1,721,048 research outputs found
Is sea level rise accelerating in the Chesapeake Bay? a demonstration of a novel new approach for analyzing sea level data
No full textSea level data from the Chesapeake Bay are used to test a novel new analysis method for studies of sea level rise (SLR). The method, based on Empirical Mode Decomposition and Hilbert-Huang Transformation, separates the sea level trend from other oscillating modes and reveals how the mean sea level changes over time. Bootstrap calculations test the robustness of the method and provide confidence levels. The analysis shows that rates of SLR have increased from ~1–3 mm y-1 in the 1930s to ~4–10 mm y-1 in 2011, an acceleration of ~0.05–0.10 mm y-2 that is larger than most previous studies, but comparable to recent findings by Sallenger and collaborators. While land subsidence increases SLR rates in the bay relative to global SLR, the acceleration results support Sallenger et al.’s proposition that an additional contribution to SLR from climatic changes in ocean circulation is affecting the region
Nonlinear sea-level trends and long-term variability on western European coasts
No full textNonlinear trends and long-term variability in sea-level measured on U.K. and western European coasts with long tide gauge records (~100-200 years) are investigated. Two different analysis ethods, a standard quadratic regression and a non-parametric, Empirical Mode Decomposition, detect similar positive sea-level accelerations over the past ~150 years: 0.014±0.003 and 0.012±0.004mm/y2, respectively; these values are close to the sea-level acceleration of the global ocean over the same period as reported by several studies. Ensemble calculations with added white noise are used to evaluate the robustness of low-frequency oscillations and estimate potential errors. Sensitivity experiments evaluate the impact of data gaps on the ability of the analysis to detect decadal variations and acceleration in sea-level. The long-term oscillations have typical periods of 15-60 years and range of 50-80 mm; these oscillations appear to be influenced by the North Atlantic Oscillation and by the Atlantic Multi-decadal Oscillation. Analysis of altimeter data over the entire North Atlantic Ocean shows that the highest impact of the North Atlantic Oscillation is on sea-level variability in the North Sea and the Norwegian coasts, while the Atlantic Multi-decadal Oscillation has the largest correlation with sea-level in the sub-polar gyre and the Labrador Sea, west of the study area
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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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Strong Mid-Depth Currents and a Deep Cyclonic Gyre in the Gulf of Mexico
Get PDFReport summary describing the work completed at Florida State University for 'Analysis and Validation of a Mechanism that Generates Strong Mid-Depth Currents and a Deep Cyclonic Gyre in the Gulf of Mexico'. It includes background information on the project funding and sponsorship, goals, methodology, and findings
Can the Gulf Stream Induce Coherent Short-Term Fluctuations in Sea level along the US East Coast?: A Modeling Study
Get PDFMuch attention has been given in recent years to observations and models that show that variations in the transport of the Atlantic Meridional Overturning Circulation (AMOC) and in the Gulf Stream (GS) can contribute to interannual, decadal, and multi-decadal variations in coastal sea level (CSL) along the US East Coast. However, less is known about the impact of short-term (time scales of days to weeks) fluctuations in the GS and their impact on CSL anomalies. Some observations suggest that these anomalies can cause unpredictable minor tidal flooding in low-lying areas when the GS suddenly weakens. Can these short-term CSL variations be attributed to changes in the transport of the GS? An idealized numerical model of the GS has been set up to test this proposition. The regional model uses a 1/12° grid with a simplified coastline to eliminate impacts from estuaries and small-scale coastal features and thus isolate the GS impact. The GS in the model is driven by inflows/outflows, representing the Florida Current (FC), the Slope Current (SC), and the Sargasso Sea (SS) flows. Forcing the model with an oscillatory FC transport with a period of 2, 5, and 10 days produced coherent CSL variations from Florida to the Gulf of Maine with similar periods. However, when imposing variations in the transports of the SC or the SS, they induce CSL variations only north of Cape Hatteras. The suggested mechanism is that variations in GS transport produce variations in sea level gradient across the entire GS length and this large-scale signal is then transmitted into the shelf by the generation of coastal-trapped waves (CTW). In this idealized model, the CSL variations induced by variations of ∼10 Sv in the transport of the GS are found to resemble CSL variations induced by ∼5ms−1 zonal wind fluctuations, though the mechanisms of wind-driven and GS-driven sea level are quite different. Better understanding of the relation between variations in offshore currents and CSL will help to improve the prediction of both short-term water level anomalies that cause flooding, as well as spatial variations in long-term sea level variability and coastal sea level rise
On the Interaction Between the Gulf Stream and the New England Seamount Chain
No full textIn the course of numerical simulations with a primitive equation regional model of the Gulf Stream, bottom topography and the New England Seamount Chain (NESC) in particular show significant influence on the variability and the energetics of the Gulf Stream system. The model is an eddy-resolving, coastal ocean model that includes thermohaline dynamics and a second-order turbulence closure scheme to provide vertical mixing coefficients; it is driven at the surface by observed monthly wind stress and heat fluxes. The surface and the deep variabilities obtained from the numerical simulations are in fair agreement with the observed variabilities inferred, for example, from the Geosat altimetry data and from measurements of eddy kinetic energy (EKE).
To study how the NESC affects the Gulf Stream dynamics, a control run without the NESC (however, leaving the other topographic features such as the continental shelf and slope intact) is compared to simulation with full bottom topography. According to the model results, the effects of the NESC on the Gulf Stream include southward deflection of the stream as it passes across the NESC and the development of several quasi-stationary, nearly barotropic recirculation cells on both sides of the Gulf Stream. Another result is an increase in the mean kinetic energy (MKE) and a decrease in the EKE in most of the water column as a result of the inclusion of the NESC. The inclusion of the NESC causes an upstream shift in the area of maximum variability compared with the case without the NESC; the maximum deep EKE is thus obtained upstream of the NESC. This study suggests that the stabilizing effects of the bottom topography dominate over possible destabilizing effects due to increase in meander amplitudes near the NESC. This study also suggests that the NESC causes a downstream decrease in the propagation speed of meanders upstream of the NESC and the development of an almost steady, large meander downstream of the NESC
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