Landfast sea ice formation and deformation near Barrow, Alaska: variability and implications for ice stability

Thesis (M.S.) University of Alaska Fairbanks, 2013Climate change in the Arctic is having large and far-reaching effects. Sea ice is declining in annual extent and thinning with a warming of the atmosphere and the ocean. As a result, sea ice dynamic behaviour and processes are undergoing major changes, interacting with socio-economic changes underway in the Arctic. Near Barrow, Alaska, landfast sea ice is an integral part of native lñupiaq culture and impacts the natural resource extraction and maritime industries. Events known as breakouts of the landfast ice, in which stable landfast ice becomes mobile and detaches from the coast, have been occurring more frequently in recent years in northern Alaska. The current study investigates processes contributing to breakout events near Barrow, and environmental conditions related to the detachment of landfast sea ice from the coast. In this study, synoptic scale sea level pressure patterns are classified in an attempt to identify atmospheric preconditioning and drivers of breakout events. An unsupervised classification approach, so called Self-Organizing Maps, is employed to sort daily sea level pressure distributions across the study area into commonly observed patterns. The results did not point to any particular distributions which favored the occurrence of breakouts. Because of the comparatively small number of breakout events tracked at Barrow to date (nine events between 2006 and 2010), continued data collection may still yield data that support a relationship between breakout events and large scale sea level pressure distributions. Two case studies for breakout events in the 2008/09 and 2009/10 ice seasons help identify contributing and controlling factors for shorefast ice fragmentation and detachment. Observational data, primarily from components of the Barrow Sea Ice Observatory, are used to quantify stresses acting upon the landfast ice. The stability of the landfast ice cover is estimated through the calculation of the extent of grounded pressure ridges, which are stabilizing features of landfast ice. Using idealized ridge geometries and convergence derived from velocity fields obtained by coastal radar, effective grounding depths can be calculated. Processes acting to destabilize or precondition the ice cover are also observed. For a medium-severity breakout that occurred on March 24, 2010, the calculated atmospheric and oceanic stresses on the landfast ice overcame the estimated grounding strength of ridge keels, although interaction with rapidly moving pack ice cannot be ruled out as the primary breakout cause. For another medium-severity breakout that took place on February 27, 2009, the landfast ice was preconditioned by reducing the draft of grounded ridge keels, with subsequent detachment from the shore during the next period of oceanic and atmospheric conditions favoring a breakout. For both of these breakouts, in addition to their potential role in destabilizing the landfast ice by overcoming the ridge grounding strength, current and/or wind forcing on the landfast ice were found to be important factors in moving the stationary ice away from shore.Chapter 1. Introduction to Barrow, Alaska and local sea ice conditions -- 1.1. Introduction -- 1.2. Barrow, Alaska and local sea ice conditions -- 1.3. The Barrow sea ice observatory -- 1.4. Thesis overview -- Chapter 2. Using self-organizing maps to identify regional weather patterns contributing to landfast sea ice breakouts near Barrow, Alaska -- 2.1. Introduction -- 2.2. Purpose -- 2.3. Background on self-organizing maps -- 2.4. Methods and data -- 2.5. Results -- 2.6. Discussion -- 2.7. Conclusions -- Chapter 3. Two case studies of landfast sea ice breakouts near Barrow, Alaska -- 3.1. Introduction -- 3.2. Background -- 3.2.1 Drift and dynamics of sea ice -- 3.2.2. Breakout events: ridge failure -- 3.2.3. Breakout events: failure in tension -- 3.2.4. Changes in sea level -- 3.3. Data for breakout case studies -- 3.3.1. Sea ice mass balance site -- 3.3.2. Marine radar and webcam -- 3.3.3. Satellite products -- 3.3.4. Offshore moorings -- 3.3.5. Local ice observations -- 3.4. Methods -- 3.4.1. Detection of breakout events -- 3.4.2. Tracking sea ice through radar imagery -- 3.4.3. Estimation of grounded ridge extent -- 3.5. Breakout events -- 3.5.1. February 27, 2009 breakout event: pre-breakout ice conditions -- 3.5.2. February 27, 2009 breakout event: conditions during the breakout event -- 3.5.3. February 27, 2009 breakout event: discussion -- 3.5.4. March 24, 2010 breakout event: pre-breakout ice conditions -- 3.5.5. March 24, 2010 breakout event: conditions during the breakout event -- 3.5.6. March 24, 2010 breakout event: discussion -- 3.6. Discussion of errors -- 3.7. Conclusions -- Chapter 4. Landfast sea ice breakout events: general conclusions -- List of symbols -- References

The Role of Morphology Transitions in Tissue-to-Blood Spread of Infestation

The fungal organism Candida albicans is a nearly ubiquitous commensal inhabitant of the human body. However, in susceptible individuals it can establish mucosal infections as well as life-threatening systemic infection. We are investigating a key contributor to C. albicans’ pathogenesis: its ability to switch among multiple growth forms in response to an array of environmental signals. We hypothesize that this ability to undergo morphological transitions mediates its ability to disseminate from localized infections to system-wide bloodstream infection. Using a transparent zebrafish embryo model of infection, we have directly assessed specific contributions of C. albicans’ morphologies in the process of tissue-to-bloodstream dissemination. We have observed that yeast is the primary form of C. albicans within the bloodstream. We have demonstrated that hyphae are not required for dissemination in our model, but they play an important role in promoting yeast cell dissemination. It is our expectation that further elucidation of the roles of morphological transitions will permit the development of more effective therapies to prevent C. albicans-related mortality in susceptible individuals

Preregistered direct replication of "Sick body, vigilant mind: the biological immune system activates the behavioral immune system"

