Fernandez Emilio

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Fernandez
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Emilio
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  • Article
    Significance of cyclonic SubTropical Oceanic Rings of Magnitude (STORM) eddies for the carbon budget of the euphotic layer in the subtropical northeast Atlantic
    (American Geophysical Union, 2003-12-20) Mourino, Beatriz ; Fernandez, Emilio ; Etienne, Helene ; Hernandez, Fabrice ; Giraud, Sylvie
    The interannual and seasonal variability of cyclonic eddies budded from the Azores Current during the period 1993–1999 in the northeast subtropical Atlantic region (20°N–34°N; 19°W–35°W) was studied by using TOPEX/Poseidon and ERS-1/2 altimeter images, the operational ocean mesoscale forecasting system SOPRANE, and a mesoscale eddies automatic detection system. Seventeen cyclonic eddies were detected and monitored for time periods ranging from 50 to 360 days. They were characterized by mean westward velocity, amplitude, diameter, and eccentricity of about 2 km d−1, 8 cm, 187 km and 0.7, respectively. The generation of cyclonic eddies was subjected to an important interannual variability, especially in 1995 when the activity of cyclonic eddies in the northeast Atlantic was more intense and associated with parallel changes in the eddy energy of the Azores Current. Seventy-five percent of the mesoscale features were generated throughout the October–February period. Significant relationships were found between the seasonal NAO index and both the annual eddy kinetic and potential energy in the Azores Current region and also the total annual area occupied by STORM eddies, calculated with a 1-year phase lag. The outcome of this study was used to estimate the contribution of STORM eddies to the organic carbon deficit measured in the northeast subtropical Atlantic. On average, these eddies accounted for <1% of the net community production in the region.
  • Article
    Constraining effect of mesoscale features on carbon budget of photic layer in the NE subtropical Atlantic
    (Inter-Research, 2005-02-18) Mourino, Beatriz ; Fernandez, Emilio ; Pingree, Robin ; Sinha, Bablu ; Escanez, Jose ; de Armas, Demetrio
    An oceanographic cruise was carried out in the subtropical NE Atlantic in April 1999 with the aim of investigating the role of the Azores Current, the STORM (subtropical oceanic rings of magnitude) cyclonic eddies and the Great Meteor Tablemount in triggering phytoplankton production. This information combined with previous studies allowed us to determine the role of these features in the carbon budget of the photic layer in this oligotrophic region. The results suggest that mesoscale dynamics, although modifying hydrographic characteristics and phytoplankton spatial distribution, do not appear to significantly affect primary production in the NE subtropical Atlantic.
  • Article
    Thermohaline structure, ageostrophic vertical velocity fields and phytoplankton distribution and production in the northeast Atlantic subtropical front
    (American Geophysical Union, 2004-04-21) Mourino, Beatriz ; Fernandez, Emilio ; Alves, Mario
    Two oceanographic cruises were carried out in the Azores Current/Subtropical Front region in July 1997 and April 1999 to study the seasonal and mesoscale spatial variability in the relationship between the hydrodynamic characteristics of the water column and the distribution of nutrients, phytoplankton biomass, and production. Both the magnitude of chlorophyll-a values and primary production rates as well as their vertical distribution varied sharply associated with subtle changes in seasonal thermal stratification. Successive upwelling and downwelling regions were detected along the track of a cyclonic meander, with maximum ageostrophic vertical velocities of 3 m d−1 and −4 m d−1, respectively, at 375 dbar. Relatively high nitrate concentrations (>3.5 μM) were found associated with denser waters at the center of the meander, where the deep chlorophyll maximum (DCM) uplifted ~20 dbar. Chlorophyll-a concentrations ranged from 0.1 to 0.4 mg m−3, with slightly higher values (>0.35 mg m−3) at the northern side of the current. A significant relationship was not detected between the vertical ageostrophic velocity field and nitrate and chlorophyll-a distributions, which were significantly correlated with the depth of the 16°C isotherm. Vertical advective fluxes of nitrate across the base of the DCM were about 2 orders of magnitude higher than vertical diffusive nitrate transport (−6.6 to 3.7 mmol m−2 d−1 versus 0.01 to 0.07 mmol m−2 d−1). Diffusive nitrate fluxes only account for <10% of the total primary production rates measured in the region.