Now showing items 1411-1430 of 3321

• #### Hydrologic Controls On Carbon Cycling In Alaskan Coastal Temperate Rainforest Soils

The northern perhumid North American Pacific coastal temperate rainforest (NCTR) extends along the coastal margin of British Columbia and southeast Alaska and has some of the densest carbon stocks in the world. Northern temperate ecosystems such as the NCTR play an important role in the global balance of carbon flows between atmospheric and terrestrial pools. However, there is little information on key components of the forest carbon budget in this region. Specifically, the large pool of soluble carbon that is transferred from soils via streamwater as dissolved organic carbon (DOC) certainly plays a role in the total carbon balance in wet forests such as the NCTR. In order to address this information gap, I applied the concept of hydropedology to define functional landscape units based on soil type to quantify soil carbon fluxes and apply these estimates to a conceptual model for determining the carbon balance in three NCTR watersheds. The strong hydrologic gradient among ecosystems served as a template for constructing a conceptual design and approach for constraining carbon budget estimates in the watersheds. Replicated hydropedologic units were identified in three classes: sloping bogs, forested wetlands, and uplands. Estimates of annual soil respiration and DOC fluxes from the hydropedologic types were obtained through seasonal measurements combined with temperature-dependent models. Soil respiration fluxes varied significantly across the hydrologic gradient where soil respiration was 78, 178, and 235 g CO2 m -2 y-1 in sloping bogs, forested wetlands and uplands respectively. Average DOC flux was 7.7, 30.3, to 33.0 g C m-2 y-1 in sloping bog, forested wetland, and upland sites respectively. Estimates of carbon efflux from the terrestrial ecosystem was combined with values of net primary productivity from remote sensing to determine net ecosystem production (NEP). The average NEP estimated in three NCTR watersheds was 2.0 +/- 0.8 Mg C ha-1. Carbon loss as DOC was 10--30% of the total carbon flux from the watersheds confirming the importance of this vector of carbon loss in the NCTR. The watershed estimates indicate that forests of the NCTR serve as a carbon sinks consistent with the average worldwide rate of carbon sequestration in terrestrial ecosystems.
• #### Hydrothermal history of the Long Valley Caldera, California: Life after collapse

Drilling of the Long Valley Exploratory Well (LVEW) on the resurgent dome in the 760 ka Long Valley Caldera opened a window to view the geologic history of the central caldera. Stratigraphic relationships indicate piston/cylinder (Valles-type) collapse for this caldera, and a resurgent structure intimately linked to post-caldera-collapse rhyolitic intrusions. Samples recovered from this and other wells proximal to the resurgent dome were characterized through isotope microanalytical techniques, petrographic and microprobe study, and analysis of fluid inclusions within alteration minerals. This work revealed the complexity of primary magmatic and secondary hydrothermal activity involved in the formation of a resurgent dome. Measurements of the $\rm\delta\sp{18}O$ composition of silicate components forming the intracaldera lithologies display disequilibrium within samples as a result of variable exchange with hydrothermal fluids. A maximum calculated temperature of $350\sp\circ\rm C$ at 1800 m depth in LVEW indicates paleohydrothermal temperatures exceeded the known present-day hydrothermal conditions by more than $100\sp\circ\rm C.$ Contouring of $\rm\delta\sp{18}O$ values from wells on a line crossing the caldera define a pattern of convective flow with upwelling beneath the resurgent dome. Although surface volcanism at the LVEW site ended about 650 ka, laser probe $\rm\sp{40}Ar/\sp{39}Ar$ microanalysis of samples from sill-like intrusions into the intracaldera ignimbrite reveals intrusive events at ${\sim}650$ ka, ${\sim}450$ ka, and ${\sim}350$ ka. Sanidine phenocrysts from the Bishop Tuff at 1772 and 1792 m depths and whole rock samples of the Mesozoic metavolcanic basement rocks at 1957 m depth record times of disturbance by hydrothermal pulses at ${\sim}530$ ka and ${\sim}350$ ka. Repeated emplacement of intrusions into the centrally located caldera ignimbrite was a primary process of resurgence. In turn, the feeders for the intrusions and the intrusions themselves supplied heat for resurgent-dome-centered hydrothermal flow. After approximately 300 ka, all activity shut off in the central caldera only to resume at ${\sim}40$ ka in response to renewed Holocene volcanic activity in the West Moat. Geophysical evidence of recent intrusive activity beneath the resurgent dome indicates this shallow magma emplacement mechanism is not totally extinct in the central caldera. Most likely a new cycle of volcanism and hydrothermal circulation is underway as the caldera matures.
• #### Hydrovolcanism in Okmok caldera, Alaska

