• Habitat selection by calving caribou of the Central Arctic Herd, 1980-95

      Wolfe, Scott Adrian (2000-12)
      Habitat selection by calving caribou (Rangifer tarandus granti) of the Central Arctic Herd, Alaska, was assessed in relation to distance from roads, vegetation type, relative plant biomass (NDVI; Normalized Difference Vegetation Index), accumulation of plant biomass during early lactation (NDVIrate), snow cover, and terrain ruggedness. From 183 calving sites of 96 radio collared- females, 1980-95, calving distribution was estimated in reference (no development) and treatment (oilfields present) zones east and west of the Sagavanirktok River, respectively. In the reference zone, caribou regularly selected wet-graminoid vegetation, above-median NDVIrate, and non-rugged terrain; concentrated calving remained in habitats with zonal average NDVI on 21 June (NDVI621). In the treatment zone, selection patterns were inconsistent; concentrated calving shifted inland to rugged terrainwith low NDVI621 and away from development. Repeated use of lower-quality habitats in the treatment zone could compromise nutrient intake by calving females, thereby depressing reproductive success of the western-segment of the herd.
    • Headwater stream invertebrate communities: a comparison across ecoregions and logging histories

      Medhurst, R. Bruce (2007-08)
      Monitoring stream condition is not always conducted with understanding how climate may influence anthropogenic disturbances. Stream monitoring has traditionally been accomplished through sampling benthic invertebrates, while sampling drifting invertebrates as a potential monitoring tool has received little attention, in spite of drift often being easier and less expensive to sample. The objectives of this study were to understand how logging influences headwater stream invertebrate communities (benthic and drift) across two ecoregions in the Cascade Range, central Washington, and to determine whether drift samples might serve as a replacement for benthic samples in assessing headwater stream condition. Benthic and drifting invertebrates were sampled from 24 headwater streams in logged and unlogged watersheds within two ecoregions (wet and dry), and community metrics contrasted. Invertebrate community responses to logging varied with ecoregion (e.g., higher shredder densities in logged watersheds of wet ecoregion only). Differences in benthic community structure were not reflected in the drift, and relationships between benthos and drift were highly variable. Although both sampling types (benthic, drift) revealed ecoregional and land-use (logging) differences in invertebrate communities, lack of consistent relationships between the sampling types suggests drift sampling does not provide more reliable information about stream benthos or headwater stream condition.
    • Health Assessment In The Bowhead Whale

      Rosa, Cheryl; Blake, John E. (2006)
      Tissue samples and morphometric data were collected from 64 bowhead whales landed during the 1998-2002 subsistence hunts in Barrow and Kaktovik, Alaska. Our primary goal was to assess the health status of the Bering-Chukchi-Beaufort Seas stock of bowhead whales. Ages of whales were determined via aspartic acid racemization of the eye lens nucleus, baleen stable carbon isotope analysis and morphometric and histologic indices. We investigated the gross and microscopic anatomy of organs and blubber, thyroid hormone concentrations, serum haptoglobin, vitamin A and E concentrations in liver, blubber and serum and essential element concentrations in liver and kidney. Thyroid hormone and vitamin A were also evaluated as potential biomarkers of organochlorine (OC) concentrations in blubber, liver and serum. Neither of these substances was found to correlate with the relatively low OC concentrations found in these mysticetes. Histological changes of interest included renal interstitial fibrosis, hepatic periportal fibrosis/pigmentation/lipidosis, splenic extramedullary hematopoiesis and pulmonary fibromuscular hyperplasia. Changes in the kidney and lung were related to both age and renal and hepatic Cd concentrations. Most of the histological differences observed did not appear to adversely affect organ function or health of the individual. Thyroid hormone concentrations were stable over age/sex/seasonal groups, however, pregnant females had significantly lower total and free thyroxine than non-pregnant adult females and other age-sex classes. Serum haptoglobin was measured as an indirect determinant of acute inflammation, with three reactors found among 51 whales examined. Liver contained the highest mean concentrations of vitamins A and E (followed by epidermis, blubber, and serum and serum, epidermis, and blubber, in order). Finally, blubber percent collagen was measured at 30 locations on each whale and was found to be stable by site and most depths, with the most internal region of the reticular dermis being the only exception. Overall, the bowhead whales were healthy. However, climate change, offshore development and increases in arctic pollution emphasize the importance of baseline data collection. An ongoing surveillance effort is recommended to ensure that the species will be viable for generations to come and to assure subsistence users of the robust and healthy status of this stock of whales.
    • Heat Increment And Methane Production By Muskoxen Fed Browse

