5,302 research outputs found
Large-scale circulation around the Crozet Plateau controls an annual phytoplankton bloom in the Crozet Basin
No full textThe circulation in the vicinity of the Crozet Plateau in the Southwest Indian Ocean sector of the Southern Ocean is examined using hydrographic sections, Argo floats, surface drifters, and satellite altimetry. All four techniques confirm that a major branch of the Antarctic Circumpolar Current, the SubAntarctic Front (SAF), flows anticyclonically round the Del Caño Rise west of the Crozet Plateau, i.e. eastward to the south of the Del Caño Rise, then northward and sometimes northwestward into the Crozet Basin, before turning back eastward in a combined front with the Agulhas Return Current and the SubTropical Front. This S-bend in the SAF is a permanent feature, controlled by the bathymetry, as has been inferred previously by Pollard and Read [Pollard, R.T., Read, J.F., 2001. Circulation pathways and transports of the Southern Ocean in the vicinity of the Southwest Indian Ridge. Journal of Geophysical Research, 106(C2), 2881–2898]. Similar, but much weaker, anticyclonic flow is found round the Crozet Plateau itself, with no more than 5?10×106 m3 s?1 turning north to the east of the Crozet Islands. Circulation north of the Crozet Plateau, between the Plateau and the S-bend of the SAF, is extremely weak, fed only by anticyclonic meanders breaking off the SAF into the area from the west or north, and occasional input from the northward, partially wind-driven (i.e. Ekman) flow south and east of the islands. In consequence of the weak circulation, dissolved iron from the land or sediments of the Crozet Plateau and Islands can build up during the winter in the Polar Frontal Zone between Crozet and the SAF, which gives rise to an annual bloom in this area. Biological evidence from satellite images, and from phytoplankton and zooplankton distributions, supports the circulation pattern we develop. This pattern confirms that patchiness of productivity in the bloom area results from close juxtaposition of water that has entered the area from the west from the SAF and from the south and east after flowing past the islands. Flow from the south and east has had a chance to entrain iron from the islands and sediments whereas flow from the west has not
Sub-mesoscale structure and the development of an eddy in the Subantarctic Front north of the Crozet Islands
No full textTwo stations only 20 km apart were observed to have quite different biological and biogeochemical characteristics. The first site had low concentrations of chlorophyll and sufficient nutrients to support phytoplankton growth. The second site had high concentrations of chlorophyll, depleted nutrient concentrations and significant export of phytodetrital material had taken place. The two sites were located in the Polar Frontal Zone of the Southern Ocean to the northwest of the Crozet Islands. The main physical difference between the two sites was in the depth of the mixed layer. At the first site, the mixed layer was deep and well mixed, whereas the second site had a shallow, stratified layer; otherwise the horizontal gradients of physical properties were weak. Survey data from the surrounding area showed that the productive site was located on the edge of a filament of water drawn into a developing meander of the Subantarctic Front. Remotely sensed data provided a history of the growth of the meander in the Subantarctic Front and its development into an eddy in the Polar Frontal Zone. The dynamics associated with the filament in the meander were clearly important in driving the primary productivity, as an intrusion of saline water into adjacent fresher water generated a shallow mixed layer and conditions suitable for phytoplankton growth. The dynamics promoting conditions favourable to phytoplankton growth continued to operate as chlorophyll was enhanced in the eddy after the main bloom had died away. Later measurements suggested that the surface layer had changed from diatom dominated to a coccolithophore or calcite-rich community
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
The marriage record of Neel, Noah A. and Allen, Isabella
No full textMarriage license for Noah A. Neel and Isabella Allen. J.F. Rodgers was the Justice of the Peace
Fabrieksschema betreffende de "Bereiding van Magnesium uit Zeewater": Deel I
No full textDocument(en) uit de collectie Chemische Procestechnologie Deel II zie: Deeg, J.F., Chemical Process Design 1101DelftChemTechApplied Science
SeaSoar and CTD sections across the Iceland-Faeroes Front and Faeroe Shetland Channel, August 1990
No full textBeatty, J.F., and the Law of Manslaughter
