1,720,965 research outputs found
Coral based reconstructions of past Sea Surface Temperature – Insights into uncertainty
No full textThe past decades have seen the development of a wide range of global gridded Sea Surface Temperature (SST) products documenting historic changes in SST based on in situ and remotely sensed data. However, there are many sources of uncertainty in these records and significant differences exist among them. This thesis uses the record of past climate contained within tropical corals to advance our understanding of these uncertainties. Specific aims of this thesis were to perform: an investigation into the relationship between the local temperature at the coral site and gridded SST, a quantification of the total uncertainty involved in coral derived SST, and finally the assessment of existing SST products in light of new coral-based estimates of historic SST change. Through intercomparisons among SST products with data from temperature loggers, the discrepancies between gridded and in situ temperatures were quantified with a focus on coral reefs. This offers insight into the limitations of existing coral reef monitoring efforts and informs the process of estimating the uncertainty in coral SST reconstructions. The process of deriving SST through coral proxies was then scrutinized, the uncertainty of each step was quantified, and the total uncertainty was estimated. The total uncertainty in a single coral SST timeseries was time dependent and for the median uncertainties ranged from 0.1 to 1.90 °C (2sd). A method to reconstruct regional SST from several corals was then applied to critically assess the accuracy of three major SST products. This independent assessment verified the warm bias of World War II (WWII) anomalies others have shown and revealed that at the beginning of the historical SST records, the variance in SST anomalies is likely overinflated. A maximum bias above 0.5 °C was estimated for ERSSTv5, while the biases of HadISST and HadSST4 were over 0.4 °C, during the WWII interval. The estimates of global and regional surface temperature trends of the SST products for 1870-1990 were also found to be overestimated by up to 0.04 °C/decade. It was shown that coral SST reconstructions can resolve issues in the historical records, especially in periods and areas of high uncertainty. Finally, the potential to further constrain the uncertainty of coral reconstructions was highlighted, which opens the door for better reconstructions, extending to the pre-industrial era, and across a wide range of paleoclimate studies
Intercomparison of satellite-derived SST with logger data in the Caribbean—Implications for coral reef monitoring
Full text linkSince the early 1980s measurements of Sea Surface Temperature (SST) derived from satellite-borne instruments have provided a wide range of global gridded products documenting changes in SST. However, there are many sources of uncertainty in these records and significant differences exist among them. One use of these products is identification of coral bleaching events, and the predictions of the impact of future warming on coral reefs. This relies on an understanding of how temperatures near reefs as recorded by SST products differ from the in-situ SST experienced by the corals. This difference is a combination of real spatio-temporal variations, inadequate in product resolution and errors in the products. This paper investigates the relationship between the local temperature measured in-situ by loggers at coral sites in the western tropical Atlantic and two high resolution satellite SST products. Using differences among ESA SST CCI v2.1 (CCI analysis SST), NOAA CoralTemp SST products and in-situ logger data from coral reefs, an assessment of the satellite products with focus on coral reef monitoring is carried out. Discrepancies between the two products can be large, especially in coastal areas and for the warmest and coldest months when there is a particular risk of bleaching. By comparison to the stable CCI analysis SST product, CoralTemp was found to overestimate the rise in SST by as much as 0.20°C per decade. In almost all cases SSTs from CCI analysis SST were more consistent with temperatures measured near the corals than those from CoralTemp
HOBO Water Temperature Pro Data Logger observations at East Snake Caye, Belize, between June 2002 and November 2007
No full textHOBO Water Temperature Pro Data Loggers (accuracy ± 0.2 °C and resolution 0.02 °C; http://www.onsetcomp.com) were installed at East Snake Caye within the inner lagoon reef and White Reef on the outer barrier reef. They recorded temperatures at 15-minute intervals from June 2002 to August 2005 and 10-minute intervals from October 2006 to December 2007. The logger observations, made at 3-6m depth were used as an in situ reference, to validate two satellite SST products (NOAA's CoralTemp and ESA CCI's SST version 2.1) used in coral reef monitoring. A full description of the installation process is available in Castillo KD, Lima FP. Comparison of in situ and satellite‐derived (MODIS‐Aqua/Terra) methods for assessing temperatures on coral reefs. Limnology and Oceanography: Methods. 2010;8(3):107-17
HOBO Water Temperature Pro Data Logger observations at Sapodilla Cayes, Belize, between July 2002 and December 2007
No full textHOBO Water Temperature Pro Data Loggers (accuracy ± 0.2 °C and resolution 0.02 °C; http://www.onsetcomp.com) were installed at East Snake Caye within the inner lagoon reef and White Reef on the outer barrier reef. They recorded temperatures at 15-minute intervals from June 2002 to August 2005 and 10-minute intervals from October 2006 to December 2007. The logger observations, made at 3-6m depth were used as an in situ reference, to validate two satellite SST products (NOAA's CoralTemp and ESA CCI's SST version 2.1) used in coral reef monitoring. A full description of the installation process is available in Castillo KD, Lima FP. Comparison of in situ and satellite‐derived (MODIS‐Aqua/Terra) methods for assessing temperatures on coral reefs. Limnology and Oceanography: Methods. 2010;8(3):107-17
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
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