      Lawler, James Patrick; White, Robert G. (2001)
      Many browse species contain anti-herbivory compounds that deter consumers by their toxicity or digestive inhibitory effects. Animals that consume browse are assumed to pay a detoxification energy cost, which increases the heat increment of feeding (HIF). Ruminants also lose potentially metabolizable energy as methane (CH4); but browse may lower CH4 production. I hypothesized that increases in energy loss to HIF by animals eating browse could be offset by a reduction in energy lost via CH4 production. Muskoxen eat both graminoids and browse and are considered to be energetically conservative due to their existence in a sparse arctic environment. These traits make them ideal for energetic studies. Muskoxen were fasted for 24 h and then fed a test meal composed of hay mixed with graded percentages of one of three browse species (Willow: S. alaxensis, S. pulchra, birch: Betula nana). Browse consisted of twigs in winter and leaves in the summer. Heat increment of feeding and CH4 production were estimated with an indirect calorimeter. Muskoxen had a 33% lower metabolic rate in winter in comparison to summer. The main increase in EE from winter to summer occurred between April and May, and the summer to winter decrease between August and September. Addition of woody twigs or leaves of birch to hay diets tended to depress HIF following the test meal. Woody twigs and leaves of willow added to hay diets tended to increase HIF. Woody browse tended to lower CH4 production when fed at >20% of the meal. Leafy browse had variable effects on CH4 production; S. alaxensis was stimulatory, S. pulchra was inhibitory, while B. nana showed not consistent pattern. Generally, CH 4 production by muskoxen was low at 2.0--3.2% of GE intake when compared with estimates for sheep and cattle (2--12% of GE intake). Although diets high in fermentable carbohydrates stimulated methane production, secondary compounds apparently had a suppressing effect as deduced from the relation of in vitro digestibility to methane production. Given the low overall CH4 production in muskoxen, and the inconsistency of the relationship of CH4 to HIF, it is unlikely that significant gains in energy retention are made by reductions in CH4 production through browse consumption.
    • Heavy metal tissue distributions in southwestern Alaskan waterfowl: total mercury assays from muscle, brain, and bone

      Rothschild, Roger F. N. (2005-08)
      Food containing mercury has been identified as a possible health risk. Total mercury (THg), which is inorganic (Hg²), and methylmercury (MeHg) species, has been found in the arctic food web. In Alaska, birds are an important seasonal component of the diet, but have not been studied extensively and characterized for the presence of mercury. Birds are good subjects for examination because they feed at different trophic levels, can be long-lived, and are both abundant and widely distributed. Not only can birds monitor local Alaskan food webs, but, if they are migratory, can be used to compare exposure in different regions. Mercury levels in muscle, brain, and bone tissue of 140 birds taken by subsistence hunters across southwestern Alaska were determined. I tested the null hypothesis of no interspecific differences in total mercury levels in the 18 species of Alaska birds surveyed. There were interspecific differences with the Lesser Scaup (Aythyra marila mariloides), and the Black Scoter (Melanita nigra Americana), having the highest levels of mercury. In general, mercury levels were higher in muscle than in brain or bone. The mean values for mercury in the species studied were lower than the levels known to cause adverse reproductive or behavioral effects.
    • Hepatitis B in Arctic ground squirrels (Spermophylus parryi): epidemiology and population biology

      Joy, Philip John (2001-05)
      Using a mark-recapture design, an epidemiological investigation of Hepatitis B was performed on four colonies of Spermophylus parryi. Animals were trapped, marked and bled. Serum samples were screened for Hepatitis B markers. Program MARK was used to estimate survival rates. Prevalence rates ranged over 55% and 1999 rates were 10% higher than 1998. Vertical transmission of the virus was not observed and juveniles were unaffected by the mother's hepatitis status. Immigrants had lower prevalence rates than residents and incidence rates accelerated throughout the study. Survival was highest during the over-winter period and adult rates were lower in 1999. Recovered animals had different survival rates than other animals and survival rates of recovered animals were lower in 1999. Evidence suggests that delayed development of disease and/or environmental conditions lowered survival rates of recovered adults in 1999. Techniques that integrated epidemiology and population biology proved fruitful and worthy of further development.
    • Herbivore-mediated effects on ecosystem processes in a near-Arctic salt marsh

