Assimilating Eulerian and Lagrangian data to quantify flow uncertainty in testbed oceanography models

Data assimilation is the act of merging observed data into a mathematical model. This act enables scientists from a wide range of disciplines to make predictions. For example, predictions of ocean circulations are needed to provide hurricane disaster maps. Alternatively, using ocean current predictions to adequately manage oil spills has significant practical applications. Predictions are uncertain and this uncertainty is encoded into a posterior probability distribution. This thesis aims to explore two overarching aspects of data assimilation, both of which address the influence of the mathematical model on the posterior distribution. The first aspect we study is model error. Error is always present in mathematical models. Therefore, characterising posterior flow information as function of model error is paramount in understanding the practical implications of predictions. In a model describing advective transport, we make observations of the underlying flow at fixed locations. We characterise the mean of the posterior distribution as a function of the error in the advection velocity parameter. When the error is zero, the model is perfect and we reconstruct the true underlying flow. Partial recovery of the true underlying flow occurs when the error is rational, the denominator of which dictates the number of Fourier modes present in the reconstruction. An irrational error leads to retrieval only of the spatial mean of the flow. The second aspect we study is the control of ocean drifters. Commonplace in oceanography is the collection of ocean drifter positions. Ocean drifters are devices that sit on the surface of the ocean and move with the flow, transmitting their position via GPS to stations on land. Using drifter data, it is possible to obtain a posterior on the underlying flow. This problem, however, is highly underdetermined. Through controlling an ocean drifter, we attempt to improve our knowledge of the underlying flow. We do this by instructing the drifter to explore parts of the flow currently uncharted, thereby obtaining fresh observations. The efficacy of a control is determined by its e↵ect on the variance of the posterior distribution. A smaller variance is interpreted as a better understanding of the flow. We show a systematic reduction in variance can be achieved by utilising controls that allow the drifter to navigate new or ‘interesting’ flow structures, a good example of which are eddies

The lesbian, gay, bisexual and transgender community online: discussions of bullying and self-disclosure in YouTube videos

Computer-mediated communication has become a popular platform for identity construction and experimentation as well as social interaction for those who identify as lesbian, gay, bisexual or transgender (LGBT). The creation of user-generated videos has allowed content creators to share experiences on LGBT topics. With bullying becoming more common amongst LGBT youth, it is important to obtain a greater understanding of this phenomenon. In our study, we report on the analysis of 151 YouTube videos which were identified as having LGBT- and bullying-related content. The analysis reveals how content creators openly disclose personal information about themselves and their experiences in a non-anonymous rhetoric with an unknown public. These disclosures could indicate a desire to seek friendship, support and provide empathy

How open science helps researchers succeed

Open access, open data, open source, and other open scholarship practices are growing in popularity and necessity. However, widespread adoption of these practices has not yet been achieved. One reason is that researchers are uncertain about how sharing their work will affect their careers. We review literature demonstrating that open research is associated with increases in citations, media attention, potential collaborators, job opportunities, and funding opportunities. These findings are evidence that open research practices bring significant benefits to researchers relative to more traditional closed practices

The exhumation history of orogenic belts from Ar-40/Ar-39 ages of detrital micas

The exhumation history of mountain belts can be derived from radiometric dating of detrital mineral grains in proximal and distal post- and synorogenic sediments. The application of single-crystal dating techniques avoids the averaging effect that characterizes multi-grain and whole-rock techniques and allows the identification of populations of grains with distinct thermal histories. Of the major single crystal dating methods available, Ar-40/Ar-39 dating of detrital K-bearing minerals, in particular white mica, is perhaps the most versatile and widely applied technique. For a closure temperature of Ar of 350-400degreesC, muscovite 40Ar/39Ar ages record the time a rock mass passed through 8-10 km beneath actively eroding mountain belts. Detrital muscovite ages eroded from orogenic mountain belts have been used extensively to identify the provenance of sediments from source regions with distinct thermal histories, determine the history and rate of exhumation of the source region, and provide an upper limit on the sediment age. Here I review the principles of 40Ar/39Ar dating of detrital muscovite and illustrate the method with examples showing how the provenance and the thermal history of sediment source regions derived from such studies can be used to constrain the exhumation and tectonic history of orogenic belts