1,720,987 research outputs found
Globorotalia truncatulinoides in Central - Western Mediterranean Sea during the Little Ice Age
Full text linkGloborotalia truncatulinoides oscillations have been recorded from different marine sediment cores collected in the central and western Mediterranean Sea. The abundances of this species over the last 500 yrs. demonstrates its potential value as bio-indicator of particular oceanographic condition during the Maunder Minimum (MM) event of the Little Ice Age (LIA). The comparison between the G. truncatulinoides abundance patterns of the Balearic Basin, central and south Tyrrhenian Sea and central and eastern Sicily Channel allows to highlight a similar response of this species during the MM event in the central-western Mediterranean Sea. The ecological meanings of this species and its peculiar high abundance percentages in the total assemblages suggest the development of enhanced vertical mixing conditions during MM winter season with a strong advection of nutrients from the nutrient-rich deeper layers and enhances the productivity levels in the mixed layer. The intensified vertical mixing could be linked to persistence of an atmospheric blocking event recorded by several authors during the MM
Holocene forest dynamics in central and western Mediterranean: Periodicity, spatio-temporal patterns and climate influence
No full textSolar forcing for nutricline depth variability inferred by coccoliths in the pre-industrial northwestern Mediterranean
Full text linkThe oceanic system has been rapidly changing under human-induced climate change that is taking place at unprecedented rates. The paleoclimate archive of the last two millennia is often adopted to discern the ongoing anthropogenic global warming from the pre-industrial natural climate variability. The Mediterranean Sea is an especially critical system, being particularly affected by climate change. A common group of marine unicellular planktonic calcifiers, coccolithophores, are forming calcite plates, coccoliths. When reaching the sediments, they have been employed as a proxy in many paleoenvironmental reconstructions and are increasingly used in the last centuries. Recent studies indicate a subtle response to historical climate changes, except for primary productivity switches during the Little Ice Age and, most importantly, across the Industrial age.
In this work, we use coccolith decadal-scale resolution data from core HER-MC-MR3.3, recovered in the Balearic Sea, exploring their variability over the pre-industrial age, from 700 BCE to 1740 CE. Results are compared to planktonic foraminifera stable isotopes, planktonic foraminiferal assemblages, alkenone-derived SSTs and foraminiferal Mg/Ca-derived SSTs, previously acquired in the same sediment core. Abundance variations in coccolith assemblages, expressed as Shannon-Wiener diversity H-index changes or as trends and fluctuations in ecological groups are associated with historical climate changes, among others the Medieval Climatic Anomaly and the Little Ice Age, indicating repeated modifications in surface water conditions, in response to hydrological and atmospheric changing patterns. A tight relationship between deep nutricline and upper water column stratified conditions, derived from high abundance of Florisphaera profunda, and high solar irradiation levels is established. The solar activity fingerprint in the F. profunda distribution pattern is further assessed by spectral analysis, with the emergence of significant periodicities observed in solar activity proxies, among others the well-known de Vries-Suess cycle. Finally, we notice small but statistically significant abundance fluctuations in holococcoliths (solution susceptible coccolith forms) that may be tied to their enhanced preservation during increased rainfall in western Europe. This implies the advection of westerlies and long-lasting blocking events that may have promoted deep-water formation and seafloor ventilation during this time. The comparison with sedimentological proxies of bottom current strength shows some inconsistencies but still defines variable and intermittent deep-water formation rates in the Gulf of Lions over the pre-industrial period
Benthic foraminiferal assemblages and biotopes in a coastal lake: the case study of Lake Varano (southern Italy)
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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
Climatic variability over the last 3000 years in the central - western Mediterranean Sea (Menorca Basin) detected by planktonic foraminifera and stable isotope records
No full textThe climate evolution of the last 2700 years in the central - western Mediterranean Sea has been reconstructed
from marine sediment records by integrating planktonic foraminifera and geochemical signals. The results
provide the characterization of six climatic phases: Balearic Bronze Age (BA), Roman Period (RP), Dark Age
(DA), Medieval Climate Anomaly (MCA), Little Ice Age (LIA) and Industrial Period (IP). Paleoclimatic curve
inferred from planktonic foraminifera associated with heavy values in δ18O Globigerinoides ruber during the BA
document two cold intervals (spanning ca. 200 years) related to the Homeric and Greek solar minima. The
dominance of Turborotalita quinqueloba –Globigerinita glutinata gr. and Globigerina bulloides during the RP suggest
high fertility surface waters condition probably triggered by the increase in precipitation. During the DA,
changes in the foraminiferal paleoclimate curve and oxygen isotope values display a cold –dry phase from
700 CE to the end of the DA (ca. 850 CE). This phase corresponds to the cold Roman IV solar minimum and
marks the beginning of a long - term cooling interval that terminates during the LIA. The MCA is characterized
by mild climatic conditions, interrupted at ca. 1050 CE by a cold - dry event. The gradually increase in abundance of G. ruber white characterize the IP warm period.
The reconstructed climate evolution in the Balearic Basin results almost time - equivalent with the
Mediterranean climate variability over the last 2700 years
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
Climatic variability over the last 3000 years in the Central-Western Mediterranean Sea (Menorca Basin) detected by planktonic foraminifera and stable isotope records.
No full textAppropriate 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
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