The Cape Verde Frontal Zone separates North and South Atlantic Central Waters in the eastern Nort... more The Cape Verde Frontal Zone separates North and South Atlantic Central Waters in the eastern North Atlantic Subtropical Gyre. CTD-02 and shipboard ADCP data from three hydrographic sections carried out in September 2003 are used to study the structure of the front. Results show the relation between spatial variations of water masses and currents, demonstrating the importance of advection in the distribution of water masses. Diapycnal diffusivities due to double diffusion and vertical shear instabilities are also estimated. Ex istence of competition between the two processes through the water column is shown. Depthaveraged diffusivities suggest that salt fingering dominates diapycnal mixing, except areas of purest South Atlantic Central Water. Here, double diffusion processes are weak and, consequently, shear of the flow is the main process. Results also show that strong mixing induced by vertical shear is associated with a large intrusion found near the front.
During Fa11 1995 and Fa11 1997 two hydrographic cruises were done with the RN Hespérides between ... more During Fa11 1995 and Fa11 1997 two hydrographic cruises were done with the RN Hespérides between the Iberian Peninsula and the Canary ArchipeIago, with special coveage of the Cape Ghir Filament region. XBT, CTD and ADCP measurements are reported for these dses . ...
The circulation patterns and the impact of the lateral export of nutrients and organic matter off... more The circulation patterns and the impact of the lateral export of nutrients and organic matter off NW Africa are examined by applying an inverse model to two hydrographic datasets gathered in fall 2002 and spring 2003. These estimates show significant changes in the circulation patterns at central levels from fall to spring, particularly in the southern boundary of the domain related to zonal shifts of the Cape Verde Frontal Zone. Southward transports at the surface and central levels at 26 • N are 5.6 ± 1.9 Sv in fall and increase to 6.7 ± 1.6 Sv in spring; westward transports at 26 • W are 6.0 ± 1.8 Sv in fall and weaken to 4.0 ± 1.8 Sv in spring. At 21 • N a remarkable temporal variability is obtained, with a northward mass transport of 4.4 ± 1.5 Sv in fall and a southward transport of 5.2 ± 1.6 Sv in spring. At intermediate levels important spatiotemporal differences are also observed, and it must be highlighted that a northward net mass transport of 2.0 ± 1.9 Sv is obtained in fall at both the south and north transects. The variability in the circulation patterns is also reflected in lateral transports of inorganic nutrients (SiO 2 , NO 3 , PO 4) and dissolved organic carbon (DOC). Hence, in fall the area acts as a sink of inorganic nutrients and a source of DOC, while in spring it reverses to a source of inorganic nutrients and a sink of DOC. A comparison between nutrient fluxes from both in situ observations and numerical modeling output is finally addressed.
Deep Sea Research Part I: Oceanographic Research Papers, 2017
An interdisciplinary survey of a subtropical intrathermocline eddy was conducted within the Canar... more An interdisciplinary survey of a subtropical intrathermocline eddy was conducted within the Canary Eddy Corridor in September 2014. The anatomy of the eddy is investigated using near submesoscale fine resolution two-dimensional data and coarser resolution threedimensional data. The eddy was four months old, with a vertical extension of 500 m and 46 km radius. It may be viewed as a propagating negative anomaly of potential vorticity (PV), 95% below ambient PV. We observed two cores of low PV, one in the upper layers centered at 85 m, and another broader anomaly located between 175 m and the maximum sampled depth in the three-dimensional dataset (325 m). The upper core was where the maximum absolute values of normalized relative vorticity (or Rossby number), |Ro| = 0.6, and azimuthal velocity, U = 0.5 m s-1 , were reached and was defined as the eddy dynamical core. The typical biconvex isopleth shape for intrathermocline eddies induces a decrease of static stability, which causes the low PV of the upper core. The deeper low PV core was related to the occurrence of a pycnostad layer of subtropical mode water that was embedded within the eddy. The eddy core, of 30 km radius, was in solid body rotation with period of 4 days. It was encircled by a thin outer ring that was rotating more slowly. The kinetic energy (KE) content exceeded that of available potential energy (APE), KE/APE = 1.58; this was associated with a low aspect ratio and a relatively intense rate of spin as indicated by the relatively high value of Ro. Inferred available heat and salt content anomalies were AHA = 2.9 × 10 18 J and ASA = 14.3 × 10 10 kg, respectively. The eddy AHA and ASA contents per unit volume largely exceed those corresponding to Pacific Ocean intrathermocline eddies. This suggests that intrathermocline eddies may play a significant role in the zonal conduit of heat and salt along the Canary Eddy Corridor.