      Person, Brian Thomas (2001-12)
      Herbivores influence, and often regulate energy flow. I investigated interactions between herbivory and the foods on which geese rely while nesting and rearing their broods on the Yukon-Kuskokwim Delta in southwestern Alaska. In a captive Cackling Canada gosling (Branta Canadensis minima) experiment I decoupled the effects of seasonal declines in forage quality and availability on gosling development. An 11% decline in forage quality translated to goslings that were structurally smaller and 100 g lighter at 31 days of age. Forage availability had similar effects on gosling size, and the combined magnitude of these effects are similar to those observed in wild populations. I manipulated within-season grazing history of 'Carex subspathacea' swards within brood-rearing areas used by Black Brant geese (Branta bernicla nigricans). Spatial variation in forage quality and availability exceeded seasonal variation. Brant consumed over 95% of the annual aboveground production of these swards without any short- or apparent long-term effects on aboveground growth. Adding grazing pressure to 'C. ramenskii, ' or removing grazing pressure from 'C. subspathacea, ' resulted in a bi-directional shift in the morphology and nutritional characteristics of these sedges. The areal extent of 'C. subspathacea' increased 2 to 8% of the Tutakoke landscape with a concomitant decrease in 'C. ramenskii' meadows between 1991-1998. Brant have been increasing the carrying capacity of the Tutakoke River colony following a population decline in the early 1980's. The population has increased beginning in 1988, yet remains below historic numbers. Density-dependent effects on gosling growth accompanied the population increase initially. However, gosling mass has increased over the past decade due to herbivore-mediated increases in the areal extent of grazing lawns.
    • High frequency backscatter from the polar and auroral e-region ionosphere

      Forsythe, Victoriya V.; Bristow, William; Conde, Mark; Sahr, John; Zhang, Hui (2017-05)
      The Earth's ionosphere contains collisional and partially-ionized plasma. The electric field, produced by the interaction between the Earth's magnetosphere and the solar wind, drives the plasma bulk motion, also known as convection, in the F-region of the ionosphere. It can also destabilize the plasma in the E-region, producing irregularities or waves. Intermediatescale waves with wavelengths of hundreds of meters can cause scintillation and fading of the Global Navigation Satellite System (GNSS) signals, whereas the small-scale waves (< 100 m) can scatter radar signals, making possible detection of these plasma structures and measurements of their characteristics such as their phase velocity and intensity. In this work, production of the decameter-scale (10 m) irregularities in the ionospheric E-region (100-120 km in altitude) at high latitudes is investigated both theoretically, using linear fluid theory of plasma instability processes that generate small-scale plasma waves, and experimentally, by analyzing data collected with the newly-deployed high-southern-latitude radars within the Super Dual Auroral Radar Network (SuperDARN). The theoretical part of this work focuses on symmetry properties of the general dispersion relation that describes wave propagation in the collisional plasma in the two-stream and gradient-drift instability regimes. The instability growth rate and phase velocity are examined under the presence of a background parallel electric field, whose influence is demonstrated to break the spatial symmetry of the wave propagation patterns. In the observational part of this thesis, a novel dual radar setup is used to examine E-region irregularities in the magnetic polar cap by probing the E-region along the same line from opposite directions. The phase velocity analysis together with raytracing simulations demonstrated that, in the polar cap, the radar backscatter is primarily controlled by the plasma density conditions. In particular, when the E-region layer is strong and stratified, the radar backscatter properties are controlled by the convection velocity, whereas for a tilted E-layer, the height and aspect angle conditions are more important. Finally, the fundamental dependence of the E-region irregularity phase velocity on the component of the plasma convection is investigated using two new SuperDARN radars at high southern latitudes where plasma convection estimates are accurately deduced from all SuperDARN radars in the southern hemisphere. Statistical analysis is presented showing that the predominance of the E-region echoes of a particular polarity is strongly dictated by the orientation of the convection plasma ow which itself has a significant asymmetry towards westward zonal flow.
    • High resolution sequence stratigraphy and geochemistry of middle and upper Triassic sedimentary rocks, northeast and central Brooks Range, Alaska

      Kelly, Landon Neal (2004-08)
      Triassic age rocks constitute an important sedimentary interval on the North Slope of Alaska, because they include organic-rich source rocks that generated much of the oil that accumulated in the Prudhoe Bay field. Three detailed measured sections in the northeast and north-central Brooks Range are characterized using sequence stratigraphy, chemostratigraphy, biostratigraphy and ichnofabric, allowing interpretations about the evolution of the depositional environment and general paleogeographic setting through the Middle and Upper Triassic. High resolution correlation provides insight into the timing and pattern of source rock accumulation in the Shublik and Otuk Formations. Sequence and chemo-stratigraphic analyses suggest that deposition took place on a broad, low-angle shelf under fluctuating paleoceanographic conditions. Recorded are three third order sequences, each containing a sea level rise and highstand. Glauconitic, phosphatic, and organic-rich rocks of the Shublik and Otuk Formations indicate deposition in an environment characterized by oceanic upwelling. Organic and inorganic geochemical data support interpretations concerning paleoxygenation gradients. The cerium anomaly, manganese, phosphorus, vanadium, total organic carbon, and calcium-manganese ratio indicate dominantly oxic bottom waters during the Middle Triassic, dominantly low oxygen or anoxic conditions during much of the Upper Triassic, and a return to more oxic conditions in the late Upper Triassic.
    • High-Resolution Paleoceanography Of The Gulf Of Alaska, Subarctic Northeast Pacific Ocean, Since The Last Glacial Maximum: Insights Into A Dynamic Atmosphere-Ocean-Ecosystem Linkage At Decadal To Millennial Timescales

