The West African coastal upwelling filaments and cross-frontal water exchange conditioned by them

Kostianoy, Andrey G.; Зацепин, А. Г.

doi:10.1016/0924-7963(95)00029-1

Cited by 51 publications

(40 citation statements)

References 20 publications

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“…In the studied region, filaments have typical lifetime of a few days, velocity between 0.1-1 m s −1 , a length of a few hundred kilometers, a width of a few ten kilometers and a depth of a few hundred meters (e.g. Kostianoy and Zatsepin, 1996;Barton et al, 1998;Peliz et al, 2002;Pelegrí et al, 2005). The wind stress curl is estimated from the SCOW climatology (Section 2.2).…”

Section: Analysis Of Orders Of Magnitudementioning

confidence: 99%

“…Remote-sensing imagery helped to identify the sites favorable to filaments (e.g, Van Camp et al, 1991;García-Weill et al, 1994;Kostianoy and Zatsepin, 1996;Hernández-Guerra and Nykjaer, 1997). Different mechanisms have been proposed for the filament generation: interaction of the upwelling jet with the topography (Ikeda and Emery, 1984;Strub et al, 1991;Hagen et al, 1996), baroclinic instability (Ikeda and Emery, 1984), meandering of the equatorward jet (Strub et al, 1991), interaction with a field of synoptic-mesoscale eddies (Mooers and Robinson, 1984;Lutjeharms et al, 1991;Strub et al, 1991;Peliz et al, 2004), influence of the wind (e.g., Kelly, 1986;Hagen et al, 1996;Castelao and Barth, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Generation of the Cape Ghir upwelling filament: A numerical study

et al. 2012

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Filaments are narrow, shallow structures of cool water originating from the coast. They are typical features of the four main eastern boundary upwelling systems (EBUS). In spite of their significant biological and chemical roles, through the offshore exportation of nutrient-rich waters, the physical processes that generate them are still not completely understood. This paper is a process-oriented study of filament generation mechanisms. Our goal is twofold: firstly, to obtain a numerical solution able to correctly represent the characteristics of the filament off Cape Ghir (30• 38'N, northwest Africa) in the Canary EBUS and secondly, to explain its formation by a simple mechanism based on the balance of potential vorticity.The first goal is achieved by the use of the ROMS model (Regional Ocean Modeling System) with embedded domains around Cape Ghir, with a horizontal resolution going up to 1.5 km for the finest domain. The latter gets its initial and boundary conditions from a parent solution and is forced by climatological, high-resolution atmospheric fields. The modeled filaments display spatial, temporal and physical characteristics in agreement with the available in situ and satellite observations. This model solution is used as a reference to compare the results with a set of process-oriented experiments. These experiments allow us to reach the second objective. The solutions serve to highlight the contributions of various processes to the filament generation. Since the study is focused on general processes present under climatological forcing conditions, inter-annual forcing is not necessary.The underlying idea for the filament generation is the balance of potential vorticity in the Canary EBUS: the upwelling jet is characterized by negative relative vorticity and flows southward along a narrow band of uniform potential vorticity. In the vicinity of the cape, an injection of relative vorticity induced by the wind breaks the existing vorticity balance. The upwelling jet is prevented from continuing its way southward and has to turn offshore to follow lines of equal potential vorticity.The model results highlight the essential role of wind, associated with the particular topography (coastline and bottom) around the cape. The mechanism presented here is general and thus can be applied to other EBUS.

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Section: Analysis Of Orders Of Magnitudementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Generation of the Cape Ghir upwelling filament: A numerical study

et al. 2012

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“…García-Muñoz et al, 2005;Pelegrí et al, 2005). The variability of the filaments, jets and eddies largely determine the particle distribution (Nykjaer and Van Camp, 1994;Kostianoy and Zatsepin, 1996). Intense and variable currents lead to resuspension of shallow sediments at rough slope topographies and to an offshore transport of particulate material (e.g., Cacchione and Southard, 1974;Huthnance, 1981;Fischer et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Spatio-temporal distribution and transport of particulate matter in the eastern tropical North Atlantic observed by Argo floats

Ohde¹,

Fiedler²,

Körtzinger³

2015

Deep Sea Research Part I: Oceanographic Research Papers

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“…Small-scale internal velocities within offshore transported upwelled water may be substantially larger. For example, Kostianoy and Zatsepin [1996] analyzed satellite images and in situ sea surface temperature to determine cross frontal water exchange. They observed an average offshore development of fast coldwater injections of 0.91 m s À1 between 15°N and 25°N off NW Africa.…”

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confidence: 99%

Northwest African upwelling and its effect on offshore organic carbon export to the deep sea

Helmke

Romero

Fischer

2005

Global Biogeochemical Cycles

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[1] We combined the analysis of sediment trap data and satellite-derived sea surface chlorophyll to quantify the amount of organic carbon export to the deep sea in the upwelling induced high production area off northwest Africa. In contrast to the generally global or basin-wide adoption of export models, we used a regionally fitted empirical model. Furthermore, the application of our model was restricted to a dynamically defined region of high chlorophyll concentration in order to restrict the model application to an environment of more homogeneous export processes. We developed a correlation-based approximation to estimate the surface source area for a sediment trap deployed from 11 June 1998 to 7 November 1999 at 21.25°N latitude and 20.64°W longitude off Cape Blanc. We also developed a regression model of chlorophyll and export of organic carbon to the 1000 m depth level. Carbon export was calculated for an area of high chlorophyll concentration (>1 mg m À3) adjacent to the coast on a daily basis. The resulting zone of high chlorophyll concentration was 20,000-800,000 km 2 large and yielded a yearly export of 1.123 to 2.620 Tg organic carbon. The average organic carbon export within the area of high chlorophyll concentration was 20.6 mg m À2 d À1 comparable to 13.3 mg m À2 d À1 as found in the sediment trap results if normalized to the 1000 m level. We found strong interannual variability in export. The period autumn 1998 to summer 1999 was exceeding the mean of the other three comparable periods by a factor of 2.25. We believe that this approach of using more regionally fitted models can be successfully transferred even to different oceanographic regions by selecting appropriate definition criteria like chlorophyll concentration for the definition of an area to which it is applicable.Citation: Helmke, P., O. Romero, and G. Fischer (2005), Northwest African upwelling and its effect on offshore organic carbon export to the deep sea, Global Biogeochem. Cycles, 19, GB4015,

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The West African coastal upwelling filaments and cross-frontal water exchange conditioned by them

Cited by 51 publications

References 20 publications

Generation of the Cape Ghir upwelling filament: A numerical study

Generation of the Cape Ghir upwelling filament: A numerical study

Spatio-temporal distribution and transport of particulate matter in the eastern tropical North Atlantic observed by Argo floats

Northwest African upwelling and its effect on offshore organic carbon export to the deep sea

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