Analysis of water level and current meter series from different locations on the island shelf of ... more Analysis of water level and current meter series from different locations on the island shelf of Gran Canaria reveals strong variations in tidal properties. Semidiurnal sea level amplitudes agree with the results obtained from global tidal models for this region only on the northern coast of the island, while they decrease towards the southwest (10 cm difference for the M2 constituent). Semidiurnal currents present maxima at the southeastern and northwestern extremities of the island (30-40 cm s-' for MJ and minima in the north-northeast and southwest (3-6 cm s-' for M,), showing simultaneous strong changes in the phase. Diurnal levels and currents display smaller variations than the semidiurnal band. The behaviour of semidiumal constituents is studied with the help of analytical and numerical solutions, in which the incident wave is modelled by a barotropic M2 Kelvin wave. The results show that the insular shelf could be a source of differences in level amplitudes around the island and could be also responsible for the enhancement of currents in the southeast and northwest. They also show that the variation of the current phases is due to the amplification of the standing character of the wave at the northeastern and southwestern parts of the shelf. 0 Elsevier,
High spatial resolution hydrographic data, including Lowered Acoustic Doppler Current Profiler (L... more High spatial resolution hydrographic data, including Lowered Acoustic Doppler Current Profiler (LADCP) measurements, were acquired along a meridional section at 24.5°W in October 2009. The data are analyzed in detail with the purpose of definitively defining and quantifying the zonal Azores Current System. The Azores Current and Azores Countercurrent are delimited, each extending meridionally for 110 km. The Azores Current is located between 33.5°N and 34.5°N, flanked to the north by the Azores Countercurrent (35.25°-36.25°N). Vertically, both currents reach the g n = 27.975 kg m −3 level (∼2000 m depth), their mass transports ranging across thermocline as well as intermediate layers. The Azores Current transports 13.9 Sv (1 Sv = 10 6 m 3 s −1 ≈ 10 9 kg s −1) eastward with its maximum associated with the Azores Front (33.75°N). The Azores Countercurrent flows below the surface, transporting 5.5 Sv westward. This contributes to a net eastward flow of 8.4 Sv across the section. At intermediate layers, the Azores Countercurrent transports mixed Mediterranean Water to the west, and the Azores Current transports mixed Sub-Arctic Intermediate Water to the east. Shipboard ADCP and satellite-derived geostrophic velocity are used to confirm the transports revealed by the hydrographic data.
Deep Sea Research Part I: Oceanographic Research Papers, 2011
We use hydrographic data collected during two interdisciplinary cruises, CIEMAR and BREDDIES, to ... more We use hydrographic data collected during two interdisciplinary cruises, CIEMAR and BREDDIES, to describe the mesoscale variability observed in the Central Basin of the Bransfield Strait (Antarctica). The main mesoscale feature is the Bransfield Front and the related Bransfield Current, which flows northeastward along the South Shetland Island Slope. A laboratory model suggests that this current behaves as a gravity current driven by the local rotation rate and the density differences between the Transitional Zonal Water with Bellingshausen influence (TBW) and the Transitional Zonal Water with Weddell Sea influence (TWW). Below the Bransfield Front we observe a narrow (10 km wide) tongue of Circumpolar Deep Water all along the South Shetland Islands Slope. At the surface, the convergence of TBW and TWW leads to a shallow baroclinic front close to the Antarctic Peninsula (hereafter Peninsula Front). Between the Bransfield Front and the Peninsula Front we observe a system of TBW anticyclonic eddies, with diameters about 20 km that can reach 300 m deep. This eddy system could be originated by instabilities of the Bransfield Current. The Bransfield Current, the anticyclonic eddy system, the Peninsula Front and the tongue of Circumpolar Deep Water, are the dynamically connected components of the Bransfield Current System.
