfare agents without further treatment to the painted surface. The synthesized additives include metal oxide nanoparticles,polyoxometallates,andmetalfunctionalizedcyclodextrins. Coatings were formulated with 1% w/w synthesized additives, and tested for their ability to decontaminate chemical warfare agent simulants of sulfur mustard and organophosphate nerve agents. The Dawson structure polyoxometallate α2- K8P2W17O61(Ni2+ ∙OH2)∙17H2O coatings exhibited percent reductions of three of the four simulants above 30% with a high of 53% reduction of Malathion in 24 hours. The nickel functionalized gamma cyclodextrin coatings exhibited percent reductions for all simulants above 28% with a high of 61% reduction of Malathion in 24 hours. Overall, coatings enhanced with additives were tested and produced painted surfaces capable of decontaminating chemical warfare agent simulants.
    • Applications Of A Time-Dependent Polar Ionosphere Model For Radio Modification Experiments

      Fallen, Christopher Thomas; Watkins, Brenton (2010)
      A time-dependent self-consistent ionosphere model (SLIM) has been developed to study the response of the polar ionosphere to radio modification experiments, similar to those conducted at the High-Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska. SCIM solves the ion continuity and momentum equations, coupled with average electron and ion gas energy equations; it is validated by reproducing the diurnal variation of the daytime ionosphere critical frequency, as measured with an ionosonde. Powerful high-frequency (HF) electromagnetic waves can drive naturally occurring electrostatic plasma waves, enhancing the ionospheric reflectivity to ultra-high frequency (UHF) radar near the HF-interaction region as well as heating the electron gas. Measurements made during active experiments are compared with model calculations to clarify fundamental altitude-dependent physical processes governing the vertical composition and temperature of the polar ionosphere. The modular UHF ionosphere radar (MUIR), co-located with HAARP, measured HF-enhanced ion-line (HFIL) reflection height and observed that it ascended above its original altitude after the ionosphere had been HF-heated for several minutes. The HFIL ascent is found to follow from HF-induced depletion of plasma surrounding the F-region peak density layer, due to temperature-enhanced transport of atomic oxygen ions along the geomagnetic field line. The lower F-region and topside ionosphere also respond to HF heating. Model results show that electron temperature increases will lead to suppression of molecular ion recombination rates in the lower F region and enhancements of ambipolar diffusion in the topside ionosphere, resulting in a net enhancement of slant total electron content (TEC); these results have been confirmed by experiment. Additional evidence for the model-predicted topside ionosphere density enhancements via ambipolar diffusion is provided by in-situ measurements of ion density and vertical velocity over HAARP made by a Defense Meteorological Satellite Program (DMSP) satellite.
    • Applying a model of orographic precipitation to improve mass balance modeling of the Juneau Icefield

      Roth, Aurora; Hock, Regine; Truffer, Martin; Aschwanden, Andy (2016-12)
      Mass loss from glaciers in Southeast Alaska is expected to alter downstream environmental conditions such as streamflow patterns, riverine and coastal ecological systems, and ocean properties. To investigate these potential changes under future climate scenarios, accurate climate data are needed to drive glacier mass balance models. However, assessing and modeling precipitation in mountainous regions remains a major challenge in glacier mass balance modeling. We have used a linear theory of orographic precipitation model (LT model) to downscale precipitation from both the Weather Research and Forecasting (WRF) model and the European Centre for Medium-RangeWeather Forecasts interim reanalysis (ERA-Interim) to the Juneau Icefield, one of the largest icefields in North America (4149 km2), over the period 1979--2013. The LT model is physically-based, combining airflow dynamics and simple cloud microphysics to simulate precipitation in complex terrain. Cloud microphysics is parameterized as a function of user-defined snow and rain fall speeds which are then used to calculate the cloud time delay, t, at every time step. We established a model reference run using literature values of snow fall speed and rain fall speed. The model was run using a 1 km digital elevation model and 6 hour timesteps. Due to a lack of precipitation observations, we validated the model with point net accumulation observations along an 8.5 km transect on Taku glacier, one of the largest and best-studied outlet glaciers of the icefield. The observations occurred in late July of 1998, 2004, 2005, 2010, and 2011. We extracted the snow portion from the modeled precipitation and accounted for melt using a temperature-index model prior to comparing results to the observations. The latter was necessary since the observations were taken when substantial melt of the winter snow cover had occurred. The results of the reference run show reasonable agreement with the available