Now showing items 21-40 of 6726

    • Understanding earthquakes by the tsunami waves they cause

      Palmer, Noah; Rybkin, Alexei; Pelinovsky, Efim (2023-04-06)
    • UAF Aero Club: Design-Build-Fly 2022-2023

      VanderHart, Micah; Thomas, Seth; Lambries, Casey; Hoover, Ethan (2023-04-06)
    • Modeling Bud Growth of Peony, Paeonia lactiflora

      Martin, Luke; Holloway, Patricia (2023-04-06)
    • Geochemical Weathering Variability in High Latitude Watersheds

      Jenckes, Jordan (Wiley, 2023)
      High latitude regions across the globe are undergoing severe modifications due to changing climate. A high latitude region of concern is the Gulf of Alaska (GoA) where these changes in hydroclimate undoubtedly effect the hydrogeochemistry of freshwater discharging to the nearshore ecosystems of the region. To fill the knowledge gap of our understanding of freshwater stream geochemistry with the GoA, we compile stream water chemistry data from 162 stream sites across the region. With an inverse model we estimate fractional contributions to solute fluxes from weathering of silicate, carbonate, and sulfide minerals, and precipitation. We asses weathering rates across the region and compare against global river yields. Median fractional contribution of carbonate weathering to total weathering products is 78% across all stream sites, however, there are several streams where silicate weathering is a dominant source of solutes. Weathering by sulfuric acid is elevated in glacierized watersheds. Finally, cation weathering rates are lower in GoA streams compared to the world’s largest rivers, however, weathering rates are similar when compared to a global dataset of glacier fed streams. Due to the climate sensitivity of chemical weathering, we expect future changes to the hydrogeochemistry of river water flux to nearshore ecosystems. We suggest that hydrologic changes driven by glacier ice loss and increased precipitation will alter river water quality and chemical weathering regimes such that silicate weathering may become a more important source of solutes and sulfide oxidation may decrease. This contribution provides a platform to build from for future investigations into changes to stream water chemistry in the region and other high latitude watersheds.
    • Alaska Earthquake Center Quarterly Technical Report January-March 2023

      Ruppert, Natalia (2023-04-26)
      This series of technical quarterly reports from the Alaska Earthquake Center (AEC) includes detailed summaries and updates on Alaska seismicity, the AEC seismic network and stations, field work, our social media presence, and lists publications and presentations by AEC staff. Multiple AEC staff members contribute to this report. It is issued in the following month after the completion of each quarter Q1: January-March, Q2: April-June, Q3: July-September, and Q4: October-December. The first report was published for January-March, 2021.
    • Drone-based Computer Vision-Enabled Vehicle Dynamic Mobility and Safety Performance Monitoring

      Zhang, Guohui; Yuan, Runze; Prevedouros, Panos; Ma, Tianwei (2023-01-30)
      This report documents the research activities to develop a drone-based computer vision-enabled vehicle dynamic safety performance monitoring in Rural, Isolated, Tribal, or Indigenous (RITI) communities. The acquisition of traffic system information, especially the vehicle speed and trajectory information, is of great significance to the study of the characteristics and management of the traffic system in RITI communities. The traditional method of relying on video analysis to obtain vehicle number and trajectory information has its application scenarios, but the common video source is often a camera fixed on a roadside device. In the videos obtained in this way, vehicles are likely to occlude each other, which seriously affects the accuracy of vehicle detection and the estimation of speed. Although there are methods to obtain high-view road video by means of aircraft and satellites, the corresponding cost will be high. Therefore, considering that drones can obtain high-definition video at a higher viewing angle, and the cost is relatively low, we decided to use drones to obtain road videos to complete vehicle detection. In order to overcome the shortcomings of traditional object detection methods when facing a large number of targets and complex scenes of RITI communities, our proposed method uses convolutional neural network (CNN) technology. We modified the YOLO v3 network structure and used a vehicle data set captured by drones for transfer learning, and finally trained a network that can detect and classify vehicles in videos captured by drones. A self-calibrated road boundary extraction method based on image sequences was used to extract road boundaries and filter vehicles to improve the detection accuracy of cars on the road. Using the results of neural network detection as input, we use video-based object tracking to complete the extraction of vehicle trajectory information for traffic safety improvements. Finally, the number of vehicles, speed and trajectory information of vehicles were calculated, and the average speed and density of the traffic flow were estimated on this basis. By analyzing the acquiesced data, we can estimate the traffic condition of the monitored area to predict possible crashes on the highways.
    • Population characteristics of lake trout in Walker Lake, Gates of the Arctic National Park and Preserve, Alaska

