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  • Institut de Ciències del Mar de Barcelona, CSIC  (6)
  • Paris, France  (3)
  • Barcelona : Inst. de Ciències del Mar  (1)
  • 1
    Type of Medium: Book
    Pages: 276 S. , Ill., graph. Darst., Kt.
    Series Statement: Scientia marina 76.2012, Suppl. 1
    Language: English
    Note: Index S. [271] - 276 , Literaturangaben
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  • 2
    Publication Date: 2021-05-19
    Description: The Cape Verde Front (CVF) separates the North Atlantic subtropical gyre (NASG) from the north-eastern North Atlantic tropical gyre (NATG). Within the NASG, the Canary Current (CC) and the Canary Upwelling Current (CUC) comprise a relatively shallow (down to about 200-300 m) flow of North Atlantic Central Waters (NACW): the CC is found far offshore as a wide and poorly defined current while the CUC is a near-slope intense baroclinic jet linked to the coastal upwelling front. Within the top 300 m of the NATG, the along-slope Mauritania Current and the Cape Verde Current (CVC, a north-eastern extension of the North Equatorial Counter Current that broadly rotates around the Guinea Dome) carry South Atlantic Central Waters northwards. As a result, the frontal system is the site of intense along-slope flow convergence and offshore transport in the top 300 m of the water column. Further deep, down to some 500 m, the interior flow is very weak in both gyres, likely dominated by mesoscale features, except along the continental slope, where the northward Poleward Undercurrent (PUC) feeds through localized inputs from the interior ocean; in particular, within the NATG the CVC appears as responsible for southward transfer of NACW, across the CVF, which eventually reaches the PUC.
    Description: Published
    Keywords: Eastern boundary currents ; Cape Verde Front ; Canary Upwelling Current ; Poleward Undercurrent ; Guinea Dome ; CCLME
    Repository Name: AquaDocs
    Type: Report Section , Refereed
    Format: pp. 81-92
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  • 3
    Publication Date: 2021-05-19
    Description: Inorganic nutrients increase with depth as a result of the enhanced remineralization of organic matter with aging waters (the time since they were last near the sea surface), and the opposite happens with dissolved oxygen (except within the saturated surface mixed layer). In the Canary Current Large Marine Ecosystem there is also a marked latitudinal gradient, with the Cape Verde Front separating relatively nutrient-poor and oxygen-rich subtropical waters from the nutrient-rich and oxygen-poor tropical waters. Along a latitudinal band off North-West Africa, coastal upwelling brings the subsurface waters towards the sea surface, locally raising the inorganic nutrient levels. This becomes an important lateral source to both gyres, especially to the nutrient-poor subtropical one, taking place through lateral mixing (mainly as a result of the instability of the coastal-upwelling baroclinic jet) and localized coastal filaments (in those regions, typically capes, where the coastal flow converges and offshore advection takes place). In the southernmost portion of our domain, within tropical waters, there is also high (wind-induced) offshore primary production. This, together with the slow ventilation of the subsurface waters, leads to much enhanced remineralization, producing a region with very low oxygen and high inorganic nutrient levels, the oxygen minimum zone of the North Atlantic Ocean.
    Description: Published
    Keywords: Cape Verde Front ; Inorganic nutrient supply ; Biogeochemical processes ; Spatial distributions ; Oxygen minimum zone ; CCLME
    Repository Name: AquaDocs
    Type: Report Section , Refereed
    Format: pp. 133-142
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  • 4
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    IOC-UNESCO | Paris, France
    Publication Date: 2021-05-19
    Description: North of Cape Blanc, the north-easterly winds cause offshore flow of surface waters that are replaced by subsurface inflow of relatively cold and nutrient-rich waters, driving the vertical cell of coastal upwelling. This vertical circulation, together with surface heating and horizontal mixing, causes the coastal upwelling front (typically about 200 m deep) that separates cold onshore from warm offshore waters. A southward baroclinic coastal jet is associated to this front, which causes vertical shear and mixing that contribute to the intensity of the vertical cell. Very importantly, this jet feeds from upstream waters, resulting in an along-slope coherent flow, or the horizontal cell of coastal upwelling – this is the Canary Upwelling Current (CUC) that connects all surface coastal African waters north of Cape Blanc. Further south, because of the northward offshore flow and the seasonality of the winds, the connection remains only during winter and spring, very close to shelf break and in the top 100 m. North of Cape Blanc, a Poleward Undercurrent (PUC) flows in the relatively homogenous upwelled waters that found over the continental slope. South of Cape Blanc the PUC appears as a nearshore expression of the Mauritania Current. Both the southward CUC and the northward PUC constitute the true skeleton of the Canary Current Large Marine Ecosystem.