glaciological observations (r2 = 0.89). We assessed the LT model results in terms of the icefield-wide average winter (October-March) precipitation amount and its spatial pattern for the 1979-2013 time period. To express the latter we calculated a precipitation index map where each grid cell of average winter precipitation was divided by the icefield-wide spatial mean. The downscaled precipitation pattern produced by the LT model is consistent with the expected orographic precipitation pattern with substantially reduced precipitation on the eastern lee-side portion of the icefield, a pattern that is absent in the coarse resolution WRF and ERA-Interim precipitation fields. To investigate the robustness of the LT model results, we performed a series of sensitivity experiments varying the LT model parameters of snow fall speed and rain fall speed, as well as the horizontal resolution of the underlying grid, and the climate input data. The precipitation pattern produced by the LT model was stable regardless of the parameter combination, horizontal resolution, and climate input data, but the precipitation amount varied strongly with these factors. For the range of snow fall speeds tested and holding all other parameters constant, the average winter precipitation spatial mean varied from 2.5 m to 4.4 m. We were unable to constrain the precipitation amount due to the scarcity of validation data. However, given the stability of the winter precipitation pattern produced by the LT model, we suggest a winter precipitation index map calculated from the LT model reference run results be used in combination with a distributed mass balance model for future mass balance modeling studies of the Juneau Icefield. More observations of total precipitation are needed to further validate the precipitation pattern of the LT model results, constrain the model parameters, and improve the estimation of total precipitation amounts by the LT model. We suggest three locations for potential weather stations that would be most beneficial for validating LT model results. The LT model could be applied to other regions in Alaska and elsewhere with strong orographic effects for improved glacier mass balance modeling and/or hydrological modeling.
    • Applying a social-ecological systems approach to human-bear encounters across the Pacific Rim: advancing resilient human-wildlife management strategies

      Jochum, Kim A.; Alessa, Lilian; Hundertmark, Kris J.; Brinkman, Todd J.; Kliskey, Andrew D. (2014-08)
      Wildlife management is challenged with addressing human resource needs while simultaneously conserving wildlife populations. Conflicts between humans and wildlife have increased across Northern countries with the expansion of human communities and environmental changes. Lack of information exists about reasons for such occurrences. This study explores adaptive capacity and resilience in coupled human-wildlife systems through the analysis of social and ecological factors contributing to perceptions of negative and positive human-bear (Ursus spp.) encounters. I first developed a theory to evaluate human perceptions and behaviors during human-wildlife encounters. Secondly I adopted an interdisciplinary framework to analyze human-bear encounters in urbanizing regions of south Sakhalin Island, Russian Far-East, and southcentral Alaska, USA. These case studies facilitate an analysis of perception development across spatial and social scales while incorporating approaches of both social and ecological sciences. Hunting, tourism and overall anthropogenic impacts are central to bear management, whereas cultural and social interests are perceived to not be considered in bear management decision-making across study regions. In Alaska, political interests are prevalent in bear management, whereas on Sakhalin, economic interests, including illegal animal trade and poaching prevail. Across study regions the perception of an encounter with a bear was dependent on the socio-economic situation of the individual having the encounter. The higher a person's socio-economic status was, the higher was their probability to perceive bear encounters as positive. Further, spatial and social scales across which perceptions vary are identified. Scales include urban-non-urban areas, wildland-urban interfaces, and a recreation-subsistence interest divide. Outside of urban areas, people's interests in recreation versus subsistence affect their perceptions toward bear encounters. Subsistence collectors of fish, game or plants are more likely to have negative encounters. Within urban areas, increased experience with encountering bears and length of residency are associated with positive encounters, whereas closeness to residences while not in sheltered environments increases negative encounters. These findings constitute spatial and social barriers and benefits to individualistic perception formation during human-bear encounters. Their identification advances resilience in researched human-wildlife systems and helps us to understand the adaptive capacities within these communities. The successful spatially-explicit integration of social and ecological variables promotes the opportunities for integrating human dimensions in wildlife management.
