• Macro description of public beach attributes that may effect turtle nesting in Playa de Coco, La Flor (Pacific, southwest Nicaragua) and Pacuare and Tortuguero, (Caribbean, Costa Rica), July 2013

      Huettmann, Falk (Maderas Rainforest Conservancy, 2013-07-29)
      We observed several macro beach features of four public sea turtle nesting beaches for Playa Coco (latitude11.15382, longitude 85.80051; geographic datum WGS84) and La Flor (latitude 11.14282, longitude 85.79418) in southwest Nicaragua (Pacific), and Pacuare Reserve (latitude10.20123, longitude, 83.25925) and Tortugero (latitude 10.59583, longitude 83.52520) in Costa Rica (Caribbean). Recorded features included the intensity of tourism, number of different predator species of sea turtle hatchlings, number of tourists, and line transects for density of plastic, wood, metal, and crab burrows. Light and sound disturbances at night were also recorded as well as man-made objects left overnight on the shore of the beaches. This data set is part of a sea turtle class with Maderas Rainforest Conservancy and provides a basic and non-invasive description and a snap shot in time and space for public nesting beaches of relevance for Olive Ridley (Lepidochelys olivacea, TSN 173840), Green (Chelonia mydas TSN 173833), Hawksbill (Eretmochelys imbricata TSN ) and Leatherback (Dermochelys coriacea TSN 173843 ) sea turtles. Some photos were taken for vizualisation purposes.
    • Mafic -Silicic Magma Interactions From Volcanic To Plutonic: Implications For The Evolution And Eruption Of Silicic Magma Chambers

      Chertkoff, Darren Grant; Eichelberger, John C. (2002)
      In order to investigate the role that mafic-silicic magma interactions play in the origin, evolution, and eruption of shallow crustal magma chambers, a three-part study was undertaken of both effusive (Mt. Dutton volcano, Alaska) and explosive (Volcan Ceboruco, Mexico) eruptions, as well as associated volcanic (Unalaska Formation) and plutonic (Captain's Bay pluton) suites. Major- and trace-element variations suggest that the eruptive products (both andesite and dacite) of Mt. Dutton are not simply a result of fractional crystallization, but instead are affected to varying degrees by two-component mixing of distinct and separate magmas. In this case, petrologic and geochemical evidence, as well as eruptive stratigraphy, suggests the evolution of shallow, silicic magmatic systems inferred to exist beneath small stratovolcanoes can be modeled as resulting from repeated intrusion of mantle-derived mafic magmas into shallow, silicic, crystal-rich, crustal magma chambers. Volcan Ceboruco, Mexico, erupted ~1000 years ago, producing the Jala Pumice and forming a ~4 km wide caldera. During that eruption, 2.8 to 3.5 km3 of rhyodacite magma and 0.2 to 0.5 km 3 of mixed dacite magma were tapped and deposited as the Jala Pumice. Subsequently, the caldera was partially filled by extrusion of the Dos Equis Dome, a low-silica dacite dome with a volume of ~1.3 km3. In this case, petrographic evidence indicates that the Jala and Dos Equis dacites originated largely through the mixing of three end-member magmas: (1) rhyodacite magma, (2) dacite magma, and (3) mafic magma. Study of the Captain's Bay pluton and Unalaska Formation volcanics from Unalaska Island, Alaska, indicates that whole-rock compositions between the two suites span a similar range and particular plutonic units correspond chemically to specific volcanic products. Plagioclase phenocrysts from these chemically similar units also display comparable textures and compositional zoning patterns. Most strikingly, magmatic enclaves found within the pluton show a chemical affinity to andesite lavas from the volcanic suite. In this case, mixing of melts and extrusion of hybrid lava may be a prompt response to recharge, whereas the enclaves may represent "leftovers" that thermally equilibrated with the reservoir as a whole.
    • Magmas In Motion: Degassing In Volcanic Conduits And Fabrics Of Pyroclastic Density Current

      Burgisser, Alain; Eichelberger, John (2003)
      Volcanoes are caused by the transport of magma batches from the Earth's crust to the surface. These magmas in motion undergo drastic changes of rheologic properties during their journey to the surface and this work explores how these changes affect volcanic eruptions. The first part of this study is devoted to the dynamic aspects of degassing and permeability in magmas with high pressure, high temperature experiments on natural volcanic rocks. Degassing is measured by the influence of decompression rate on the growth of the bubbles present in the magma while permeability is deduced from the temporal evolution of these bubbles. The parameterization of our results in a numerical model of volcanic conduit flow show that previous models based on equilibrium degassing overestimate the acceleration and the decompression rate of the magma. Assessing permeability effects derived form our results show that the transition between explosive and effusive eruptions is a strong function of the magma initial ascent rate. The second part of this work is a unification of two end-members of pyroclastic currents (highly concentrated pyroclastic flows and dilute, turbulent pyroclastic surges) using theoretical scaling arguments based on multiphase physics. Starting from the dynamics of the particle interactions with a fundamental eddy, we consider the full spectrum of eddies generated within a turbulent current. We demonstrate that the presence of particles with various sizes induces a density stratification of the current, leading to its segregation into a basal concentrated part overlain by a dilute cloud. To verify our predictions on the interactions of such a segregated pyroclastic current with its surroundings (hills and sea), we studied the products of the 2050 BP caldera-forming eruption of Okmok Volcano (Alaska). This field study allowed us to reconstruct the eruptive sequence and to validate the main aspects of our theoretical model, such as the superposition of a dense and dilute part, their decoupling at sea entrance and the characteristics of the particles they transport.
    • Magnetic Reconnection As A Chondrule Heating Mechanism

