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Understanding how the surface dynamics of the ocean influence the spawning and larval ecology of many large pelagic species, in particular tuna species, is a major challenge. For temperate tunas, the selection of geographically restricted spawning grounds is influenced by environmental conditions, but the influence of surface mixing properties on the early life stages of these species remains poorly understood. Here, based on ichthyoplankton samples collected over 4 yr and satellite-derived finite size Lyapunov exponents (FSLEs), we examined how horizontal mixing activity drives the probability of presence of Atlantic bluefin tuna Thunnus thynnus larvae. We further analyzed the spatial and temporal scales of the FSLE variability at which the relationship between larval presence and mesoscale activity is maximized. We found that moderate mixing activity strongly favors the spatial-temporal distribution of larval habitats, evidencing an optimal environmental window of bluefin tuna spawning and early life development within the meso scale dynamics. During the spawning season, the Balearic Sea presents a unique spatial and temporal hydrodynamic scenario within the Western Mediterranean. These results can be used for developing oceanographic indicators and improving larval abundance indices that are currently used in Atlantic bluefin tuna stock assessments., This study was funded by the BLUE-FIN TUNA project (SOCIB and IEO joint action), the PANDORA project from the EU2020 Program (Grant Agreement No 773713), and MINECO/FEDER Project MOCCA 256RTI2018-093941-B-C31). I.H.C. acknowledges the Vicenç Mut contract funded by the Government of the Balearic Islands and the European Social Fund (ESF) Operational Programme. The multimission altimeter product was produced by Ssalto/Duacs and provided by CMEMS (http://marine.copernicus.eu).

This article presents a 60 years wave hindcast from 1958 to 2017, covering the Colombian Caribbean basin. Each output consists on 6-hour field of significant wave height , mean wave period , and mean direction with a resolution of 11.8 11.4 . The simulation was performed using SWAN model forced with JRA-55 wind fields. Model data is validated against NOAA buoy 42058 located in the central Caribbean. The resolution and time spam of this database allows to perform either coastal engineering projects as well as to perform research in seasonal and interannual wave climate variability including large return periods to evaluate coastal vulnerability., AOR is supported by COLCIENCIAS (Departamento Administrativo de Ciencia, Tecnología e Innovación) through a PhD grant from “Convocatoria 727” and from a POGO fellowship at the Mediterranean Institute for Advanced Studies. Authors acknowledge financial support from the Spanish Government MICINN/FEDER through MOCCA Project (RTI2018-093941-B-C31).

Trabajo presentado en la Ocean Sciences Meeting, celebrada en San Diego del 16 al 21 de febrero de 2020., Physical factors induced by the turbulent flow play a crucial role in regulating marine ecosystems. Here we show that the combination of complementary Lagrangian diagnostics provides an improved description of the geometrical and kinetic properties of the flow, which facilitates the interpretation of physical mechanisms affecting phytoplankton composition, dynamics and patchiness. The influence of small-scale dynamics (O(3.5-25) km, i.e. spanning upper submesoscale and mesoscale processes) on phytoplankton in surface waters derived from satellite chlorophyll-a (chl a) is studied using Lagrangian metrics computed from High-Frequency Radar currents over the Ibiza Channel. Attracting small-scale flow structures are associated to filaments of accumulated negative divergence where particles and chl a standing stocks cluster. Regions of accumulated positive divergence, representing large accumulated upward vertical velocities and suggesting accrued injection of subsurface nutrients, match areas with large chl a concentrations. Furthermore the composition of phytoplankton community was studied regarding the sustained kinematic properties of the flow during the formation of an intense filament. In this regard new metrics accounting for the Lagrangian evolution of the turbulent and topological properties along fluid parcel trajectories have been developed. Here we provide observational evidences, during the SHEBEX cruise (May 2015) in the western Mediterranean and altimetry-derived Lagrangian computations, that fluid parcels associated with high Lagrangian turbulent kinetic energy and Lagrangian positive vorticity host higher relative abundance of larger pennate diatoms (i.e. Pseudo-nitzschia spp). Our findings indicate that the combination of these diagnostics provides an improved description of the turbulent dynamics showing that the Lagrangian properties of the flow have important biological consequences.