    • Architectural analysis and fold geometry of syntectonic fluvial conglomerate in the Nanushuk Formation, Brooks Range foothills, Alaska

      Finzel, Emily Suzanne (2004-12)
      The fluvial style and syntectonic deposition of conglomerate in the upper part of the Nanushuk Formation are resolved using facies architectural analysis and structural geometry. Along the Kanayut River in the northern foothills of the Brooks Range, Alaska, fluvial conglomerate is exposed as benches on the north and south flanks of the Arc Mountain anticline. Photo mosaics of each bench on the north side, along with thirty-three detailed measured sections, were used to evaluate facies architecture. Eight lithofacies were described that characterize six facies associations including longitudinal and transverse gravel bars, diffuse gravel sheets, sediment gravity flow deposits, crevasse splay and floodplain deposits, and scour fills of a gravel-bed braided river. Strata on the south limb of the anticline show characteristics of syndeformational deposition during the growth of the south limb of the Arc Mountain anticline. These structural data provide new evidence for syndepositional contractional deformation during the mid-Cretaceous at this locality in the northern foothills of the Brooks Range. These results provide clues to the character and extent of potential reservoir rocks from the Nanushuk Group that are present in the subsurface of the National Petroleum Reserve in Alaska, which is important for continued recovery of natural resources on the North Slope.
    • Arctic Alaskan Shrub Growth, Distribution, And Relationships To Landscape Processes And Climate During The 20Th Century

      Tape, Ken D.; Ruess, Roger; Welker, Jeffrey; Chapin, F. S. III; Sturm, Matthew; Walker, D. A. (2011)
      The primary change underway in the tundra of Arctic Alaska is the increase in air temperature and expansion of deciduous shrubs since 1980. I explored relationships between shrub expansion and relevant ecosystem properties such as climate, soil characteristics, erosion, and herbivory. Alnus viridis ssp. fruticosa (Siberian alder) shrubs located along streams, rock outcrops, or other features with active disturbance regimes showed a positive correlation between growth ring widths and March through July air temperature. Climate-growth relationships were much weaker for alder in adjacent tussock tundra. Additionally, tussock tundra sites had different vegetation composition, shallower thaw, lower mean annual ground temperature, lower mean growing season temperature, higher soil moisture, more carbon in mineral soil, and higher C:N values in shrub leaves than nearby non-tussock alder. Growth rings and site characteristics imply that preexisting soil conditions predispose alder shrubs growing in non-tussock tundra to respond rapidly to warming. Analysis of temporal series of aerial photography from 1950 and 2000 and of Landsat imagery from 1986 and 2009 showed an increase in percent cover of shrubs, primarily in riparian areas. This increase in shrubs is contemporaneous with a decline in peak discharge events from the Kuparuk River and a lengthening of the growing season since 1980, both of which may have caused the decline in sediment deposition observed in 3 of 4 lake sediment cores dated with lead and cesium isotopes. Both alder shrub growth and erosion are particularly sensitive to runoff dynamics during the snowmelt and green-up period, and these dynamics are affected by spring temperatures. Ptarmigan, moose, and hares forage heavily on shrubs protruding above the deepening snow during the late-winter, and selective browsing on willow vs. alder is likely influencing shrub community composition. The increase in shrubs during the 20th century may represent additional habitat for these herbivores, and herbivore-mediated changes in shrub architecture may have important implications for how shrubs trap snow and ultimately affect surface energy balance. Evidence from this thesis indicates shrub growth and cover have increased in response to persistent warming, particularly in areas where the organic layer is thinner and active layer deeper.
