Now showing items 21-40 of 8577

    • Seismic Tremor Reveals Spatial Organization and Temporal Changes of Subglacial Water System

      Vore, Margot E.; Bartholomaus, Timothy, C.; Winberry, J. Paul; Walter, Jacob I.; Amundson, Jason M. (American Geophysical Union, 2019-02-09)
      Subglacial water flow impacts glacier dynamics and shapes the subglacial environment. However, due to the challenges of observing glacier beds, the spatial organization of subglacial water systems and the time scales of conduit evolution and migration are largely unknown. To address these questions, we analyze 1.5‐ to 10‐Hz seismic tremor that we associate with subglacial water flow, that is, glaciohydraulic tremor, at Taku Glacier, Alaska, throughout the 2016 melt season. We use frequency‐dependent polarization analysis to estimate glaciohydraulic tremor propagation direction (related to the subglacial conduit location) and a degree day melt model to monitor variations in melt‐water input. We suggest that conduit formation requires sustained water input and that multiconduit flow paths can be distinguished from single‐conduit flow paths. Theoretical analysis supports our seismic interpretations that subglacial discharge likely flows through a single‐conduit in regions of steep hydraulic potential gradients but may be distributed among multiple conduits in regions with shallower potential gradients. Seismic tremor in regions with multiple conduits evolves through abrupt jumps between stable configurations that last 3–7 days, while tremor produced by single‐conduit flow remains more stationary. We also find that polarized glaciohydraulic tremor wave types are potentially linked to the distance from source to station and that multiple peak frequencies propagate from a similar direction. Tremor appears undetectable at distances beyond 2–6 km from the source. This new understanding of the spatial organization and temporal development of subglacial conduits informs our understanding of dynamism within the subglacial hydrologic system.
    • Meltwater Intrusions Reveal Mechanisms for Rapid Submarine Melt at a Tidewater Glacier

      Kienholtz, C.; Sutherland, D. A.; Jackson, R. H.; Nash, J. D.; Amundson, J. M.; Motyka, R. J.; Winters, D.; Skyllingstad, E.; Pettit, E. C. (American Geophysical Union, 2019-11-25)
      Submarine melting has been implicated as a driver of glacier retreat and sea level rise, but to date melting has been difficult to observe and quantify. As a result, melt rates have been estimated from parameterizations that are largely unconstrained by observations, particularly at the near-vertical termini of tidewater glaciers. With standard coefficients, these melt parameterizations predict that ambient melting (the melt away from subglacial discharge outlets) is negligible compared to discharge-driven melting for typical tidewater glaciers. Here, we present new data from LeConte Glacier, Alaska, that challenges this paradigm. Using autonomous kayaks, we observe ambient meltwater intrusions that are ubiquitous within 400 m of the terminus, and we provide the first characterization of their properties, structure, and distribution. Our results suggest that ambient melt rates are substantially higher (×100) than standard theory predicts and that ambient melting is a significant part of the total submarine melt flux. We explore modifications to the prevalent melt parameterization to provide a path forward for improved modeling of ocean-glacier interactions.
    • On-Shelf Transport of Oceanic Zooplankton in the Bering Sea

      Gibson, Georgina; Coyle, Ken; Hedstrom, Kate; Curchitser, Enrique (2012-10)
      A poster about a project to determine the most significant factors affecting timing, location, and intensity of on-shelf zooplankton transport in the Eastern Bering Sea.
    • Foods and foraging ecology of oldsquaws (Clangula hyemalis L.) on the arctic coastal plain of Alaska

      Taylor, Eric John (1986-09)
      The study was conducted from June to September during 1979 and 1980 in the the West Long Lake area of the National Petroleum Reserve-Alaska. Additional oldsquaws were collected in the inland wetlands near the northwest boundary of the reserve at Ice Cape. West Long Lake and the adjacent Goose Lake are located 15 miles south of the Beaufort Sea and immediately west of Teshekpuk Lake.
    • Enabling Data-Driven Transportation Safety Improvements in Rural Alaska

      Bennett, F. Lawrence; Metzgar, Jonathan B.; Perkins, Robert A. (2019-12)
      Safety improvements require funding. A clear need must be demonstrated to secure funding. For transportation safety, data, especially data about past crashes, is the usual method of demonstrating need. However, in rural locations, such data is often not available, or is not in a form amenable to use in funding applications. This research aids rural entities, often federally recognized tribes and small villages acquire data needed for funding applications. Two aspects of work product are the development of a traffic counting application for an iPad or similar device, and a review of the data requirements of the major transportation funding agencies. The traffic-counting app, UAF Traffic, demonstrated its ability to count traffic and turning movements for cars and trucks, as well as ATVs, snow machines, pedestrians, bicycles, and dog sleds. The review of the major agencies demonstrated that all the likely funders would accept qualitative data and Road Safety Audits. However, quantitative data, if it was available, was helpful.
    • Alaska Map of Bark Beetle Presence in 2016 and 2017