      Lazerson, Samuel A.; Wiechen, Heinz (2010)
      The origin of chondrules (sub-millimeter inclusions found in stony meteorites) remains today an open question despite over century of examination. The age of these proto-solar relics shows a well defined cutoff of around 4.5 billion years ago. This places them as the oldest solids in the solar system. Chemical examination indicates that they experienced heating events on the order of 5000 K/hr for periods of around 30 minutes, followed by extending periods of cooling. Additional examination indicates the presence of large magnetic fields during their formation. Most attempts to explain chondrule formation in the proto-solar nebula neglect the existence of a plasma environment, with even less mention of dust being a charge carrier (dusty plasma). Simulations of magnetic reconnection in a dusty plasma are forwarded as a mechanism for chondrule formation in the proto-solar nebula. Here large dust-neutral relative velocities are found in the reconnection region. These flows are associated with the dynamics of reconnection. The high Knudsen number of the dust particles allows for a direct calculation of frictional heating due to collisions with neutrals (allowing for the neglect of boundary layer formation around the particle). Test particle simulations produce heating equivalent to that recorded in the chondrule mineral record. It is shown that magnetic reconnection in a dusty plasma is of fundamental importance to the formation of the most primitive solids in the solar system.
    • Magnetic reconnection in the presence of sheared plasma flow

      La Belle-Hamer, Annette Louise; Lee, L. C. (1994)
      Classical models of magnetic reconnection consist of a small diffusion region bounded by two slow shocks, across which the plasma is accelerated. Most space plasma current sheets separate two different plasmas, violating symmetry conditions across the current sheet. One form of asymmetry is a sheared plasma flow. In this thesis, I investigate the magnetic reconnection process in the presence of a shear flow across the current sheet using two-dimensional magnetohydrodynamic (MHD) simulations. The results show that only for sheared flow below the average Alfven velocity of the inflow regions can steady state magnetic reconnection occur. A detailed examination of the Rankine-Hugoniot jump conditions reveals that the two slow shocks of earlier models are replaced by a strong intermediate shock and a weaker slow shock in the presence of shear flow. Both symmetric and asymmetric density profiles are examined. Depending upon the direction of the flow in the adjacent inflow region, the effects from the sheared flow and the effects from the density asymmetry will compete with or enhance each other. The results are applied to the dayside and flank regions of the magnetosphere. For tailward flow in the flanks, the two asymmetries compete making the magnetic field transition layer broad with the high speed flow contained within the transition region. For the dayside region, the magnetic field transition region is thin and the accelerated flow is earthward of the sharp current layer (magnetopause). These results are consistent with the data. A velocity shear in the invariant direction was examined under otherwise symmetric conditions. With the magnetic field initially only in the $x-y$ plane, $B\sb{z},$ and consequently field-aligned current, is generated by the initial $v\sb{z}.$ The field-aligned current depends on the velocity profiles in all directions. For a velocity sheared in both the z and the y direction, the results show a very localized region of large field-aligned currents.
    • Magnetohydrodynamic Simulations Of Plasma Dynamics In The Magnetospheric Cusp Region

      Adamson, Eric T.; Otto, Antonius (2012)
      The Earth's magnetospheric cusp regions are rich in interesting plasma physics. The geomagnetic cusps offer solar wind plasma a relatively easy entry point into the magnetosphere through magnetic reconnection with the interplanetary magnetic field. The cusp regions are characterized by various interesting and important observations such as low energy particle precipitation, significant outflow of ionospheric material, and the frequent presence of energetic particles in regions of depressed magnetic field strength. The physical mechanisms that lead to these observations is often unresolved, for instance the acceleration mechanism for energetic cusp populations is not understood, nor is it known what implications they may have on magnetospheric dynamics. It is however, well accepted that magnetic reconnection plays a critical role in the vicinity of the cusps and is likely responsible for much of the dynamics in the region. Modeling of the geomagnetic cusps is notoriously challenging. Global magnetospheric models have proven indispensable in the study of the interaction of the solar wind plasma with the Earth's magnetosphere, however, the exterior cusp region poses a significant challenge for these models due to their relatively small scale. I have developed a mesoscale cusp-like magnetic field model in order to provide a better resolution (up to 300 km) of the entire cusp region than is possible in these global models. Typical observational features of the high-altitude cusps are well reproduced by the simulation. Results for both strongly northward and strongly southward interplanetary magnetic field indicate extended regions of depressed magnetic field and strongly enhanced plasma beta (cusp diamagnetic cavities). The Alfvenic nature of the outer boundary between the cusp and magnetosheath, in addition to the flow characteristics in the region, indicate that magnetic reconnection plays an important role in structuring the high-altitude cusp region. The inner boundaries with magnetosphere are gradual transitions forming a clear funnel. These cavities further present a unique configuration in which reconnecting magnetic flux tubes may gain a significant amount of flux tube entropy (H = p1/gammaV) through topological changes due to magnetic reconnection.
    • Magnetospheric imaging of EUV emissions at 83.4 and 30.4 nm wavelengths