    • Arctic fox winter movement and diet in relation to industrial development on Alaska's North Slope

      Lehner, Neil S.; Person, Brian; Kielland, Knut; O'Brien, Diane; Hunter, Christine (2012-12)
      I examined winter movement and diet of Arctic foxes (Vulpes lagopus) in the Prudhoe Bay oilfields and an adjacent undeveloped area (National Petroleum Reserve-Alaska (NPR-A)). Movement metrics were compared between these areas using data from satellite collars. Daily travel rate was approximately 5 times greater in the undeveloped area than in Prudhoe Bay. Four adult foxes collared in NPR-A used the sea ice for extensive time periods. One of these foxes traveled 338 km in three days while another traveled to Banks Island (Northwest Territories, Canada), over 1050 km from its capture location. Prudhoe Bay foxes did not make these long distance movements and remained near their summer capture location throughout winter. I used stable isotope analysis and a mixing model (SIAR) to estimate the contribution of marine, terrestrial, and anthropogenic foods to fox diet. Based on muscle tissue, the average contribution of anthropogenic foods to Prudhoe Bay fox diet was more that 50%. Marine foods were utilized in NPR-A, but not in Prudhoe Bay. Results demonstrate that anthropogenic foods are heavily utilized by foxes that overwinter in the oilfields and this food source is likely responsible for reduced winter movements of Prudhoe Bay foxes. Therefore, industrial development strongly affects winter movement and diet of foxes.
    • Arctic landscape dynamics: modern processes and pleistocene legacies

      Farquharson, Louise M.; Mann, Daniel; Romanovsky, Vladimir; Grosse, Guido; Jones, Benjamin M.; Swanson, David (2017-12)
      The Arctic Cryosphere (AC) is sensitive to rapid climate changes. The response of glaciers, sea ice, and permafrost-influenced landscapes to warming is complicated by polar amplification of global climate change which is caused by the presence of thresholds in the physics of energy exchange occurring around the freezing point of water. To better understand how the AC has and will respond to warming climate, we need to understand landscape processes that are operating and interacting across a wide range of spatial and temporal scales. This dissertation presents three studies from Arctic Alaska that use a combination of field surveys, sedimentology, geochronology and remote sensing to explore various AC responses to climate change in the distant and recent past. The following questions are addressed in this dissertation: 1) How does the AC respond to large scale fluctuations in climate on Pleistocene glacial-interglacial time scales? 2) How do legacy effects relating to Pleistocene landscape dynamics inform us about the vulnerability of modern land systems to current climate warming? and 3) How are coastal systems influenced by permafrost and buffered from wave energy by seasonal sea ice currently responding to ongoing climate change? Chapter 2 uses sedimentology and geochronology to document the extent and timing of ice-sheet glaciation in the Arctic Basin during the penultimate interglacial period. Chapter 3 uses a combination of surficial geology mapping and remote sensing to explore the distribution and vulnerability of modern day landscapes on the North Slope of Alaska to thermokarst caused by rapid warming. Chapter 4 uses high spatial and temporal resolution remote sensing data and field surveys to show how sea ice decline is causing AC coastlines to become more geomorphologically dynamic. Together the results of this research show that the AC is a highly dynamic system that can respond to climate warming in complex and non-linear ways. Chapter 2 provides terrestrial evidence that ice-sheet glaciation occurred offshore in the Arctic Ocean in the later stages of the last interglacial period at a time when lower latitude sections of the Laurentide and Cordilleran were in retreat. These findings have important implications for how Arctic ice sheets respond to increased moisture availability caused by sea ice decline and atmospheric warming. This study also provides a new approach to reconstructing and establishing an absolute chronology for periods of Arctic Ocean glaciation during the mid- to late-Pleistocene. Chapter 3 illustrates how Pleistocene-legacy effects exert important influences over the vulnerability of Arctic lowlands to climate warming. Striking differences are revealed in Holocene thermokarst activity between different surficial geology units. During the Holocene, regions of marine silts have been the most susceptible to thermokarst, while regions of ice-poor aeolian sand have seen the least thermokarst activity. In future decades, areas of ice-rich aeolian silt will be most vulnerable to rapid warming because these areas contain large amounts of ground ice that have so far undergone little thermokarst development during the Holocene. Findings from this study have important implications for understanding future landscape evolution and carbon cycling in the Arctic. Chapter 4 shows that permafrost coastlines in the Kotzebue Sound region are already responding to ongoing climate change. Remote sensing data demonstrates that declines in the extent and timing of sea ice are causing an increasingly dynamic coastal system. Rates of change along the coast are more dynamic now than at any time during the past 64 years, and these geomorphic responses to sea ice decline are non-linear. Furthermore, future coastal change will not necessarily be characterized by higher erosion rates, because accretion rates are simultaneously rising. In general, the research described in this dissertation illustrates that the future response of AC components to ongoing climate change will be complex and nonlinear. These results serve to emphasize the value of using past responses of the AC to better understand its possible future trajectories. They also highlight the importance of taking into account a wide variety of processes operating across a wide range of spatial and temporal scales to refine future projected changes.