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (United States Department of Agriculture - US Forest Service, 2019)
      This is a shape file of 68 species locations surveyed by the USFS from 2016 to 2017 that consists of 3 bark beetle species. The geographic projection of the map is NAD 1983 Alaska Albers.
    • Alaska Map of 1-km Space Grid Points

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      This is a lattice point grid with a 1-km Euclidean distance in a total point number of 1,522,655 in Alaska. The map is prepared as a shape file and the geographic projection is NAD 1983 Alaska Albers.
    • Alaska Map of Bark Beetle Pseudo-Absence

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      This is a shape file of 5000 pseudo-absence points created across the state of Alaska without prior assumption such as a minimum or a maximum distance between these points or from bark beetle presence locations. The geographic projection is NAD 1983 Alaska Albers.
    • Alaska Map of Bark Beetle Presence

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (University of Alaska Museum; http://arctos.database.museum/SpecimenSearch.cfm, 2019)
      For this study, we created a shape file from 838 records of 68 bark beetle species, as the presence points for the model, provided by the University of Alaska Museum (UAM; http://arctos.database.museum/SpecimenSearch.cfm) as a tabulated file. The year the species were identified varied from 1953 to 2018, with nearly half being observed after 2011. Among the pooled bark beetle species, the most dominant genera were, Dryocoetes (n=133), Trypodendron (n=107), Ips (n=104), and Dendroctonus (n=83) (Appendix I). And, the most common species were the striped ambrosia beetle (Trypodendron lineatum (n=74)), Dryocoetes affaber (n=69), the spruce beetle (Dendroctonus rufipennis (n=66)), and the northern spruce engraver (Ips perturbatus (n=52)). The host evergreen trees from which the bark beetle specimens were collected consisted of white spruce (Picea glauca), black spruce (P. mariana), Sitka spruce (P. sitchensis), western hemlock (Tsuga heterophylla), lodgepole pine (Pinus contorta), mountain hemlock (Tsuga mertensiana), Lutz spruce (P.a x lutzii), Tamarack (Larix laricina), Yellow cedar (Cupressus nootkatensis), and Western red cedar (Thuja plicata)). The geographic projection of the map is NAD 1983 Alaska Albers.
    • Simple book enclosure instructions

      Gatlabayan, Mariecris; Schmuland, Arlene B. (2020)
    • Final Map (Figure 7)

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2020)
      This map shows bark beetles absent from mixed and evergreen forests (value 0), present in mixed forest (value 1) and present in evergreen forest (value 2), all as derived from the binary map of model 2 (Figure 6). The 2011 NLCD was the reference map to extract forest type and area across the state of Alaska. The map is prepared at 1 km spatial resolution and the geographic projection is NAD 1983 Alaska Albers.
    • Binary Map (Figure 6)

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2020)
      Classified prediction map of multi-species bark beetle occurrence using 95% confidence interval of validation points to differentiate predicted index of relative occurrence (RIO) of the ecological model (model without spatially-dependent predictors). Value 1 (presence) represents the potential ecological niche and value 0 (absence) represents regions that may not be occupied by scolytines community based on the current climatic conditions and biophysical attributes of the landscape. The map is prepared at 1 km spatial resolution and the geographic projection is NAD 1983 Alaska Albers.
    • Model 3 (Appendix IV)

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2020)
      Predicted distribution map of bark beetles in Alaska using model 3 (model with excluded roads). The map is prepared at 1 km spatial resolution and the geographic projection is NAD 1983 Alaska Albers.
    • Model 2 (Figure 3)

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2020)
      Predicted distribution map of bark beetles in Alaska using model 2 or ecological model (model without spatially-dependent predictors). The map is prepared at 1 km spatial resolution and the geographic projection is NAD 1983 Alaska Albers.
    • Model 1 (Appendix III)

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2020)
      Predicted distribution map of bark beetles in Alaska using model 1 (full model). The map is prepared at 1 km spatial resolution and the geographic projection is NAD 1983 Alaska Albers.
    • Maritime Guidance for Distant and Local Source Tsunami Events: Whittier Harbor, Alaska

      Nicolsky, Dmitry; Suleimani, Elena; Gardine, Lea (2020-02-27)
    • Maritime Guidance for Distant and Local Source Tsunami Events: Valdez Harbor, Alaska

      Nicolsky, Dmitry; Suleimani, Elena; Gardine, Lea (2020-02-27)
    • Maritime Guidance for Distant and Local Source Tsunami Events: Seward Harbor, Alaska

      Nicolsky, Dmitry; Suleimani, Elena; Gardine, Lea (2020-02-27)
    • Maritime Guidance for Distant and Local Source Tsunami Events: Seldovia Harbor, Alaska

      Nicolsky, Dmitry; Suleimani, Elena; Gardine, Lea (2020-02-27)
    • Maritime Guidance for Distant and Local Source Tsunami Events: Homer Harbor, Alaska

      Nicolsky, Dmitry; Suleimani, Elena; Gardine, Lea (2020-02-27)