Now showing items 21-40 of 10495

    • 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.
    • Juneau, Alaska’s Successful Response to COVID-19: A Case Study of Adaptive Leadership in a Complex System

      Powell, James E.; Orttung, Robert W.; Topkok, Sean Asiqłuq; Akselrod, Hana; Little, Joseph; Wilcox, Peggy (Sage, 2022)
      Juneau, Alaska, kept COVID-19 deaths lower than in other similar jurisdictions. We argue that adaptive leadership—the early decisions and actions of Juneau’s leaders, effective communications, and emergent new collaborative structures—in the context of municipal ownership of key assets enabled Juneau’s success. The result of 61 interviews and follow-up research, this case study contributes a better understanding of which institutional design, communication, and collaborative factors mattered in responding to the pandemic. Adaptive leadership provides a better explanation for Juneau’s success than alternatives that focus on its isolation, home-rule status, and socio-economic structure.
    • A new conceptual framework for the transformation of groundwater dissolved organic matter

      McDonough, Liza K.; Andersen, Martin S.; Behnke, Megan; Rutlidge, Helen; Oudone, Phetdala; Meredith, Karina; O’Carrol, Denis M.; Santos, Isaac R.; Marjo, Christopher E.; Spencer, Robert G. M.; et al. (Nature Communications, 2022-04-20)
      Groundwater comprises 95% of the liquid fresh water on Earth and contains a diverse mix of dissolved organic matter (DOM) molecules which play a significant role in the global carbon cycle. Currently, the storage times and degradation pathways of groundwater DOM are unclear, preventing an accurate estimate of groundwater carbon sources and sinks for global carbon budgets. Here we reveal the transformations of DOM in aging groundwater using ultra-high resolution mass spectrometry combined with radiocarbon dating. Long-term anoxia and a lack of photodegradation leads to the removal of oxidised DOM and a build-up of both reduced photodegradable formulae and aerobically biolabile formulae with a strong microbial signal. This contrasts with the degradation pathway of DOM in oxic marine, river, and lake systems. Our findings suggest that processes such as groundwater extraction and subterranean groundwater discharge to oceans could result in up to 13 Tg of highly photolabile and aerobically biolabile groundwater dissolved organic carbon released to surface environments per year, where it can be rapidly degraded. These findings highlight the importance of considering groundwater DOM in global carbon budgets.
    • Effects of spatially heterogeneous lakeside development on nearshore biotic communities in a large, deep, oligotrophic lake

      Meyer, Michael F.; Ozersky, Ted; Woo, Kara H.; Shchapov, Kirill; Galloway, Aaron W. E.; Schram, Julie B.; Rosi, Emma J.; Snow, Daniel D.; Timofeyev, Maxim A.; Karnaukhov, Dmitry Yu.; et al. (Association for the Sciences of Limnology and Oceanography, 2022)
      Sewage released from lakeside development can reshape ecological communities. Nearshore periphyton can rapidly assimilate sewage-associated nutrients, leading to increases of filamentous algal abundance, thus altering both food abundance and quality for grazers. In Lake Baikal, a large, ultra-oligotrophic, remote lake in Siberia, filamentous algal abundance has increased near lakeside developments, and localized sewage input is the suspected cause. These shifts are of particular interest in Lake Baikal, where endemic littoral biodiversity is high, lakeside settlements are mostly small, tourism is relatively high ( 1.2 million visitors annually), and settlements are separated by large tracts of undisturbed shoreline, enabling investigation of heterogeneity and gradients of disturbance. We surveyed sites along 40 km of Baikal’s southwestern shore for sewage indicators—pharmaceuticals and personal care products (PPCPs) and microplastics—as well as periphyton and macroinvertebrate abundance and indicators of food web structure (stable isotopes and fatty acids). Summed PPCP concentrations were spatially related to lakeside development. As predicted, lakeside development was associated with more filamentous algae and lower abundance of sewage-sensitive mollusks. Periphyton and macroinvertebrate stable isotopes and essential fatty acids suggested that food web structure otherwise remained similar across sites; yet, the invariance of amphipod fatty acid composition, relative to periphyton, suggested that grazers adjust behavior or metabolism to compensate for different periphyton assemblages. Our results demonstrate that even low levels of human disturbance can result in spatial heterogeneity of nearshore ecological responses, with potential for changing trophic interactions that propagate through the food web.
    • Climate Soundscapes

      Sandoval, Artemio Katooneh; Pearson, Heidi C. (Con Brio Chamber Series, 2022-11-19)
      Con Brio Chamber Series Presents CLIMATE SOUNDSCAPES Friday, November 18, 2022, 7:30 PM Kunéix Hidi Northern Light United Church Saturday, November 19, 2022, 2:00 PM Atrium at the APK State Library, Archives and Museum
    • Climate Soundscapes