      Addison, Jason A.; Beget, James E.; Finney, Bruce P.; Bigelow, Nancy H.; Naidu, A. Sathy; Stockwell, Dean A.; Wooller, Matthew J. (2009)
      Environmental conditions in the Subarctic Northeast Pacific Ocean are an important component of North American climate patterns, as well as a potential driver of Northern Hemisphere climate variability. The North Pacific Ocean is also the terminus of modern global thermohaline circulation, suggesting that paleoceanographic records from this region have the potential to preserve evidence of both climate forcing and response on regional and global scales. A suite of high-resolution marine sediment cores collected from the Gulf of Alaska margin in 2004 provide new paleoceanographic records at decadal and centennial timescales from fjord and continental slope environments. Key findings include: (i) decadal oscillations in marine productivity correlate with previously identified terrestrial records, indicative of forcing by the Aleutian Low pressure cell; (ii) the standard binary model of the modern Pacific Decadal Oscillation (PDO) as the major pattern of ocean-atmosphere variability is insufficient to describe the full range of Holocene paleoenvironmental fluctuations observed in Gulf of Alaska records of marine productivity, freshwater discharge, and bottom-water anoxia; (iii) the North Pacific ecosystem is a sensitive recorder of abrupt climate events observed in global records; and (iv) the fjords of Southeast Alaska contain a detailed record of volcanic activity and fallout events useful for developing composite chronological models of sedimentation that correlate with other regionally important stratigraphic records. Collectively, the results presented here will potentially redefine current theoretical models of atmosphere-ocean-ecosystem variability in the North Pacific Ocean, as well as contribute to a growing body of high-resolution paleoenvironmental time-series datasets from the high latitudes.
    • Histone H2A-S122 is required for nuclear and mitochondrial genome stability

      Uffenbeck, Shannon R.; Krebs, Jocelyn; Kuhn, Thomas; Ii, Miki; O'Brien, Kristin (2013-08)
      Organization and maintenance of the mitochondrial and nuclear genomes are vastly different, yet I have shown that a single serine in the H2A C-terminal tail (H2A-S122) is critical for stability of both genomes in the budding yeast, Saccharomyces cerevisiae. Phosphorylation of H2A-S 122 has previously been implicated in the spindle assembly checkpoint (SAC), however I show that by mutating the serine to an alanine (H2A-S122A), the resulting aneuploidy occurs at a much higher rate than is observed by deleting its immediate downstream kinase BUB1. Furthermore, the H2A-S122A mutant displays an increased susceptibility to DNA damaging agents that is not observed in bubΔ1 deletion cells. Our studies also implicate H2A-S122 as critical to the maintenance of the mitochondrial genome, as upon introduction of the H2A-S122A mutation, cells rapidly lose their mitochondrial genomes.
    • History of the Chukchi borderland and the Amerasia basin, Arctic Ocean

