Retrieval of eddy dynamics from SMOS sea surface salinity measurements in the Algerian Basin (Mediterranean Sea)

Isern‐Fontanet, Jordi; Olmedo, Estrella; Turiel, Antonio; Ballabrera-Poy, Joaquim; Garcı́a-Ladona, Emilio

doi:10.1002/2016gl069595

Cited by 26 publications

(29 citation statements)

References 27 publications

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“…For instance, the number of eddies with radius larger than 80 km (50 km) in the North Atlantic (Mediterranean) is largely overestimated in the satellite‐like products (Figures a and e). It is important to remark that, in some cases, the altimetry can correctly capture individual eddies but that is the least likely scenario and should be confirmed by other independent data sets (e.g., Isern‐Fontanet et al, ).…”

Section: Discussionmentioning

confidence: 88%

Up to What Extent Can We Characterize Ocean Eddies Using Present‐Day Gridded Altimetric Products?

et al. 2018

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The most common methodology used to detect and characterize mesoscale eddies in the global ocean is to analyze altimetry-based sea-level gridded products with an automatic eddy detection and tracking algorithm. However, a careful look at the location of altimetry tracks shows that their separation is often larger than the Rossby radius of deformation. This implies that gridded products based on the information obtained along track would potentially be unable to characterize the mesoscale variability and, in particular, the eddy field. In this study, we analyze up to what extent sea-level gridded products are able to characterize mesoscale eddies with a special focus on the North Atlantic Ocean and the Mediterranean Sea. In order to perform this task, we have generated synthetic sea level anomaly maps using along-track data extracted from realistic high-resolution ocean model simulations and applying an optimal interpolation procedure. Then, we have used an eddy detection and tracking algorithm to the gridded synthetic product and to the original model outputs and compared the characteristics of the resulting eddy fields. Our results suggest that gridded products largely underestimate the density of eddies, capturing only between 6% and 16% of the total number of eddies. The main reason is that the spatial resolution of the gridded products is not enough to capture the small-scale eddies that are the most abundant. Also, the unresolved structures are aliased into larger structures in the gridded products, so those products show an unrealistic number of large eddies with overestimated amplitudes. Plain Language SummaryMesoscale eddies are ocean vortexes that are found all across the global ocean. These structures can move water inside their interiors and stir the surrounding waters, resulting in a net transport of water properties, such as heat and salt. The most common way to study these eddies is by using satellite-based observations of the signature that most of eddies have on the sea surface. We show, by using a new generation of numerical models and mimicking the measuring process that satellites do, that the vast majority of the eddy field is missed because the available observations do not have enough resolution to resolve the smaller vortexes. Moreover, the mapping procedure used tends to merge several smaller eddies into a larger one, making the true detection of eddies with size enough to be correctly captured by satellite measurements not reliable.

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Section: Discussionmentioning

confidence: 88%

Up to What Extent Can We Characterize Ocean Eddies Using Present‐Day Gridded Altimetric Products?

et al. 2018

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“…Resent state of the art satellite observations of SSS, by NASA's Aquarius/SAC-D satellite [Lagerloef et al, 2008] and ESA's Soil Moisture and Ocean Salinity (SMOS) satellite [Kerr et al, 2010], present an opportunity to complement the existing satellite observations of SST, surface winds, air-sea fluxes, and other variables, to observe the signature of mesoscale eddies. The potential of new satellite measurements to observe mesoscale features and eddies have been demonstrated in a few recent studies [Reul et al, 2014;Umbert et al, 2015;Isern-Fontanet et al, 2016]. Yet extracting such information from medium-resolution and noisy satellite data requires application of selective data analysis tools.…”

Section: Introductionmentioning

confidence: 99%

Signature of mesoscale eddies in satellite sea surface salinity data

Melnichenko

Amores

Maximenko

et al. 2017

J. Geophys. Res. Oceans

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A persistent signature of coherent mesoscale eddies in sea surface salinity (SSS) is revealed by analyzing the relationship between satellite SSS and sea surface height (SSH) variability in an eddy‐following reference frame. Our analysis focuses on mid‐ocean eddies in two representative regions, the southern Indian Ocean and the North Atlantic subtropical gyre. The resulting composite averages reveal a clear signature of mesoscale eddies in satellite SSS with typical SSS anomalies of 0.03–0.05 psu. The spatial structure of eddy‐induced SSS perturbations can be characterized as a superposition of a dipole structure, arising from horizontal advection of the background SSS gradient by eddy velocity field, and a monopole structure related to the eddy core. The observed relationships between SSS and SSH anomalies are used to provide a regional assessment of the role of mesoscale eddies in the ocean freshwater transport in the North Atlantic subtropical gyre.