Observational evidence demonstrates the signature of near-inertial wave (NIW) trapping by a long-... more Observational evidence demonstrates the signature of near-inertial wave (NIW) trapping by a long-lived westward propagating mesoscale anticyclonic eddy under normal atmospheric conditions. Cross-eddy sections of density and shipboard acoustic Doppler current profiler data show the downward (upward phase) propagation of NIW packets with vertical wavelengths of 200 m within the eddy, and wave energy amplification in a critical vertical layer located near the base of the anticyclone. Elevated strain variance, enhanced turbulent kinetic energy dissipation rates obtained from a fine-scale parameterization, and the occurrence of low (≤1) gradient Richardson numbers are consistent with turbulence production and mixing from 400 m to at least the maximum sampling depth of 725 m associated with the trapped NIWs. The observation of NIW packets near the eddy base at two different stages of the survey separated by 10 days and the persistence of low to moderate winds before and during the eddy sampling strongly suggest that our findings may be common in similar open-ocean anticyclonic eddies under normal wind conditions. Plain Language Summary Near-inertial waves-or internal gravity waves with a frequency near the inertial frequency-are typically excited at the sea surface by variable wind stress forcing. These waves can be trapped and amplified at the base of mesoscale (horizontal scales of about 10-100 km) anticyclonic eddies, especially after storms or strong wind events, situations in which high near-inertial energy is generated. In this article we present observational evidence of near-inertial wave trapping during low to moderate wind conditions. We also show that these trapped waves lead to deep mixing near the base of the eddy. The observation of near-inertial wave packets on two different dates and the low to moderate winds persistent during the survey suggest that our findings may be common in other similar open-ocean eddies. Mesoscale anticyclonic eddies of the World Ocean may therefore act as deep mixing structures as they propagate westward.
Deep Sea Research Part I: Oceanographic Research Papers, 2009
We report, from remote sensing and in situ observations, a new type of permanent structure in the... more We report, from remote sensing and in situ observations, a new type of permanent structure in the eastern subtropical Atlantic Ocean, that we call the ''Canary Eddy Corridor''. The phenomenon, is a zonal long-lived (43 months) mesoscale eddy corridor, whose source is the flow perturbation of the Canary Current and the Trade Winds at the Canary Islands. The latitudinal range of the corridor spans 221N-291N and extends from the Canaries to at least 32 % oW, near the mid-Atlantic. This is the main region of longlived westward-propagating eddies in the subtropical northeast Atlantic. From a agedistribution study we observe that at least 10% of mesoscale eddies in this region are long-lived, with a dominance of anticyclones over cyclones. Another four westwardpropagating eddy corridors were also detected: two small corridors north and south of the Azores Front; a small zonal corridor located near 31 % oN, south of the island of Madeira; and a small corridor located near the Cape Blanc giant filament. The existence of these corridors may change, at least for the northeastern subtropical Atlantic, the general idea that mesoscale eddies are disorganized, ubiquitous structures in the ocean. The Canary Eddy Corridor constitutes a direct zonal pathway that conveys water massand biogeochemical properties offshore from the Canary Island/Northwest Africa upwelling system, and may be seen as a recurrent offshore pump of organic matter and carbon to the oligotrophic ocean interior. Estimates of volume and mass transport indicate that Canary Eddy Corridor westward transport is more than one-fourth of the southward transport of the Canary Current. The westward transport of kinetic energy by the eddies of the Canary Corridor is as important as the southward transport by the Canary Current. The total primary production related to the Corridor may be as high as the total primary production of the northwest Africa upwelling system for the same latitude range.