      Adams, Francis Jeffrey (1990-05)
      The population of lake trout in Walker Lake, southern Brooks Range, was investigated during summers. 1987 and 1988. Adults were most abundant at stream mouths after ice-out. Juveniles were most abundant in pelagic areas. Fingerlings preferred stream mouths. Ages ranged from 5 to 26 years. Lengths ranged from 203 to 924 mm; weights from 83 to 8,500 g. Both sexes had similar condition and matured at age 12. Fecundity increased with length and age. Females spawn every other year. Comparisons of growth curves and fecundity- at-length curves among populations in various Alaskan lakes suggested that lake trout in Walker Lake have not experienced heavy exploitation. The lake trout population in Walker Lake should be monitored in the future through angler surveys and selected studies of life history.

      Ban, Xuegang (Jeff); Abramson, Daniel; Zhang, Yiran; Lukins, Sarah; Goodrich, Kevin; Mirante, Andrea; Lambert, Rachel; Yankey, Mykala (2023-02)
      Transportation and traffic safety is a primary concern within Rural, Isolated, Tribal and Indigenous (RITI) communities in Washington State. Emerging technologies such as connected and autonomous vehicles, sensors and drones have been tested and developed to improve traffic safety, but these advances have largely been limited to urban areas. This project identified opportunities and challenges of adopting drone technologies in RITI communities, and explored context-sensitive applications to traffic safety and related goals. In three phases, the team conducted community workshops, online surveys and other outreach activities with state and county agencies responsible for emergency management and crisis response in coastal Tribal and non-tribal communities; a planning studio and Comprehensive Plan Update for the City of Westport and its surrounding South Beach community straddling two rural counties and including the Shoalwater Bay Indian Tribe; and a pilot educational program with the School District that serves it. To be effective in rural contexts, adoption of drone technology depends on a broadening of local skill development and needs to target diverse community goals. In short, it needs to be broadly embedded in the community. Taking this sociotechnical approach, we focused on long-term workforce development and designed and implemented an after-school program (October 2021 – June 2022) for Ocosta Junior High School students. The course taught students how to assemble and pilot drones and apply them to a variety of practical needs including public works inspection, search and rescue, and environmental monitoring of coastal flooding.
    • Comparison of Arctic Alaska historical snow data with satellite-derived benchmarks and model results using ILAMB software

      Szatkowski, Mary; Bolton, W. Robert; Stuefer, Svetlana; Bennett, Katrina (2022-12)
      Understanding and modeling the permafrost system, hydrologic cycle, energy balance, and biologic systems in the Arctic are dependent, in part, on snow depth and snow distribution. Point-source snow measurements provide ground-truth observations of snow depth and snow water equivalent, although these measurements may be limited in their spatial and temporal distributions. Satellite-derived remote sensing products and gridded model output provide spatial coverage of snow properties, but their applicability is affected by their balance of resolution, computational speed, and accuracy confidence. The goal of this research is to assess the performance of three snow data products derived from remote sensing techniques as well as model output across the North Slope of Alaska with the International Land Model Benchmarking (ILAMB) Project software. Historic ground-based snow data, collected by agencies, academia, and industry, and dating from 1902 to 2021, was curated to create an ILAMB-compatible benchmark dataset for end-of-winter (EOW) snow depth and snow water equivalent (SWE) for the evaluation of the three snow data products: Canadian Sea Ice and Snow Evolution (CanSISE) network SWE; Arctic Boreal Vulnerability Experiment (ABoVE) snow depth; and Energy Exascale Earth System Model (E3SM) Earth Land Model (ELM) snow depth. The ILAMB evaluation results showed that the ABoVE data product is effective in providing the average EOW snow depth for regions of the North Slope but lacks representation of interannual and spatial variability of snow depth. Comparatively, the CanSISE data product and ELM results are inaccurate in magnitude for applicability across the North Slope of Alaska in addition to lacking representation of snow condition spatial variability. In interpreting ILAMB results, factors to consider were representation bias from inconsistent benchmark site distribution throughout the evaluated time period, the range of dates considered to represent the spring snow data, and uncertainty within the individual benchmark values. Future analysis of the same datasets with ILAMB could include diagnostic tests to understand the sources of error better. Thorough spring snow data collection should continue on the North Slope of Alaska to inform and improve Earth System Models.
    • 2022 Alaska Seismicity Summary

