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Pegliasco C.,CNRS Geophysical Research and Oceanographic Laboratory | Chaigneau A.,CNRS Geophysical Research and Oceanographic Laboratory | Chaigneau A.,Instituto Del Mar Of Peru | Morrow R.,CNRS Geophysical Research and Oceanographic Laboratory
Journal of Geophysical Research: Oceans

In the four major Eastern Boundary Upwelling Systems (EBUS), mesoscale eddies are known to modulate the biological productivity and transport near-coastal seawater properties toward the offshore ocean, however little is known about their main characteristics and vertical structure. This study combines 10 years of satellite-altimetry data and Argo float profiles of temperature and salinity, and our main goals are (i) to describe the main surface characteristics of long-lived eddies formed in each EBUS and their evolution, and (ii) to depict the main vertical structure of the eddy-types that coexist in these regions. A clustering analysis of the Argo profiles surfacing within the long-lived eddies of each EBUS allows us to determine the proportion of surface and subsurface-intensified eddies in each region, and to describe their vertical structure in terms of temperature, salinity and dynamic height anomalies. In the Peru-Chile Upwelling System, 55% of the sampled anticyclonic eddies (AEs) have subsurface-intensified maximum temperature and salinity anomalies below the seasonal pycnocline, whereas 88% of the cyclonic eddies (CEs) are surface-intensified. In the California Upwelling System, only 30% of the AEs are subsurface-intensified and all of the CEs show maximum anomalies above the pycnocline. In the Canary Upwelling System, 40% of the AEs and 60% of the CEs are subsurface-intensified with maximum anomalies extending down to 800 m depth. Finally, the Benguela Upwelling System tends to generate 40-50% of weak surface-intensified eddies and 50-60% of much stronger subsurface-intensified eddies with a clear geographical distribution. The mechanisms involved in the observed eddy vertical shapes are discussed. © 2015. American Geophysical Union. All Rights Reserved. Source

Chaigneau A.,Institute Of Recherche Pour Le Developpement | Chaigneau A.,French National Center for Scientific Research | Dominguez N.,Instituto Del Mar Of Peru | Eldin G.,Institute Of Recherche Pour Le Developpement | And 6 more authors.
Journal of Geophysical Research: Oceans

The near-coastal circulation of the Northern Humboldt Current System is described analyzing ∼8700 velocity profiles acquired by a shipboard acoustic Doppler current profiler (SADCP) during 21 surveys realized between 2008 and 2012 along the Peruvian coast. This data set permits observation of (i) part of the Peru Coastal Current and the Peru Oceanic Current that flow equatorward in near-surface layers close to the coast and farther than ∼150 km from the coast, respectively; (ii) the Peru-Chile Undercurrent (PCUC) flowing poleward in subsurface layers along the outer continental shelf and inner slope; (iii) the near-surfacing Equatorial Undercurrent renamed as Ecuador-Peru Coastal Current that feeds the PCUC; and (iv) a deep equatorward current, referred to as the Chile-Peru Deep Coastal Current, flowing below the PCUC. A focus in the PCUC core layer shows that this current exhibits typical velocities of 5-10 cm s -1. The PCUC deepens with an increasing thickness poleward, consistent with the alongshore conservation of potential vorticity. The PCUC mass transport increases from ∼1.8 Sv at 5°S to a maximum value of ∼5.2 Sv at 15°S, partly explained by the Sverdrup balance. The PCUC experiences relatively weak seasonal variability and the confluence of eddy-like structures and coastal currents strongly complicates the circulation. The PCUC intensity is also affected by the southward propagation of coastally trapped waves, as revealed by a strong PCUC intensification in March 2010 coincident with the passage of a downwelling coastal wave associated with a weak El Niño event. © 2013. American Geophysical Union. All Rights Reserved. Source

Cambon G.,French National Center for Space Studies | Goubanova K.,French National Center for Space Studies | Goubanova K.,Instituto Geofisico del Peru | Goubanova K.,Instituto Del Mar Of Peru | And 6 more authors.
Ocean Modelling

Simulating the oceanic circulation in Eastern Boundary Upwelling Systems (EBUS) is a challenging issue due to the paucity of wind stress products of a sufficiently high spatial resolution to simulate the observed upwelling dynamics. In this study, we present the results of regional simulations of the Humboldt current system (Peru and Chile coasts) to assess the value of a statistical downscaling model of surface forcing. Twin experiments that differ only from the momentum flux forcing are carried out over the 1992-2000 period that encompasses the major 1997/98 El Niño/La Niña event. It is shown that the mean biases of the oceanic circulation can be drastically reduced simply substituting the mean wind field of NCEP reanalysis by a higher resolution mean product (QuikSCAT). The statistical downscaling model improves further the simulations allowing more realistic intraseasonal and interannual coastal undercurrent variability, which is notoriously strong off Central Peru and Central Chile. Despite some limitations, our results suggest that the statistical approach may be useful to regional oceanic studies of present and future climates. © 2013 Elsevier Ltd. Source

Chaigneau A.,Laboratoire Doceanographie Et Of Climatologie Experimentation Et Analyse Numerique | Chaigneau A.,Instituto Del Mar Of Peru | Chaigneau A.,Laboratoire dEtudes en Geophysique et Oceanographie Spatiale | Le Texier M.,CNRS Institute of Fluid Mechanics of Toulouse | And 3 more authors.
Journal of Geophysical Research: Oceans

The mean vertical structure of mesoscale eddies in the Peru-Chile Current System is investigated by combining the historical records of Argo float profiles and satellite altimetry data. A composite average of 420 (526) profiles acquired by Argo floats that surfaced into cyclonic (anticyclonic) mesoscale eddies allowed constructing the mean three-dimensional eddy structure of the eastern South Pacific Ocean. Key differences in their thermohaline vertical structure were revealed. The core of cyclonic eddies (CEs) is centered at ∼150 m depth within the 25.2-26.0 kg m-3 potential density layer corresponding to the thermocline. In contrast, the core of the anticyclonic eddies (AEs) is located below the thermocline at ∼400 m depth impacting the 26.0-26.8 kg m-3 density layer. This difference was attributed to the mechanisms involved in the eddy formation. While intrathermocline CEs would be formed by instabilities of the surface equatorward coastal currents, the subthermocline AEs are likely to be shed by the subsurface poleward Peru-Chile Undercurrent. In the eddy core, maximum temperature and salinity anomalies are of ±1°C and ±0.1, with positive (negative) values for AEs (CEs). This study also provides new insight into the potential impact of mesoscale eddies for the cross-shore transport of heat and salt in the eastern South Pacific. Considering only the fraction of the water column associated with the fluid trapped within the eddies, each CE and AE has a typical volume anomaly flux of ∼0.1 Sv and yields to a heat and salt transport anomaly of ±1-3 × 1011 W and ±3-8 × 103 kg s-1, respectively. Copyright 2011 by the American Geophysical Union. Source

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