      Garrido, Dante Espino; Smith, R. W. (1994)
      Magnetospheric images are constructed from resonant scattering of emissions by He$\sp+$ 30.4-nm and O$\sp+$ 83.4-nm ions from different spatial locations to study the structure of the intensities and its relation to the distribution of He$\sp+$ and O$\sp+$ ions around the Earth. The image intensities at these EUV wavelengths were obtained from a knowledge of ion scattering rates and available data on ion densities. This particular approach is called forward modelling and consists of the calculation of simulated EUV images of the magnetosphere. Different regions in the magnetosphere have been considered in this study to determine the dependence of the image intensities on ion energies and ion drift speeds with respect to the Sun-Earth line. Hot O$\sp+$ ions in the energy range from 1 keV to 50 keV are present in the plasma sheet with typical densities of the order of 0.1 ions cm$\sp{-3}$ arising during disturbed times. Image intensities of the order of a few millirayleighs were obtained in our simulations for these densities. During quiet times the densities are of the order of 0.05 ions cm$\sp{-3}.$ The reduction of the image intensities as a result of Doppler shifts caused by ion motion relative to the Sun-Earth line is discussed in detail and the effects of ion dynamics (particle acceleration) in the polar cap on the image intensities have also been analyzed for both He$\sp+$ and O$\sp+$ ions. The possibility of detecting polar outflows may also depend on the location of the imager. Simulated images of the plasmasphere and trough regions in both 30.4-nm and 83.4-nm wavelengths have been obtained to reflect the relative abundance of the ions in these regions. Photometric intensities of He$\sp+$ at 30.4 nm were obtained from a spinning rocket at an altitude of 435 km. The different viewing angles covered a wide range of regions in the magnetosphere, and this particular rocket geometry offered the possibility of obtaining the He$\sp+$ ion distribution from the measured intensities. This method (forward inversion) can be applied to 2-D images and it is shown that it is possible to extract 3-D ion distributions from the images.
    • Managing The National Wildlife Refuge System With Climate Change: The Interaction Of Policy, Perceptions, And Ecological Knowledge

      Magness, Dawn Robin (2009)
      The National Wildlife Refuge System (NWRS) is committed to conserving fish, wildlife, and plants for current and future generations of Americans. Given a rapidly changing climate, managers may employ various adaptation strategies to meet legislated mandates. I explore how ecological context, policy, perceptions and available ecological knowledge inform adaptation strategies. In Chapter 2, I develop an ecosystem vulnerability framework to better understand how climate change risk and ecosystem resilience interact to impact the NWRS. With GIS, I rank refuges based on historic temperature change, historic precipitation change, and sea-level rise risk. To index resilience, I rank refuges based on refuge size, landscape road density, and elevation range. Using this GIS analysis and the ecosystem vulnerability framework, I categorize the 527 refuges into four groups (refugia, ecosystem maintenance, facilitate transitions, and experiments in natural adaptation) that provide a necessary context for national, strategic adaptation planning. In Chapter 3, I survey 32% of NWRS biologists and managers to understand how policy and their perceptions of climate change influence adaptation choice. Currently, managers and biologists independently decide if climate change is natural or anthropogenic for wildlife management, and this conceptualization becomes important for deciding whether reactionary or anticipatory adaptation approaches are more appropriate. Although respondents considered practicability, they prefer historic condition. Respondents also prefer ecosystems and species adapt naturally. In a rapidly changing climate, natural adaptation may not be feasible without large-scale extinction. Nonetheless, many biologists and managers are uncomfortable with the alternative of manipulating ecosystems and species assemblages toward future conditions. Finally, understanding climate change impacts requires the analysis of complex ecological relationships over time and this complexity creates another barrier for implementing a national adaptation strategy. In Chapter 4, using a data-mining approach on data from scaled-down GCMs and an atypical monitoring approach, I build bioclimatic envelope models to show how the distributions of two passerines will potentially shift in response to climate change over the next 100 years on Kenai National Wildlife Refuge. In order to effectively manage species within the context of strategic adaptation planning, the NWRS must design future biological monitoring approaches with spatial modeling in mind.
    • Mapping methods and observations of surficial snow/ice cover at Redoubt and Pavlof volcanoes, Alaska using optical satellite imagery