Vertical motions play a key role in the enhancement of primary production within mesoscale eddies... more Vertical motions play a key role in the enhancement of primary production within mesoscale eddies through the introduction of nutrients into the euphotic layer. However, the details of the vertical velocity field w driving these enhancements remain under discussion. For the first time the mesoscale w associated with an intrathermocline eddy is computed and analyzed using in situ high-resolution three-dimensional (3D) fields of density and horizontal velocity by resolving a generalized omega equation valid for high Rossby numbers. In the seasonal pycnocline the diagnosed w reveals a multipolar structure with upwelling and downwelling cells located at the eddy periphery. In the main pycnocline w is characterized by a dipolar structure with downwelling velocities upstreamof the propagation path and upwelling velocities downstream.Maximumvalues of w reach 6.4m day. An observed enhancement of chlorophyll-a at the eddy periphery coincides with the location of the upwelling and downwelling...
... del estudio acoplado de ambos sistemas, a escalas temporales estacionales y anuales, bajo la ... more ... del estudio acoplado de ambos sistemas, a escalas temporales estacionales y anuales, bajo la hipótesis de que el acoplamiento geostróflco rio dehc responder a pulsos de viento cortos (días o semanas) que caracterizan a la dinánitca del afloramiento más superficial. ...
A traves de este estudio se han analizado medidas de niveles y corrientes de marea en la platafor... more A traves de este estudio se han analizado medidas de niveles y corrientes de marea en la plataforma que rodea la isla de Gran Canaria. Los resultados del estudio muestran importantes variaciones en las mareas de la isla.
Las mareas oceánicas inducen oscilaciones en las corrientes horizontales que se pueden descompone... more Las mareas oceánicas inducen oscilaciones en las corrientes horizontales que se pueden descomponer en un número finito de armónicos, cuyas frecuencias principales son diurnas y semidiurnas. Es bien sabido que en aguas poco profundas las corrientes de marea pueden ser asimétricas, lo que genera una corriente media conocida como corriente residual de marea. Esta deformación no lineal de la marea produce además la aparición de nuevas componentes en los espectros de corrientes, llamadas sobremareas, cuyas amplitudes y fases están relacionadas con la intensidad y dirección de la corriente residual [ lI . El objetivo del presente estudio es el de analizar las comentes de marea en la plataforma de la isla de Gran Canaria y proponer un método empírico que permita cuantificar la importancia de la corriente residual. Para ello se realiza primero un análisis armónico [2] de las series temporales de comentes registradas en diversas estaciones alrededor de la isla. Los resultados del análisis mu...
Este trabajo se enmarca dentro de los trabajos desarrollados para el proyecto: Flujo dc carbono c... more Este trabajo se enmarca dentro de los trabajos desarrollados para el proyecto: Flujo dc carbono cn la región Canaria: acoplamiento entre exportación costera y dcmanda oceánica (COCA). Uno de los objetivos principales de este proyecto es cuantificar si el transporte de excedentes de producci6n orgánica de carbono de las zonas costeras al océano oligotrófico es suficiente para aportar el subsidio de carbono orgánico demandado por la comunidad plaiictónica. La región Canaria es un escenario ideal para abordar este estudio ya que supone una zona de lransición entre la zona altamente productiva del afloramiento costero del noroeste de Africa y las aguas oceánicas del Giro Subtropical del Atlántico Norte. Se desarrollaron dos campañas oceánicas en septiembre de 2002 y junio de 2003 con el buque oceanográfiw HespCridcs para medir las diferentes magnitudes fisicas, biolbgicas y químicas, figura l . Se obtuvieron secciones de temperatura, salinidad y densidad potencial, estimhiose los flujos...
