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The interaction of shielded vortices, with a continuous vorticity distribution, and a shear current of weak vorticity amplitude but similar velocity compared to the vortex amplitude is numerically investigated in two-dimensional isochoric flows. Different types of axisymmetric shielded vortices, namely, a neutral unstable vortex, a neutral robust vortex, and a non-neutral vortex are considered. The vortices are linear combinations of vorticity layer-modes, which consist of conveniently normalized cylindrical Bessel functions of order 0, truncated by a zero of the Bessel function of order 1. The vortex–current interaction is investigated by superposing initially the vortices at different initial locations along the cross-flow axis in the shear current. The numerical results show that some shielded vortices, as well as the shear current, remain robust while the vortices cross the shear current and reach a stable equilibrium location, which is of the same sign vorticity as its amount of circulation. There exist two unstable equilibrium locations where most of the vortices persist during a relatively short time interval before heading to their stable equilibrium region in the shear current

We investigate numerically the elastic interaction between an eddy-pair and an axisymmetrical eddy in inviscid isochoric two-dimensional (2D) flows, as well as in three-dimensional (3D) flows under the quasi-geostrophic (QG) approximation. The eddy-pair is a straight moving Lamb-Chaplygin dipole where the absolute value of either its positive or negative amount of vorticity equals the vorticity of the axisymmetrical eddy. The results for the 2D and 3D cases show that interactions with almost no vorticity exchange, or vorticity loss to the background field between ocean eddies, but causing changes in their displacement velocity, are possible. When the eddy-pair approaches the axisymmetrical eddy, their respective potential flows interact, the eddy-pair's trajectory acquires curvature and their vorticity poles separate. In the QG dynamics, the eddies suffer little vertical deformation, being the barotropic effects dominant. At the moment of highest interaction, the anticyclonic eddy of the pair elongates, simultaneously the cyclonic eddy of the pair evolves toward spherical geometry, and the axisymmetrical eddy acquires prolate ellipsoidal geometry in the vertically stretched QG space. Once the eddy-pair moves away from the axisymmetrical eddy, its poles close, returning to their original geometry, and the anticyclonic and cyclonic eddies continue as an eddy-pair with a straight trajectory but along a new direction. The interaction is sensitive to the initial conditions and, depending on the initial position of the eddy-pair, as well as on small changes in the vorticity distribution of the axisymmetrical eddy, inelastic interactions may instead occur

We provide exact solutions of axisymmetric neutral vortices, that is, vortices with zero amount of potential vorticity anomaly (PVA), in three-dimensional (3D) quasi-geostrophic (QG) flows with distributed vorticity and density stratification. These solutions are linear combinations of PVA spherical layer-modes, which consist of conveniently normalized spherical Bessel functions of order 0, truncated by a zero of the spherical Bessel function of order 1. It is shown that, depending on the superposition of the different spherical layer-modes, some vortices remain axisymmetrically robust to small amplitude PVA perturbations, while other vortices evolve to stable QG tripoles. The robust axisymmetric 3D QG vortices analyzed here do not generate exterior potential flow and may provide an explanation to the persistence of baroclinic eddies in the ocean

On June 22, 2023, the second online meeting ofthe Blue Genes initiative took place, unitingmembers of the Blue Genes Community. The aimwas to exchange experiences, discuss initiatives,and share insights concerning the Ocean andWaters. Over 30 participants joined this virtual assembly. Following a series of inspiringpresentations delivered by several of the community members, the meetingtransitioned into an interactive session, enabling attendees to activelyparticipate in discussions and to share their viewpoints. Among other relevantconversations, the meeting proposed to target a milestone: to organize aSatellite Event during the 2024 UN Ocean Decade Conference, which will takeplace in Barcelona in April 2024, as an open space to explore how to search fornew ways to increase our connection with Nature, with the ocean as its centralcomponent. The participants felt this in-person meeting would be an excellentvenue to work towards defining the priorities and strategies for the future ofthe Blue Genes community, as well as to engage a wider number of actors

The South Atlantic Ocean is one of the central components of the climate system as it regulates the intensity of the Atlantic South Overturning Circulation (AMOC), which determines the amount of equatorward heat gained and transported to high latitudes (Garzoli and Matano, 2011). The main goal of the SAGA10W oceanographic cruise, carried out between March 7 and April 15 2021, was installing the appropriate equipment to perform a long time monitoring of the interior-ocean zonal flows linking the eastern and western South Atlantic basins. The equipment selected to perform the monitoring as well as the logistic of its installation was not trivial. It consisted of four PIES (Pressure Inverted Eco Sounder), and three 2000- m instrumented moorings installed along 10W on the spurs of the Mid-Atlantic Ridge between 34º20'S and 19º20'S. This vertical section takes place the verge of the subtropical and tropical gyres, in a region that has been recently identified as a pathway for both the starting and returning limbs of the AMOC: the South Atlantic Gateway (SAGA). To properly install the four PIES and three moorings it was absolutely necessary to perform a previous study of the bottom topography with enough resolution to decide the right location. Considering the period of planned monitoring (4 yrs), it was absolutely necessary to adequately prepare all submerged instrumentation. The detailed multibeam scanning of the bottom relief was performed around the points selected by GEBCO. The multibeam scanning covered a 20x20 nautical mile square and consisted of 5 meridional tracks 5 miles apart that allowed to obtain a real acoustic image of the bottom relief with a spatial resolution of 25 meters. Here, we present our experience in preparing the equipments, the cruise operations and the final setup of the entire SAGA array