      Ruppert, Natalia (2023-02-09)
      The Alaska Earthquake Center reported 47,045 seismic events in Alaska and neighboring regions in 2022. The largest earthquake was a magnitude 6.8 event that occurred on January 11 in the Fox Islands region of the Aleutian Islands. Other active spots include two M6.3 earthquakes in the Rat Islands on June 4 and December 14, both of which were followed by moderate aftershock sequences. A magnitude 5.4 earthquake was recorded in an unusual location in the Bering Sea, east of St. George Island, on July 4. The two largest earthquakes in mainland Alaska, both magnitude 5.2, occurred in the Yakutat Bay region on January 8 and in central Alaska on February 6. We continued to monitor ongoing activity within the 2018 M7.1 Anchorage, 2018 M6.4 Kaktovik, 2018 M7.9 Offshore Kodiak, 2020 M7.6 Simeonof, and 2021 M8.2 Chignik aftershock sequences, the Purcell Mountains earthquake swarm, and the Wright Glacier cluster northeast of Juneau. All aftershock sequences continued to slow down compared to the previous years.
    • Development of an Acoustic Method to Collect Studded Tire Traffic Data

      Chang, Kevin; Alhasyah, Meeloud (2023-02)
      Travel during winter months remains particularly problematic in the Pacific Northwest due to the regular occurrence of inclement weather in the form of snow and ice during freezing and sub-freezing conditions. For travelers and commuters alike, vehicle traction in the form of studded tires serves to provide an added level of driving confidence when weather conditions deteriorate. However, recurring studded tire usage causes damage to the roadway infrastructure in the form of surface wear and rutting over time. Left unattended, this damage contributes to challenging and potentially dangerous driving conditions in the form of standing water and the increased potential for hydroplaning. Currently, an efficient and automated method to collect site-specific studded tire traffic volumes is lacking. While studded tire usage can be locally estimated based on manual roadway traffic counts, parking lot counts, or household surveys, the lack of real-world traffic volumes prevents the fine-tuning of roadway deterioration models that measure performance and estimate infrastructure life. This project tested the use of off-the-shelf sound meters to determine if an acoustic method could be developed to measure studded tire volumes. Based on the results, a prediction model was developed to allow for data-driven solutions that will benefit local transportation officials, planners, and engineers responsible for managing highways and roadways.
    • Control and inverse problems for the wave equation on metric graphs

      Zhao, Yuanyuan; Avdonin, Sergei; Rhodes, John; Rybkin, Alexei; Avdonina, Nina (2022-12)
      This thesis focuses on control and inverse problems for the wave equation on finite metric graphs. The first part deals with the control problem for the wave equation on tree graphs. We propose new constructive algorithms for solving initial boundary value problems on general graphs and boundary control problems on tree graphs. We demonstrate that the wave equation on a tree is exactly controllable if and only if controls are applied at all or all but one of the boundary vertices. We find the minimal controllability time and prove that our result is optimal in the general case. The second part deals with the inverse problem for the wave equation on tree graphs. We describe the dynamical Leaf Peeling (LP) method. The main step of the method is recalculating the response operator from the original tree to a peeled tree. The LP method allows us to recover the connectivity, potential function on a tree graph and the lengths of its edges from the response operator given on a finite time interval. In the third part we consider the control problem for the wave equation on graphs with cycles. Among all vertices and edges we choose certain active vertices and edges, and give a constructive proof that the wave equation on the graph is exactly controllable if Neumann controllers are placed at the active vertices and Dirichlet controllers are placed at the active edges. The control time for this construction is determined by the chosen orientation and path decomposition of the graph. We indicate the optimal time that guarantees the exact controllability for all systems of a described class on a given graph. While the choice of the active vertices and edges is not unique, we find the minimum number of controllers to guarantee the exact controllability as a graph invariant.
    • Thermokarst-pond plant community characteristics and effects on icewedge degradation in the Prudhoe Bay region, Alaska

