
Jordi Isern-FontanetInstitut de Ciències del Mar · Departament d'Oceanografia Física i Tecnològica
Jordi Isern-Fontanet
Doctor
About
60
Publications
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2,532
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Introduction
Additional affiliations
October 2014 - present
December 2006 - November 2008
September 2005 - November 2006
Education
October 1999 - December 2003
September 1993 - June 1998
Publications
Publications (60)
This study assesses the capability of Surface Quasi-Geostrophy (SQG) to reconstruct the three-dimensional (3D) dynamics in four critical areas of the Arctic Ocean: the Nordic, Barents, East Siberian, and Beaufort Seas. We first reconstruct the upper ocean dynamics from TOPAZ4 reanalysis of sea surface height (SSH), surface buoyancy (SSB), and surfa...
The knowledge about the variability of the surface ocean currents is essential to support medium and long-term decision-making in a different problem related to the ocean currents: the spills of hydrocarbons or chemical products that can be dumped by ships, oil rigs, or
other industries. Traditionally, the prediction of the evolution of the pollut...
High-resolution satellite images of ocean color and sea surface temperature reveal an abundance of ocean fronts, vortices and filaments at scales below 10 km but measurements of ocean surface dynamics at these scales are rare. There is increasing recognition of the role played by small scale ocean processes in ocean-atmosphere coupling, upper-ocean...
In addition to their ecological and environmental value, coastal areas are of major economic and social importance. Therefore, they are one of the marine environments most affected by anthropogenic pressures, in the form of high population densities and intense human activities. Anthropogenic pressures produce an excess of nutrients which are deliv...
This oceanographic dataset was gathered during the TIC-MOC cruise, which was designed to characterize the dynamics of the Brazil-Malvinas Confluence. The cruise was carried on board the R/V Hespérides, with departure from Ushuaia and arrival to Salvador de Bahía. A total of 66 conductivity-temperature-depth (CTD) stations were completed between 8 a...
Ocean currents play a key role in Earth's climate – they impact almost any process taking place in the ocean and are of major importance for navigation and human activities at sea. Nevertheless, their observation and forecasting are still difficult. First, no observing system is able to provide direct measurements of global ocean currents on synopt...
Ocean currents play a key role in Earth’s climate, they are of major importance for navigation and human activities at sea, and impact almost all processes that take place in the ocean. Nevertheless, their observation and forecasting are still difficult. First, direct measurements of ocean currents are difficult to obtain synoptically at global sca...
Any ocean perturbation trends to find an equilibrium situation where the dominant forces are pressure gradients and Coriolis force: the name of this equilibrium are geostrophic balance. Any movement that represents a desviation from this balance we identified with the name of ageostrophic movement. At large spatial and temporal scales these desviat...
Any ocean perturbation tends towards an equilibrium situation where the vertical balance is hydrostatic and the dominant horizontal forces are pressure gradients and Coriolis force, the so called geostrophic balance. Any motion that represents a desviation from this balance is named ageostrophic. At spatial and temporal scales of order 10-100 km (m...
Blooms of the benthic dinoflagellate Ostreopsis have been related to sporadic acute respiratory symptoms and general malaise in people exposed to marine aerosols on some Mediterranean beaches. However, the direct link between recurrent Ostreopsis blooms and health problems has not been clearly established. In order to establish and elucidate the co...
Since the mid-1980s, physical oceanographers at the Institute of Marine Sciences have been involved in the use of Lagrangian drifters as a complementary technology for their oceanographic research. As Lagrangian observations became more feasible, these researchers continued developing their own drifters in what was to be the seed of current technol...
The potentiality of retrieving high spatial resolution velocity fields by exploiting the synergy between nearly simultaneous observations of infrared SST and along-track altimetry is shown here through a case study in the Gulf Stream region. The presented approach relies on the characterization of a transfer function between the SST observations an...
The circulation in the Algerian Basin is characterized by the presence of fresh-core eddies that propagate along the coast or at distances between 100 and 200 km from the coast. Enhancements in the processing of the Soil Moisture and Ocean Salinity (SMOS) data have allowed to produce, for the first time, satellite sea surface salinity (SSS) maps in...
In March 2015, the R/V Hespérides carried out the TIC-MOC cruise, a 14-day oceanographic expedition in the Brazil-Malvinas Confluence (BMC) region. One principal objective of this cruise was to characterize the fine structure of the frontal system (or front) between the subtropical and subantarctic waters. The surface position of the front (sea-sur...
The Brazil-Malvinas Confluence (BMC) is the encountering site, in the South West Atlantic, of waters of subtropical and subantarctic origin. During March 2015, the R/V Hespérides carried out the TIC-MOC cruise, with 14 days of measurements in the BMC region. The instabilities caused by the encounter of warm waters flowing from the north and cold wa...
The phytoplankton bloom in the Liguro-Provençal deep convection region represents one of the main fertilization mechanisms in the Mediterranean. This communication examines nano- and microphytoplankton observations, and measurements of primary production and chlorophyll a concentration (Chl a) in the southwestern part of the deep convection region,...
