Browsing by Author "Garçon, Veronique"

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    Inference of super-resolution ocean pCO₂ and air-sea CO₂ fluxes from non-linear and multiscale processing methods
    (EGU General Assembly, 2014) Hernández Carrasco, Ismael; Sudre, Joel; Garçon, Veronique; Yahia, Hussein; Dewitte, Boris; Garbe, Christoph; Illig, Serena; Montes Torres, Ivonne; Dadou, Isabelle; Paulmier, Aurélien; Butz, André
    In recent years the role of submesoscale activity is emerging as being more and more important to understand global ocean properties, for instance, for accurately estimating the sources and sinks of Greenhouse Gases (GHGs) at the air-sea interface. The scarcity of oceanographic cruises and the lack of available satellite products for GHG concentrations at high resolution prevent from obtaining a global assessment of their spatial variability at small scales. In this work we develop a novel method to reconstruct maps of CO₂ fluxes at super resolution (4km) using SST and ocean colour data at this resolution, and CarbonTracker CO₂ fluxes data at low resolution (110 km). The responsible process for propagating the information between scales is related to cascading properties and multiscale organization, typical of fully developed turbulence. The methodology, based on the Microcanonical Multifractal Formalism, makes use, from the knowledge of singularity exponents, of the optimal wavelet for the determination of the energy injection mechanism between scales. We perform a validation analysis of the results of our algorithm using pCO₂ ocean data from in-situ measurements in the upwelling region off Namibia.
    Palabras clave:Greenhouse gasesAir-sea interactionOceanography
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    Los remolinos oceánicos y la Zona de Mínima de Oxígeno
    (Instituto Geofísico del Perú, 2015-11) Montes Torres, Ivonne; Dewitte, Boris; Garçon, Veronique
    Los océanos tienen propiedades físicas, químicas y biológicas heterogéneas debido a una circulación compleja caracterizada por una diversidad de fenómenos a distintas escalas de variabilidad espacial y temporal. Si nos referimos a las propiedades físicas, las características más resaltantes del océano son las estructuras de circulación circulares, denominadas remolinos o vórtices, que se pueden observar como núcleos de mayor o menor nivel del mar (Chaigneau et al., 2009; Chelton et al., 2011; Figura 1) y por su efecto en la temperatura superficial del mar (Chelton and Xie, 2010); además están presentes también debajo de la superficie (Hormazabal et al., 2013; Combes et al., 2015). Estos remolinos oceánicos forman parte de la variabilidad de “mesoescala” del océano y, además, son los responsables de que al océano se le identifique y denomine como un sistema turbulento; ello debido a que, dependiendo de su localización, los remolinos pueden ser muy energéticos, tener un tiempo de vida considerable (que va de días a meses), ocupar varios kilómetros (del orden de 1 km a 200 km) y desplazarse a grandes distancias, influenciando así el medio que los rodea (e.g., Biastoch et al., 2008; Stramma et al., 2013).
    Palabras clave:Circulación oceánicaZonas de mínimo oxígenoOceános
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    Seasonal variability of the oxygen minimum zone off Peru in a high-resolution regional coupled model
    (European Geosciences Union (EGU), 2016-08-08) Vergara, Oscar; Dewitte, Boris; Montes Torres, Ivonne; Garçon, Veronique; Ramos, Marcel; Paulmier, Aurélien; Pizarro, Oscar
    In addition to being one of the most productive upwelling systems, the oceanic region off Peru is embedded in one of the most extensive oxygen minimum zones (OMZs) of the world ocean. The dynamics of the OMZ off Peru remain uncertain, partly due to the scarcity of data and to the ubiquitous role of mesoscale activity on the circulation and biogeochemistry. Here we use a high-resolution coupled physical/biogeochemical model simulation to investigate the seasonal variability of the OMZ off Peru. The focus is on characterizing the seasonal cycle in dissolved O₂ (DO) eddy flux at the OMZ boundaries, including the coastal domain, viewed here as the eastern boundary of the OMZ, considering that the mean DO eddy flux in these zones has a significant contribution to the total DO flux. The results indicate that the seasonal variations of the OMZ can be interpreted as resulting from the seasonal modulation of the mesoscale activity. Along the coast, despite the increased seasonal low DO water upwelling, the DO peaks homogeneously over the water column and within the Peru Undercurrent (PUC) in austral winter, which results from mixing associated with the increase in both the intraseasonal wind variability and baroclinic instability of the PUC. The coastal ocean acts therefore as a source of DO in austral winter for the OMZ core, through eddy-induced offshore transport that is also shown to peak in austral winter. In the open ocean, the OMZ can be divided vertically into two zones: an upper zone above 400 m, where the mean DO eddy flux is larger on average than the mean seasonal DO flux and varies seasonally, and a lower part, where the mean seasonal DO flux exhibits vertical–zonal propagating features that share similar characteristics than those of the energy flux associated with the annual extratropical Rossby waves. At the OMZ meridional boundaries where the mean DO eddy flux is large, the DO eddy flux has also a marked seasonal cycle that peaks in austral winter (spring) at the northern (southern) boundary. In the model, the amplitude of the seasonal cycle is 70 % larger at the southern boundary than at the northern boundary. Our results suggest the existence of distinct seasonal regimes for the ventilation of the OMZ by eddies at its boundaries. Implications for understanding the OMZ variability at longer timescales are discussed.
    Palabras clave:Seasonal variationsMinimum oxygen zonesOceanography