The tendency to attend to and avoid cues to pathogens varies across individuals and contexts. Researchers have proposed that this variation is partially driven by immunological vulnerability to infection, though support for this hypothesis is equivocal. One key piece of evidence (Miller & Maner, 2011) shows that participants who have recently been ill—and hence may have a reduced ability to combat subsequent infection—allocate more attention to faces with infectious-disease cues than do participants who have not recently been ill. The current article describes a direct replication of this study using a sample of 402 individuals from the University of Michigan, the University of Glasgow, and Vrije Universiteit Amsterdam—more than 4 times the sample size of the original study. No effect of illness recency on attentional bias for disfigured faces emerged. Though it did not support the original finding, this replication provides suggestions for future research on the psychological underpinnings of pathogen avoidance

Two-Point Focused Laser Differential Interferometry Second-Mode Measurements at Mach 6

A two-point focused laser differential interferometer (FLDI) is used to make measurements of density fluctuations on a 7 degree half-angle cone in a Mach 6 flow. The system was first characterized in the laboratory using laser induced breakdown to provide a well defined density fluctuation. The speed of the shock wave generated by the breakdown is verified using simultaneous high-speed schlieren. The FLDI system is then installed at the NASA Langley 20-Inch Mach 6 air tunnel to make measurements in the boundary layer of the 7 degree half-angle cone model and in the tunnel freestream for a unit Reynolds number range of 3.0 to 8.22 x 10(exp 6)/ft. Second-mode packets are visible in the spectra, with peak frequencies increasing linearly and peak amplitude increasing as a function of unit Reynolds number. The two-point measurement allows for the calculation of the second-mode wavepacket speeds, which propagate between 88% and 92% of the freestream velocity of the tunnel for all Reynolds numbers. The FLDI measurements are compared to surface-mounted fast-response pressure transducer measurements, where second-mode frequencies and wavepacket speeds are in good agreement

Neonatal NMDA receptor blockade disrupts spike timing and glutamatergic synapses in fast spiking interneurons in a NMDA receptor hypofunction model of schizophrenia

The dysfunction of parvalbumin-positive, fast-spiking interneurons (FSI) is considered a primary contributor to the pathophysiology of schizophrenia (SZ), but deficits in FSI physiology have not been explicitly characterized. We show for the first time, that a widely-employed model of schizophrenia minimizes first spike latency and increases GluN2B-mediated current in neocortical FSIs. The reduction in FSI first-spike latency coincides with reduced expression of the Kv1.1 potassium channel subunit which provides a biophysical explanation for the abnormal spiking behavior. Similarly, the increase in NMDA current coincides with enhanced expression of the GluN2B NMDA receptor subunit, specifically in FSIs. In this study mice were treated with the NMDA receptor antagonist, MK-801, during the first week of life. During adolescence, we detected reduced spike latency and increased GluN2B-mediated NMDA current in FSIs, which suggests transient disruption of NMDA signaling during neonatal development exerts lasting changes in the cellular and synaptic physiology of neocortical FSIs. Overall, we propose these physiological disturbances represent a general impairment to the physiological maturation of FSIs which may contribute to schizophrenia-like behaviors produced by this model

Land Use and Land Cover Change Dynamics across the Brazilian Amazon: Insights from Extensive Time-Series Analysis of Remote Sensing Data

Throughout the Amazon region, the age of forests regenerating on previously deforested land is determined, in part, by the periods of active land use prior to abandonment and the frequency of reclearance of regrowth, both of which can be quantified by comparing time-series of Landsat sensor data. Using these time-series of near annual data from 1973–2011 for an area north of Manaus (in Amazonas state), from 1984–2010 for south of Santarém (Pará state) and 1984–2011 near Machadinho d’Oeste (Rondônia state), the changes in the area of primary forest, non-forest and secondary forest were documented from which the age of regenerating forests, periods of active land use and the frequency of forest reclearance were derived. At Manaus, and at the end of the time-series, over 50% of regenerating forests were older than 16 years, whilst at Santarém and Machadinho d’Oeste, 57% and 41% of forests respectively were aged 6–15 years, with the remainder being mostly younger forests. These differences were attributed to the time since deforestation commenced but also the greater frequencies of reclearance of forests at the latter two sites with short periods of use in the intervening periods. The majority of clearance for agriculture was also found outside of protected areas. The study suggested that a) the history of clearance and land use should be taken into account when protecting deforested land for the purpose of restoring both tree species diversity and biomass through natural regeneration and b) a greater proportion of the forested landscape should be placed under protection, including areas of regrowth

Giant Impacts and Debris Disk Morphology

Certain debris disks have non-axisymmetric shapes in scattered light which are unexplained. The appearance of a disk depends on how its constituent Keplerian ellipses are arranged. The more the ellipses align apsidally, the more non-axisymmetric the disk. Apsidal alignment is automatic for fragments released from a catastrophic collision between solid bodies. We synthesize scattered light images, and thermal emission images, of such giant impact debris. Depending on the viewing geometry, and if and how the initial apsidal alignment is perturbed, the remains of a giant impact can appear in scattered light as a one-sided or two-sided "fork", a lopsided "needle", or a set of "double wings". Double wings are difficult to reproduce in other scenarios involving gravitational forcing or gas drag, which do not align orbits as well. We compare our images with observations and offer a scorecard assessing whether the scattered light asymmetries in HD 15115, HD 32297, HD 61005, HD 111520, HD 106906, beta Pic, and AU Mic are best explained by giant impacts, gravitational perturbations, or sculpting by the interstellar medium.Comment: Final ApJ-proofed version with updated references to summary Table 1. Animations available at https://github.com/joshwajones/jones_etal_animations