The Cape Verde Frontal Zone separates North and South Atlantic Central Waters in the eastern Nort... more The Cape Verde Frontal Zone separates North and South Atlantic Central Waters in the eastern North Atlantic Subtropical Gyre. CTD-02 and shipboard ADCP data from three hydrographic sections carried out in September 2003 are used to study the structure of the front. Results show the relation between spatial variations of water masses and currents, demonstrating the importance of advection in the distribution of water masses. Diapycnal diffusivities due to double diffusion and vertical shear instabilities are also estimated. Ex istence of competition between the two processes through the water column is shown. Depthaveraged diffusivities suggest that salt fingering dominates diapycnal mixing, except areas of purest South Atlantic Central Water. Here, double diffusion processes are weak and, consequently, shear of the flow is the main process. Results also show that strong mixing induced by vertical shear is associated with a large intrusion found near the front.
During Fa11 1995 and Fa11 1997 two hydrographic cruises were done with the RN Hespérides between ... more During Fa11 1995 and Fa11 1997 two hydrographic cruises were done with the RN Hespérides between the Iberian Peninsula and the Canary ArchipeIago, with special coveage of the Cape Ghir Filament region. XBT, CTD and ADCP measurements are reported for these dses . ...
The circulation patterns and the impact of the lateral export of nutrients and organic matter off... more The circulation patterns and the impact of the lateral export of nutrients and organic matter off NW Africa are examined by applying an inverse model to two hydrographic datasets gathered in fall 2002 and spring 2003. These estimates show significant changes in the circulation patterns at central levels from fall to spring, particularly in the southern boundary of the domain related to zonal shifts of the Cape Verde Frontal Zone. Southward transports at the surface and central levels at 26 • N are 5.6 ± 1.9 Sv in fall and increase to 6.7 ± 1.6 Sv in spring; westward transports at 26 • W are 6.0 ± 1.8 Sv in fall and weaken to 4.0 ± 1.8 Sv in spring. At 21 • N a remarkable temporal variability is obtained, with a northward mass transport of 4.4 ± 1.5 Sv in fall and a southward transport of 5.2 ± 1.6 Sv in spring. At intermediate levels important spatiotemporal differences are also observed, and it must be highlighted that a northward net mass transport of 2.0 ± 1.9 Sv is obtained in fall at both the south and north transects. The variability in the circulation patterns is also reflected in lateral transports of inorganic nutrients (SiO 2 , NO 3 , PO 4) and dissolved organic carbon (DOC). Hence, in fall the area acts as a sink of inorganic nutrients and a source of DOC, while in spring it reverses to a source of inorganic nutrients and a sink of DOC. A comparison between nutrient fluxes from both in situ observations and numerical modeling output is finally addressed.
Deep Sea Research Part I: Oceanographic Research Papers, 2017
An interdisciplinary survey of a subtropical intrathermocline eddy was conducted within the Canar... more An interdisciplinary survey of a subtropical intrathermocline eddy was conducted within the Canary Eddy Corridor in September 2014. The anatomy of the eddy is investigated using near submesoscale fine resolution two-dimensional data and coarser resolution threedimensional data. The eddy was four months old, with a vertical extension of 500 m and 46 km radius. It may be viewed as a propagating negative anomaly of potential vorticity (PV), 95% below ambient PV. We observed two cores of low PV, one in the upper layers centered at 85 m, and another broader anomaly located between 175 m and the maximum sampled depth in the three-dimensional dataset (325 m). The upper core was where the maximum absolute values of normalized relative vorticity (or Rossby number), |Ro| = 0.6, and azimuthal velocity, U = 0.5 m s-1 , were reached and was defined as the eddy dynamical core. The typical biconvex isopleth shape for intrathermocline eddies induces a decrease of static stability, which causes the low PV of the upper core. The deeper low PV core was related to the occurrence of a pycnostad layer of subtropical mode water that was embedded within the eddy. The eddy core, of 30 km radius, was in solid body rotation with period of 4 days. It was encircled by a thin outer ring that was rotating more slowly. The kinetic energy (KE) content exceeded that of available potential energy (APE), KE/APE = 1.58; this was associated with a low aspect ratio and a relatively intense rate of spin as indicated by the relatively high value of Ro. Inferred available heat and salt content anomalies were AHA = 2.9 × 10 18 J and ASA = 14.3 × 10 10 kg, respectively. The eddy AHA and ASA contents per unit volume largely exceed those corresponding to Pacific Ocean intrathermocline eddies. This suggests that intrathermocline eddies may play a significant role in the zonal conduit of heat and salt along the Canary Eddy Corridor.