      Pearson, Heidi C.; Sandoval, Artemio Katooneh (Con Brio Chamber Series, 2022-11-19)
      Con Brio Chamber Series Presents CLIMATE SOUNDSCAPES Friday, November 18, 2022, 7:30 PM Kunéix Hidi Northern Light United Church Saturday, November 19, 2022, 2:00 PM Atrium at the APK State Library, Archives and Museum
    • Seasonal and interannual variation in high‑latitude estuarine fsh community structure along a glacial to non‑glacial watershed gradient in Southeast Alaska

      Beaudreau, Anne H.; Bergstrom, Carolyn A.; Whitney, Emily Jean; Duncan, Douglas H.; Lundstrom, Nina (Springer, 2022-03-23)
      Along the Gulf of Alaska, rapid glacier retreat has driven changes in transport of freshwater, sediments, and nutrients to estuary habitats. Over the coming decades, deglaciation will lead to a temporary increase, followed by a long-term decline of glacial influence on estuaries. Therefore, quantifying the current variability in estuarine fish community structure in regions predicted to be most affected by glacier loss is necessary to anticipate future impacts. We analyzed fish community data collected monthly (April through September) over 7 years (2013–2019) from glacially influenced estuaries along the southeastern Gulf of Alaska. River delta sites within estuaries were sampled along a natural gradient of glacial to non-glacial watersheds to characterize variation in fish communities exposed to varying degrees of glacial influence. Differences in seasonal patterns of taxa richness and abundance between the most and least glacially influenced sites suggest that hydrological drivers influence the structure of delta fish communities. The most glacially influenced sites had lower richness but higher abundance overall compared to those with least glacial influence; however, differences among sites were small compared to differences across months. Two dominant species—Pacific staghorn sculpin and starry flounder—contributed most to spatial and temporal variation in community composition; however, given only small interannual differences in richness and abundance over the period of the study, we conclude that year-to-year variation at these sites is relatively low at present. Our study provides an important benchmark against which to compare shifts in fish communities as watersheds and downstream estuaries continue to transform in the coming decades.
    • Glacier runoff influences biogeochemistry and resource availabilityin coastal temperate rainforest streams: Implications for juvenile salmon growth

      Fellman, Jason B.; Bellmore, J. Ryan; Johnson, Connor; Dunkle, Matthew R.; Hood, Eran (Association for the Sciences of Limnology and Oceanography, 2022-10-01)
      Meltwater contributions to watersheds are shrinking as glaciers disappear, altering theflow, temperature, andbiogeochemistry of freshwaters. A potential consequence of this landscape change is that streamflow patternswithin glacierized watersheds will become more homogenous, potentially altering the capacity of watersheds tosupport Pacific salmon. To assess heterogeneity in stream habitat quality for juvenile salmon in a watershed inthe Alaska Coast Mountains, we collected organic matter and invertebrate drift and measured streamwater phys-ical and biogeochemical properties over the main runoff season in two adjacent tributaries, one fed mainly byrain and the other partially by glacier ice/snowmelt. We then used bioenergetic modeling to evaluate how tem-poral patterns in water temperature and invertebrate drift in each tributary influence juvenile salmon growthpotential. Across the study period, average invertebrate drift concentrations were similar in non-glacierizedMontana (0.33 mg m 3) and glacier-influenced McGinnis Creeks (0.38 mg m 3). However, seasonal patterns ofinvertebrate drift were temporally asynchronous between the two streams. Invertebrate drift and modeledfishgrowth were generally higher in McGinnis Creek in the spring and Montana Creek in the Summer. For juvenilesalmon, tracking these resource asynchronies by moving between tributaries resulted in 20% greater growththan could be obtained within either stream alone. These results suggest that hydrologic heterogeneity withinwatersheds may enhance the diversity of foraging and growth opportunities for mobile aquatic organisms,which may be essential for supporting productive and resilient natural salmon runs.
    • Seasonal and interannual variation in high‑latitude estuarine fsh community structure along a glacial to non‑glacial watershed gradient in Southeast Alaska