International audience; A new methodology has been developed in order to improve the description of the spatial and temporal variability of not well-resolved oceanic variables from other well-observed high-resolution oceanic variables. The method is based on the cross-scale inference of information, incorporating the common features of different multifractal high-resolution variables into a coarser one. An exercise of validation of the methodology has been performed based on the outputs of coupled physical-biogeochemical Regional Ocean Modeling System adapted to the eastern boundary upwelling systems at two spatial resolutions. Once the algorithm has been proved to be effective in increasing the spatial resolution of modeled partial pressure of CO2 at the surface ocean (pCO 2), we have investigated the capability of our methodology when it is applied to remote sensing data, focusing on the improvement of the temporal description. In this regard, we have inferred daily pCO 2 maps at high resolution (4 km, i.e., 1/24 •) fusing monthly pCO 2 data at low resolution (100 km, i.e., 1 •) with the small-scale features contained in daily high-resolution maps of satellite sea surface temperature and Chlorophyll-a. The algorithm has been applied to the South Eastern Atlantic Ocean opening the possibility to obtain an accurate quantification of the CO 2 fluxes in relevant coastal regions, such as the eastern boundary upwelling systems. Outputs of our algorithm have been compared with in situ measurements, showing that daily maps inferred from monthly products are in average 6 µatm closer to the in situ values than the original coarser monthly maps. Furthermore, values of pCO 2 have been improved in points close to the coast with respect to the original input data.

International audience; Seabird trajectories can be used as proxies to investigate the dynamics of marine systems and their spatiotemporal evolution. Previous studies have mainly been based on analyses of long range flights, where birds are travelling at high velocities over long time periods. Such data have been used to study wind patterns, and areas of avian feeding and foraging have also been used to study oceanic fronts. Here we focus on " slow moving " periods (which we associate to when birds appear to be drifting on the sea surface), in order to investigate bird drift as a proxy for sea surface currents in the western Mediterranean Sea. We analyse trajectories corresponding to " slow moving " periods recorded by GPSs attached to individuals of the species Calonectris diomedea (Scopoli's shearwater) from mid August to mid September 2012. The trajectories are compared with sea level anomaly (SLA), sea surface temperature (SST), Finite Size Lyapunov Exponents (FSLE), wind fields, and the outputs from an automated sea-surface-height based eddy tracker. The SLA and SST datasets were obtained from the Copernicus Marine Environment Monitoring Service (CMEMS) with a spatial resolution of 1/8 ˚ and 1/100˚respectively100˚100˚respectively while the FSLEs were computed from the SLA dataset. Finally, the wind data comes from the outputs of the CCMPv2 numerical model. This model has a global coverage with a spatial resolution of 1/4 ˚. Interesting relationships between the trajectories and SLA fields are found. According to the angle between the SLA gradient and the trajectories of birds, we classify drifts into three scenarios: perpendicular, parallel and other, which are associated with different driving forces. The first scenario implies that bird drift is driven by geostrophic sea surface currents. The second we associate with wind drag as the main driving force. This is validated through the wind dataset. Moreover, from the SST, FSLEs and the eddy tracker, we obtain supplementary information on the presence of oceanic structures (such as eddies or fronts), not observed in the SLA field due to its limited spatial and temporal resolutions. Therefore, this data helps to explain some of the third case scenario trajectories.