      Ilhan, Ibrahim; Coakley, Bernard J.; Johnson, Christopher A.; Houseknecht, David W.; Whalen, Michael T. (2018-08)
      Structural and stratigraphic interpretation of 2D multi-channel seismic (MCS) reflection profiles through recognition of the sub-surface reflection patterns and integration of the seismic interpretation with the other geophysical and geological data reveal the history of the Chukchi Borderland. This investigation provides new constraints for the tectonic development of the Amerasia Basin. North-striking normal faults of the Chukchi Borderland dissect the continental basement into the Chukchi Plateau, Northwind Basin and Northwind Ridge from west to east. A well-developed angular unconformity (Au) separates the stratigraphic section into sub and super-Au seismic units. Sub-Au units include: (1) seaward dipping reflections (SDRs) observed in the juncture between the North Chukchi-Toll Basins and Chukchi Plateau; (2) growth and folded strata in the Northwind Basin; (3) thrust faults in the Northwind Basin and over the Northwind Ridge; and (4) a clinoform sequence that downlaps onto the extended continental crust of the Canada Basin, supported by presence of SDRs and diapiric reflections within the crust. Au is inferred to correlate to the Hauterivian (LCu) and the Middle Jurassic (Ju) unconformities of the Alaska North Slope. The SDRs indicate that the southwestern margin of the Chukchi Borderland may be a rifted continental margin. Loosely constrained age control of a super-Au unit (inferred condensed section, perhaps correlative to Hauterivian pebble shale or the Jurassic upper Kingak shale units of Alaska North Slope) implies that the rifted margin subsided no later than the earliest Cretaceous, providing a plausible time constraint for Middle Jurassic-earliest Cretaceous rifting in the North Chukchi Basin. The growth strata and north-striking normal faults of the Northwind Basin are continuous with the extensional structures of the Mississippian Hanna Trough, providing a geologic linkage between the two. The folding and thrust faults reveal a phase of contraction confined to sub-Au units of the south and eastern Northwind Basin and Northwind Ridge. The clinoform sequence of the Northwind Ridge-Canada Basin is inferred to correlate with the Upper Jurassic-Lower Cretaceous Kingak shale unit of Alaska North Slope, implying that the extension of the crust beneath the western Canada Basin occurred no later than the Middle Jurassic. Super-Au strata (~16 km) onlap the condensed section, SDRs, growth and passive margin strata from west to east, tapering down to a few kilometers north and eastward across the seismic grid. These are part of the Aptian through Cenozoic Brookian megasequence, a series of clinothems, deposited across the foreland of the Chukotka and Brooks Range orogens. These strata were deposited by northward-migrating depositional systems that progressively filled the North Chukchi Basin and buried the southern flank of the Chukchi Borderland, and deposited along the Northwind margin of the Canada Basin. Another unit of growth strata is observed in the Northwind Basin, indicating another phase of extension of the Boderland. The Upper Cretaceous section of the Brookian megasequence is displaced by normal faults over the Chukchi Plateau and inferred age-equivalent strata over the Northwind Ridge. These constrain the second phase of extension of the interior Borderland to the Late Cretaceous to Paleocene. The recognition of the sub-Au units and continuity of the super-Au units across the area, north-striking normal faults, and the absence of east-directed thrust faults between the Northwind Ridge and Canada Basin invalidate one model proposed for tectonic development of the Amerasia Basin. Models that require significant relative motion between the Chukchi Shelf and Borderland since the Middle Jurassic are precluded by these observations.
    • Home range, habitat selection, and movements of lynx (Lynx canadensis) in eastern interior Alaska

      Perham, Craig J.; Follmann, Erich H.; Rextad, Eric A.; Cook, Joseph; Jenkins, K. (1995-12)
      Lynx home ranges, habitat selection, and daily track deposition rates were determined in interior Alaska. Male home ranges averaged 167 km2 in 1991-92 and 127 km2 in 1992-93, but varied (14-270 km2); females averaged 33 km2 in 1991-92 and 48 km2 in 1992-93. Nomadic lynx displayed erratic movements and large ranges, whereas others dispersed from the study area. Lynx with small home ranges may use snowshoe hare refugia whereas other lynx may range over expanded areas to acquire food. Lynx preferred broadleaf and mixed forests and avoided dwarf shrub/tundra. Lynx used a 1959 burn more than expected; more recent burns (<11 years) were used less than expected. Track deposition was significantly related to snowfall, temperature and barometric pressure change (P< 0.001), the overall model, however, explained only 16% of the variation in deposition (R2 = 0.162). Temperature was most related to track deposition; as temperature increased, track deposition became more variable.
    • Hormonal regulation of alternative reproductive strategies