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.
• #### I have a secret: choosing the persons to whom secrets are revealed

This Human Science research on secrecy is focused on the choices individuals make in choosing with whom they will share a secret. Specifically, this research probes the lived experience of women regarding their decision making about secret sharing and about choosing a person with whom to share a secret. In-depth, conversational interviews were conducted with five women. Narrative analysis was used to interpret the capta, resulting in three main themes. The findings show that characteristics such as trusting the potential secret keeper, predicting their possible reaction, and what benefits might be derived from self-disclosure are important for the participants in choosing to whom they will reveal secrets.
• #### "I'm a winner": the influences of group exercise on identity construction in cancer survivors

This research addresses the lived experience of individuals that have been diagnosed with cancer and who have participated in an oncology rehabilitation program as part of their treatment. Specifically, it examined the influence of the rehabilitation program in reshaping the participant's sense of identity. The study employs conversational interviewing to access the participant's understandings of the experience of the exercise program during cancer treatment, and utilizes thematic analysis in identifying three major themes emerged: 'I'm a Proactive Person', 'We're in the Same Boat', and 'There are Second Chances... You Better Make the Best of it'. Directions for future research include a study incorporating men and women, longitudinal studies, and research examining participants with a greater age range.
• #### Ice -wedge networks and "whale-hole" ponds in frozen ground

The patterns of ice-wedge networks and of whale-hole ponds in frozen ground self-organize by strong interactions between pattern elements. Mechanisms for the consistent spacing (15--25 m) and orientation between ice wedges are examined in a model encapsulating the opening of fractures under a combination of thermally-induced tensile stress, stress reduction near open fractures, and heterogeneity of frozen ground and insulating snow. Modeled networks are similar to ice-wedge networks on the Espenberg coastal plain, Bering Land-Bridge National Park, Alaska, at the level of variation among Espenberg networks, as indicated by: (i) comparisons of distributions of relative orientation and spacing between wedges; and (ii) application of nonlinear spatial forecasting to modeled and Espenberg network patterns. Spacing in modeled networks is sensitive to fracture depth and weakly sensitive to thermally-induced tensile stress and substrate strength, consistent with the narrow range of spacing between natural ice wedges in different regions. In an extended model that includes recurring fractures over thousands of winters, networks similar to natural ice-wedge networks form. The annual pattern of fractures diverges from the ice-wedge pattern, with only &frac12;--&frac34; of wedges fracturing in a single year at a steady-state reached after approximately 103 y. Short-lived sequences of extreme stress from cooling can permanently alter the spacing between and the fracture frequency of modeled ice wedges, suggesting that the existence and characteristics of existing and relic natural ice-wedge networks reflect extreme, not mean, climate conditions. Ponds on the Espenberg beach-ridge plain, approximately 2 m across and 1 m deep and surrounded by raised rings of ice-rich permafrost 2 m across and 0.5 m high, form through an interplay between localized bacterial decomposition of peat, thawing of frozen ground and frost heaving of peat in rings. Groups of hundreds of ponds at Espenberg assemble through time because new ponds are favored to form adjacent to raised rings around existing ponds. The nonlinear behavior that results from strong interactions in patterns of ice-wedge networks and in ponds suggests general limitations in the application of linear approaches to inferring the response of geomorphic systems to changes in forcing, such as climate change.
• #### Ice clouds over Fairbanks, Alaska