Trabajo presentado en el Non Linear Processes in Atmospheric and Oceanic flows, celebrado en Madrid, España, del 6 al 8 de julio de 2016

Trabajo presentado en el Non Linear Processes in Atmospheric and Oceanic flows, celebrado en Madrid, España, del 6 al 8 de julio de 2016

This work is a contribution to ESA Support To Science Element Grant N◦ 400014715/11/I-NB OceanFlux- Upwelling Theme. The Surface Ocean CO2 Atlas (SOCAT) is an international effort, supported by the International Ocean Carbon Coordination Project (IOCCP), the Surface Ocean Lower Atmo- sphere Study (SOLAS), and the Integrated Marine Biogeochem- istry and Ecosystem Research program (IMBER), to deliver a uni- formly quality-controlled surface ocean CO2 database. The many researchers and funding agencies responsible for the collection of data and quality control are thanked for their contributions to SO- CAT; International audience; An accurate quantification of the role of the ocean as source/sink of Green House Gases (GHGs) requires to access the high-resolution of the GHG air-sea flux at the interface. In this paper we present a novel method to reconstruct maps of surface ocean partial pressure of CO 2 (pCO 2) and 5 air-sea CO 2 fluxes at super resolution (4 km) using Sea Surface Temperature (SST) and Ocean Colour (OC) data at this resolution, and CarbonTracker CO 2 fluxes data at low resolution (110 km). Inference of super-resolution of pCO 2 , and air-sea CO 2 fluxes is performed using novel nonlinear signal 10 processing methodologies that prove efficient in the context of oceanography. The theoretical background comes from the Microcanonical Multifractal Formalism which unlocks the geometrical determination of cascading properties of physical intensive variables. As a consequence, a multiresolution 15 analysis performed on the signal of the so-called singularity exponents allows the correct and near optimal cross-scale inference of GHGs fluxes, as the inference suits the geometric realization of the cascade. We apply such a methodology to the study offshore of the Benguela area. The inferred rep-20 resentation of oceanic partial pressure of CO 2 improves and enhances the description provided by CarbonTracker, capturing the small scale variability. We examine different combinations of Ocean Colour and Sea Surface Temperature products in order to increase the number of valid points and the 25 quality of the inferred pCO 2 field. The methodology is validated using in-situ measurements by means of statistical errors. We obtain that mean absolute and relative errors in the inferred values of pCO 2 with respect to in-situ measurements are smaller than for CarbonTracker.

Tesis doctoral presentada para optar al título de Doctor en la Universitat de les Illes Balears., Horizontal transport and mixing processes are central to the study of the physical, chemical, and biological dynamics of the ocean. Correct understanding and precise modelling of them are relevant from a theoretical viewpoint and crucial for a range of practical issues, such as plankton dynamics or the fate of pollutant spills. In this regard, the last few years have seen the appearance of interesting new developments on the Lagrangian description of transport and mixing phenomena, many of them coming from the area of nonlinear dynamics. Such approaches do not aim at predicting individual tracer trajectories, but at locating spatial structures that are known from dynamical systems theory to act as templates for the whole flow (Leong and Ottino, 1989; Wiggins, 1992). This is mainly due to the capacity of the Lagrangian diagnostics to exploit the spatiotemporal variability of the velocity field by following fluid particle trajectories, at di erence of Eulerian ones which analyze frozen snapshots of data. Among these Lagrangian techniques, a powerful class consists in the computation of local Lyapunov exponents (LLE) which measure the relative dispersion of transported particles. In particular, there are the so called finite-size Lyapunov exponents (FSLEs) where one computes the time taken by two trajectories, initially separated by a finite distance, to reach a larger final finite distance.