Ocean currents are a key component to understanding many oceanic and climatic phenomena and knowledge of them is crucial for both navigation and operational applications. Currently, they are derived from Sea Surface Height (SSH) measurements provided by altimeters. However, distances between tracks and the limited number of available altimeters lea...
The real transfer function and the phase shift between sea surface height (SSH) and sea surface buoyancy (SSB) were estimated from the output of a realistic eddy-resolving model of the Mediterranean Sea circulation. The analysis of their temporal evolution unveiled the existence of a clear seasonal cycle closely related to that of the mixed layer d...
The repeated observation of the same signatures of mesoscale and submesoscale features in different ocean variables indicates that some common, non-linear processes affect them to a significant extent. A new method to exploit these common signatures to improve the quality of a noisy variable (i.e. increasing the signal-to-noise ratio) using another...
The noise present in infrared satellite measurements of Sea Surface Temperature (SST) hampers the use of Surface Quasi-Geostrophic (SQG) equations to diagnose ocean dynamics at high resolutions. Here, we propose a methodology to reduce the contribution of noise when diagnosing surface vorticity, divergence and vertical velocity from SST able to ret...
In this work we evaluate surface ocean current reconstruction at a global scale using a new methodology that combines the benefits of microwave and altimetry measurements. The combined method is based on SQG theory and combines the information about the energy spectrum provided by altimeters with SST microwave measurements. We compare ocean surface...
Sea Surface Height (SSH) measurements provided by satellite altimeters
have been widely used to recover surface velocities in the Mediterranean
Sea. However, its sampling geometry and the presence of noise in the
observations, restricts its spatial resolution and can induce important
errors in the location of mesoscale features. On the contrary, Se...
Recent advances in our understanding of the dynamics in the upper layers
of the ocean have allowed us to develop methodologies to recover high
resolution velocities from surface measurements such as Sea Surface
Heights (SSH) and Sea Surface Temperatures (SST). These methods are
based on the combined use of advanced signal processing techniques, suc...
Ocean currents are a key element for the understanding of many oceanic and climatic phenomena and their knowledge is crucial for navigation and operational applications. Therefore, a key problem in oceanography is the estimation of the synoptic velocity field. Currently, global ocean surface velocities are routinely estimated from precise Sea Surfa...
WeusedatafromahydrographiccruiseinNovember2003overSedloSeamount,inconjunctionwith
historical hydrographicandaltimeterdata,todescribethecirculationpatternsneartheseamountand
withintheregion.Amixingmodelthatincorporatestwowatertypesandtwowatermassesassessesthe
watercompositionwithintheregion,andaninversemodelprovidesestimatesofmasstransports
withindi...
A surface Quasi-Geostrophy based (eSQG) method to diagnose the vertical velocity field from Sea Surface Height (SSH) is assessed using high resolution simulations. These simulations concern a turbulent eddy field with large Rossby numbers and energetic wind-driven motions. Results indicate that low-frequency vertical velocities (and also horizontal...
Satellite altimetry has significantly advanced the study of ocean variability. However, noise level and track separation has limited the investigation of scales smaller than 100 km. In contrast to altimeters, other sensors such as visible and infrared radiometers and imaging radars such as SAR have demonstrated their capability to provide measureme...
Transport and mixing properties of surface currents can be detected from altimetric data by both Eulerian and Lagrangian diagnostics. In contrast with Eulerian diagnostics, Lagrangian tools like the local Lyapunov exponents have the advantage of exploiting both spatial and temporal variability of the velocity field and are in principle able to unve...
We summarize recent work on the location of Lagrangian structures in velocity fields obtained from realistic simulations and from satellite altimetry of the surface layers of the Mediterranean sea. Finite-size Lyapunov exponents are found to be useful quantities to characterize stretching and compressing structures, and their implications for mixin...
The ability to reconstruct the three-dimensional (3D) dynamics of the ocean by an effective version of Surface Quasi-Geostrophy (eSQG) is examined. Using the fact that surface density plays an analogous role as interior potential vorticity (PV), the eSQG method consists in inverting the QG PV generated by sea-surface density only. We also make the...
Because of the optimal features of wavelet processing, the use of wavelets for describing and analyzing signals in 2D turbulence has been generalized since a decade ago. In spite of the close analogy between 2D turbulence and geophysical fluid dynamics, few works have tried to generalize the rich framework of wavelet techniques to the study of expe...
In this paper we investigate the validity of the multifractal formalism to study sea surface temperature (SST). It is shown that SST patterns observed in moderate resolution SST images have anomalous scaling properties characteristic of a multifractal structure. The most probable origin of the observed structures is the turbulent character of the o...
Here we tested whether the dispersal of loggerhead sea turtles in the western Mediterranean was affected by the pattern of surface currents and whether temporary mesoscale eddies were favoured habitats by comparing the distribution of ten satellite-tracked turtles (average straight carapace length = 46.3 cm; range: 37.1–61.1 cm) with satellite imag...
A realistic 4-year dataset of the surface velocity field of the western Mediterranean Sea obtained with the Mediterranean Forecasting System and the GFDL-MOM model was used to obtain the finite-scale Lyapunov exponents (FSLE) and finite-size diffusion coefficients. Dispersive properties and Lagrangian parameters in four sub-basins are discussed, an...