      Rahilly, Kristen E.; Dehn, Jonathan; Pettit, Erin; Webley, Peter (2014-08)
      Alaska is a natural laboratory for the study of how active volcanism interacts with underlying seasonal snow, perennial snow, and glacial ice cover. While over half of the historically active volcanoes in Alaska have some degree of perennial snow or glacial ice, all Alaskan volcanoes have a covering of seasonal snow for a period of time throughout the year. Previous research has centered on how volcanic deposits erode away the underlying snow/ice cover during an eruption, producing volcanic mudflows called lahars. Less emphasis has been placed on how variations in the snow/ice cover substrate effect the efficiency of meltwater generation during a volcanic eruption. Glacial ice, perennial snow, and seasonal snow can all contribute significantly to meltwater, and therefore the variations in the types of snow/ice cover present at Alaskan volcanoes must be analyzed. By examining the changing spatial extent of seasonal snow present at a volcano during multiple Alaskan summers, the approximate boundaries of perennial snow and ice can be mapped as the snow/ice cover consistently present at the end of each ablation season. In this study, two methods of snow/ice cover mapping for Redoubt and Pavlof volcanoes are analyzed for efficiency and accuracy. Identification of the best method allows for mapping of the snow/ice cover consistently present during each Alaskan summer month over at least two different years. These maps can serve as approximations for the snow/ice cover likely to be present at both volcanoes during each summer month. Volcanic deposits produced during the 2009 Redoubt and 2013 Pavlof eruptions are spatially linked to these snow/ice cover maps so that future research can focus on the interaction between deposits and type of snow/ice substrate. Additional observations and conclusions are made regarding how the visible snow/ice cover varies during and after each eruption.
    • Marine boat surveys for the olive ridley sea turtle (Lepidochelys olivacea) off of the coast of La Flor Playa de Coco, Nicaragua, 9th and 13th July 2013

      Huettmann, Falk (2013-07)
      Two marine monitoring boat surveys were conducted off the coasts of La Flor and Playa de Coco, southwest Nicaragua. Single and mating pairs of Olive Ridley sea turtles (Lepidochelys olivacea, TSN 1738400), were observed and activity and geo-referencing recorded with a GPS (decial latitude and longitude, geographic datum WGS84). Single turtles were seen basking and breathing at the surface of the water and subsequently would dive into the water. Mating pairs were also observed. Males held onto the females via a hook on the front flippers, scars were observed but no tumors were detected. Some photos were taken for visualisation.
    • Marine surveys (at sea and 16 ports) of Atlantic seabirds, passerines and marine mammals during Semester at Sea cruise fall 2014

      Huettmann, Falk (2014-12-08)
      This data set was collected during the Fall 2014 cruise with Semester at Sea (SAS). It covers 2 MS Excel files of marine species surveys (three worksheets: opportunistic 5 minutes, and Distance Sampling 10 minutes, Individual Sightings) as well as harbour species surveys (one file with one worksheet). The SAS cruise of fall 2014 took place in the Atlantic, southern Baltic, the Mediterrean and Caribbean Seas and has the following bounding box coordinates (decimal degrees of latitude and longitude WGS 1984): Highest latitude 59.88929 North, lowest latitude -22.28687 South, most western longitude -81.80984, most eastern longitude -40.91894. The following 16 ports were covered: Southampton (UK), St. Petersburg (Russia), Gdansk (Poland), Rostock (Germany), Antwerp (Belgium), Le Havre (France), Dublin (Ireland), Lisbon (Portugal), Cadiz (Spain), Casablanca (Morocco), Citivecchia (Italy), Barcelona (Spain), Rio De Janeiro (Brazil), Salvador (Brazil), Bridgetown (Barbados), Havanna (Cuba) and Fort Lauderdale (Florida US). The starting date was August 21st and the ending date was Dec 7th 2014. The cruise included app. 632 students and 380 staff and crew (including professors). This dataset includes data from opportunistic 5 minute surveys ('presence only'), as well as 10minute long Distance Sampling surveys (abundances) done 2-3 times per day. All data are geo-referenced. In addition, many additional individual sigthings by the shipboard community and local excursion (terrestrial) data are also included, photos were collected whenever possible. Additional data like state of the ocean, plastic pollution, vessels in view, and weather were also collected. This data set can serve as a basic quantitative large-scale snapshot for the Atlantic region and its ecosystem in fall 2014. The 5 minute-long opportunistic at-sea surveys featured app 102 species; more species were detected in the other surveys. Most of these species are seabirds, with a few mamrine mammals, squid, fish sightings etc. Noteworthy are the high ocurrences of passerines at sea! This dataset has maximum 29 columns, and 314 rows (5 minute Opportunistic Survey), 146 rows (10min abundance surveys) and 271 rows (Individual Opportunistic Sightings); it is <1MB in size. A few photos exist and can be obtained upon request.
    • Marine turtle nesting track survey on Playa de Coco, Nicaragua, and Playa Vigilada (Pacuare) and Tortuguero, Costa Rica, July 2013