Recent work on Lagrangian descriptors has shown that Finite Time Lyapunov Exponents (FTLE) or Finite Size Lyapunov Exponents (FSLE) can be applied to real or simulated data to characterize the mixing properties and transport barriers of the oceanic flow. However, a more detailed analysis on regional and seasonal variability, and its interpretation, was still lacking. In this paper, we have analyzed the near-surface velocity field derived from the Ocean general circulation model For the Earth Simulator (OFES) using Finite-Size Lyapunov Exponents (FSLE). We have characterized regional and seasonal variability by means of some statistical descriptors. Our results show that horizontal mixing, as measured by FSLEs, is seasonally-varying, attaining its maximum in Summer. FSLEs also strongly vary depending on the region: with our descriptors we have first characterized the mixing properties of Northern and Southern Hemispheres, then the main oceanic basins and ocean currents. We have finally studied the relation between Lagrangian FSLEs and some Eulerian descriptors such as Eddy Kinetic Energy (EKE) and vorticity (w) over the different regions. We have found that Lagrangian and Eulerian descriptors are linked by means of dispersion relations. These relations are useful to characterize the dynamics of different ocean areas, and undoubtedly have an influence on the evolution of biological markers, among other variables., I.H.-C., C.L. and E.H.-G. acknowledge support from MICINN and FEDER through project FISICOS (FIS200760327); A. Turiel has received support from Interreg TOSCA project (G-MED09-425) and Spanish MICINN project MIDAS-6 (AYA2010-22062-C05- 01). The OFES simulation was conducted on the Earth Simulator under the support of JAMSTEC. We thank Earth Simulator Center-JAMSTECH team for providing these data., I.H.-C., C.L. and E.H.-G. acknowledge support from MICINN and FEDER through project FISICOS (FIS200760327); A. Turiel has received support from Interreg TOSCA project (G-MED09-425) and Spanish MICINN project MIDAS-6 (AYA2010-22062-C05-01).

Recent studies, both based on remote sensed data and coupled models, showed a reduction of biological productivity due to vigorous horizontal mixing in upwelling systems. In order to better understand this phenomenon, we have considered a system of oceanic flow in the Benguela area coupled with a simple biogeochemical model of Nutrient-Phyto-Zooplankton (NPZ) type. For the flow three different surface velocity fields are considered: one derived from satellite altimetry data, and the other two from a regional numerical model at two different spatial resolutions. We computed horizontal particle dispersion in terms of Lyapunov Exponents, and analyzed their correlations with phytoplankton concentrations. Our modelling approach confirms that in the south Benguela, there is a reduction of biological activity when stirring is increased. Two-dimensional offshore advection seems to be the dominant process involved. In the northern area, other factors not taken into account in our simulation are influencing the ecosystem. We provide explanations for these results in the context of studies performed in other Eastern Boundary upwelling areas., I.H-C was awarded a FPI grant from MICINN to visit LEGOS. V.R thanks funding from OCEANTECH project (CSIC PIF-2006) to visit IFISC. V.R. was partly supported 417 by a DGA grant and an Australian Research Council Grant DP1093510 while nishing this work. I.H-C, C.L and E.H-G acknowledge support from MICINN and FEDER through Hiresubcolor project.

Preprint enviado al 3rd Conference on Nonlinear Science and Complexity, Ankara, July 2010 , Springer (2012), The Lagrangian description of fluid transport has been largely enriched with the introduction of stretching quantifiers such as the different types of Lyapunov exponents. Here we will focus on the finite-size Lyapunov exponent case, as applied to horizontal ocean flows estimated from satellite altimetry. The influence on biological organisms of the structures revealed by the Lyapunov analysis will be illustrated with examples from the bottom and from the top of marine ecosystems: the distribution of phytoplankton in ocean upwelling areas, and the trajectories of frigatebirds in the West Indian Ocean, which fly on top of the ridges of Lyapunov structures. The convenience of moving from a two-dimensional to a fully three-dimensional description is highlighted, IFISC contribution supported by MICINN and FEDER (Spain) trough project FISICOS (FIS200760327).

62 pages, 21 figures, 6 chapters, 3 appendix.-- Presented to The University of Balearic Islands in Partial Fulfillment of the Requirements for the Degree of Master of Science.-- Directors: López, Cristóbal; Hernández-Gracía, Emilio, We have analyzed surface velocity data of the Mediterranean Sea as obtained from a primitive equation circulation model (Diecast model). We have computed the Finite Size Lyapunov Exponents (FSLEs) from this data set, which provide a measure of oceanic horizontal stirring, as well as reveal with their extreme values the barriers of transport. A particular property of the FSLE is that it is able to study spatial structures at scales under the resolution of the velocity data used in this computation. In this way, we can obtain information of submesoscales and mesoscales structures (1-100km). We investigate here how reliable are the results of a Lagrangian diagnosis at a similar and at a finer resolution than that of the velocity data. We address this work by the analysis of two properties: - Multifractal character of the spatial distribution of the FSLE, in order to study its scale invariance properties. - Relative error of the FSLE for three cases: a) by introducing a random perturbation in the velocity data, b) by decreasing the resolution of the velocity field, and finally, c) by adding white noise in the computation of the particle\'s trajectories.