Analysis of water level and current meter series from different locations on the island shelf of ... more Analysis of water level and current meter series from different locations on the island shelf of Gran Canaria reveals strong variations in tidal properties. Semidiurnal sea level amplitudes agree with the results obtained from global tidal models for this region only on the northern coast of the island, while they decrease towards the southwest (10 cm difference for the M2 constituent). Semidiurnal currents present maxima at the southeastern and northwestern extremities of the island (30-40 cm s-' for MJ and minima in the north-northeast and southwest (3-6 cm s-' for M,), showing simultaneous strong changes in the phase. Diurnal levels and currents display smaller variations than the semidiurnal band. The behaviour of semidiumal constituents is studied with the help of analytical and numerical solutions, in which the incident wave is modelled by a barotropic M2 Kelvin wave. The results show that the insular shelf could be a source of differences in level amplitudes around the island and could be also responsible for the enhancement of currents in the southeast and northwest. They also show that the variation of the current phases is due to the amplification of the standing character of the wave at the northeastern and southwestern parts of the shelf. 0 Elsevier,
High spatial resolution hydrographic data, including Lowered Acoustic Doppler Current Profiler (L... more High spatial resolution hydrographic data, including Lowered Acoustic Doppler Current Profiler (LADCP) measurements, were acquired along a meridional section at 24.5°W in October 2009. The data are analyzed in detail with the purpose of definitively defining and quantifying the zonal Azores Current System. The Azores Current and Azores Countercurrent are delimited, each extending meridionally for 110 km. The Azores Current is located between 33.5°N and 34.5°N, flanked to the north by the Azores Countercurrent (35.25°-36.25°N). Vertically, both currents reach the g n = 27.975 kg m −3 level (∼2000 m depth), their mass transports ranging across thermocline as well as intermediate layers. The Azores Current transports 13.9 Sv (1 Sv = 10 6 m 3 s −1 ≈ 10 9 kg s −1) eastward with its maximum associated with the Azores Front (33.75°N). The Azores Countercurrent flows below the surface, transporting 5.5 Sv westward. This contributes to a net eastward flow of 8.4 Sv across the section. At intermediate layers, the Azores Countercurrent transports mixed Mediterranean Water to the west, and the Azores Current transports mixed Sub-Arctic Intermediate Water to the east. Shipboard ADCP and satellite-derived geostrophic velocity are used to confirm the transports revealed by the hydrographic data.
Deep Sea Research Part I: Oceanographic Research Papers, 2011
We use hydrographic data collected during two interdisciplinary cruises, CIEMAR and BREDDIES, to ... more We use hydrographic data collected during two interdisciplinary cruises, CIEMAR and BREDDIES, to describe the mesoscale variability observed in the Central Basin of the Bransfield Strait (Antarctica). The main mesoscale feature is the Bransfield Front and the related Bransfield Current, which flows northeastward along the South Shetland Island Slope. A laboratory model suggests that this current behaves as a gravity current driven by the local rotation rate and the density differences between the Transitional Zonal Water with Bellingshausen influence (TBW) and the Transitional Zonal Water with Weddell Sea influence (TWW). Below the Bransfield Front we observe a narrow (10 km wide) tongue of Circumpolar Deep Water all along the South Shetland Islands Slope. At the surface, the convergence of TBW and TWW leads to a shallow baroclinic front close to the Antarctic Peninsula (hereafter Peninsula Front). Between the Bransfield Front and the Peninsula Front we observe a system of TBW anticyclonic eddies, with diameters about 20 km that can reach 300 m deep. This eddy system could be originated by instabilities of the Bransfield Current. The Bransfield Current, the anticyclonic eddy system, the Peninsula Front and the tongue of Circumpolar Deep Water, are the dynamically connected components of the Bransfield Current System.