      Beaudreau, Anne H.; Bergstrom, Carolyn A.; Whitney, Emily Jean; Duncan, Douglas H.; Lundstrom, Nina (Springer, 2022-03-23)
      Along the Gulf of Alaska, rapid glacier retreat has driven changes in transport of freshwater, sediments, and nutrients to estuary habitats. Over the coming decades, deglaciation will lead to a temporary increase, followed by a long-term decline of glacial influence on estuaries. Therefore, quantifying the current variability in estuarine fish community structure in regions predicted to be most affected by glacier loss is necessary to anticipate future impacts. We analyzed fish community data collected monthly (April through September) over 7 years (2013–2019) from glacially influenced estuaries along the southeastern Gulf of Alaska. River delta sites within estuaries were sampled along a natural gradient of glacial to non-glacial watersheds to characterize variation in fish communities exposed to varying degrees of glacial influence. Differences in seasonal patterns of taxa richness and abundance between the most and least glacially influenced sites suggest that hydrological drivers influence the structure of delta fish communities. The most glacially influenced sites had lower richness but higher abundance overall compared to those with least glacial influence; however, differences among sites were small compared to differences across months. Two dominant species—Pacific staghorn sculpin and starry flounder—contributed most to spatial and temporal variation in community composition; however, given only small interannual differences in richness and abundance over the period of the study, we conclude that year-to-year variation at these sites is relatively low at present. Our study provides an important benchmark against which to compare shifts in fish communities as watersheds and downstream estuaries continue to transform in the coming decades.
    • Blonde Indian: Audiobook

      Hayes, Ernestine (2023)
      In the spring, the bear returns to the forest, the glacier returns to its source, and the salmon returns to the fresh water where it was spawned. Drawing on the special relationship that the Native people of southeastern Alaska have always had with nature, Blonde Indian is a story about returning.
    • From canopy to consumer: what makes and modifes terrestrial DOM in a temperate forest

      Behnke, Megan; Fellman, Jason B.; D'Amore, David V.; Gomez, S. M.; Spencer, R. G. M. (Springer, 2022-03-02)
      To investigate how source and processing control the composition of “terrestrial” dissolved organic matter (DOM), we combine soil and tree leachates, tree DOM, laboratory bioincubations, and ultrahigh resolution Fourier-transform ion cyclotron resonance mass spectrometry in three common landscape types (upland forest, forested wetland, and poor fen) of Southeast Alaska’s temperate rainforest. Tree (Tsuga heterophylla and Picea sitchensis) needles and bark and soil layers from each site were leached, and tree stemflow and throughfall collected to examine DOM sources. Dissolved organic carbon concentrations were as high as 167 mg CL−1 for tree DOM, suggesting tree DOM fluxes may be substantial given the hypermaritime climate of the region. Condensed aromatics contributed as much as 38% relative abundance of spruce and hemlock bark leachates suggesting coniferous trees are potential sources of condensed aromatics to surface waters. Soil leachates showed soil wetness dictates DOM composition and processing, with wetland soils producing more aromatic formulae and allowing the preservation of traditionally biolabile, aliphatic formulae. Biodegradation impacted soil and tree DOM differently, and though the majority of source-specific marker formulae were consumed for all sources, some marker formulae persisted. Tree DOM was highly biolabile (> 50%) and showed compositional convergence where processing homogenized DOM from different tree sources. In contrast, wetland and upland soil leachate DOM composition diverged and processing diversified DOM from different soil sources during bioincubations. Increasing precipitation intensity predicted with climate change in Southeast Alaska will increase tree leaching and soil DOM flushing, tightening linkages between terrestrial sources and DOM export to the coastal ocean.
    • From canopy to consumer: what makes and modifies terrestrial DOM in a temperate forest

      Behnke, Megan; Fellman, Jason B.; D'Amore, David V.; Gomez, S. M.; Spencer, R. G. M. (Springer, 2022-03-02)
      To investigate how source and processing control the composition of “terrestrial” dissolved organic matter (DOM), we combine soil and tree leachates, tree DOM, laboratory bioincubations, and ultrahigh resolution Fourier-transform ion cyclotron resonance mass spectrometry in three common landscape types (upland forest, forested wetland, and poor fen) of Southeast Alaska’s temperate rainforest. Tree (Tsuga heterophylla and Picea sitchensis) needles and bark and soil layers from each site were leached, and tree stemflow and throughfall collected to examine DOM sources. Dissolved organic carbon concentrations were as high as 167 mg CL−1 for tree DOM, suggesting tree DOM fluxes may be substantial given the hypermaritime climate of the region. Condensed aromatics contributed as much as 38% relative abundance of spruce and hemlock bark leachates suggesting coniferous trees are potential sources of condensed aromatics to surface waters. Soil leachates showed soil wetness dictates DOM composition and processing, with wetland soils producing more aromatic formulae and allowing the preservation of traditionally biolabile, aliphatic formulae. Biodegradation impacted soil and tree DOM differently, and though the majority of source-specific marker formulae were consumed for all sources, some marker formulae persisted. Tree DOM was highly biolabile (> 50%) and showed compositional convergence where processing homogenized DOM from different tree sources. In contrast, wetland and upland soil leachate DOM composition diverged and processing diversified DOM from different soil sources during bioincubations. Increasing precipitation intensity predicted with climate change in Southeast Alaska will increase tree leaching and soil DOM flushing, tightening linkages between terrestrial sources and DOM export to the coastal ocean.
    • 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.