ilustraciones, diagramas Debido a su inherente naturaleza turbulenta, la dinámica de los océanos es muy compleja. Podemos modelar los principales patrones de transporte de la circulación oceánica en meso- y submeso-escalas, O (0,1-100 km, horas-meses) utilizando enfoques de sistemas dinámicos, pero la riqueza extrema en microescalas O (0,001-10 m, segundos) y sus patrones de circulación, hace que la evaluación de los fenómenos de transporte oceánico sea una tarea extraordinariamente complicada. En la microescala podemos encontrar ecosistemas de arrecifes coralinos, que en los últimos años han cobrado notoria importancia por los efectos que pueden generar sobre la hidrodinámica del flujo incidente, en áreas que van desde la biología hasta la ingeniería debido a su papel como estructuras de protección costera. A pesar de los estudios realizados para comprender la hidrodinámica en torno a estos ecosistemas, aún no existe una idea clara de cómo los diferentes tipos de geometría de las colonias de coral condicionan los patrones de transporte que se desarrollan en el flujo. Uno de los tipos de técnicas que más contribuye a la comprensión de los patrones de transporte y a la descripción de la topología del flujo es la conocida con el nombre de Estructuras Coherentes Lagrangianas (LCS por sus siglas en inglés), que es una generalización de las variedades inestables y estables de puntos hiperbólicos en sistemas dependientes del tiempo. En esta tesis evaluamos la viabilidad de utilizar el concepto LCS para describir las propiedades de transporte y mezcla en flujos altamente fluctuantes a microescala alrededor de geometrías de coral. En particular, estudiamos los patrones de transporte inducidos por la interacción entre una ola solitaria y objetos sumergidos de diferente geometría, que se aproximan a la geometría presente en los corales. Usamos datos de velocidad de las salidas del modelo RANS-VOF. Los escenarios analizados consisten en la variación del número de Reynolds, la relación entre la altura de la ola, H, y la profundidad del agua, h, con la altura del coral, L (H/L y h/L , respectivamente) y la forma de éste. Los patrones de transporte se estudian mediante el cálculo de estructuras coherentes lagrangianas con la implementación del método del exponente de Lyapunov de tiempo finito (FTLE por sus siglas en inglés), y se comparan con el campo de vorticidad y el campo de criterio Q (Okubo-Weiss). Encontramos que el campo de vorticidad tiene una mejor correlación con el campo FTLE (geometría LCS) que con el campo Q, lo que sugiere que la topología de flujo está más controlada por el proceso de vorticidad obtenido por un flujo cortante que por los mismos vórtices(regiones de rotación pura). Para los corales representados por geometrías rectangulares, las LCS tienen forma de espiral, se forman sobre y en la parte posterior del coral. Ambas LCS permanecen adheridas al objeto sumergido una vez que h/L y H/L comienzan a disminuir. Para los corales con geometrías triangulares, la geometría de las LCS se caracteriza por una doble espiral que permanece unida a la cresta del coral. La doble espiral es generada por un anillo vorticial(vortex ring) que aparece cuando la ola pasa sobre el coral. Cuando la altura del coral comienza a ser comparable con la profundidad del agua, los patrones LCS descritos anteriormente comienzan a deformarse debido a la falta de profundidad del agua para evolucionar, por lo tanto, para las geometrías triangulares y rectangulares, tenemos un proceso de ruptura de olas, donde parece que el LCS actúa como un "falso fondo'' generando inestabilidades en la ola incidente que inducen la ruptura de la misma. Las LCS más cercanas a la superficie libre también parecen controlar la curvatura de la misma después de que se produzcan las roturas. Las LCS para el coral triangular presentan valores mayores del campo FTLE que el rectangular, lo que sugiere que los corales que tienen una forma aproximadamente triangular aumentan la mezcla del flujo con un gran impacto en la dispersión del material transportado (es decir, nutrientes, oxígeno, etc.), respecto a las geometrías rectangulares. (Texto tomado de la fuente) Owing to its inherent turbulent nature, ocean dynamics is highly complex. We can model the main transport patterns of the ocean