1] In this paper, we examine the emerging potential offered by satellite microwave radiometer SST measurements to complement altimeter data to quantitatively derive surface ocean currents. The proposed methodology does not follow standard sequential temporal analysis but follows the application of the Surface Quasi-Geostrophic (SQG) theory. Accordi...
Velocity probability density functions (PDFs) are a key tool to study complex flows and are of great importance to model particle dispersion. The PDFs of geostrophic velocities derived from sea level anomalies maps for the Mediterranean Sea have been computed and analyzed, guided by recent results found in studies of two-dimensional and geostrophic...
The presence of coherent vortices makes observed mesoscale fields of the ocean resemble two-dimensional turbulence. Using this analogy, a common definition of a coherent structure has been used to study the statistical properties of Mediterranean Sea vortices observed by satellite altimeters over a 7-yr period. A vortex has been defined as the simp...
The presence of coherent vortices makes observed mesoscale fields of the ocean resemble two-dimensional turbulence. Using this analogy, a common definition of a coherent structure has been used to study the statistical properties of Mediterranean Sea vortices observed by satellite altimeters over a 7-yr period. A vortex has been defined as the simp...
Multifractal or multiaffine analysis is a promising new branch of methods in nonlinear physics for the study of turbulent flows and turbulentlike systems. In this Letter we present a new method based on the multifractal singularity extraction technique, the maximum singular stream-function method (MSSM), which provides a first order approximation t...
Three Algerian eddies (open sea big anticyclonic eddies in the Algerian basin, western Mediterranean sea) are studied in detail using altimetric and in situ data. To characterize their spatial structure we make use of the Okubo–Weiss parameter, which allows to separate the flow into vorticity-dominated and deformation-dominated regions. The applica...
In May 1998 a big and deep open ocean anticyclonic eddy (AE 98-1) was sampled in the Algerian basin (western Mediterranean sea) in a region south of the Balearic islands. Fifteen surface Lagrangian buoys, tracked by satellite, were released across the eddy and were used for a few months to observe the continuity of the anticyclonic motion and the w...
In May 1998 a big and deep open ocean anticyclonic eddy (AE 98-1) was sampled in the Algerian basin (western Mediterranean sea) in a region south of the Balearic islands. Fifteen surface Lagrangian buoys, tracked by satellite, were released across the eddy and were used for a few months to observe the continuity of the anticyclonic motion and the w...
In May 1998 a big and deep open ocean anticyclonic eddy (AE 98-1) was sampled in the Algerian basin (western
Mediterranean sea) in a region south of the Balearic islands. Fifteen surface Lagrangian buoys, tracked by satellite, were
released across the eddy and were used for a few months to observe the continuity of the anticyclonic motion and the w...
A procedure is presented to detect eddy cores from sea level anomaly (SLA) maps obtained from altimetric measurements. The method is based on finding the sign of Q, which is an invariant of the velocity gradient tensor (▽u). This parameter, commonly used in studies of two-dimensional turbulence, measures the relative contribution of deformation and...
The properties of Mediterranean eddies (size, circulation, energy, ...) are studied using results of the high resolution MED16 model, which has been developed in the context of the MERCATOR project. The numerical model is an extended version of the primitive equation model OPA (LODYC, Paris) with a rigid lid. It uses a 1/16 degree horizontal grid m...
The Algerian Basin dynamics is dominated by the presence of very energetic mesoscale structures. Deep open sea eddies are key features that influence the regional circulation of water masses at all depths. In May 1998, an open sea eddy was sampled near 38°N 2°E by means of CTD, Acoustic Doppler Current Profiler (ADCP) and surface Lagrangian drifter...
The Algerian Basin is characterised by the presence of mesoscale open-sea eddies generated by the instabilitzation of the Algerian Current. These eddies play a key role to understand the dynamics of the Western Mediterranean sea. Here, their evolution for the period October 1992-October 1999 is systematically analyzed from altimetric maps. First, e...
Mesoscale eddies are a key element to understand the dynamics of the Mediterranean sea, but their role in the general circulation of the basin is not still well understood. In this contribution we present a statistical analysis of the properties of mesoscale eddies observed in Sea Level Anomalies maps for the period October 1992-October 1999. We ha...
The evolution of an open-sea eddy, previously detected by IR imagery, is studied using Sea Level Anomalies (SLA) maps. This evolution is compared with the information given by surface drifters deployed along eddy diameter, during ALGERS98 cruise in western Mediterranean. Preliminary results show a good agreement between the structure observed form...
Velocity probability density functions (PDF) are a key element to understand mixing in the ocean. Two-dimensional turbulence results show that vortices are the responsible for the deviation of PDF from gaussianity. These results have been confirmed in the ocean by recent works that analyzed TOPEX/Poseidon and Lagrangian data. Our objective is to an...
In two dimensional flows the observed structure of an eddy consists on an inner part called the core and an outer part called the circulation cell. The core is characterized by a dominance of vorticity while the circulation cell is dominated by deformation. This relative dominance is usually measured by the Okubo-Weiss parameter (W) which is negati...