scholarly journals Plate tectonic reconstructions and paleogeographic maps of the central and North Atlantic oceans 1This article is one of a series of papers published in this CJES Special Issue on the theme of Mesozoic–Cenozoic geology of the Scotian Basin. 2Earth Sciences Sector Contribution 20120172.

2012 ◽  
Vol 49 (12) ◽  
pp. 1395-1415 ◽  
Author(s):  
Jean-Claude Sibuet ◽  
Stéphane Rouzo ◽  
Shiri Srivastava
Keyword(s):  
Nova Scotia ◽  
North America ◽  
Magnetic Anomaly ◽  
Late Cretaceous ◽  
North Atlantic ◽  
West African ◽  
Late Triassic ◽  
West African Coast ◽  
African Coast ◽  
Salt Deposits

We have established a new plate kinematic model of the central and North Atlantic oceans between North America, Africa, Meseta, Iberia, Flemish Cap, and Galicia Bank from Late Triassic to Late Cretaceous to better understand the nature and timing of rifting of Nova Scotia and Morocco conjugate continental margins since Late Triassic. The maps of salt distributions at the Sinemurian–Pliensbachian limit (190 Ma; after salt deposition) and in middle Bajocian (170 Ma) show that an area of the Nova Scotia margin is devoid of allochthonous salt and that an area of similar size located oceanward of the West African Coast Magnetic Anomaly shows salt deposits, suggesting that a portion of the Nova Scotia margin with its overlying salt deposits could have been transferred onto the Moroccan side right after the formation of the conjugate East Coast Magnetic Anomaly and West African Coast Magnetic Anomaly. Seven paleogeographic maps, from Late Triassic to Late Cretaceous, are presented with structural elements and magnetic lineations. They show that the connection between the Central Atlantic and the Tethys, with an aborted rift between Iberia and North America ending in the north against the Flemish Cap – Galicia Bank dam, started to deepen at the end of the first rifting phase (190 Ma ago) after the rupture of the thinned continental crust. It is only during the Early Cretaceous, after the rupture of the Flemish Cap – Galicia Bank dam, that the deep connection around Iberia was finally established between the Central and North Atlantic, the Tethys, and the Bay of Biscay.

On vortices initiated over West Africa and their impact on North Atlantic tropical cyclones

2020 ◽  
Author(s):  
Jean-Philippe Duvel
Keyword(s):  
West Africa ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
West African ◽  
Synoptic Scale ◽  
Low Level ◽  
Potential Index ◽  
West African Coast ◽  
African Coast ◽  
Low Levels

AbstractUsing 38 years of the ERA Interim dataset, an objective tracking approach is used to analyze the origin, characteristics and cyclogenesis efficiency (CE) of synoptic-scale vortices initiated over West Africa and the Atlantic Ocean. Many vortex tracks initiated near the coast or over the ocean result from a vertical expansion of a “primary” vortex track that was initiated earlier over West Africa. Low-level (850hPa) primary vortices are initiated mainly in July near the Hoggar mountains (5°E, 24°N), while mid-level (700 hPa) primary vortices are initiated mainly in August-September near Guinea highlands (10°W, 10°N). The CE of all these vortices is about 10% in July and 30% in August. The average CE is however smaller for low-level “Hoggar” vortices because they peak in July when the cyclogenesis potential index of the Atlantic Ocean is weak. Seasonal and interannual modulations of the cyclogenesis is related more to this index than to the number of vortices crossing the West African coast. Cyclogenesis is nearly equally distributed between the coast and 60°W, but the part of the cyclogenesis due to vortices initiated over West Africa decreases from 80% near the coast to about 30% at 60°W. The most probable delay between the vortex vertical expansion and cyclogenesis is 2 days, but it can be up to 10 days. This analysis also confirms previous results, such as the larger CE for vortices extending at low-levels over the continent at 10°N, or the delayed and therefore west-shifted cyclogenesis of low-level “Hoggar” vortices.