circulation at meso- and submeso-scales, O(0.1-100 km, hours-months) using dynamical systems approaches, but the extreme richness at microscales O(0.001-10m, seconds) circulation patterns, makes the assessment of water pathways and the study of oceanic transport phenomena an extraordinarily complicated task. At microscales we can find coral reef ecosystems, which in recent years have gained notorious importance regarding the effects they can generate on the hydrodynamics of the incident flow, in areas from biology to engineering due to their role as structures of coastal protection. Despite the studies carried out to understand the hydrodynamics around these ecosystems, there is still not a clear idea of how the different types of geometry of the coral colonies condition the transport patterns that develop in the flow. One type of techniques contributing most to the understanding of transport patterns and the description of flow’s topology is the one known under the name of Lagrangian Coherent Structures, which is a generalization of the unstable and stable manifolds of hyperbolic points in time independent systems to finite-time and time-dependent systems. In this thesis we evaluate the feasibility of using the LCS concept to describe the transport and mixing properties in highly fluctuating flows at microscales around coral geometries. In particular, we study the transport patterns induced by the interaction between a solitary wave with submerged objects of different geometry, that approximate the geometry present in corals. We use velocity data from RANS-VOF model outputs. The analized scenarios consist in variation of Reynolds number, the ratio between the wave height, H, and the water depth, h, with the coral heigth, L (H/L and h/L, respectively) and shape. The transport patterns are studied through the computation of Lagrangian coherent structures with the implementation of the finite-time Lyapunov exponent (FTLE) method, and compared with the vorticity field and the Q criterion field. We found that vorticity field has a better correlation with the FTLE field (LCS geometry) than the Q field, suggesting that the flow topology is controled more for vorticity process obtained by a shear flow than for vortices itself (pure rotation regions). For corals represented by rectangular geometries, the LCS have an spiral form, and are formed above and at the lee side of the coral. Both LCS remain attached to the submerged object once h/L and H/L starts to decrease. For the corals with triangular geometries, the LCS geometry is characterized by a double spiral that remains attached to coral’s crest. The double spiral is generated by a vortex ring that appears when the wave pass over the coral. When coral’s height starts to be comparable to the water depth, the LCS patterns described above, start to be deformed due to the lack of water depth to evolve, so for both triangular and rectangular geometries, we have a wave breaking process, where it seems that the LCS acts like a “fake bottom” generating instabilities in the incident wave that induce the break of it. The closest LCS ridges to the free surface also appears to control the curvature of it after the breaks takes place. The LCS for the triangular coral presents larger values of the FTLE field than the rectangular one, suggesting that corals that have an approximately triangular shape increase the flow mixing processes with a large impact on the spreading of the transported material (i.e nutrients, oxygen, etc), with respect to the rectangular ones. Maestría Magíster en Ingeniería - Recursos Hidráulicos Se usa la metodología de los FTLE para obtener los campos de las estructuras coherentes lagrangianas (LCS) para el estudio de patrones de mezcla,transporte y rotura del oleaje al interacturar con un obstáculo sumergido (coral) Interacción flujo estructura en ecosistemas marinos Área Curricular de Medio Ambiente

Memoria de tesis doctoral presentada por Verónica Morales Márquez para obtener el título de Doctora en Física por la Universitat de les Illes Balears (UIB), realizada bajo la dirección del Dr. Alejandro Orfila Forster, del Dr. Ismael Hernández Carrasco del Instituto Mediterráneo de Estudios Avanzados (IMEDEA-CSIC) y del Dr. Gonzalo Simarro Grande del Institut de Ciències del Mar (ICM-CSIC)