      Huettmann, Falk (Maderas Rainforest Conservancy, 2013-07)
      Marine turtle tracks were observed on the beaches of Playa de Coco (Pacific, southwest Nicaragua; latitude 11.15382 , longitude 85.80051; WGS 84 ), Playa Vigilada (Pacuare; latitude 10.20123, longitude 83.25925) and Tortuguero (Caribbean, Costa Rica; latitude 10.59583, longitude 83.52520) during the early morning hours. Number of sea turtle tracks were counted along a transect. This was done by walking along the shore every morning to look for specific tracks that matched the tracks of sea turtle species. Maximum number of tracks observed was 8, while the minimum number obsereved was 0. Tracks had distinct features with flipper tracks visible on the edges of the tracts with a single line down the middle were the tail would drag. Tracks were seen to go straight onto the shore while some came up the shore and curved slightly before going back to the ocean. Tracks were observed near resturants and hotels. We observed Olive Ridely sea turtle (Lepidochelys olivacea, TSN 173840) in Playa de Coco, hatchling Leatherback sea turtles (Dermochelys coriacea, TSN 173843), and Green sea turtles (Chelonya mydas, TSN173833) in Playa Vigilada and Tortuguero,
    • Marine-derived nutrients in riverine ecosystems: developing tools for tracking movement and assessing effects in food webs on the Kenai Peninsula, Alaska

      Rinella, Daniel J. (2010-05)
      Marine-derived nutrients (MDN) delivered by spawning Pacific salmon (Oncorhynchus spp.) contribute to the productivity of riverine ecosystems. Optimizing methods for measuring MDN assimilation in food webs will foster the development of ecologically based resource management approaches. This dissertation aims to better understand relationships among spawning salmon abundance, biochemical measures of MDN assimilation, and the fitness of stream-dwelling fishes. The goals of my first research chapter were (1) to understand the factors that influence stable isotope ([delta]¹³C, [delta]¹⁵N, and [delta]³⁴S) and fatty acid measures of MDN assimilation in stream and riparian biota, and (2) to examine the ability of these measures to differentiate among sites that vary in spawning salmon biomass. For all biota studied, stable isotopes and fatty acids indicated that MDN assimilation increased with spawner abundance. Among Dolly Varden (Salvelinus malma), larger individuals assimilated proportionately more MDN. Seasonal effects were detected for aquatic macroinvertebrates and riparian horsetail (Equisetum fluviatile), but not for Dolly Varden. Of all dependent variables, Dolly Varden [delta]¹⁵N had the clearest relationship with spawner abundance, making this a good measure for monitoring MDN assimilation. Expanding on these results, two chapters examined potential fisheries management applications. The first sought to identify spawner levels above which stream-dwelling Dolly Varden and coho salmon (O. kisutch) parr cease to gain physiological benefits associated with MDN. RNA-DNA ratios (an index of recent growth rate) and energy density indicated saturation responses where values increased rapidly with spawner abundance up to approximately 1 kg/m² and then leveled off. In coho salmon parr, energy density and RNA-DNA ratios correlated significantly with [delta]¹⁵N. These results show strong linkages between MDN and fish fitness responses, while the saturation points may indicate spawner densities that balance salmon harvest with the ecological benefits of MDN. The second application tested a quick and inexpensive method for estimating, spawning salmon abundance based on [delta]¹⁵N in stream-dwelling fishes. Estimates made with coho salmon pair were unbiased, tightly correlated with observed values, and had a mean absolute deviation of 1.4 MT spawner biomass/km. Application of this method would allow estimates of annual escapement to be made on a potentially large number of streams.
    • Mass Balances And Dynamic Changes Of The Bering, Malaspina, And Icy Bay Glacier Systems Of Alaska, United States, And Yukon, Canada