    • Arctic sea ice trafficability: new strategies for a changing icescape

      Dammann, Dyre Oliver; Eicken, Hajo; Mahoney, Andrew R.; Meyer, Franz J.; Bhatt, Uma S.; Meek, Chanda L. (2017-08)
      Sea ice is an important part of the Arctic social-environmental system, in part because it provides a platform for human transportation and for marine flora and fauna that use the ice as a habitat. Sea ice loss projected for coming decades is expected to change ice conditions throughout the Arctic, but little is known about the nature and extent of anticipated changes and in particular potential implications for over-ice travel and ice use as a platform. This question has been addressed here through an extensive effort to link sea ice use and key geophysical properties of sea ice, drawing upon extensive field surveys around on-ice operations and local and Indigenous knowledge for the widely different ice uses and ice regimes of Utqiaġvik, Kotzebue, and Nome, Alaska. A set of nine parameters that constrain landfast sea ice use has been derived, including spatial extent, stability, and timing and persistence of landfast ice. This work lays the foundation for a framework to assess and monitor key ice-parameters relevant in the context of ice-use feasibility, safety, and efficiency, drawing on different remote-sensing techniques. The framework outlines the steps necessary to further evaluate relevant parameters in the context of user objectives and key stakeholder needs for a given ice regime and ice use scenario. I have utilized this framework in case studies for three different ice regimes, where I find uses to be constrained by ice thickness, roughness, and fracture potential and develop assessment strategies with accuracy at the relevant spatial scales. In response to the widely reported importance of high-confidence ice thickness measurements, I have developed a new strategy to estimate appropriate thickness compensation factors. Compensation factors have the potential to reduce risk of misrepresenting areas of thin ice when using point-based in-situ assessment methods along a particular route. This approach was tested on an ice road near Kotzebue, Alaska, where substantial thickness variability results in the need to raise thickness thresholds by 50%. If sea ice is thick enough for safe travel, then the efficiency of travel is relevant and is influenced by the roughness of the ice surface. Here, I develop a technique to derive trafficability measures from ice roughness using polarimetric and interferometric synthetic aperture radar (SAR). Validated using Structure-from-Motion analysis of imagery obtained from an unmanned aerial system near Utqiaġvik, Alaska, I demonstrate the ability of these SAR techniques to map both topography and roughness with potential to guide trail construction efforts towards more trafficable ice. Even when the ice is sufficiently thick to ensure safe travel, potential for fracturing can be a serious hazard through the ability of cracks to compromise load-bearing capacity. Therefore, I have created a state-of-the-art technique using interferometric SAR to assess ice stability with capability of assessing internal ice stress and potential for failure. In an analysis of ice deformation and potential hazards for the Northstar Island ice road near Prudhoe Bay on Alaska's North Slope I have identified a zone of high relative fracture intensity potential that conformed with road inspections and hazard assessments by the operator. Through this work I have investigated the intersection between ice use and geophysics, demonstrating that quantitative evaluation of a given region in the ice use assessment framework developed here can aid in tactical routing of ice trails and roads as well as help inform long-term strategic decision-making regarding the future of Arctic operations on or near sea ice.