Arctic clouds have been recognized long ago as one of the key elements modulating the global climate system. They have gained much interest in recent years because the availability of new continuous datasets is opening doors to explore cloud and aerosol properties as never before. This is particularly important in the light of current climate change studies that predict changing weather scenarios around the world. This research investigates the occurrence and properties of a few types of ice clouds over the Arctic region with datasets available through the Arctic Facility for Atmospheric Remote Sensing (AFARS; 64.86° N, 147.84° W). This study exclusively focuses on ice clouds that form in the upper (cirrus clouds) and midlevels of the troposphere, and that are transparent to laser pulses (visible optical depth τ< 3.0 - 4.0). Cirrus clouds are icedominated clouds that are formed in the upper levels of the troposphere and are relatively thin such that their visual appearances range from bluish to gray in color. Mid-level ice clouds are those clouds primarily composed of ice crystals forming in the midlevels of the troposphere. It is hypothesized that unlike the basic midlevel cloud type (altostratus), other varieties of midlevel ice clouds exist at times over the Arctic region. The midlevel ice clouds studied here are also transparent to laser pulses and sometimes appear as a family of cirrus clouds to a surface observer. Because of their intermediate heights of occurrence in the troposphere, these could have microphysical properties and radiative effects that are distinct from those associated with upper level ice clouds in the troposphere. A ground-based lidar dataset with visual observations for identifying cloud types collected at AFARS over eight years is used to investigate this hypothesis. Cloud types over AFARS have been identified by a surface observer (Professor Kenneth Sassen) using established characteristics traits. Essential macrophysical properties of the clouds are derived from the lidar data, which serves as a climatological representation for the visually identified cirrus and mid-level ice clouds over a typical sub-Arctic location. Synoptic-scale weather patterns conducive for such cloud type formations are derived using a clustering technique applied to a re-analysis dataset. The cloud properties derived from ground-based lidar over AFARS are used to assess the cloud observations from the CALIPSO satellite.
• #### Ice, bedload transport, and channel morphology on the upper Kuparuk River

The objective of this study was to quantify the impact of bottom ice on sedimentation processes at a study site on the Upper Kuparuk River, in Northern Alaska. The approach taken was to use the Meyer-Peter and Mueller (1948) and Parker (1990) equations to determine bedload rating curves at four cross sections within the study reach, and to apply these rating curves to the ten year flow history of the study site to determine the total potential bedload transport that was suppressed during snowmelt runoff. In conjunction with this analysis, a tracer rock study was performed at the study site. During the first two years of the project, the field study yielded little bedload transport information, as there were no competent flows during this time. However, the storm of record occurred in August 02 2002, which provided an opportunity to observe the geomorphic response to a major event, to estimate an average bedload transport rate based on the virtual velocity of the recovered tracer rocks, and to compare the predictive methods to the tracer data based calculations. The results suggest that the potential bedload transport (500 m³) over the ten-year flow history is comparable to the amount of transport that occorred during the extreme event of August 2002 (870 m³), and that the suppression of bedload transport, due to an ice covered bed surfaces, likely affects the morphology and sediment supply of the river.
• #### Ichthyoplankton vertical distribution and vertical migration in Auke Bay, Alaska

Vertical distributions of larval fishes were examined in Auke Bay, Alaska using an opening/closing 1.0 m² Tucker trawl horizontally towed, at six depths, every four hours for 24 hours. In daytime, larval fishes concentrated at 5-10 m depths, coincident with highest prey densities. At night, osmerids ascended to the surface, walleye pollock and northern smoothtongue descended, whereas other species simply dispersed. A significant relationship existed between larval walleye pollock length and depth distribution with larger larvae migrating further than smaller larvae. Yolk-sac larvae were randomly distributed vertically. Larval walleye pollock are daytime feeders, primarily on copepod nauplii. Larval pollock approximately 7.0 - 7.5 mm standard length expand their diet to include copepodites.
• #### Idealized Modeling Of Circulation Under Landfast Ice

Idealized analytical and numerical models are used to elucidate the effects of a spatially variable landfast ice cover on under-ice circulation. Three separate forcing mechanisms are investigated; lateral inflow onto an ice-covered shelf (an elevated sea level at the western boundary), a spatially uniform upwelling wind blowing along the seaward landfast ice edge and a buoyant inflow under the ice cover that enters the domain through the southern coastal wall. The idealized models are configured to resemble the shallow Alaskan Beaufort Sea shelf. Models show that the inclusion of landfast ice means shelf response is substantially different from an ice-free shelf. In the case of a lateral inflow, landfast ice spreads the inflow offshore (in a manner similar to bottom friction) but the change in surface stress across the ice edge (from ice-covered to ice-free) limits the offshore spreading. In the case of an upwelling wind along the ice edge, the low sea level at the ice edge (due to ice edge upwelling) leads to a cross-shore sea level slope between the coast (high sea level) and the ice edge (low sea level), which drives a geostrophically balanced flow upwind. In the absence of along-shore changes in wind or ice the circulation does not vary along the shelf and currents near the coast are O(10 -3) m s-1. Along- and cross-shore variations in the ice-ocean friction coefficient introduce differences in the response time of the under-ice flow and can lead to along-shore sea level slopes, which drive along-shore flows near the coast (< 0.06 m s-1). In the case of a time dependent buoyant inflow, the landfast ice spreads the buoyant inflow much farther offshore (~ 9 times the local baroclinic Rossby radius, ~ 45 km) than in the ice-free case (< 30 km). When the ice width is finite, the change in surface across the ice edge acts to restrict offshore flow (in the anti-cyclonic bulge) and inhibits onshore flow farther downstream.
• #### Idealized Modeling Of Seasonal Variation In The Alaska Coastal Current