      Muskett, Reginald R.; Lingle, Craig (2007)
      The Bering and the Malaspina Glacier systems of south-central Alaska, U.S.A., and southwest Yukon Territory, Canada, in the Saint Elias Mountains constitute the two largest temperate surge-type piedmont glaciers on Earth. This is largest region of glaciers and icefields in continental North America. Determining and understanding the causes of wastage of these two glaciers is important to understanding the linkages of glacier mass balance to climate change, glacier dynamics, and the contributions of the glaciers of northwestern North America to rising sea level. Presented are the first detailed estimate of the net mass balances of the Bering and Malaspina Glacier systems, the effects of glacier dynamics on their accumulation areas, and the wastage of the tidewater glaciers of Icy Bay. The combined wastage of the Bering and Malaspina Glacier systems from 1972 to 2003, 254 +/- 16 km 3 water equivalent over a glacier area of 7734 km2, is equivalent to an area-average mass balance of -1.06 +/- 0.07 m/y over that time period. This represents a contribution to global sea-level rise of 0.70 +/- 0.05 mm, 0.023 +/- 0.002 mm/yr from 1972 to 2003. This is roughly 0.8% of the modern sea-level rise as estimated from tide-gauges and satellites, and roughly 9% of the contribution from non-polar glaciers and ice caps. Glacier wastage has been caused by climate warming (negative mass balance) superimposed on the effects of glacier dynamics. Near-concurrent surge of the three largest glaciers of the Malaspina Glacier piedmont were observed during 1999 to 2002. In addition, the tidewater Tyndall Glacier, whose retreat since 1910 was interrupted in 1964 by a major surge, also surged during 1999 to 2002. These four surges have occurred roughly 23 years after the 1976/77 shift of the Pacific Decadal Oscillation to its current warm-wet phase. Despite the increase of high-elevation snow accumulation observed on Mt. Logan, the accumulation areas of the Bering and Malaspina Glacier systems are being drawn down by the effects of glacier dynamics. Wastage has accelerated since 2000.
    • Maximizing qiviut growth in muskoxen

      Robertson, Morgan A. (2000-05)
      Qiviut, the insulating underwool grown annually by muskoxen, is the basis of a successful knitting industry in Alaska. This study tested the hypothesis that the dietary sulfur-amino acid methionine could limit qiviut growth. Effects of commercial rumen-protected methionine supplements were measured in three experiments. In Experiment 1, emergent qiviut growth began in May and June, peaked in August and declined substantially by October. Three commercial methionine supplements were palatable and promoted fiber growth in subadult and adult muskoxen. In Experiment 2, the methionine supplement Smartamine promoted qiviut quality, growth, annual yield and strength. In a commercial enterprise, Experiment 3, Smartamine stimulated qiviut yield. For lactating muskoxen, qiviut responses were independent of nutrition, whereas effects on body weight and protein deposition were confined to females on a low plane of nutrition. It was concluded that addition of rumen-protected methionine to diets of farmed muskoxen can effectively promote qiviut production.
    • Measurement And Evolution Of The Thickness Distribution And Morphology Of Deformed Features Of Antarctic Sea Ice

      Tin, Tina; Jeffries, Martin O. (2003)
      Antarctic sea ice thickness data obtained from drilling on sea ice floes were examined with the goal of enhancing our capability to estimate ice thickness remotely, especially from air- or space-borne altimetry and shipboard visual observations. The state of hydrostatic equilibrium of deformed ice features and the statistical relationships between ice thickness and top surface roughness were examined. Results indicate that ice thickness may be estimated fairly reliably from surface measurements of snow elevation on length scales of ?100 m. Examination of the morphology of deformed ice features show that Antarctic pressure ridges are flatter and less massive than Arctic pressure ridges and that not all surface features (ridge sails) are associated with features underwater (ridge keels). I propose that the differences in morphology are due to differences in sampling strategies, parent ice characteristics and the magnitude and duration of driving forces. As a result of these findings, the existing methodology used to estimate ice thickness from shipboard visual observations was modified to incorporate the probability that a sail is associated with a keel underwater, and the probability that keels may be found under level surfaces. Using the improved methodology, ice thickness was estimated from ship observations data obtained during two cruises in the Ross Sea, Antarctica. The dynamic and thermodynamic processes involved in the development of the ice prior to their observation were examined employing a regional sea ice-mixed layer-pycnocline model. Both our model results and previously published ice core data indicate that thermodynamic thickening is the dominant process that determines the thickness of first year ice in the central Ross Sea, although dynamic thickening also plays a significant role. Ice core data also indicate that snow ice forms a significant proportion of the total ice mass. For ice in the northeast Ross Sea in the summer, model results and evidence from ice core and oceanographic data indicate that dynamic thickening, snow ice formation and bottom melting compete to determine the ice thickness during mid and late winter.
    • Measurement of field aligned electron density distribution, ducts, and Z mode cavities from ducted and nonducted fast Z mode echoes observed on the image satellite