      Morgan, Tawna (2010-05)
      Variation in reproductive behavior permits individuals to optimize fitness given their genetics, physiological condition, social status, age and current environmental conditions. For species with alternative reproductive strategies, behavioral differences are driven by natural and sexual selection and further mediated by the endocrine system. In this study, I explore endocrinological mechanisms associated with alternative reproductive strategies in the ruff (Philomachus pugnax). Ruffs breed on leks, where males use one of three genetically determined alternative reproductive strategies or phenotypes. Resident males rely on male-male aggression, colorful plumage, large body size and intensive display activity to establish courts on a lek and attract females. Satellite males operate outside the dominance hierarchy of the lek, relying on semi-cooperative displays with residents, lighter display plumage coloration and agility to access receptive females. Males using the third male strategy, considered 'sneakers' or 'female mimics', completely forgo typical male breeding plumage, territoriality and obvious display behaviors to obtain clandestine access to females. The differences in level of aggression and display behaviors among phenotypes suggest predictable differences in steroid hormone concentrations, which play a critical role in breeding behavior in birds. I therefore examined seasonal hormone profiles of male ruffs and applied predictions from the challenge hypothesis, which posits circulating androgen concentration will vary in relation to intensity of male-male competition during the breeding season. Consistent with the challenge hypothesis, androgen levels were higher during periods of lek instability in territorial resident ruffs. In contrast, when housed in large flocks, androstenedione was elevated during the breeding season in satellite ruffs and followed the pattern typically observed for testosterone in polygamous birds. In response to distinctly different seasonal androgen and androstenedione profiles, I further examined the activational role of androstenedione on satellite male breeding behavior. Androstenedione stimulated both resident and satellite typical behaviors consistent with genetic morph, and thus did not specifically activate the satellite phenotype.
    • Host-parasite ecophysiology of overwintering

      Larson, Don J.; Barnes, Brian; O'Hara, Todd; Sikes, Derek; Wipfli, Mark (2019-12)
      To survive extreme winters, parasites must overwinter either in a host, as free-living larvae, or be reintroduced yearly through migratory hosts. This thesis examines interrelations between host parasite overwintering physiology and behavior in Alaska between the trematode Ribeiroia ondatrae and their host, wood frogs (Lithobates sylvaticus). The first chapter examines overwintering physiology and behavior of wood frogs in the field. The second chapter creates a laboratory method for determining physiological responses of wood frogs to environmental transitions from summer to fall. The third chapter examines if and how R. ondatrae survive within a frozen wood frog. Free-living wood frogs investigated over two winters in Fairbanks, AK remained frozen for up to 7 months and survived temperatures as low as -18°C, values much more extreme than those previously reported (Chapter 1). Alaskan wood frogs also synthesized and released approximately one order of magnitude greater concentrations of cryoprotectant (glucose) in multiple tissues than levels previously reported. Wood frogs in the field did not experience the same slow and continuous cooling that researchers routinely subject frogs to under experimental conditions. Instead they cooled at rates of up to -1.5°C h⁻¹ for short periods in a diurnal freeze-thaw pattern repeated over one to three weeks until remaining frozen for the rest of winter. Since wood frogs only produce glucose at the initiation of freezing, I hypothesized that freeze-thaw cycling within hibernacula allowed for incremental increases of glucose resulting in higher concentrations in field wood frogs than found in laboratory frozen wood frogs. I compared patterns of diurnal freeze-thaw cycling with the standard laboratory freezing protocols for wood frogs. Wood frogs that experienced multiple freeze-thaw events responded with significant increases in glucose concentration in liver, leg, and heart tissues at each freezing with no significant losses in glucose with each following thaw period (Chapter 2). This incremental increase in glucose within wood frogs may also assist in parasite survival. Trematode metacercariae may be absorbing host glucose and using this cryoprotectant to enhance their survival (Chapter 3). This result provides evidence that host physiology in winter may both hinder (through freezing) and facilitate (through cryoprotectant production) parasite survival.
    • Hot flow anomalies at earth's bow shock and their magnetospheric-ionospheric signatures