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“…can be written for SSH(Isern-Fontanet et al, 2008) b s (k, z) = n e gkη exp(n 0 kz) within this framework, SST and SSH contain the same information and, once buoyancy and the stream function are15 known at all depths, vertical velocities can be estimated(Lapeyre and Klein, 2006;LaCasce and Mahadevan, 2006;Klein et al, 2009;Isern-Fontanet and Hascoët, 2014) LaCasce and Mahadevan (2006). andIsern-Fontanet et al (2006b) demonstrated, for the first time, that this approach can be used to derive ocean currents from real SST measurements and, later,Isern-Fontanet et al (2016b) that it is also possible to use SSS from SMOS. Moreover, the eSQG approach has shown to provide good results in highly variable areas such as the Alboran Sea(Isern-Fontanet, 2016; Isern-Fontanet et al, 2017b) and for small (∼ 10 20 km) coastal eddies(Isern-Fontanet et al, 2017a…”

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Retrieval and assimilation of velocities at the ocean surface

Isern‐Fontanet

Ballabrera-Poy

Turiel

et al. 2017

Preprint

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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 scale. Consequently, it has been necessary to use Sea Surface Height and Sea Surface Temperature measurements and refer to dynamical frameworks to derive the velocity field. Second, the assimilation of the velocity field into numerical models of ocean circulation is difficult 5 mainly due to lack of data. Recent experiments assimilating coastal-based radar data have shown that ocean currents will contribute to increase the forecast skill of surface currents, but require to be applied in multi-data assimilation approaches to allow better identification of the thermohaline structure of the ocean. In this paper we review the current knowledge on these fields and provide global and systematic view on the technologies to retrieve ocean velocities in the upper ocean and the available approaches to assimilate this information into ocean model. 10 15pollutants. Strong ocean currents define corridors used by marine mammals, birds and fishes, and sustain their migrations in search for food, breeding sites and spawning areas. As a result, knowledge of the detailed structure and variability of ocean currents is required for fisheries and environmental management. On the other hand, surface currents directly affect many important socio-economic activities as global marine trade and shipping or marine pollution and safety, to mention a few.Ocean surface currents appear as the result of a non-trivial combination of different types of periodic and aperiodic phe-20 nomena whose ranges span a continuous spectra of space and time scales, from basin-wide motions ( 1000 km) to fast narrow currents and mesoscale eddies (30-100 km wide), submesoscale features (1-10 km), and turbulence scales (1-100 m). Different components of the current ocean observing system capture different parts of this range. Land-based coastal HF radars are able to resolve rapid changes. However, although the number of HF radars has rapidly increased in the last decades, they coverage remains limited. Currents are also observed at a few moorings. Until now, Lagrangian drifters and satellite altimeter-derived 25 surface geostrophic currents have been the only sources of information able to provide global coverage. Drifters are able to 1 Nonlin. Processes Geophys. Discuss., provide hourly observations but with irregular coverage with approximately one point within a 5 degree box (Dohan and Maximenko, 2010). At global scale observations using moored instruments in both the ocean surface and the water column are distributed mostly near and along the coasts, particularly in the northern hemisphere (see figure 1 Holloway, 2008; Scott et al., 2010). These are often arrays of point-based currentmeters or current profilers from oc...

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Retrieval of eddy dynamics from SMOS sea surface salinity measurements in the Algerian Basin (Mediterranean Sea)

Cited by 26 publications

References 27 publications

Up to What Extent Can We Characterize Ocean Eddies Using Present‐Day Gridded Altimetric Products?

Up to What Extent Can We Characterize Ocean Eddies Using Present‐Day Gridded Altimetric Products?

Signature of mesoscale eddies in satellite sea surface salinity data

Retrieval and assimilation of velocities at the ocean surface

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