1,720,978 research outputs found
Mixing in the Deep Waters of the Western Mediterranean
No full textIn terms of the overall mixing environment, the Mediterranean Sea has relatively small tides and relatively weak winds compared with the greater ocean environment, so vertical diffusion due to mechanical mixing is likely to be generally smaller than in the open ocean. As the western Mediterranean deep water (WMDW) is naturally fresher and colder than the Levantine intermediate water (LIW), salinity and temperature both decrease downward below the LIW core toward the deep water. In the halocline-thermocline between the core of LIW and the deep water, warmer saltier waters overlie colder fresher waters and in such a region salt finger mixing processes can be effective mixing agents transporting salt, heat, and density downward. For the deep western Mediterranean, vertical diffusion due to mechanical mixing is expected to be small; and downward mixing of heat salt and density is expected to be substantial in the halocline-thermocline 400–1500-m depth
Thermohaline staircases in the western Mediterranean Sea
Full text linkThermohaline staircase structures are commonly observed in the western Mediterranean Sea within the halocline-thermocline connecting the Levantine Intermediate Water at about 400 m depth with the western Mediterranean deep waters below 1,500 m. In this halocline-thermocline where warmer, saltier waters overlie colder, fresher deep waters, salt finger mixing processes are thought to be active and produce staircases with layers of order 75 m thickness containing nearly constant properties separated by sharp steps of order 6 m thickness with jumps in properties between the layers. While the layers have nearly constant salinity, potential temperature, and potential density, each property decreases very slightly downward through the layer so that it appears that salinity, heat, and density are being put into the top of each layer and then convectively mixing downward through the layer. Such observations are consistent with salt finger processes that transport salinity, heat and density downward through the halocline-thermocline.Using repeat occupations of stations across the southern western Mediterranean Sea in 2006, 2008, and 2010, we have calculated downward salt transport, FS,of 5.35×10?8 psums?1, and downward heat transport, FT,of 12.4×10?8? Cms?1. After multiplying these fluxes by haline contraction (?) and thermal expansion (?) coefficients respectively, the buoyancy flux ratio, ?FT/?FS, is found to be 0.74 and there is a downward density flux of 1.0×10?10 Wkg?1. The halocline-thermocline in this region between 600 and 1,400 dbar has a background vertical salinity gradient of 0.95×10?4m?1 and a vertical temperature gradient of 4.1×10?4?Cm?1 so the background density ratio is R?=(? d? /dz)/(? dS/dz) is 1.28. Dividing the downward fluxes by the background vertical gradients yields vertical diffusivities kS=5.6×10?4m 2s?1 and kT=3.0×10?4m 2s?1. These downward fluxes of salt and heat are compared with estimates based on salt finger experiments and theory and with the long-term increases in salinity and temperature in the deep western Mediterranean Sea over the past 40 years
Thermohaline evolution at 400 m depth in the Sicily Channel, a choke point of the Mediterranean Sea
No full textThe Sicily Channel (SC) site has been monitored for thermohaline properties and water mass exchanges since 1993 by two moorings located within parallel trenches in the 150 km-long transect between Tunisia and Sicily. They form two of the longest Mediterranean time series of thermohaline properties. Due to the Coriolis effect, the IW core at the sill that funnel its westward flow is squeezed to the right, in both trenches, with the 400 m deep record in the north-eastern mooring (called C01) showing slightly warmer (by about 0.04 °C) and saltier (by about 0.01) values than the south-western one (called C02). As the temperature (T) and salinity (S) time series at both sites are very similar only the C02 (WMO code: 6101022, position: 37.2843° N, 11.4995° E) time series is presented here. The nominal depth of the instruments is 400 m, which is however subject to slight variations between servicing of the mooring, of the order of few tens of meters.
From 1993 to November 2002 temperature and conductivity have been recorded by means of Aanderaa RCM7 current meters, with an accuracy of 0.05 °C and 0.05 for T and S, respectively. Since November 2002, SBE37 probes have been used, which further improved the quality of the measurements, yielding 0.002 °C and 0.001 for T and S, respectively. Both types of instruments (RCM and SBE) have been regularly calibrated (at least on an annual basis)
IAPSO: tales from the ocean frontier
Full text linkOur 21st century perspective on the oceans is due to the realization that knowledge of them and specifically their role in earth's climate are central to determining the future health of our planet. This present knowledge of the oceans builds on the farsighted work of people who, over the past century, worked to address seemingly intractable problems. The International Association for the Physical Sciences of the Oceans (IAPSO) has, over that long time span, promoted and supported the international approach that is now commonplace and has championed the provision of cross-cutting activities, the value of which we now fully recognize. This paper describes the key events in IAPSO's history and the roles played by the scientists involved
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
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
- …