      Chu, Christina Seiman; Zhang, Hui; Otto, Antonius; Ng, Chung-Sang; Sibeck, David (2017-08)
      Hot flow anomalies (HFAs) are typically observed upstream of bow shocks. They are characterized by a significant increase in particle temperature and substantial flow deflection from the solar wind flow direction coinciding with a decrease in density. HFAs are important to study and understand because they may play an important role in solar wind-magnetosphere coupling. They may drive magnetopause motion, boundary waves, and flux transfer events. They can excite ultra low frequency waves in the magnetosphere, drive magnetic impulse events in the ionosphere, and trigger aurora brightening or dimming. Studying HFAs will aid in the understanding of fundamental processes that operate throughout the heliosphere such as particle energization and shocks. This dissertation presents statistical and case studies of hot flow anomalies identified in Time History of Events and Macroscale Interactions During Substorms (THEMIS) satellite data from 2007-2009. The characteristics and occurrence of HFAs, their dependence on solar wind/interplanetary magnetic field (IMF) conditions and location, and their magnetospheric-ionospheric signatures, have been investigated using in-situ spacecraft observations and ground based observations. THEMIS observations show that HFAs span a wide range of magnetic local times (MLTs) from approximately 7 to 16.5 MLT. HFAs were observed up to 6.3 Earth radii (RE) upstream from the bow shock. It has been found that the HFA occurrence rate depends on solar wind and interplanetary magnetic field (IMF) conditions as well as distance from the bow shock. HFA occurrence decreases with distance upstream from the bow shock. HFAs are more prevalent when there is an approximately radial interplanetary magnetic field. No HFAs were observed when the Mach number was less than 5, suggesting there is a minimum threshold Mach number for HFAs to form. HFAs occur most preferentially for solar wind speeds from 550-600 km/s. Multiple THEMIS spacecraft observations of the same HFA provide an excellent opportunity to perform a spatial and temporal analysis of an HFA. The leading edge, tangential discontinuity inside the HFA, and trailing shock boundaries for the event were identified. The boundaries' orientations and motion through space were characterized. The HFA expansion against the solar wind was 283 km/s. The spatial structure of the HFA was deduced from multiple spacecraft observations. The HFA is thicker closer to the bow shock. The magnetospheric-ionospheric signatures of an HFA have been investigated using in-situ spacecraft observations and ground based observations. Magnetic field perturbations were observed by three GOES spacecraft at geostationary orbit and high-latitude ground magnetometers in both hemispheres. Observations from magnetometers located at different MLTs showed that the perturbation propagates tailward at 0.32°/s or 9 km/s (1.27°/s or 21 km/s) for the northern (southern) hemisphere, which is consistent with an HFA propagating tailward along the dawn flank. SuperDARN radar observations showed a change in plasma velocity shortly after the HFA was observed by THEMIS.
    • Human impacts to fire regime in Interior Alaska

      DeWilde, La'ona (2003-12)
      A thorough analysis of human impacts on interior Alaska's fire regime demonstrates that human activities have effects in populated areas. Two approaches were used to determine impacts: I examined three regions with very different populations, and also one large region to analyze suppression, ignition, and vegetation interactions. The Fairbanks Region, with a large human population and an extensive road system, differs from two other regions with low human populations and few roads. In the Fairbanks Region, humans have impacted fire regime by causing more fires in certain fuel types and doubling the length of the fire season. The Fairbanks Region, with a higher level of suppression than the other two regions, has less area of land burn, even after controlling for fuel type and a higher number of human ignitions. In areas designated for high protection, there is less area burned and more human caused starts. For interior Alaska as a whole, human ignitions and suppression have only a minor effect on fire regime, and climate strongly influences the total area burned. However, in populated areas and areas designated for high protection, human ignitions account for most of the area burned, and less area bums overall due to suppression.
    • Human-bear interactions in the North Slope oilfields of Alaska (USA): characteristics of grizzly bear sightings and use of infrared for bear den detection

      Pedersen, Nils J. S.; Brinkman, Todd J.; Shideler, Richard T.; Brainerd, Scott; Lindberg, Mark (2019-05)
      Minimizing unsafe human-bear (Ursus spp.) interactions in the North Slope oilfields of Alaska (USA) requires knowledge of where they occur and methods to prevent them. My research goals were to characterize the spatial and temporal dynamics of grizzly bear (U. arctos) sightings during the non-denning season around industrial infrastructure in the North Slope oilfields over the past 25 years (Chapter 2), and to evaluate the efficacy of forward-looking infrared (FLIR) systems to detect grizzly bears and polar bears (U. maritimus) in their winter dens (Chapter 3). I used reports (n = 2,453) of summer grizzly bear sightings collected by oilfield security officers from 1990-2014 to estimate how the spatial distribution of sightings for food-conditioned (FC) and natural food (NF) bears changed following restriction of bear access to anthropogenic food waste (to be known hereafter as "treatment") in 2001. I found that concentrations of FC bear sightings shifted toward the landfill with medium-low effect (Hedges' g = 0.41), one of the only remaining areas with available food waste, after the treatment. The treatment also decreased NF bear sighting distances to landfill with low effect (Hedges' g = 0.15). My findings suggested that grizzly bear access to food waste should be prevented to minimize negative human-bear interactions and that an active bear reporting system facilitates adaptive management of human-bear interactions. During the winter, grizzly bears and pregnant female polar bears enter dens in areas that overlap anthropogenic activity. FLIR techniques have been used to locate occupied dens by detecting heat emitted from denned bears. However, the effects of environmental conditions on den detection have not been rigorously evaluated. I used a FLIR-equipped Unmanned Aircraft System (UAS) to collect images of artificial polar bear (APD) and grizzly bear (AGD) dens from horizontal and vertical perspectives from December 2016 to April 2017 to assess how odds of detection changed relative to den characteristics and environmental conditions. I used logistic regression to estimate effects of 11 weather variables on odds of detection using 291 images. I found that UAS-FLIR detected APDs two times better than AGDs, vertical perspective detected 4 times better than horizontal, and that lower air temperatures and wind speeds, and the absence of precipitation and direct solar radiation increased odds of detection for APDs. An increase of 1°C air temperature lowered the odds of detection by 12% for APD, and 8% for AGDs, but physical den characteristics such as den snow wall thickness determined detectability of AGDs. UAS-FLIR surveys should be conducted on cold, clear days, with calm winds and minimal solar radiation, early in the denning season. UAS-FLIR detectionof bear dens can be effective but should be confirmed by a secondary method.
    • Hydroclimate in Eurasia from the Arctic to the Tropics