      Mayank, Kumar; Newman, David; Simpson, William; Truffer, Martin; Braddock, Joan (2015-05)
      Z mode (ZM) sounding from the Radio Plasma Imager (RPI) onboard the Imager for Magnetopause to Aurora Global Exploration (IMAGE) satellite has provided a new method to measure the geomagnetic field aligned electron density (Ne) distribution, magnetospheric ducts, and Z mode cavities in the low- to mid-latitude region of the magnetosphere from the ducted and nonducted fast ZM echoes observed from radio sounding at 20-1000 kHz. Z mode is a trapped wave mode of the plasma confined in frequency between the ZM cutoff frequency, fz, and the upper hybrid resonance frequency, fuh. In the past, trapped ducted Z mode echoes in the ZM cavity were used to measure field aligned electron density thousands of kilometers above the satellite altitude. However, no attempt was made to study the properties of the ducts that can guide ZM waves. Magnetospheric ducts play an important role in the propagation of plasma waves, wave particle interactions, particle acceleration, and precipitation. In the past, ducts have been known since the discovery of the plasmasphere, but there is limited knowledge of the properties of ducts, their origins and occurrence patterns, and their distribution on a global scale in the magnetosphere especially for ducts extending to high altitudes (above 1000 km). Analysis of ducted echoes from the conjugate and local hemispheres has enabled nearly instantaneous magnetic field aligned electron density profiles. Field aligned density distribution plays an important role in magnetospheric dynamics. Despite its importance, there is a lack of accurate representation of the latitudinal dependence of density distribution along the field lines by the existing empirical models, due to limited measurement of off-equatorial electron density profiles and availability of relatively fewer measurements of Ne at higher altitudes. There is also a need to describe the transition of field aligned electron densities from the topside ionosphere into the plasmasphere properly. RPI on IMAGE, designed to sweep from 3 kHz to 3 MHz, has observed both ducted and nonducted ZM echoes in the frequency range of 40 - 800 kHz in an altitude range of ~600-10,000 km, invariant latitude of ~20°-90°, at all magnetic local times (MLTs) and for an fpe/fce range of 0.25-6, where fpe and fce are electron plasma frequency and electron gyro frequency respectively. About 72,000 plasmagrams have been surveyed, out of which ~1500 cases of ducted- and ~3500 cases of nonducted fast ZM echoes have been identified. Two cases of ducted, two cases of nonducted, and a set of seven successive cases of nonducted and ducted fast ZM echoes have been analyzed to study the propagation, reflection, and guidance of fast ZM waves in the magnetosphere and measure: (1) field aligned electron density distribution; (2) duct parameters (half-width ΔL and density variation ΔN/N); and (3) Z mode cavity parameters. In absence of ducts, four nonducted echoes are obtained, each reflecting from locations where fz ~f, where f is the wave frequency. Three of the echoes retrace their path after reflection and one forms a loop. When a Ne depletion duct is present inside a Z mode cavity, fast Z mode waves can be guided within the duct and propagate back and forth between their reflection points above and below the satellite altitude. Ray tracing calculations of ducted Z mode echoes show that: (1) in the presence of ducts, both nonducted and ducted echoes are obtained, and echoes are formed from both looping as well as retracing paths; (2) average time delays (tg) depend upon the electron density distribution along geomagnetic field lines and the shape of the Z mode cavity; (3) time delay spread (Δtg) and upper cutoff frequency (fuc) depend upon duct half-width (ΔL) and density perturbation (ΔN/N); (4) echoes are obtained from local as well as conjugate hemispheres when the duct extends to the conjugate hemisphere; and (5) the discovery of a new phenomenon of gap in frequency for echoes reflecting from below the satellite altitude. The gap frequency range depends upon the duct parameters and is a consequence of the peculiar shape of the refractive index surface for f~fpe. From ZM soundings of 11 case studies, it is found that the measured ducts have half-widths of ~160-500 km at the equator and density depletions of ~1%-6%, covering an altitude range of ~1000-10,000 km. The first quantitative measurements of ZM cavities have been presented in this thesis. The bandwidth and the length of ZM cavities lie in the range of ~10-50 kHz and ~3800-15,000 km, respectively. From the inversion of time delay versus frequency dispersion of the fast ZM echoes, field aligned electron density distributions both above and below the satellite from an altitude of ~1000-10,000 km (and ~90- 10,000 km if accompanied by Whistler mode echoes) are obtained. The electron density profiles obtained from ZM sounding are in good agreement with in-situ electron density measurements from the CHAMP (~350 km) and DMSP (~850 km) satellites, from RPI passive measurements, and give a better estimate of electron density as compared to empirical density models. Our results demonstrate that ZM sounding is a new and powerful method to measure field aligned electron density distribution, magnetospheric ducts, and ZM cavities in the altitude range of ~1000-10,000 km (and ~90-10,000 km if accompanied by Whistler mode echoes) at low- to mid-latitude region of the magnetosphere. These measurements can improve the existing empirical density models and provide a new understanding of the magnetospheric ducts as well as of waves propagating therein.
    • Mechanism of impact and potential recovery of pigeon guillemots (Cepphus columba) after the Exxon Valdez oil spill

      Seiser, Pamela (2000-05)
      The abundance of pigeon guillemots in oiled areas of Prince William Sound, Alaska, failed to increase after the 1989 Exxon Valdez oil spill. Population growth may be constrained by the physiological effects of oil exposure, food availability, and nest predation." The author "conducted a comparative study among unoiled, oiled, and pre-spill data sets, to provide insight on factors limiting population recovery in oiled areas. Blood samples from chicks in oiled and unoiled areas provided little evidence of physiological effects of exposure to oil. Pigeon guillemot diet, productivity, growth rates, and fledging weights in unoiled areas of southwestern Prince William Sound from 1994 to 1998 indicate oiled areas had a lower proportion of high-lipid fish in the chick diet and lower fledging weights, compared to unoiled and pre-spill studies. These results suggest that the lack of recovery in oiled areas is associated with a prey base that results in lower fledging weights, which may reduce juvenile survival.
    • Mechanisms and implications of changes in the timing of ocean freeze-up