      Watson-Cook, Emily; Walker, Donald A.; Breen, Amy L.; Raynolds, Martha K.; Ruess, Roger W. (2022-12)
      Ice-wedge thermokarst ponds are forming in many areas of the Arctic as a result of climate warming and infrastructure development. Previous research suggests that development of aquatic vegetation within these ponds may create negative feedbacks to the process of ice-wedge degradation by reducing pond-bottom temperatures and thaw depths. The objectives of this research were to characterize thermokarst-pond plant communities and to evaluate the effects of vegetation on within-pond sediment temperatures and thaw depths. Aquatic vegetation was sampled in 39 plots within 29 thermokarst ponds in the Prudhoe Bay region of Alaska. Five floristically distinct plant communities were identified: Calliergon richardsonii comm., Scorpidium scorpioides comm., Pseudocalliergon turgescens comm., Hippuris vulgaris comm., and Ranunculus gmelinii comm. These communities had low species diversity (mean species richness 3.2 ± 1.5 SD) and were best differentiated by the single dominant species included in plant-community names. Ordination of species composition data revealed a temperature gradient, along which high biomass was associated with low sediment temperature and shallow thaw depth. The C. richardsonii and P. turgescens moss-dominated communities had very high biomass values (3079 g/m² ± 1895 SD and 3135 g/m² ± 585 SD, respectively). Examinations of temperature and thaw differences between communities were limited by sample size, as several communities were described based on only two plots each. To evaluate the potential insulative role of pond vegetation on pond-bottom temperature and thaw depth, differences between broad vegetation types (i.e., moss, forb, sparse) rather than communities were examined. Vegetation cover, total biomass, biomass of plant functional types, and soil organic horizon thickness were sampled, along with mean thaw depth and sediment temperature. Linear mixed-effects models were used to identify vegetation-related parameters with the highest predictive power of thaw and temperature. Mean sediment temperatures measured during 19 July - 23 August 2021 were warmest in the sparse plots (8.9 °C ± 0.2 SE) compared to the forb plots (8.2 °C ± 0.3 SE) and the moss plots (6.7 °C ± 0.4 SE). Moss plots also had shallower late-August thaw depths (42.5 cm ± 1.3 SE) compared to forb (52.7 cm ± 1.7 SE) and sparse (52.7 cm ± 1.4 SE) plots. Vegetation cover was negatively correlated with sediment temperature, whereas vegetation cover, moss thickness, and organic layer thickness were all negatively correlated with thaw depth. The stronger relationships observed between vegetation-related factors and thaw depth compared to sediment temperature were probably affected by the short period of temperature observations within this study. Although stochastic factors likely play a role in community establishment within thermokarst ponds, additional sampling is needed across all pond ages, ice-wedge degradation/stabilization stages, and a broader range of habitats within ponds to discern if there is a clear successional trajectory for thermokarst-pond plant communities. This study provided descriptions of relatively understudied aquatic plant communities that play an important role in Arctic landscape change. Notably, very high biomass values were found in young ponds (one with an age of only 8 years) dominated by moss communities. Results indicate that aquatic plant communities with high moss biomass have high capacity for insulation that potentially reduces permafrost thaw and ice-wedge degradation, leading to ice-wedge stabilization.
    • Exploring the North American Arctic benthos: community structure and oil degradation potential of sediment bacteria and archaea