      Majhi, Ipshita; Bhatt, Uma S.; Zhang, Xiangdong; Molders, Nicole; Walsh, John; Krishnamurthy (2018-05)
      Hydrometeorology in Eurasia connects the Arctic with lower latitudes through exchanges in moisture and teleconnections influencing climate variability. This thesis investigates the role of dams on the Kolyma basin, of precipitation and temperature change on a pristine permafrost lined basin of the Yana, and of changing snow cover over Eurasia on the Indian Monsoon. These three pieces of work illustrate different aspects of a changing climate that impact Eurasian hydrometeorological variations. The Kolyma is one of the large rivers which flows into the Arctic Ocean where there has been a large winter increase and summer decrease in flow over the 1986-2000 period. Winter months are characterized by low flow while summer months by high flow. Reservoir regulation was identified as the main cause of changes in the discharge pattern, since water is released in winter for power generation and stored in summer for flood control. The overall discharge to the Arctic Ocean has decreased for Kolyma basin, despite the increase during winter. This study documents how human activities (particularly reservoirs) impact seasonal and regional hydrological variations. The Yana Basin is a small pristine basin that has experienced minimal human impact and is ideal for investigating the role of climate variability on discharge. The precipitation discharge and temperature discharge analysis for Ubileinaya suggests that increased precipitation and higher temperatures resulted in higher discharge, but other parameters also come into play since greater precipitation does not always yield higher discharge. Overall our analysis for this station has increased our understanding of natural basins and how the climate variables like precipitation and temperature play a role. Recent increases in May-June Indian monsoon rain fall were investigated in the context of Eurasian snow cover variations since the onset of the monsoon has long been linked to Himalayan snow cover. Himalayan snow cover and depth have decreased and this study argues that this is the driver of increased rainfall during May-June, the pre-monsoon and early monsoon period. In addition, there has been an increase in snow water equivalent in Northern part of Eurasia and decrease in Southern part, suggesting that the anomalies are large-scale. Storm track analysis reveals an increase in the number of storms in northern and a decrease in southern Eurasia. The large-scale Eurasian snow increases have been shown by other studies to be linked to Arctic sea ice decline. The direct linkage between fall Arctic sea ice decline and an increase in May-June Indian monsoon rainfall is proposed in this work but the exact climate mechanism is tenuous at this point. This study is focused on understanding changing Arctic rivers and the connection of the Arctic with the Indian monsoon. Our study has shed some light into the connection between the Arctic and the tropics. This study could benefit from modeling study where we could have case study with and without sea ice to understand better how that could impact the monsoon and the hydrological cycle in the present and the future. Better understanding of the mechanism would help us take steps towards better adaptation policies.
    • Hydrovolcanism in Okmok caldera, Alaska

      Almberg, Leslie Deanne (2003-12)
      Hydrovolcanic activity in Okmok Caldera predominated on the crater floor during approximately the first 775 years after the caldera collapsed at 2050 yr. B.P. Interactions between rising magma and shallow water (<100 m) controlled the development of lithofacies observed in the early post-caldera deposits. The distinctive lithofacies reflect the eruptive processes active as Cone D, a composite tuff, lava flow, and cinder cone, breached the surface of a lake which once covered the caldera floor. Three phases of eruptive activity constructed Cone D: first, a subaqueous cycle; second, emergent; and finally a purely subaerial strombolian and hawaiian phase built the edifice to its current height. Radiocarbon dates provide constraining ages for a catastrophic flood that emptied the 4.3 x 10⁹ m³ caldera lake and exposed the subaqueous lithofacies. An effusion rate of 2.7 x 10⁶ m³yr⁻¹ for this early eruptive period is calculated using eruptive volumes determined from a 5-m resolution DEM, based on AirSAR data. The prehistoric effusion rate determined for Cone D is on the same order of magnitude as the calculated historic effusion rate of 5.3 x 10⁶ m³yr⁻¹ from Cone A, based on mapped extents and thicknesses of lava flows and the cone itself.