1,720,977 research outputs found
Physical drivers of pelagic sargassum bloom interannual variability in the Central West Atlantic over 2010–2020
No full textSince 2011, unprecedented pelagic sargassum seaweed blooms have occurred across the tropical North Atlantic, with severe socioeconomic impacts for coastal populations. To investigate the role of physical drivers in post-2010 sargassum blooms in the Central West Atlantic (CWA), conditions are examined across the wider tropical North Atlantic, using ocean and atmospheric re-analyses and satellite-derived datasets. Of particular consequence for the growth and drift of sargassum are patterns and seasonality of winds and currents. Results suggest that in years of exceptionally large sargassum blooms (2015, 2018), the Intertropical Convergence Zone (ITCZ), an area of maximum wind convergence where sargassum naturally accumulates, shifted southward, towards nutrient-rich waters of the Amazon River plume and the equatorial upwelling zone further stimulating sargassum growth. These changes are associated with modes of natural variability in the tropical Atlantic, notably a negative phase of the Atlantic Meridional Mode (AMM) in 2015 and 2018, and a positive phase of the Atlantic Niño in 2018. Negative AMM in these 2 years is also associated with stronger trade winds and enhanced northwest Africa upwelling, probably resulting in stronger southwestward nutrient transport into the eastern part of CWA. Moreover, in contrast with most years, important secondary winter blooms took place in both 2015 and 2018 in the northern part of CWA, associated with excessive wind-driven equatorial upwelling and anomalously strong northwestward nutrient transport.</p
A biophysical and socioeconomic review of the Volta Delta, Ghana
No full textDelta regions are dynamic and rich environments with diverse economic activities and are often densely populated.Deltas are being shaped by multiple drivers, including changes in sediment delivery to the coastal zone due to catchment changes, especially construction of dams on major rivers, intensified agriculture and/or aquaculture, mining, urbanisation, human-induced subsidence, climate change, and sea-level rise. These environmental challenges have significant implications for the livelihoods of delta residents. Thus, the integrated assessment of deltas is now attracting the attention of the scientific research community to analyse and understand deltas as coupled biophysical and socioeconomic systems. Most attention has been focussed on the major deltas. This review focusses on the smaller but regionally significant Volta delta, Ghana. Previous scientific studies are limited, with more focus upstream on the Volta River basin. Many contemporary problems are recognised in the Volta delta, especially erosion and flooding of the open coast fringe, such as at the town of Keta. However, these problems are treated independently, which may hinder identifying the root causes and the most effective solutions. Equally, the emergence of new problems might be anticipated and hence better managed or even avoided. This paper reviews the present delta with emphasis on biophysical processes and socioeconomic characteristics and considers in particular the current drivers and challenges.With this information, a research agenda will be established for a more systemic approach to understanding the Volta delta, including its residents and development
What are the implications of sea-level rise for a 1.5°C, 2°C and 3°C rise in global mean temperatures in the Ganges-Brahmaputra-Meghna and other vulnerable deltas?
No full textEven if climate change mitigation is successful, sea levels will keep rising. With subsidence, relative sea-level rise represents a long-term threat to low-lying deltas. A large part of coastal Bangladesh was analysed using the Delta Dynamic Integrated Emulator Model to determine changes in flood depth, area and population affected given sea-level rise equivalent to global mean temperature rises of 1.5°C, 2.0°C and 3.0°C with respect to pre-industrial for three ensemble members of a modified A1B scenario. Annual climate variability today (with approximately 1.0°C of warming) is potentially more important, in terms of coastal impacts, than an additional 0.5°C warming. In coastal Bangladesh, the average depth of flooding in protected areas is projected to double to between 0.07m to 0.09m when temperatures are projected at 3.0°C compared with 1.5°C. In unprotected areas, depth of flooding is projected to increase by approximately 50% to 0.21-0.27m, whilst the average area inundated increases 2.5 times (from 5% to 13% of the region) in the same temperature frame. The greatest area of land flooded is projected in the central and north-east regions. In contrast, lower flood depths, less land area flooded and fewer people are projected in the poldered west of the region. Over multi-centennial timescales, climate change mitigation and controlled sedimentation to maintain relative delta height are key to a delta’s survival. With slow rates of sea-level rise, adaptation remains possible, but further support is required. Monitoring of sea-level rise and subsidence in deltas is recommended, together with improved data sets of elevation. <br/
Unleashing potential: collaborative research as a catalyst for capacity building and enhancement
No full textDetection, measurement and prediction of shoreline recession in Accra, Ghana
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
Sargassum Biomass Movement and Proliferation in the Eastern Tropical Atlantic
Get PDFSince 2011, pelagic sargassum blooms (S. fluitans and S. natans) have impacted coastal communities, aquaculture, tourism, and biodiversity across the Tropical Atlantic region. Whilst the initial event is generally attributed to an anomalous North Atlantic Oscillation (2009–2010), the drivers of sargassum movement and proliferation remain unclear. This research gap is particularly evident in West Africa, where annual and seasonal sargassum variability is under-researched, and a lack of consensus exists on seasonal and annual trends. This paper addresses these gaps by (1) providing a first attempt at characterising the seasonal and annual trends of sargassum biomass in the Eastern Tropical Atlantic, through using satellite imagery to create a time-series for 2011–2022; and (2) exploring the hypothetical drivers of movement and proliferation of sargassum for this area, through assessing its co-variation with potential drivers including atmospheric, oceanic, and policy, establishing a historical timeline of events. The time-series analysis reveals an annual biomass peak in September and a second peak between March and May. The exploration of potential drivers reveals that alongside sea surface temperature there are multiple factors that could be influencing sargassum biomass, and that further research is necessary to clarify primary and secondary drivers. The results contribute to understanding drivers, impacts, and predictions of sargassum blooms in the Eastern Tropical Atlantic. We anticipate that our findings will enable sargassum-affected areas to better anticipate the size and timing of sargassum events in West Africa and offer researchers a new perspective on possible drivers of proliferation within the wider Tropical Atlantic region
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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