      Walker, Alexis M.; Mincks, Sarah L.; Leigh, Mary Beth; Islas, Ana Aguilar; Lopez, Andres; Collins, Eric R. (2022-12)
      The Chukchi and Beaufort seas benthic habitats are home to a multitude of ecologically and commercially important organisms that are subject to ongoing environmental changes, including the impacts of climate change and increased exposure to contaminants. Benthic bacteria and archaea can be considered biogeochemical engineers. They play a major role in organic matter (OM) degradation and nutrient cycling and their community structure can reflect changes in environmental conditions such as OM composition and quantity, nutrient availability, redox conditions, and natural/anthropogenic contaminants (e.g. petroleum hydrocarbons). Yet, sediment microbial communities have rarely been examined in these marginal seas of North American Arctic. In this dissertation, I characterized marine sediment microbial communities along environmental gradients in the Beaufort (Chapter 2) and Chukchi seas (Chapter 3) and assess Arctic benthic microbial community response to oil exposure (Chapter 4). I assessed diversity, community structure, and environmental correlates of prokaryotic communities via 16S rRNA amplicon sequencing in surface sediments (upper 1 cm) from the Northern Bering Sea to the Amundsen Gulf in the southern Beaufort Sea. On a broad spatial scale encompassing the whole study area, I observed three distinct microbial assemblages. One assemblage was characteristic of the Northern Bering-Chukchi seas shelf, and two distinguished nearshore and offshore sediments in the Beaufort Sea. Within the Beaufort Sea, four assemblages were identified, reflecting habitat heterogeneity with respect to OM loading, water depth, and nearshore/riverine input, including a major influence of the Mackenzie River. Two assemblages were distinguished within the Bering-Chukchi region, including one representative of suboxic sediments and one suggesting influence of phytodetrital OM input as evidenced by the abundance of diatom/particle-associated microbes. These two assemblages may also reflect differences between local versus advective OM inputs. Incubation experiments exposing Arctic marine sediments to fresh and weathered crude oil under anaerobic and aerobic conditions were performed to assess oil biodegradation potential and identify putative oil-degrading microbes in the benthos. Molecular analyses revealed that significant community shifts occurred in the oiled treatments, with distinct communities emerging following exposure to fresh versus weathered oil, and in oxic versus anoxic conditions. The work presented here constitutes the first large-scale survey of benthic microbes in this region of the North American Arctic, including their response to petroleum contamination, generating valuable baseline data for the changes to come.
    • Seaweeds across ecosystem boundaries: from habitat formation to harvest implications

      Ulaski, Brian P.; Konar, Brenda; Iken, Katrin; Otis, Edward O.; Gorman, Kristen B.; Sikes, Derek S. (2022-12)
      This dissertation broadly investigates the response of wild stock seaweeds to harvesting, and their role as biogenic habitat formers when cast ashore. Seaweeds are important primary producers and foundation species that maintain their functional roles across coastal ecosystem boundaries. Climate-driven loss of seaweed biomass, including that of kelp forests, is exacerbated by other human-related activities that directly impact their persistence, such as overharvesting. Attached rockweeds and kelps are commonly harvested for food, while diverse assemblages of beach-cast seaweed wrack are collected for fertilizer. The importance of wrack habitat in Alaska has not been extensively explored, especially in regions where there is a growing interest in harvesting by coastal communities. This research explores precautionary approaches to lessen wild stock seaweed decline in the face of increased harvest interests by: 1) characterizing information on reproductive timing, standing crop, and regrowth potential of attached populations; 2) investigating reproductive viability of seaweed wrack and identifying how landscape variables influence wrack distribution through paired on-the-ground and aerial surveys; and 3) characterizing wrack-associated macrofaunal communities and determining successional states in aging wrack. Regrowth following harvest of attached focal seaweeds (i.e., Fucus distichus, Saccharina latissima, and Nereocystis luetkeana) was generally low after two months, but the amount of biomass after four- and six-months post-harvest was more comparable to non-harvested areas. Depending on the species (e.g., F. distichus), attached individuals that became reproductive at larger sizes were associated with lower density and lower biomass areas with slower recovery. Differences in diversity and composition of wrack were correlated with coastline (substrate type, slope, and exposure) and adjacent watershed characteristics (percent glacial cover and range in seawater salinity). On-the-ground and drone-based surveys of beach-cast wrack both revealed seasonal patterns of patchy (spring) and continuous (summer) distribution. Macroinvertebrate community diversity was positively correlated with seaweed biomass and tidal height of the wrack line. Furthermore, succession experiments revealed that aged wrack harbored diverse and changing macroinvertebrate communities over time, with decomposers being early colonizers, and predators arriving later. Altogether, the findings of this research offer key information to developing sustainable harvest regulations in Alaska, as human use of seaweed increases.
    • Compound-specific stable isotopes of amino acids reveal the influence of trophic level and primary production sources on mercury concentrations in fishes from the Aleutian Islands, Alaska