Observational evidence demonstrates the signature of near-inertial wave (NIW) trapping by a long-... more Observational evidence demonstrates the signature of near-inertial wave (NIW) trapping by a long-lived westward propagating mesoscale anticyclonic eddy under normal atmospheric conditions. Cross-eddy sections of density and shipboard acoustic Doppler current profiler data show the downward (upward phase) propagation of NIW packets with vertical wavelengths of 200 m within the eddy, and wave energy amplification in a critical vertical layer located near the base of the anticyclone. Elevated strain variance, enhanced turbulent kinetic energy dissipation rates obtained from a fine-scale parameterization, and the occurrence of low (≤1) gradient Richardson numbers are consistent with turbulence production and mixing from 400 m to at least the maximum sampling depth of 725 m associated with the trapped NIWs. The observation of NIW packets near the eddy base at two different stages of the survey separated by 10 days and the persistence of low to moderate winds before and during the eddy sampling strongly suggest that our findings may be common in similar open-ocean anticyclonic eddies under normal wind conditions. Plain Language Summary Near-inertial waves-or internal gravity waves with a frequency near the inertial frequency-are typically excited at the sea surface by variable wind stress forcing. These waves can be trapped and amplified at the base of mesoscale (horizontal scales of about 10-100 km) anticyclonic eddies, especially after storms or strong wind events, situations in which high near-inertial energy is generated. In this article we present observational evidence of near-inertial wave trapping during low to moderate wind conditions. We also show that these trapped waves lead to deep mixing near the base of the eddy. The observation of near-inertial wave packets on two different dates and the low to moderate winds persistent during the survey suggest that our findings may be common in other similar open-ocean eddies. Mesoscale anticyclonic eddies of the World Ocean may therefore act as deep mixing structures as they propagate westward.
Deep Sea Research Part I: Oceanographic Research Papers, 2009
We report, from remote sensing and in situ observations, a new type of permanent structure in the... more We report, from remote sensing and in situ observations, a new type of permanent structure in the eastern subtropical Atlantic Ocean, that we call the ''Canary Eddy Corridor''. The phenomenon, is a zonal long-lived (43 months) mesoscale eddy corridor, whose source is the flow perturbation of the Canary Current and the Trade Winds at the Canary Islands. The latitudinal range of the corridor spans 221N-291N and extends from the Canaries to at least 32 % oW, near the mid-Atlantic. This is the main region of longlived westward-propagating eddies in the subtropical northeast Atlantic. From a agedistribution study we observe that at least 10% of mesoscale eddies in this region are long-lived, with a dominance of anticyclones over cyclones. Another four westwardpropagating eddy corridors were also detected: two small corridors north and south of the Azores Front; a small zonal corridor located near 31 % oN, south of the island of Madeira; and a small corridor located near the Cape Blanc giant filament. The existence of these corridors may change, at least for the northeastern subtropical Atlantic, the general idea that mesoscale eddies are disorganized, ubiquitous structures in the ocean. The Canary Eddy Corridor constitutes a direct zonal pathway that conveys water massand biogeochemical properties offshore from the Canary Island/Northwest Africa upwelling system, and may be seen as a recurrent offshore pump of organic matter and carbon to the oligotrophic ocean interior. Estimates of volume and mass transport indicate that Canary Eddy Corridor westward transport is more than one-fourth of the southward transport of the Canary Current. The westward transport of kinetic energy by the eddies of the Canary Corridor is as important as the southward transport by the Canary Current. The total primary production related to the Corridor may be as high as the total primary production of the northwest Africa upwelling system for the same latitude range.