The Cyclonic Disturbances of the Sub-Tropical Eastern North Atlantic

1944 ◽  
Vol 25 (1) ◽  
pp. 2-16 ◽  
Keyword(s):  
North Atlantic ◽  
Middle Latitude ◽  
Low Pressure ◽  
West African ◽  
Trade Wind ◽  
The West ◽  
West African Coast ◽  
African Coast ◽  
Eastern North Atlantic

The “Hoffmeyer Charts”, a joint publication of the Deutsche Seewarte and the Netherlands Meteorological Institute, covering the years 1881–1911, offer an extraordinary opportunity to study the types and behavior of pressure disturbances which form in the trade-wind belt of the eastern North Atlantic. Such disturbances occur relatively infrequently, so that they can only be studied when data from such a long period of years is available. A systematic review of the “Hoffmeyer Charts” revealed that there are four principal types of disturbances, none of which is as intense in character as middle latitude cyclones, but which nevertheless have definite types of weather phenomena associated with them which may be of considerable significance to ocean and air transportation. These disturbances were classified as follows: Type 1 is a low pressure area centered in middle or higher latitudes of the North Atlantic Ocean, whose influence, however, extends as far south as 25° N. Lat. or more: Type 2 is a disturbance centered at about 30°N, 30°W. Both type 1 and 2 derive from middle latitude disturbances, and usually begin as a secondary. Type 3 is a low-pressure center near the Canary Islands, which may originate on the West African coast south of 20° N and move westward toward the Canaries, or may originate near the Canaries and travel eastward along the same route, or, as is most frequently the case, may originate near or just north of the Canaries, expand or fill up on the spot, or perhaps attach itself to a low moving eastward in higher latitudes. Type 4 is a low on the West African coast between 5° and 20° N which moves westward. These usually move along the southern edge of the trade-wind belt. “The tracks and monthly frequency of disturbances of these various types is discussed in considerable detail, as well as the duration and tendency to repetition. A detailed synoptic analysis of a type 4 disturbance is given.”

A large Cirroteuthis magna (Cephalopoda: Cirroctopoda) caught on the Cape Verde Terrace (North Atlantic)

2001 ◽  
Vol 81 (2) ◽  
pp. 357-358 ◽  
Author(s):  
Martin A. Collins ◽  
Mary O'Dea ◽  
Camila Henriques
Keyword(s):  
North Atlantic ◽  
Mature Female ◽  
West African ◽  
Cape Verde ◽  
The West ◽  
Development Stages ◽  
Wide Range ◽  
West African Coast ◽  
African Coast ◽  
Formalin Preservation

A large, mature, female cirrate octopod, Cirroteuthis magna, was caught in a research trawl at 3200-m depth on the Cape Verde Terrace off the west African coast in November 1999. It is only the fourth recorded specimen of this species and the largest specimen (1,700 mm TL; 330 mm ML) of cirrate octopod ever caught. Detailed measurements were taken of the fresh and preserved specimen and indicated considerable shrinkage (17–32%) during formalin preservation. Careful dissection revealed large mature eggs (12·5–14 mm long) in the proximal oviduct, and a wide range of egg sizes and development stages in the ovary. The taxonomy and ecology of the species is briefly discussed.

Informed Consent: Ezenwa–Ohaeto between Past and Future Uses of Pidgin

Matatu ◽  
2006 ◽  
Vol 33 (1) ◽  
pp. 115-134 ◽  
Author(s):  
Chantal Zabus
Keyword(s):  
Informed Consent ◽  
First Language ◽  
West African ◽  
The Other ◽  
Wole Soyinka ◽  
The West ◽  
West African Coast ◽  
African Coast ◽  
The 1950S ◽  
The One

The essay shows how Ezenwa–Ohaeto's poetry in pidgin, particularly in his collection (1988), emblematizes a linguistic interface between, on the one hand, the pseudo-pidgin of Onitsha Market pamphleteers of the 1950s and 1960s (including in its gendered guise as in Cyprian Ekwensi) and, on the other, its quasicreolized form in contemporary news and television and radio dramas as well as a potential first language. While locating Nigerian Pidgin or EnPi in the wider context of the emergence of pidgins on the West African Coast, the essay also draws on examples from Joyce Cary, Frank Aig–Imoukhuede, Ogali A. Ogali, Ola Rotimi, Wole Soyinka, and Tunde Fatunde among others. It is not by default but out of choice and with their 'informed consent' that EnPi writers such as Ezenwa–Ohaeto contributed to the unfinished plot of the pidgin–creole continuum.