      Rolph, Rebecca J.; Mahoney, Andrew; Walsh, John; Eicken, Hajo; Winsor, Peter; Loring, Philip (2018-08)
      The shift to an Arctic seasonal sea ice cover in recent years motivates a deeper understanding of freeze-up processes and implications of a lengthened open water season. As the sea ice boundary between the Arctic ocean and atmosphere covers a smaller area, the effects of enhanced wind mixing become more pronounced. Winds are important for ocean circulation and heat exchange. Ultimately, they can influence when freeze-up can occur, or can break up new ice as it forms. The chapters of this thesis are motivated by the substantial social and geophysical consequences of a lengthening open water season and linked through discussion of what controls freeze-up timing. Implications of a declining sea ice cover as it pertains to the three Arctic Alaska coastal communities of Kotzebue, Shishmaref, and Utqiaġvik are explored in depth. Indices of locally-relevant metrics are developed by using physical climate-related thresholds found by other studies to impact Alaska communities and coastal erosion rates. This allows for a large-scale climate dataset to be used to define a timeseries of these indices for each community. We found a marked increase in the number of false freeze-ups and break-ups, the number of days too windy to hunt via subsistence boat, and in Utqiaġvik, an approximate tripling of erosion-capable wind events from 1979-2014. The WRF-downscaled ERA-Interim dataset (ERA-Interim for sea ice) was also used in the analysis of all chapters. The cumulative wind energy input into the upper ocean was calculated for the Chukchi, southern Beaufort, and northeast Bering Seas at time periods up to three months prior to freeze-up, and then correlated with the timing of freeze-up. We have found that increased wind energy input into the upper ocean 2-3 months prior to freeze-up is positively and most strongly correlated with the date of freeze-up in the Chukchi Sea. Analysis of wind climatology shows winds are increasing in the period prior to freeze-up as a delayed freeze-up moves into the fall storm season. A negative correlation is found in the Bering Sea over shorter timescales, suggesting that storms promote the arrival of sea ice there. Case studies are evaluated for the Chukchi Sea and Bering Sea, to illustrate mechanisms at play that cause the positive and negative correlations in these seas, respectively. Ice advection and high winds from northerly directions are shown to hasten the timing of freeze-up in the Bering Sea. In the Chukchi Sea, higher winds from the dominant northeasterly direction promote upwelling of warm and salty water up onto the shelf, which suggests a mechanism for why high winds are associated with a delayed freeze-up there. We next examine the effect of winds on freeze-up timing by using a 1-D vertical column model of the mixed layer. The model is initialized using temperature and salinity profiles obtained from a freeze-up buoy deployed in 2015 in the north-east part of the Chukchi Sea. The meteorological forcing used to drive the model experiments comes from a WRF-downscaled ERA-Interim Reanalysis dataset. Our results show that vertical wind-driven mixing leads to enhanced heat loss. In light of the previously found positive correlation between wind energy input and freeze-up timing, the mixing model results suggest horizontal advection not captured by the 1-D column model can dominate wind-driven vertical mixing to promote freeze-up.
    • Mechanisms of modulation of nicotinic acetylcholine receptors

      Demmerly, Arianna L.; Edmonds, Brian; Schulte, Marvin; Dunlap, Kriya; Kuhn, Thomas (2016-12)
      Inappropriate expression of nicotinic acetylcholine receptors in the central nervous system is associated with nicotine addiction, Alzheimer's disease, Parkinson's disease and other disorders. Modulators (drugs) have the potential to restore circuit properties that arise from inappropriate expression of nicotinic receptor's. Compounds that interact with allosteric sites have a distinct advantage over agonists and partial agonists, in that, they retain normal activation patterns by allowing binding of the endogenous ligand. Positive allosteric modulators boost the receptors ability to respond to agonist. Studies of these modulators constitute a first step toward the identification and development of better compounds that minimize signaling errors at cholinergic synapses. We have used single molecule methods to investigate the action of a novel positive allosteric modulator, desformylflustrabromine (dFBr), on nicotinic receptors. Our studies were focused on the α4β2 subtype of nicotinic receptors in the brain. These receptors exist in two forms with low sensitivity (α4₃β2₂) or, alternatively, high sensitivity (α4₂β2₃) to agonist. Our experiments allowed us to develop detailed gating models for high and low sensitivity receptors, as well as gain new insights regarding the mechanisms that underlie potentiation by allosteric modulators. We found that dFBr potentiates low sensitivity receptors by destabilizing desensitized states of the receptor. In contrast, potentiation of high sensitivity receptors arises from a synchronization of openings following an application of agonist due to an increase in the opening rate. Based on our results we now have a better understanding of the advantages of dFBr on high and low sensitivity receptors.