Vertical motions play a key role in the enhancement of primary production within mesoscale eddies... more Vertical motions play a key role in the enhancement of primary production within mesoscale eddies through the introduction of nutrients into the euphotic layer. However, the details of the vertical velocity field w driving these enhancements remain under discussion. For the first time the mesoscale w associated with an intrathermocline eddy is computed and analyzed using in situ high-resolution three-dimensional (3D) fields of density and horizontal velocity by resolving a generalized omega equation valid for high Rossby numbers. In the seasonal pycnocline the diagnosed w reveals a multipolar structure with upwelling and downwelling cells located at the eddy periphery. In the main pycnocline w is characterized by a dipolar structure with downwelling velocities upstreamof the propagation path and upwelling velocities downstream.Maximumvalues of w reach 6.4m day. An observed enhancement of chlorophyll-a at the eddy periphery coincides with the location of the upwelling and downwelling...
... del estudio acoplado de ambos sistemas, a escalas temporales estacionales y anuales, bajo la ... more ... del estudio acoplado de ambos sistemas, a escalas temporales estacionales y anuales, bajo la hipótesis de que el acoplamiento geostróflco rio dehc responder a pulsos de viento cortos (días o semanas) que caracterizan a la dinánitca del afloramiento más superficial. ...
A traves de este estudio se han analizado medidas de niveles y corrientes de marea en la platafor... more A traves de este estudio se han analizado medidas de niveles y corrientes de marea en la plataforma que rodea la isla de Gran Canaria. Los resultados del estudio muestran importantes variaciones en las mareas de la isla.
Las mareas oceánicas inducen oscilaciones en las corrientes horizontales que se pueden descompone... more Las mareas oceánicas inducen oscilaciones en las corrientes horizontales que se pueden descomponer en un número finito de armónicos, cuyas frecuencias principales son diurnas y semidiurnas. Es bien sabido que en aguas poco profundas las corrientes de marea pueden ser asimétricas, lo que genera una corriente media conocida como corriente residual de marea. Esta deformación no lineal de la marea produce además la aparición de nuevas componentes en los espectros de corrientes, llamadas sobremareas, cuyas amplitudes y fases están relacionadas con la intensidad y dirección de la corriente residual [ lI . El objetivo del presente estudio es el de analizar las comentes de marea en la plataforma de la isla de Gran Canaria y proponer un método empírico que permita cuantificar la importancia de la corriente residual. Para ello se realiza primero un análisis armónico [2] de las series temporales de comentes registradas en diversas estaciones alrededor de la isla. Los resultados del análisis mu...
Este trabajo se enmarca dentro de los trabajos desarrollados para el proyecto: Flujo dc carbono c... more Este trabajo se enmarca dentro de los trabajos desarrollados para el proyecto: Flujo dc carbono cn la región Canaria: acoplamiento entre exportación costera y dcmanda oceánica (COCA). Uno de los objetivos principales de este proyecto es cuantificar si el transporte de excedentes de producci6n orgánica de carbono de las zonas costeras al océano oligotrófico es suficiente para aportar el subsidio de carbono orgánico demandado por la comunidad plaiictónica. La región Canaria es un escenario ideal para abordar este estudio ya que supone una zona de lransición entre la zona altamente productiva del afloramiento costero del noroeste de Africa y las aguas oceánicas del Giro Subtropical del Atlántico Norte. Se desarrollaron dos campañas oceánicas en septiembre de 2002 y junio de 2003 con el buque oceanográfiw HespCridcs para medir las diferentes magnitudes fisicas, biolbgicas y químicas, figura l . Se obtuvieron secciones de temperatura, salinidad y densidad potencial, estimhiose los flujos...
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