      Barst, Benjamin; Wooller, Matthew; Horstmann, Lara (2022-12)
      Total mercury (THg) concentrations exceed thresholds of concern in some Steller sea lion (Eumetopias jubatus; SSL) tissues from certain portions of the Aleutian Islands, Alaska. Here, compound-specific stable isotope analyses (CSIA) of carbon in essential amino acids ([delta]¹³CEAA values) and nitrogen in AAs ([delta]¹⁵NAA values) in fish muscle tissue was applied to quantify the proportional contributions of primary production sources and trophic positions of eight prey species (n = 474 total) that are part of SSL diets. Previous THg analyses of fish muscle, coupled with additional monomethylmercury (MMHg) analyses of a subset of samples, substantiated previous findings that fishes from the west of Amchitka Pass, a discrete oceanographic boundary of the Aleutian Archipelago, have higher muscle THg concentrations relative to fishes from east of the pass. All fish muscle samples were analyzed separately for, both, CSIA-AA of carbon and nitrogen. The [delta]¹³CEAA values in fish muscle demonstrated that although most fishes obtained their EAAs primarily from algae, some species varied in the extent to which they relied on this primary production source. Certain [delta]¹⁵NAA values of the same fish samples indicated that trophic positions of fishes were higher from the west relative to the east of the pass for some species. Total Hg was positively correlated with bulk [delta]¹⁵N values, [delta]¹⁵N values of glutamic acid ([delta]¹⁵NGlu), and trophic positions. However, only trophic magnification slopes using [delta]¹⁵NGlu values indicated a higher rate of Hg biomagnification to the west of Amchitka Pass. Broad and species-level multiple linear regression models revealed that trophic position was the most important driver of fish muscle THg with a smaller amount of variation explained by other parameters, such as proportional contributions of primary production sources, fish body condition, and catch location. Collectively, results indicate that differences in fish trophic positions were the most consistent determinants of the higher fish THg concentrations to the west of Amchitka Pass. However, a higher rate of THg biomagnification to the west of Amchitka Pass may also play a role in the regional differences in fish muscle THg.
    • Drivers of functional ecology of the Alaskan Arctic epibenthos

