1,720,986 research outputs found
Results for Modeling dissolved and particulate 230-Th in the Canada Basin: Implications for recent changes in particle flux and intermediate circulation
No full textThe results of three runs of a 230-Th model coupled to the Arctic Ocean model ANHA4. These results are the basis of the publication Yu et al, Modeling dissolved and particulate 230-Th in the Canada Basin: Implications for recent changes in particle flux and intermediate circulation. Accepted by the Journal of Geophysical Research, Oceans in January 2020.
The four runs are:
* BaseRun.nc: base run with scavenging, variation in currents and variation in ice
* Exp1.nc: base run but no extra bottom boundary scavenging
* Exp2.nc : base run but with the circulation from 2002 used for every year
* Exp3.nc : base run but with the ice field (used for particle flux) from 2002 used for every yea
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Wind-driven upwelling and nutrient supply in a productive estuarine sea
No full textMarine ecosystems are under increasing pressure due to climate change. Wind-driven circulation in the upper ocean is one of the primary ways that climate determines ecosystem behavior. One example is wind-driven upwelling of nutrients to the euphotic zone. In small enclosed seas where stratification is often strong and wind sporadic, the significance of nutrient upwelling is not well-established. These small systems can be important habitats for juvenile migrating fish such as Pacific salmon. In this thesis, wind-driven upwelling and the effect on surface nitrate availability were investigated in the Strait of Georgia on the Canadian Pacific coast using a high-resolution, coupled biophysical ocean model. This investigation was conducted in three parts. First, the model skill was evaluated against observations from local monitoring programs, and the sensitivity of tuning the surface wave breaking parameterization using wave model results from the region was tested. Second, principal component analysis (PCA) was performed on five years of modelled hourly surface nitrate and temperature fields to identify the wind-driven upwelling modes and determine their significance relative to other processes. Spectral analysis of the principal component (PC) loadings and correlations between the PC loadings and the surface wind stress were used to attribute the dominant PCA modes to physical phenomena. Third, depth of upwelling estimates from cross-shore density transects during a comprehensive set of wind events across the five-year simulation were compared to a theoretical cross-shore upwelling model depending only on wind stress, stratification and cross-shore bottom slope to identify the physical parameters that control upwelling. Upwelling accounted for approximately one-third of summer surface nitrate variance based on the PCA results. Modelled upwelling depth generally agreed with the theoretical prediction and was thus interpreted to depend primarily on wind stress and stratification. The deepest upwelling and strongest nitrate anomalies occurred in the northern Strait of Georgia, which is consistent with the presence of an along-axis stratification gradient due to the Fraser River. These results establish a direct link between climate forcing and the factors that determine upwelling in the Strait of Georgia, with strong implications for summer productivity in the region.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat
Pacific sources of biologically significant constituents in the Salish Sea using Lagrangian particle tracking
No full textThe Salish Sea is a semi-enclosed coastal sea between Vancouver Island and the coast of British Columbia and Washington State, invaluable from both an economic and ecologic perspective. Pacific inflow to the Sea is the main contributor of many biologically important constituents. The contribution of Pacific water masses to the flow through Juan de Fuca Strait (JdF), the Salish Sea’s primary connection to the Pacific Ocean, is explored. Quantitative Lagrangian particle tracking within Ariane, an offline Lagrangian tool capable of volume transport calculations, was applied to two numerical ocean models to track the paths and properties of water parcels before entering JdF and within the Salish Sea. The Coastal Ice Ocean Prediction System (CIOPS) for the west coast was used to track water parcels from JdF backwards in time to analyse their paths on the shelf and offshore before entering the Salish Sea, while SalishSeaCast was used to track water parcels forwards in time to assess the success of the water masses identified in the CIOPS analysis at reaching the Sea’s inner basins as opposed to being advected back out to the shelf region. During summer upwelling, intermediate flow from the north shelf and offshore dominate inflow, while during winter downwelling, intermediate flow from the south shelf and surface flow from the Columbia River plume are the dominant sources. A weaker and less consistent estuarine flow regime in the winter leads to less Pacific inflow overall and a smaller percentage of said inflow reaching the Salish Sea's inner basins than in the summer. Nevertheless, it was found that winter dynamics are the main driver of interannual variability, in part due to the strongly anti-correlated behaviour and distinct properties of the two dominant winter sources. This analysis extends the knowledge on the dynamics of Pacific inflow to the Salish Sea and highlights the importance of winter inflow to the interannual variability in biogeochemical conditions in the region.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat
Modeling freshwater from a subset of rivers throughout the Salish Sea using dye tracers
No full textThe Salish Sea is a biologically productive coastal sea that is home to a human population of over 8.9 million residents shared between the USA and Canada, and supports high but threatened ecosystem diversity and species richness. It is an estuarine system with freshwater inputs from numerous rivers that influence ocean dynamics, biogeochemistry, and ecosystem processes. While previous studies have examined circulation and salinity patterns of freshwater, primarily focusing on the Fraser River in the Strait of Georgia or Puget Rivers in Puget Sound, the relative influence of different riverine sources on basins other than the one they directly feed into is unclear. This study first evaluates the performance of the SalishSeaCast model at capturing salinity patterns in small river plume regions for 11 key rivers using two different model versions, finding that the newer version with daily estimates of river flow improves the model's performance. Then, passive model dye tracers are used to examine the distribution of freshwater from river inputs in the Salish Sea from those 11 rivers using the new model version, with emphasis on examining inter-basin transport between the Strait of Georgia and Puget Sound. The study utilizes a physics-only version of SalishSeaCast, a 3-D ocean model built on the NEMO framework with half-kilometer horizontal grid resolution. Model results indicate that while the Fraser River has the largest influence on riverine freshwater compared to any other individual river, smaller rivers are non-negligible in relative magnitude and their influences are present throughout the Salish Sea. The findings suggest that smaller rivers play a role in salinity distributions and freshwater content throughout the Salish Sea, highlighting the need to consider their contributions in model development and analyses across Salish Sea basins. By advancing the understanding of freshwater dynamics in the Salish Sea, this study provides insights for future research on estuarine circulation, ecosystem impacts, and climate change resilience.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Tracing ocean pathways : modelling manganese and lead in the Canadian Arctic
No full textHuman-induced climate change is rapidly altering the Arctic sea ice regime, ocean dynamics, and freshwater cycle. These changes impact biogeochemical cycling, including the cycling of trace elements, but the exact manifestations remain unclear. Over the past decade, the international GEOTRACES program has greatly expanded the coverage of trace element observations in the Arctic Ocean, capturing the current state of the system. These observations, in conjunction with improvements in model representations, allow the development of trace element models to investigate drivers of the spatial distribution and seasonal variability of trace element concentrations, and to estimate sensitivity of trace element cycling to climate change.
This dissertation describes some of the first three-dimensional models of the dissolved micronutrient manganese (Mn) and pollutant lead (Pb) in the Canadian Arctic Ocean, including the Canada Basin, the Canadian Arctic Archipelago (CAA), and Baffin Bay. I highlight sources that control the distributions of Mn and Pb in this region, and use Mn and Pb to trace sea ice sediments and river runoff, and Atlantic Water. The Mn model highlights the significance of the long-range transport of sediments by sea ice for micronutrients such as Mn in the Canada Basin. The disruption of the transpolar sea ice drift could reduce Mn supply to the Canada Basin and downstream. Sensitivity experiments varying the Mn content in runoff identify distinct continental and glacial runoff fingerprints of influence in the southwestern and northern CAA, respectively. Glacial runoff carries micronutrients southward from Nares Strait in the late summer and may help support longer phytoplankton blooms in the Pikialasorsuaq Polynya. The Pb model illustrates the continued impact of anthropogenic pollution on Pb concentrations in the Arctic through aerosol deposition, boundary transport, and, likely, river runoff and sediment resuspension. The Labrador Sea is a net source of Pb to Baffin Bay via the West Greenland Current and Pb highlights pathways of Atlantic Water in Baffin Bay.
The model results presented in this thesis highlight trace element concentrations and supply mechanisms in the Arctic Ocean and their sensitivity to climatic changes, and illustrates the use of trace element models in extending knowledge gained from observations.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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