    Description: Published
    Keywords: Coastal upwelling ; Recirculation cells ; Canary Upwelling Current ; Poleward Undercurrent ; CCLME ; ASFA15::E::Ekman transport
    Repository Name: AquaDocs
    Type: Report Section , Refereed
    Format: pp. 93-103
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  • 5
    Publication Date: 2012-09-12
    Description: The field of physical oceanography has undergone exponential growth in Spain during the last few decades. From a handful of self-taught researchers in the late 1960s there are now several hundred physical oceanographers distributed in some 20 Spanish institutions, and many more working overseas. The First Spanish Physical Oceanography Meeting (EOF1), held in Barcelona in October 2010, was a good example of the high quality and large variety of this research. The facilities and human resources are excellent but the alarming decrease in public investment in science due to the economic crisis must lead the Spanish physical oceanography community to define its current priorities. In this introductory paper to EOF1 we revise our history and where we are now, and suggest that progress in the near future will rely on our intelligence to sustain and enhance human capital, partnership and society-oriented research.
    Print ISSN: 0214-8358
    Electronic ISSN: 1886-8134
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 6
    Publication Date: 2012-09-12
    Description: The regional ocean circulation within the Canary Upwelling System between 31°N and 35°N is studied using numerical tools. Seasonal mean and near-instantaneous velocity fields from a previously-generated climatological Regional Ocean Modelling System (ROMS) solution of the Canary Basin are used to force a series of offline Lagrangian particle-tracking experiments. The primary objective is to identify the pathways through which water parcels arrive at the upwelling region north of Cape Ghir. Examining year-long pathways, the Azores Current contributes over 80% of particles annually, of which a large proportion arrive directly from offshore (from the northwest), while others travel along the shelf and slope from the Gulf of Cadiz. The remaining ~20% originate within the Gulf of Cadiz or come from the south, although the southern contribution is only significant in autumn and winter. When season-long pathways are considered, the alongshore contributions become increasingly important: northern contributions reach 40% in spring and summer, while southern values exceed 35% in winter. This study also shows that coastal upwelling changes both spatially and temporally. Upwelling becomes intensified near Cape Beddouza, with most upwelling occurring within ~40 km from shore although significant values may reach as far as 120 km offshore north of Cape Beddouza; at these locations the offshore integrated upwelling reaches as much as 4 times the offshore Ekman transport. In the Cape Beddouza area (32°N to 33°N), upwelling is negligible in February but intensifies in autumn, reaching as much as 3 times the offshore Ekman transport.
    Print ISSN: 0214-8358
    Electronic ISSN: 1886-8134
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 7
    Publication Date: 2012-09-12
    Description: We use hydrographic, velocity and drifter data from a cruise carried out in November 2008 to describe the continental slope current system in the upper thermocline (down to 600 m) between Cape Verde and the Canary Islands. The major feature in the region is the Cape Verde Frontal Zone (CVFZ), separating waters from tropical (southern) and subtropical (northern) origin. The CVFZ is found to intersect the slope north of Cape Blanc, between 22°N and 23°N, but we find that southern waters are predominant over the slope as far north as 24°N. South of Cape Blanc (21.25°N) the Poleward Undercurrent (PUC) is a prominent northward jet (50 km wide), reaching down to 300 m and indistinguishable from the surface Mauritanian Current. North of Cape Blanc the upwelling front is found far offshore, opening a near-slope northward path to the PUC. Nevertheless, the northward PUC transport decreases from 2.8 Sv at 18°N to 1.7 Sv at 24°N, with about 1 Sv recirculating ofshore just south of Cape Blanc, in agreement with the trajectory of subsurface drifters. South of the CVFZ there is an abrupt thermohaline transition at σ ϴ =26.85 kg m –3 , which indicates the lower limit of the relatively pure (low salt and high oxygen content) South Atlantic Central Water (SACW) variety that coexists with the dominant locally-diluted (salinity increases through mixing with North Atlantic Central Water but oxygen diminishes because of enhanced remineralization) Cape Verde (SACWcv) variety. At 16°N about 70% of the PUC transport corresponds to the SACW variety but but this is transformed into 40% SACWcv at 24°N. However, between Cape Verde and Cape Blanc and in the 26.85 〈 σ ϴ 〈 27.1 layer, we measure up to 0.8 Sv of SACWcv being transported south. The results strongly endorse the idea that the slope current system plays a major role in tropical-subtropical water-mass exchange.