      Sutton, Lauren; Iken, Katrin; Bluhm, Bodil; Hauri, Claudine; Konar, Brenda; Mueter, Franz (2022-12)
      This dissertation explored multiple facets of functional diversity for epibenthic invertebrate communities of Alaskan Arctic shelves. Functional diversity is the range of organismal traits within a community that determines ecosystem functioning. As a complement to taxonomic diversity, functional diversity reflects what species "do" as opposed to "who" they are, providing information on community-level ecosystem resilience and vulnerability. The Alaskan Arctic marine system is presently changing at an unprecedented rate, which impacts the biomass-rich benthos that is of great importance to upper trophic level fishes, birds, and marine mammals as a food source. In my first chapter, I tested the Biodiversity-Ecosystem-Functioning hypothesis that states ecosystem functioning increases with increasing diversity, using the functional composition of epibenthic communities on the Beaufort and Chukchi Sea shelves as case studies. Functional diversity generally followed taxonomic diversity patterns on both shelves; however, functional composition was more similar between the two shelf systems compared to taxonomic composition. Higher functional diversity on the Beaufort Sea shelf resulted from a more even distribution of functional traits, pointing to stronger resource partitioning and niche complementarity. This, in turn, suggests stronger maintenance of ecosystem function through more efficient nutrient cycling, energy turnover, and recovery from disturbances. In chapter 2, I applied the Community Assembly Theory that assumes species assemble in a non-random way due to a series of biotic and environmental filters using the same Chukchi and Beaufort seas epibenthic communities. Environmental conditions in the Chukchi Sea exerted a stronger environmental filter (i.e., stronger influence of cumulative environmental drivers) on epibenthic functional diversity, especially through gradients in temperature, depth, and mud, compared to weaker depth- and salinity-related filters in the Beaufort Sea. This suggests that the Beaufort Sea community may be less affected by climatic change compared to those in the Chukchi Sea. Strong environmental filtering in the Chukchi Sea can act as a barrier to invading taxa, who must possess a suite of functional traits that allows them to survive in the specific Arctic environment. Continued warming and declining sea ice are assumed to encourage poleward movements of boreal taxa, a process especially likely for taxa migrating from the Bering Sea into the Chukchi Sea. Thus, in the third chapter, I modeled future functional composition of epibenthic communities in the Northern Bering and Chukchi seas, based on past (2009-2019) and predicted environmental conditions under a warmer and fresher, "worst case" scenario for mid- and end of-century timeframes. All regions exhibited functional changes over time associated with specific shifts in trait composition in each region; however, the magnitude of these functional shifts varied among time periods. The rate of functional changes suggests that Northern Bering Sea and Chukchi Sea communities may have already undergone a major transformation during the past decade, with fewer shifts expected by the mid-century. This dissertation employed a new approach of using functional traits to examine Arctic epibenthic community function and stability in relation to environmental conditions. It created a much-needed benchmark to assess regions of ecosystem vulnerability and resilience in the Alaskan Arctic.
    • Finding solutions to the world's pending critical minerals supply crisis: developing new geochemical analytical methods and evaluating the potential for Te and Bi extraction from existing Au mines

      Spaleta, Karen Joy; Newberry, Rainer J.; Hayes, Sarah M.; Keskinen, Mary J.; Piatak, Nadine M.; Trainor, Thomas P. (2022-12)
      Bismuth (Bi) and tellurium (Te) are technologically critical elements (TCEs), also known as critical minerals, primarily recovered as byproducts in the extraction of lead (Pb) and copper (Cu), respectively. Global demand for Bi and Te is expected to rise signicantly in the coming decades as energy production becomes carbon neutral. In order to meet this demand, alternative sources of Bi and Te must be identifed. Bismuth and Te are commonly enriched in granitoid-related gold (Au) deposits and epithermal Au-Ag-Te deposits but are not presently recovered. Identifying which Bi and Te minerals are present throughout the Au extraction process is essential to determining where these elements might be recovered and in what quantities. Concurrent with the need to identify potential sources of TCEs is the need to validate advancements in analytical geochemical methods. Energy Dispersive Spectrometry (EDS) methods have become a go-to mineralogical identication tool in the mineral exploration and mining industries due to their rapid automated analysis. However, little cross-validation has been done to verify the results and determine the limitations of these tools. Here I present the results of three studies: 1) an EDS bulk mineralogy phase mapping method validation study on Au and Cu mill processing samples; 2) a detailed elemental composition and mineralogical analysis of samples from the Pogo Mine Mill (Interior Alaska, USA) identifying potential annual byproduct recovery of 13.5 and 7.5 metric tonnes of Bi and Te, respectively; and 3) a detailed elemental composition and mineralogical analysis of mill samples from the Golden Sunlight Mine Mill (Whitehall, Montana, USA) identifying Te primarily hosted in pyrite. Using this approach for similar metallurgical studies at other Au mines with known signicant Bi and Te could yield additional targets for recovery and provide a framework for identifying other potential TCEs/critical minerals in other deposits.