The Royal African Company of England's West African Correspondence, 1681-1699

1993 ◽  
Vol 20 ◽  
pp. 173-184 ◽  
Author(s):  
Robin Law
Keyword(s):  
West Africa ◽  
Sierra Leone ◽  
West African ◽  
Gold Coast ◽  
Original Form ◽  
Cape Coast ◽  
General Terms ◽  
West African Coast ◽  
African Coast ◽  
History Of

This paper draws attention to an ambitious project in the publication of source material for the precolonial history of West Africa, which has recently been approved for inclusion in the Fontes Historiae Africanae series of the British Academy. In addition to self-promotion, however, I wish also to take the opportunity to air some of the problems of editorial strategy and choice which arise with regard to the editing and presentation of this material, in the hope of provoking some helpful feedback on these issues.The material to be published consists of correspondence of the Royal African Company of England relating to the West African coast in the late seventeenth century. The history of the Royal African Company (hereafter RAC) is in general terms well known, especially through the pioneering (and still not superseded) study by K.G. Davies (1957). The Company was chartered in 1672 with a legal monopoly of English trade with Africa. Its headquarters in West Africa was at Cape Coast (or, in the original form of the name, Cabo Corso) Castle on the Gold Coast, and it maintained forts or factories not only on the Gold Coast itself, but also at the Gambia, in Sierra Leone, and at Offra and Whydah on the Slave Coast. It lost its monopoly of the African trade in 1698, and thereafter went into decline, effectively ceasing to operate as a trading concern in the 1720s, although it continued to manage the English possessions on the coast of West Africa until it was replaced by a regulated company (i.e., one open to all traders), the Company of Merchants Trading to Africa, in 1750.

scholarly journals Trains of African Easterly Waves and Their Relationship to Tropical Cyclone Genesis in the Eastern Atlantic

2017 ◽  
Vol 145 (2) ◽  
pp. 599-616 ◽  
Author(s):  
Abdou L. Dieng ◽  
Saidou M. Sall ◽  
Laurence Eymard ◽  
Marion Leduc-Leballeur ◽  
Alban Lazar
Keyword(s):  
West African ◽  
Dynamical Structure ◽  
African Easterly Waves ◽  
The South ◽  
The West ◽  
Easterly Waves ◽  
West African Coast ◽  
African Coast ◽  
Tropical Depressions ◽  
The Relationship

In this study, the relationship between trains of African easterly waves (AEWs) and downstream tropical cyclogenesis is studied. Based on 19 summer seasons (July–September from 1990 to 2008) of ERA-Interim reanalysis fields and brightness temperature from the Cloud User Archive, the signature of AEW troughs and embedded convection are tracked from the West African coast to the central Atlantic. The tracked systems are separated into four groups: (i) systems originating from the north zone of the midtropospheric African easterly jet (AEJ), (ii) those coming from the south part of AEJ, (iii) systems that are associated with a downstream trough located around 2000 km westward (termed DUO systems), and (iv) those that are not associated with such a close downstream trough (termed SOLO systems). By monitoring the embedded 700-hPa-filtered relative vorticity and 850-hPa wind convergence anomaly associated with these families along their trajectories, it is shown that the DUO generally have stronger dynamical structure and statistically have a longer lifetime than the SOLO ones. It is suggested that the differences between them may be due to the presence of the previous intense downstream trough in DUO cases, enhancing the low-level convergence behind them. Moreover, a study of the relationship between system trajectories and tropical depressions occurring between the West African coast and 40°W showed that 90% of tropical depressions are identifiable from the West African coast in tracked systems, mostly in the DUO cases originating from the south zone of the AEJ.

A New Lautoconus Species Radiation from Gambia, West Africa

The Festivus ◽  
2018 ◽  
Vol 50 (3) ◽  
pp. 164-172
Author(s):  
Edward Petuch ◽  
David Berschauer
Keyword(s):  
New Species ◽  
West Africa ◽  
River Mouth ◽  
Sympatric Species ◽  
West African ◽  
The West ◽  
Species Radiation ◽  
West African Coast ◽  
African Coast ◽  
Reef Fauna

Six sympatric species of the cone shell genus Lautoconus Monterosato, 1923 have been discovered on an isolated rock reef near the Gambia River Mouth, Gambia, West Africa. Of these, four were found to be new to science and, together, they represent a previously unknown Gambian endemic species radiation. These include: Lautoconus fernandi new species, L. gambiensis new species, L. rikae new species, and L. wolof new species. The poorly-known Gambian endemic cone, Lautoconus orri (Ninomiya and da Motta, 1982) was also found to be a component of the rock reef fauna, as was the wide-ranging L. guinaicus (Hwass, 1792) (Senegal to Ghana). The Gambian cluster of sibling species represents the farthest-south separate radiation of Lautoconus known from the West African coast.

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