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.

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.

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.

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.

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.

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.

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.