    Print ISSN: 0214-8358
    Electronic ISSN: 1886-8134
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 8
    Publication Date: 2012-09-12
    Description: This study investigates the advection of positive-salinity anomalies by the Equatorial Undercurrent (EUC) and their potential importance in inducing vertical convective mixing. For this purpose we use hydrographic and velocity observations taken in April 2010 along the western Atlantic equatorial ocean (32 to 43°W). The high-salinity EUC core is a few tens of metres thick and occupies the base of the surface mixed layer and the upper portion of the surface thermocline. It leads to high positive values of the vertical salinity gradient, which in many instances cause statically unstable conditions in otherwise well-stratified regions. The unstable regions result in vertical convection, hence favouring the occurrence of step-like features. We propose that this combination of horizontal advection and vertical-instability leads to a sequence of downward-convective events. As a result the EUC salinity is diffused down to a potential density of 26.43, or about 200 m deep. This mechanism is responsible for water-mass and salt downwelling in the equatorial Atlantic Ocean, with a potentially large influence on the tropical and subtropical cells.
    Print ISSN: 0214-8358
    Electronic ISSN: 1886-8134
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 9
    Publication Date: 2012-09-12
    Description: We use three transatlantic cruises (1957, 1993 and 2010) along 7.5°N to analyse inter-decadal variations of the neutral buoyancy frequency (with neutral density replacing potential density) and Turner angle. We also use Argo data from the 2003-2011 period to show that, within central and intermediate waters, the changes between the three sections are slightly greater than the seasonal and inter-annual variations, so they may be interpreted as actual inter-decadal variations. The results point to a generalized sinking of isoneutrals between 1957 and 2010, with maximum zonally-averaged values of about 100 m in the central and upper deep layers. They also reveal the occurrence of substantial changes in the intermediate and neighbouring water strata, with differential vertical sinking of isoneutrals and the transformation of their thermohaline characteristics. The neutral buoyancy frequency increased in the lower central and upper intermediate layers and decreased in the lower intermediate and upper deep layers. The distributions of Turner angle highlight a predominance of salt-fingering in the North Atlantic, except for a gravitationally doubly-stable layer located immediately below the intermediate water core; this stable layer thinned substantially between 1957 and 2010 because of the sinking of the lower intermediate isoneutrals acting together with actual water transformations from Antarctic Intermediate Waters into North Atlantic Deep Waters. We conclude that a significant portion of the water column underwent both increased vertical stratification and enhanced salt-fingering, two mechanisms with opposite effects on the effective vertical diffusion.
    Print ISSN: 0214-8358
    Electronic ISSN: 1886-8134
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 10
    Publication Date: 2012-09-12
    Description: Despite the considerable impact of meddies on climate through the long-distance transport of properties, a consistent observation of meddy generation and propagation in the ocean is rather elusive. Meddies propagate at about 1000 m below the ocean surface, so satellite sensors are not able to detect them directly and finding them in the open ocean is more fortuitous than intentional. However, a consistent census of meddies and their paths is required in order to gain knowledge about their role in transporting properties such as heat and salt. In this paper we propose a new methodology for processing high-resolution sea surface temperature maps in order to detect meddy-like anomalies in the open ocean on a near-real-time basis. We present an example of detection, involving an atypical meddy-like anomaly that was confirmed as such by in situ measurements.
    Print ISSN: 0214-8358
    Electronic ISSN: 1886-8134
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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