No full textIn this article, the author argues that the recent Supreme Court of Canada decisions in R. v. Beatty and R. v. J.F. have clarified several of the issues that have plagued the increasingly complicated offence of manslaughter. In particular, the decisions address the redundancy among the many manslaughter provisions in the Criminal Code, the need to define a clear separation between actus reus and mens rea, and the need to establish distinct categories of objective fault for different types of manslaughter offences. The author examines the legal background of these decisions as well as the current state of the law. He concludes by identifying emerging issues relating to the offence of manslaughter, arguing that the law remains convoluted and in need of urgent reform despite the progress made in the Beatty and J.F. decisions
FISHES 2001 and Vivaldi 1996: two recent surveys of the subpolar northeast Atlantic (abstract of paper presented at ASLO/AGU Ocean Sciences Meeting, Honolulu, HI, 11-15 Feb 2002)
No full textRRS Discovery Cruise 321, 24 Jul-23 Aug 2007. Biophysical interactions in the Iceland Basin 2007
No full textD321 was the first of three National Oceanography Centre ‘process study’ research cruises to be run by the Ocean Biogeochemistry and Ecosystems research group under the NERC Oceans 2025 research programme. The scientific work began by carrying out some of the extended Ellett Line stations on the way out to our study region; which centred around the historical JGOFS Ocean Weather Station India site (~ 59° N, ~ 19° W) and the northward turn of the extended Ellett line at 20° W. The Iceland Basin, like much of the N. Atlantic subpolar gyre, is characterised by a ‘bloom and bust’ seasonal cycle. Spring stratification triggers a major diatom dominated bloom event. This bloom is short lived, limited by silicate (orthosilicic acid) exhaustion (Brown et al., 2003). Two community succession pathways commonly follow the demise of the diatom bloom; typically through dinoflagellate and/or coccolithophore production. The spring bloom is dominated by eddy scale (several 10's of km) patchiness, driven by the upward and downward pumping effect of eddies on the newly forming spring stratification. However these eddy structures have another, more important, impact on phytoplankton production (Allen et al., 2005). In the release of potential energy, eddies effect a real three dimensional exchange of water across the thermocline bringing new dissolved nutrients from deeper waters up into the photic zone and transporting biogenic particles into the deep ocean. Thin ribbon like structures around the edges of eddies are clearly seen in ocean colour satellite images. The four repeated surveys carried out during D321 observed the evolution of an ‘eddy dipole’ in a background ocean full of eddies and other turbulent motions. Daily, near real-time, satellite images and in-situ vessel mounted acoustic current profiling were used to determine the movement of the eddy centres and the dipole central jet. Targeted nets and water collection within the various components of the eddy dipole enabled the assessment of its biological impacts.Since 1996 NOCS and SAMS have been occupying an extended version of the Ellett Line that runs all the way to Iceland. The Extended Ellett line is important oceanographically because it completes the measurements of the warm saline water flowing into the Nordic Seas from the eastern North Atlantic. It also monitors around half of the returning deep and cold current, the overflow water (the rest returns to the Atlantic via the Denmark Strait to the west of Iceland).There is little added cost, either in time or financially, in making a number of biogeochemical measurements using water samples from the hydrographers' CTD stations. Thus, recently, the scientific interests in the Extended Ellett line have become more multidisciplinary; the 2006 occupation was no exception. Samples were filtered for POC, HPLC studies and trace aluminium concentration determination, in addition some extra time was found for a number of zooplankton net hauls.<br/
Bouwen aan de delta: Gerealiseerde waterbouwkundige werken, Inzendingen prof. dr. ir. J.F. Agemaprijs 2015
No full textDe afgelopen jaren (2010 - 2015) zijn er in Nederland vele in het oog springende waterbouwkundige projecten gerealiseerd. Aansprekende voorbeelden betreffen onder meer Maasvlakte 2, de Zandmotor, de ontpoldering van de Noordwaard en de omlegging van de Zuid-Willemsvaart. Ook in de lokale watersystemen zijn diverse interessante projecten gebouwd. Veel van deze projecten hebben zich aangemeld voor de prof. dr. ir. J.F. Agemaprijs, dé prijs voor het beste en meest innovatieve waterbouwkundige project dat daadwerkelijk gebouwd is. Dit boek toont foto’s en projectinformatie, en bevat achtergrondinformatie over de Agemaprijs en essays van experts. De verschillende projecten geven een fraai beeld van de veelzijdigheid en innovativiteit van de Nederlandse (water)bouwers. Het boek geeft inzicht in de huidige en toekomstige manier waarop deltagebieden kunnen worden ingericht.Delft University of Technolog
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