1,721,065 research outputs found
Dispersion of deep-sea hydrothermal vent effluents and larvae by submesoscale and tidal currents
No full textDeep-sea hydrothermal vents provide sources of geochemical materials that impact the global ocean heat and chemical budgets, and support complex biological communities. Vent effluents and larvae are dispersed and transported long distances by deep ocean currents, but these currents are largely undersampled and little is known about their variability. Submesoscale (0.1–10 km) currents are known to play an important role for the dispersion of biogeochemical materials in the ocean surface layer, but their impact for the dispersion in the deep ocean is unknown. Here, we use a series of nested regional oceanic numerical simulations with increasing resolution (from View the MathML sourceδx=6km to View the MathML sourceδx=0.75km) to investigate the structure and variability of highly-resolved deep currents over the Mid-Atlantic Ridge (MAR) and their role on the dispersion of the Lucky Strike hydrothermal vent effluents and larvae. We shed light on a submesoscale regime of oceanic turbulence over the MAR at 1500 m depth, contrasting with open-ocean – i.e., far from topographic features – regimes of turbulence, dominated by mesoscales.Impacts of submesoscale and tidal currents on larval dispersion and connectivity among vent populations are investigated by releasing neutrally buoyant Lagrangian particles at the Lucky Strike hydrothermal vent. Although the absolute dispersion is overall not sensitive to the model resolution, submesoscale currents are found to significantly increase both the horizontal and vertical relative dispersion of particles at O(1-10) km and O(1-10) days, resulting in an increased mixing of the cloud of particles. A fraction of particles are trapped in submesoscale coherent vortices, which enable transport over long time and distances. Tidal currents and internal tides do not significantly impact the horizontal relative dispersion. However, they roughly double the vertical dispersion. Specifically, particles undergo strong tidally-induced mixing close to rough topographic features, which allows them to rise up in the water column and to cross topographic obstacles.The mesoscale variability controls at first order the connectivity between hydrothermal sites and we do not have long enough simulations to conclude on the connectivity between the different MAR hydrothermal sites. However, our simulations suggest that the connectivity might be increased by submesoscale and tidal currents, which act to spread the cloud of particles and help them cross topographic barriers
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
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
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
NBC rings identification (Napolitano et al.)
No full text<p>Open research information for <strong>Napolitano et al., 2024: </strong><em>Vertical interaction between NBC rings and its implications for South Atlantic Water export</em></p>
<p>This dataset includes:</p>
<p>Py-eddy-tracker tutorial [minimal example data included]</p>
<p>Animation of all identified eddies </p>
<p>The trajectory files and the results of coupling/splitting shown in Napolitano et al., 2024</p>
<p> </p>
Dynamics of oceanic vortex and filaments coupled with the atmosphere at mesoscale and submesoscale
No full textLe but de cette thèse est de décrire l’influence du couplage entre l’océan et l’atmosphère sur des résultats analytiques bien connus à propos de la stabilité de certaines structures océaniques. Ce manuscrit s’articule autour de trois études et quatre articles publiés. La première étude met en évidence un phénomène de résonance qui peut apparaître entre un système de deux tourbillons et le vent si la force de celui-ci est périodique. À certaines conditions paramétriques que l’on calcule analytiquement, la variation du vent peut entrer en résonance avec les tourbillons, pourtant stables sans vent. La seconde étude porte sur la dynamique des perturbations dans un tourbillon étendu verticalement. D’abord analytiquement, on développe la dynamique des perturbations et met en évidence la présence d’instabilités baroclines. Puis une étude paramétrique réalisée numériquement permet de discriminer, en fonction des nombreux paramètres, les différents types d’instabilités du système. Enfin, la troisième étude porte sur un système SQG 4couches : deux représentant l’océan et deux l’atmosphère, couplés thermiquement (flux de chaleur) ou mécaniquement (frottement du vent sur l’océan). Les instabilités baroclines d’Eady sont développées pour l’océan et l’atmosphère.The aim of this thesis is to describe the influence of the coupling between the ocean and the atmosphere on well-known analytical results concerning the stability of some oceanic structures.This manuscript is structured around three studies and four published articles. The first study highlights a resonance phenomenon that can occur between a system of two eddies and the wind if the wind velocity isperiodic. Under certain parametric conditions, which are calculated analytically, the wind excites the perturbation and a resonance phenomenon with the vortices appears, even though the vortices are stable without wind. The second study focuses on the dynamics of disturbances in a vertically extended eddy.First analytically, we develop the dynamics of the perturbations and highlight the presence of baroclinic instabilities. Then a numerically-resolved parametric study is used to discriminate, with respect to numerous parameters, the different types of instability in the system. Finally, the third study concerns a 4-layer SQG system : two representing the ocean and two the atmosphere, coupled thermally (heat flux) or mechanically (wind friction on the ocean). Eady baroclinic instabilities are developed for the ocean and the atmosphere
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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