Analytical and idealized-numerical models were used to understand the physical processes that govern the seasonal variation and fate of the freshwater in the Alaska Coastal Current (ACC). The ACC is forced by freshwater inflow and by mean easterly winds that cause downwelling over the shelf. Two-dimensional modeling using a line-source buoyant inflow gives the coastal current depth $<f> H=<fr><nu>3<sup>2/3</sup></nu><de>2</de></fr><fen lp="par"><fr><nu> f<sup>2</sup>Q<sup>2</sup></nu><de>g<sup>'</sup></de></fr> <rp post="par"></fen>t<sup>2/3</sup></f>$ and coastal current width $<f> Y<inf>2D</inf>=3<sup>1/3</sup><fen lp="par"><fr><nu>g<sup>' </sup>Q</nu><de>f<sup>2</sup></de></fr><rp post="par"></fen><sup> 1/3</sup>t<sup>1/3</sup></f>$, where f is the Coriolis frequency, g ' is reduced gravity, Q is inflow rate and t is time since inflow began. Addition of downwelling wind-stress causes a steep coastal current front that intersects the bottom and is either convecting, stable and steady, or stable and oscillatory depending on $<f> <fr><nu>D</nu><de><g>d</g><inf>*</inf></de></fr></f>$ and $<f> <fr><nu>b<inf>y</inf></nu><de>f<sup>2</sup></de></fr></f>$, where D is bottom depth, delta* is an Ekman depth and by is the cross-shelf buoyancy gradient. Three-dimensional modeling of a half-line source initially develops two-dimensionally but becomes three-dimensional from a balance between coastal influx of buoyancy and its downstream transport. This balance results in a coastal current depth limit $<f> H<inf><rf>max</rf></inf>=<fen lp="par"><fr><nu>2Qf</nu><de>g<sup> '</sup></de></fr><rp post="par"></fen><sup>1/2</sup>x<sup> 1/2</sup></f>$, where x is along-shelf distance. This limit is unchanged under downwelling wind-stress and is reached on time scales of less than 1 month for the ACC. The half-line source coastal current width develops as $<f> Y<inf>2D</inf></f>$ away from the beginning of the line source. Imposition of a downwelling wind-stress tau results in an approximate balance among wind-stress and along- and cross-shelf momentum advection so that the current width is reduced to $<f> Y<inf>wind</inf>&ap;L<inf>D</inf><fen lp="par"><fr><nu>Qf</nu> <de><g>t</g>/<g>r</g><inf>0</inf></de></fr><rp post="par"></fen><sup> 1/2</sup></f>$, where LD is the Rossby radius of deformation. Waves and eddying motions eventually grow in the half-line source coastal current with wavelengths proportional to the coastal current width and with a downstream phase speed slower than the maximum current speed. These features cause an offshore flux of buoyant water, a broader coastal current and accumulation of buoyancy on the shelf. Increasing downwelling wind stress reduces the effects of the instabilities. Although buoyancy accumulates on the shelf during most model runs, there is little accumulation under maximum winter downwelling wind-stress. This suggests that freshwater accumulates on the shelf from spring through fall, but is then transported downstream during winter.
• #### Identification and application of molecular markers to chum salmon population genetics

I developed a new technique, DEco-TILLING (an adaptation of Eco-TILLING), to discover useful single nucleotide polymorphisms (SNPs) rapidly and inexpensively. Some chum salmon (Oncorhynchus keta) populations have declined in Western Alaska and in other areas of their geographic range. Possible reasons include climate shifts, by- catch in fisheries, and other perturbations. Genetics offers powerful tools that can be used to monitor this species on the high seas in stock mixtures aiding management of by- catch identification and other contributors to declines. Single nucleotide polymorphisms are a genetic marker that can be easily and rapidly surveyed on many individuals. Tools like SNPs offer advantages in discriminating stocks in mixtures. However, tens or hundreds of informative SNPs must be discovered from among the millions in the chum salmon genome. Available discovery methods introduce ascertainment bias into this process, which can result in uninformative SNPs or the failure to identify useful ones. I incorporated and improved a genotyping assay to screen SNPs in thousands of individuals for a tenth of the cost of the standard available assay, and improved an assay to resolve the phase of linked SNPs. I show that the SNPs that I discovered are informative and can be use for mixed stock analysis.
• #### Identification and characterization of inconnu spawning habitat in the Sulukna River, Alaska