Long-lived eddies are found over all the oceans. Monopolar spiral eddies in the South Atlantic (Beron-Vera, 2008), warm core rings in the Gulf of Mexico (Meunier et al., 2021) or Mediterranean eddies are only some examples of long-lived, monopolar and three-dimensional (3D) baroclinic vortices in the ocean. These eddies consist of an inner vorticity core and an outer ring of opposite vorticity sign, and are found in an approximately axisymmetric isolated state where the azimuthal velocity rapidly vanishes with the radial distance beyond the radius of maximum speed (Viudez, 2021). We called them neutral vortices, as they carry a zero amount of potential vorticity anomaly. However, sign changing potential vorticity gradients cause flow instabilities, implying that isolated geophysical vortices, should be unstable (Benilov, 2003), contradicting the long persistence of those eddies. This paradox has been considered previously in a theoretical and numerical way using rings of piecewise-constant vorticity (Benilov, 2003; Carton, 2009; Flierl, 1988; Kloosterziel & Carnevale, 1992). In particular, some piecewiseconstant neutral vorticity monopoles were found to be stable when the outer ring was sufficiently thick relative to the vortex core (Flierl, 1988). Moreover, Viudez (2021) found two-dimensional numerical solutions of axisymmetric neutral vortices which remain robust to small amplitude vorticity perturbations. We will continue the work of Viudez (2021) and expand these solutions to 3D quasi geostrophic geophysical flows. In this work we present the first exact solutions of stable neutral axisymmetric vortices under the QG approximation in 3D. The vorticity field analyzed is a finite combination of truncated, shifted and normalized spherical Bessel modes of order zero j0(kr), each one occupying a circular layer, whose boundary radius krp is given by a zero krp =j3/2,p of the first-order spherical Bessel function j1(kr). In this approach, each PV layer-mode carries the

This study describes the spatial distribution and abundance of siphonophores concerning oceanographic variables (temperature, salinity, and dissolved oxygen) in the northern Chilean Patagonian Fjord Ecosystem, from Guafo Passage (43°30’S) to Elefantes Gulf (46°40’S) during the winter of 2012. Twelve species were identified, ten belonging to suborder Calycophorae and two assigned to suborder Physonectae. The species Chelophyes appendiculata and Sphaeronectes gamulini are new records for this study area. Dominant species were Muggiaea atlantica (63.15%), Lensia conoidea (21.85%), and Sphaeronectes koellikeri (9.91%). Species richness showed a negative latitudinal gradient, and the highest densities were found in North Moraleda Channel (5316 ind 1000 m-3) and the lowest in South Moraleda Channel, near Elefantes Gulf (71 ind 1000 m-3). Some species showed a significant and positive association with some oceanographic variables, e.g., M. atlantica showed a positive association with dissolved oxygen, L. conoidea with temperature and negative association with dissolved oxygen, Sphaeronectes fragilis, S. koellikeri, and C. appendiculata showed a positive association with salinity. Eudoxids (sexual reproductive stage) were found for M. atlantica, L. conoidea, and Dimophyes arctica, indicating that the PFE conditions are suitable for some siphonophore species even in winter., Postprint (published version)

This study describes the spatial distribution and abundance of siphonophores concerning oceanographic variables (temperature, salinity, and dissolved oxygen) in the northern Chilean Patagonian Fjord Ecosystem, from Guafo Passage (43º30'S) to Elefantes Gulf (46º40'S) during the winter of 2012. Twelve species were identified, ten belonging to suborder Calycophorae and two assigned to suborder Physonectae. The species Chelophyes appendiculata and Sphaeronectes gamulini are new records for this study area. Dominant species were Muggiaea atlantica (63.15%), Lensia conoidea (21.85%), and Sphaeronectes koellikeri (9.91%). Species richness showed a negative latitudinal gradient, and the highest densities were found in North Moraleda Channel (5316 ind 1000 m-3) and the lowest in South Moraleda Channel, near Elefantes Gulf (71 ind 1000 m-3). Some species showed a significant and positive association with some oceanographic variables, e.g., M. atlantica showed a positive association with dissolved oxygen, L. conoidea with temperature and negative association with dissolved oxygen, Sphaeronectes fragilis, S. koellikeri, and C. appendiculata showed a positive association with salinity. Eudoxids (sexual reproductive stage) were found for M. atlantica, L. conoidea, and Dimophyes arctica, indicating that the PFE conditions are suitable for some siphonophore species even in winter