Effects of mesoscale processes on phytoplankton chlorophyll off Baja California

Using satellite sea surface height (SSH) and chlorophyll (CHL), the year 2000 is analyzed to characterize the effects of mesoscale circulation patterns on phytoplankton spatial variability in the California Current (CC) off Baja California. Satellite data are combined with and compared to in situ field measurements (chlorophyll-a and hydrographic variables) along vertical alongshore sections located similar to 130 km offshore between similar to 24.5 degrees -33 degrees N. Monthly average maps of SSH and surface geostrophic velocities depict the characteristics of mesoscale meanders and eddies, which correspond well with the subsurface hydrographic and velocity fields. Satellite-derived pigment (CHL) represent in situ fields in the upper 0-20 m (overall r = 0.53; p < 0.05), but their representation of peak values in Deep Chlorophyll Maxima (DCM) at similar to 50 m depth are inaccurate. DCM are traced in all three seasons (January-July), descending from near the surface (north of 31 degrees N) to 50 m over a large extent of the transect to the south, approximately following the 24.7-25.1 isopycnals as they and the isotherms deepen to the south. In January, phytoplankton chlorophyll concentrations in the DCM are relatively uniform, originating during upwelling events that occur farther north, then following the equatorward flow of the CC. During April and July, the discrete maxima in the DCM occur at the centers of cyclonic meanders and the chlorophyll concentrations inside these maxima are enhanced as a result of local coastal upwelling off Baja California. Phytoplankton blooms created by coastal upwelling spread offshore and subduct along the 24.7-25.1 isopycnals, creating the DCM along the inner part of the meandering jet.KEYWORDS: Current system, Satellite, Pigment, State, Temperature, El Nino, Salinity, Evolution, Interannual variability, Coastal transition zon

Mesoscale eddies in the northeastern Pacific tropical-subtropical transition zone: Statistical characterization from satellite altimetry

International audienceMesoscale eddies in the northeastern Pacific tropical-subtropical transition zone (16°N-30°N; 130°W-102°W) are analyzed using nearly 18 years of satellite altimetry and an automated eddy-identification algorithm. Eddies that lasted more than 10 weeks are described based on the analysis of 465 anticyclonic and 529 cyclonic eddy trajectories. We found three near-coastal eddy-prolific areas: (1) Punta Eugenia, (2) Cabo San Lucas, and (3) Cabo Corrientes. These three areas are located in places where the coastal morphology changes abruptly and strong surface current intensification occurs at some phase of the seasonal cycle. Although mesoscale eddies in these areas have been previously reported, this study provides their first statistically supported characterization. Punta Eugenia showed the highest eddy production (with more cyclones generated), followed by Cabo Corrientes (also with more cyclones) and Cabo San Lucas (with more anticyclones). Cabo Corrientes eddies showed the highest mean values in propagation speed, swirling speed and eddy kinetic energy, whereas Punta Eugenia eddies showed the lowest values. Cyclonic eddies increased their distance traveled and duration from south to north; in contrast anticyclonic eddies increased from north to south. In average, anticyclones tend to travel faster than cyclones in all the subregions. These long-lived eddies were mainly nonlinear and therefore can redistribute coastal waters relatively far into the open ocean. The peaks in the seasonal signal of eddy generation can be associated with the peaks in the strength of the offshore currents and/or in the Coastal Upwelling Index. No clear relationship could be established between El Niño events and eddy generation

Anatomy and evolution of a cyclonic mesoscale eddy observed in the northeastern Pacific tropical-subtropical transition zone

In November 2005 off Cabo Corrientes, a cyclonic eddy was sampled from (i) remotely sensed data of sea level anomaly, near-surface wind, chlorophyll-a concentration and sea surface temperature and (ii) direct observations from a lowered Acoustic Doppler profiler, and a conductivity, temperature, and depth sensor. The sea level anomaly data set and an automated eddy detection method showed that this vortex formed near the Mexican coast and traveled westward/northwestward, approximate to 1000 km into the open ocean for approximate to 8 months. Surface winds and currents indicated that the cyclone was generated during a coastal upwelling event that occurred simultaneously with an equatorward flow located close to the coast. During its growing phase, the eddy extended from the surface to 750 m depth and mixed the water column in the first approximate to 100 m, showing an eastward shift of the eddy axis toward the sea surface of 1.5 degrees of longitude, that generated a southward meridional heat transport in the upper layers. Integrated in the vertical, this heat transport accounted for a total of -105 x 10(12) W, within the region of the eddy. The estimation of the available heat and salt anomaly contents revealed that the eddy transported relatively cold, salty, and anoxic waters associated with the Subtropical Subsurface water mass. While traveling offshore, the cyclonic eddy also exhibited relatively higher chlorophyll a concentrations at the sea surface than its surroundings. Comparison of some surface properties estimated from satellite and in situ data showed that satellite data tend to underestimate its amplitude and orbital geostrophic velocity

Para um novo estado de bem estar na América Latina For a new welfare state in Latin America

Os determinantes políticos e econômicos para um novo Estado de bem estar social na América Latina e os desafios que essa tarefa propõe são discutidos com base no exame da políticas sociais no contexto do ajuste estrutural em curso nas economias latinoamericanos.<br>The political and economic determinants of a new welfare state in Latin America and the challenges put forward by this task are discussed on the basis of an analysis of the social policies in the context of the context of the ongoing structural adjustment of latinoamerican economie