Inconnu (Stenodus leucichthys) is present throughout much of the Yukon River drainage in Alaska, but only five spawning areas have been identified. Spawning habitat requirements are therefore thought to be very specific; however, the physical qualities of these habitats have only been characterized in general terms. The Sulukna River is one of five identified inconnu spawning areas within the Yukon River drainage. A systematic sampling design was used in September and October of 2007-2008 to define Sulukna River spawning locations. Presence of inconnu was identified using hook and line sampling methods and spawning was verified by catching broadcast eggs in plankton nets. Small-scale, large-scale, and chemical habitat variables were sampled at transects located every 1.8 river kilometer (rkm). Project results indicate that spawning habitat was confined to a narrow reach of approximately 20 rkm. Spawning habitat occurred significantly more often in transects characterized with substrate between 6 and 12 cm, a width to depth ratio between 15 - 36, and water conductivity between 266 - 298 microsiemens per centimeter. Similar studies on other known spawning habitats would reveal whether these qualities are common to all inconnu spawning populations or unique to the Sulukna River.
• #### Identification and evolution of tectonic faults in the greater Fairbanks area, Alaska

I have identified evidence for potentially active northeast-striking faults in the greater Fairbanks area and have developed a model for their evolution that defines the character of faults and timing of structural events. Seismicity, topographic data, and geological and geophysical maps show that potentially active faults correspond with previously mapped bedrock faults, topographic lows, and magnetic anomalies. Seismicity indicates that faults in Interior Alaska have low to moderate tectonic activity; geomorphic and structural analyses of mapped faults indicate they are dominantly left-lateral strike-slip, but have smaller normal or reverse components. The normal component of slip increases to the west toward the Nenana basin based on tilted fault block geometries observed in seismicity. Deformed Pliocene to Quaternary strata, placer deposits presumably related to tectonic-induced stream capture events, and geomorphic anomalies such as valley and basin asymmetry, barbed drainages, and changes in river morphology all suggest Pliocene-Quaternary tectonic activity along northeast-striking left-lateral faults. Northeast-striking faults have been at least episodically active since the late Cretaceous. Northeast-striking fault-hosted gold deposits related to ~90 Ma intrusions suggest that fault parallel extension fractures or tension veins formed at ~90 Ma during a period of northwest-southeast extension. Thermochronological data are consistent with exhumation at ~56-42 Ma, possibly resulting from dextral shearing between the Denali and Tintina faults. Northeast-striking faults were reactivated as normal faults along pre-existing extensional trends. Thermochronological data suggest that strike-slip displacement on the Tintina fault significantly decreased at ~42 Ma. However, dip-slip motion continued along northeast-striking faults after 42 Ma as a result of contraction related to northward plate convergence. Drainage restorations, high-levels of background seismicity, and focal mechanisms support the hypothesis that at ~6 Ma, significant left-lateral motion occurred along northeast-striking faults and has continued to the present.
• #### Identification And Function Of Male Moose Urinary Pheromones

Olfactory communication and associated scent-marking activities play a major role in the behavioral ecology of many mammals. During the mating season (rut), scent marking associated with urine of male cervids is an important chemical cue to relay information to conspecifics. Specifically, adult male moose (Alces alces) dig rutting pits in which they urinate, and females respond strongly to urine deposited in pits. A behavioral bioassay was developed to aid in the identification and function of adult male moose urinary pheromones, which elicited the behaviors observed in females during rut. Several behavioral bioassays were conducted to delineate the putative pheromones(s). It was experimentally established that when female moose were presented with urine from the pre-rut and rut periods, females preferred the urine from rut. Moreover, this experiment documented that females responded markedly to constituent(s) in rut urine by wallowing. Rut urine can be chemically extracted and maintain its bioactivity when presented to female moose, the partition of the urine that had bioactivity was delineated. Information was provided on the chemical and physical nature of the chemosignal---not a protein, or carbohydrate, relatively non-polar, and of low molecular weight. Urinary constituents that may function as the putative pheromone(s) were characterized. Some of the chemical differences that existed in rut urine and may not function as chemical signals were eliminated. Also provided, was evidence that female moose may utilize the main olfactory system to detect chemosignals present in rut urine.